Soniferous Fish of SEQ

[Slider]

For those that might find this interesting -

A soniferous fish is a fish that vocalises by drumming muscles against the swim bladder which amplifies the sound. Most species have several different vocalisations and as many as 9 different vocalisations from 1 species have been recorded. Generally though, fish will have one they use when spawning, one for alarm and one for feeding. Some fish have weak vocalisations that may only travel 50m in the water whilst others such as yellowfin tuna can be heard with hydrophones from 65km away.

Today I started making a list of species that exist in SEQ that have been recorded elsewhere in the world on hydrophones and their vocalisations placed on the world wide database of fish vocalisations. So far the following are confirmed as being soniferous.

Dart, Tailor, Mulloway, Sea Mullet, Tarpon, Bonefish, Snub Nosed Dart, Golden Trevally, Giant Trevally, Big Eye Trevally, Estuary Cod, Snapper, Garfish, Catfish, Groper, Yellowfin Tuna, longtail Tuna, Mackerel Tuna,

So pretty well all surf species that have been studied are soniferous. Bream and whiting have never been studied as they mainly only exist in Australian waters and we trail the rest of the world in this department by decades. I'll bet my ring gear that they too are soniferous though.

It would be safe to say that all the trevally and cods are soniferous and black jew have been recorded in West Australia. From memory all lutjanids are soniferous and it would seem that the vast majority of fish in fresh and salt water are in fact soniferous.

I'll add to the list as time permits.

Lindsay

[HeadBanger]

Thanks for that information Lindsay, found it very interesting.

Would it be safe to say that as a fish grows larger, its vocalisations would be stronger?

Would territorial species, such as mangrove jack give off 'aggressive' vocalisations towards larger fish (not prey) entering their territory? Or is there no information regarding that yet?

Cheers,
Kaidon

[Slider]

Kaidon, as fish grow larger their vocalisations would become louder due to a larger swim bladder and greater amplification. This is how researchers can determine the size of fish being listened to on a hydrophone. In various parts of the world, stock assessments are carried out using static and mobile hydrophones which determine stocks (numbers, size, sometimes sex) and spawning locations without the requirement for tagging or sampling. A fish's vocalisation can positively identify the species - once its vocalisation is on the database. This is part of my motivation for listing the species that are found in Australian waters and that have been recorded overseas. If Fisheries in Australia are to manage our fisheries to the best possible standard and accurate stock assessments and spawning locations established, this available technology needs to be implemented. As it stands, a level of assumption and guesswork is our standard of fishery management.
As to aggressive vocalisations - I dare say that some species would have such in their repertoire, but these species I would expect would live in murky water where 'body language' is less effective than it would be in clear water. With most of these things, attributes evolve for a reason. But that is guesswork on my part as I haven't seen any literature that delves into this field - and haven't looked either.

[Slider]

Another interesting fact about soniferous fish - Dolphins target soniferous fish over non - soniferous fish because they can hear them. When fish hear dolphins nearby, they stop vocalising in the hope that the dolphins won't find them. So when you hook a tailor in the surf and see a dolphin heading towards you from a kilometre away (as I have countless times), it's because the dolphin has heard the tailor's alarm vocalisation. Remembering that dolphins don't have a lateral line to detect vibration as a fish can. Further, it is incorrect that dolphins locate fish using their sonar from distances. They initially locate the fish from the vocalisations of the prey, then when the fish stop vocalising on hearing the dolphins, the sonar comes into play and at a closer range where the sonar is effective.

[Slider]

Let's go one step further and bring in an angling scenario involving vocalisations and hydrophones. It will occur (if it hasn't already) that an angler will be able to listen for a target species on a hydrophone dropped over the side of the boat, determine what direction it is from the boat and how far away. The angler can then drive the boat to the fish and throw lures at the location that the fish has been determined to be. It is envisaged that standard electronics on a fishing boat will include the gps, sounder and hydrophone/computer that will identify the fish species being heard on the hydrophone and its location.

[Slider]

Also, fish can be attracted to a location by recording prey vocalisations, or prey been fed on by predators and those recordings being played into the water. For instance - if we wanted to attract spotty mackerel to a location (and they are in the general neck of the woods), then playing a recording of say anchovy being fed on by spotty mackerel into the water will attract the fish to where we want them to be. This technology is being developed at the moment and has been demonstrated to work any number of times. It isn't quite as simple as that, but that is the gist of it.

[HeadBanger]

Thanks for the reply, finding it all very interesting.

Almost seems like playing god, in regards to recording fish vocalisations to bring fish on the chew in the general area. Then again, I suppose people felt the same way with the invention of sounders. I'm sure it's things like these that can really effect both our commercial and recreational fisheries?

Thanks again,
Kaidon

[cuzzamundi]

Thanks for the info, Slider. I always find these posts very informative.

I've actually wondered over the years what is happening when I'm castnetting, as quite often, I'll work an area, and upon netting more mullet, the poddies that are elready in the bucket of water go berserk for a period of time. It's as if they can sense the other fish being caught/trapped. Maybe this is all due to vocalisation? I find it fascinating that fish in a bucket ten or more metres away can tell that other of their kind are being pulled from the water. Could this be the case? I'm not sure, and I guess it would depend on whether their vocalisations can travel through the air.

Great topic.

Cuzza

[Slider]

Is a bit scary the fish attraction thing Kaidon. Who knows where technology like that is heading as far as maintaining the world's fisheries. However, I think that there is a limiting factor in the over use of the technology. Fish won't continually be drawn to a sound source if they continually find that there is no reward there. And if they are continually netted when they do respond to the sound, then they would eventually start to swim the other way. Which may have consequences to their normal day to day prey locating in that they won't trust 'real' sounds. It has already been established that fish won't continually be attracted to the same sound being played into the water and that variations of the sound are required to keep attracting the fish. ie changing prey species, predator species, prey and predator species.

Cuzza, there certainly hasn't been any studies into that one - but, there is no reason why the mullet in the bucket wouldn't hear the vocalisations of the mullet in the cast net. Sound travels much better in water - 5 times the speed that it does in air and for far greater distances. But fish sounds do travel through air - we've all heard trevally vocalisations when we catch them, though these vocalisations are at abnormally high frequency for a fish. But not all vocalisations are as strong as a trevally's or at such a high frequency. So it boils down to whether the mullet vocalisations are strong enough to travel through air the distance between the cast net and the bucket. An interesting experiment that could be conducted by altering distances between and seeing at what distance the mullet stop reacting. Excellent observation by the way Cuzza.

We have to keep in mind that most fish vocalisations are at frequencies too low for humans to hear and a mullet's vocalisation wouldn't be heard by humans.

Has anyone noticed that when fishing for a species other than trevally, that the target fish go off the bite for a while if a trevally is caught? Is a regular thing when fishing for tailor.

It has been found that the strength of a fish's vocalisation is directly proportionate to the size of their otolith (ear). Which stands to reason as a fish with a refined sense of hearing would also have refined communicating abilities.

On sound in water - a humpback whale's vocalisations at the Antartic can be heard by another humpback at the equator providing there isn't a land mass in between to stop the sound. Sound in water travels for enormous distances. Thus the ability to hear yellowfin tuna from 65km on a hydrophone. But a fish's acoustic abilities are more refined at listening to sounds in the water than is a man made hydrophone. So when researchers are able to hear a species' 'weak' vocalisations at just 50m, then fish are likely to hear that same vocalisation at far greater distances.

[caster226]

this is like watching the local alcoholic wandering along the road. the final destination is always the same.

[Slider]

Having just read every one of your posts since joining this site caster, I notice a few things about you. Firstly, you are an expert on every fish, method of catching and every location known to man. Secondly, you seem to have an affinity with beach haulers, but little knowledge about the business at all. And thirdly, I can't find a single thread with fish you have caught despite telling everyone about the supposed fish you catch of every species known to man.
I will ask the question that others have already asked - what is your agenda? And why are you continually knocking me for doing my best to help recreational fishing? Is it just a jealousy thing you've got going?

Note to self - I should just ignore twits like caster.

[chisel]

Very interesting info Lindsay. Thanks for posting.

[sleepygreg]

Thanks Slider. Some extremely interesting information there. That would explain the 'prey wash' systems employed by many Gamefishing boats. I knew it worked, but not quite sure why. I suppose this would also link in with frequencies being experimented with in Shark attraction/deterence. Bloody fascinating.....more please?

Greg

[FishHunter]

Having just read every one of your posts since joining this site caster, I notice a few things about you. Firstly, you are an expert on every fish, method of catching and every location known to man. Secondly, you seem to have an affinity with beach haulers, but little knowledge about the business at all. And thirdly, I can't find a single thread with fish you have caught despite telling everyone about the supposed fish you catch of every species known to man.
I will ask the question that others have already asked - what is your agenda? And why are you continually knocking me for doing my best to help recreational fishing? Is it just a jealousy thing you've got going?

Note to self - I should just ignore twits like caster.

Very interesting reading, thanks

Unfortunately the internet abounds with people like this who feel that as they are safe behind their keyboard they can get away with anything. My inclination is to find them and punch them in the head

[bondy99]

Slider,

I like what I read, you should be a marine biologist or better still come over to uni and get some of those academics onboard and listen to reality instead of theory and computer modelling.

You getting any tailor your way? I'm itching to come up.

Cheers, Peter

[Slider]

Can add queenfish, yellowtailed and black kingfish to the list of soniferous fish.

Greg, I'm no gamefisherman and I haven't heard of 'prey wash' - or is that the use of water being sprayed on the surface to keep pelagics on the chew?

Fishhunter, I've always believed the pen is mightier than the sword, but there are times ...

Bondy, I am speaking with a couple of marine scientists at UQ at the moment who are showing appropriate interest. Not many tailor being caught here at the moment, but I expect that to change fairly soon. That keg is still in the garage too.

Was pleasing to read research being conducted in Western Australia into yellowtailed kingies - the researchers were using hydrophones to assess spawning locations by listening for their 'mating calls'.

[bondy99]

Slider, good to hear.

I'm also at UQ, can you pm the marine scientists, I may know of them.

Send me your addy with phone number and I'll come up.
Cheers, bondy

[caster226]

every year since i joined this site you post the same old thing. always the same info about fish vocalisations. never really sourcing it to the people that actually did the various studies. presenting it as as though it could be your research. maybe drop the name of a few scientists you have emailed. then you make assumptions well beyond those studies that you present as fact. you ignore or attack anyone that disagrees. then fan the anti netter fires on your unproven guesswork. you then go on to try and sell your homemade lures. am i worng with where this is heading again. so which one of us has an agenda.

[Slider]

Everybody knows my agenda caster so there's not much point in trying to hide it.
I periodically write these things on Ausfish due to the fact that new members sign up here every day who have never heard this stuff before and who on learning about these things may become my allies in assisting me to alter inshore netting practices - sorry for that, but you don't have to read my posts. It is apparent that even long term members of this site find this material to be very interesting - and it is fascinating that fish behave the way they do.

If you think I am fabricating all of this, perhaps you could do some research of your own and check up on me - you have a computer. But I suspect that the content of the research papers would be above your level of understanding and your experience level is obviously such that you wouldn't be able to correlate that content with the things that people all around the world are noticing when they are fishing in netted areas. If you are as expert as you say you are, then I greatly doubt that you would be dismissing my assertions as readily as you are. And it is a bit hard to take you seriously when you can't offer anything at all that might bring into question these assertions. The reality is that nobody has yet been able to offer anything that realistically questions these assertions - for very good reasons. To say "that's bullshit", which is effectively all that has been presented so far, isn't really of any value to anyone.

So tell me, which part of what I am saying isn't right?

That fish vocalise alarm signals and release alarm chemicals?

That fish develop (learn) antipredator behaviour to any predator that might kill them?

That fish swim away from a predator that might kill them?

That schreckstoff causes fish to stay away from an area known to hold predators?

That nets are a fish's ultimate predator?

That fish populations bounce back when netting is banned in an area whilst rec fishing continues?

I can prove beyond reasonable doubt that all those things are indeed the case.

When I have completed my proposal for the creation of Rec Fishing Havens for Cooloola and Fraser and it is released for all to see, there will be references for every single piece of research that I quote. The paper I produce would be a worthless document without those references. You, caster, will have the opportunity then to offer whatever feedback you desire on the content of that proposal. So unless you can come up with something constructive to add to this thread as others are doing, then go and talk nonsense elsewhere.

[Slider]

Sorry Greg, I overlooked responding to the bit about shark pingers - was busy dealing with trivial matters.

To my way of thinking there is no reason at all why the pingers wouldn't be effective in repelling sharks and cetaceans and probably fish - though I don't know much about this scenario. It must have taken an awful lot of trial and error though to establish what sounds annoy the animals sufficiently to repel them. Especially when you consider that the Japanese very successfully draw dolphins into a certain bay by banging iron bars against the side of iron boats - you'd think that would annoy them. I suppose curiosity of the animal is a factor in that regard.

An interesting thing I saw repeated several times at Sandy Cape the other week that I can't recall seeing before - when a net was shot next to Breaksea Spit for whiting, a number of sharks of differing species would turn up 10 or 15 minutes later in feeding mode. They would head directly to where the net had been shot, but because the fish were either on the beach or the fish that hadn't been netted had bolted to the hills, there was nothing for them to feed on - though the hammerheads don't seem to mind the stingrays that aren't spooked by the net.
It would be likely and logical, that the sharks have heard the alarm vocalisations of the netted fish which has functioned as an attractant. Vibrations of the panicked fish in the net is probably also a factor. Similarly, when offshore fishing and a good red emperor is hooked (for example) the bronzies or tigers suddenly turn up to relieve you of the red. Always seems to be the reds they come for and it can be assumed that is due to vocalisations of the hooked fish and their preference for the species. They don't seem to like cobia as much despite cobes being very vocal and every pig fish seems to make it to the surface without any probs. Of course sharks are scavengers who don't mind a free feed and I strongly suspect that they are these days drawn to the sound of boats. They know that there will be chum and 'prone' fish available when they get there. I also think that this is a factor when the subject of shark populations comes up and boaties claim that there are heaps of sharks out there cause they always see them when fishing offshore.

[caster226]

im just spinning my wheels as you are never going to give straight answer. you just keep hiding behind other peoples research. the personal attacks i expected but i wont tolerate whats probably one of your cronies suggesting i be hunted down and assaulted. ive never claimed to be an expert on any subject in my life. in nearly 50 years of fishing both recreationally and a good portion of that was in the charter and tackle industry i have fished a lot of the coasts of west aussie qld and central and northern nsw. so yeah i have a bit of experince in a few fishing styles. but i guess that doesnt qualify me to answer any questions by your measure. so its time to take my bat ball and offensive posts and leave you with it. its not worth risking violence to try and share my knowledge.

[Slider]

Specify a straight question and I'll provide a straight answer. I would also like to know how I can 'hide' behind other people's research when I'm the one that is bringing it to the attention of everyone. If this helps - the other people whose research I am 'hiding' behind is that of the likes of - Brian Wisenden, Doug Chivers, Patrice Brehmer, Thomas Holmes, Mark McCormick, Milton Suboski, Maud Ferrari, Smith and Mowbray, Donald Baltz, Rodney Rountree, Culum Brown, Kurt Schaefer, Douglas Mann, Joseph Luczkovich, John hayes and Roger Young, Carl safina and Joanna Burger, Jan Smith, Mark Abrahams, Mary Louise Keefe, Mark Collins, and there are many more that I couldn't be bothered putting up. For a start caster, google Brian Wisenden and have a look at his research.

Btw - fishfeeder and I do not know each other and the statement that you would be 'risking violence to try and share my knowledge' is laughable - and I did laugh. Also, I don't have 'cronies' - I have many supporters who believe in what I do and have noticed the same things about nets that I have, or have seen the stock depletion first hand and are aware that something needs to be done about that soon - from Karumba to Cooktown to Cooloongatta. They know that my motivations are genuine, there are no hidden agendas, I aim to benefit recreational fishing and conservation of species is central to the whole deal. But you think caster that I have a vested interest somewhere don't you - what, may I ask do you believe that interest to be?

[Horse]

Caster226, you obviously do not agree with Lindsays point of view. Thats fine, its a free world but rather than snipe at a thread why not put your thoughts together and start a thread putting forward your opinions and the justification behind it.

[HeadBanger]

Ignore him, Slider. I am very much appreciating the information given here, and the more I read about it, the more and more interesting it becomes. And when looking back through the thread, the majority of posters are appreciating the information as well. Keep the info coming!

Cheers,
Kaidon

[NorthC]

Slider,

Very interested in your hypothesis for a variety of reasons.

But for the time being I am interested in your interpretation of how your hypothesis reconciles with annual migrations and feeding frenzies observed each year in south east Queensland (and many other places) where masses upon masses of pilchards and anchovies are balled up against the coastline and "lunched" on repeatedly by piscivorous predators over many days. This is an amazing spectacle, yet there is no obvious flight response or area abandonment by these species in reaction to this event. Based on your hypothesis, audible alarm and/or chemical alarm cues would be abundant and these bait fish should be fleeing these areas with some haste?

Thanks
Andrew

[FishHunter]

im just spinning my wheels as you are never going to give straight answer. you just keep hiding behind other peoples research. the personal attacks i expected but i wont tolerate whats probably one of your cronies suggesting i be hunted down and assaulted. ive never claimed to be an expert on any subject in my life. in nearly 50 years of fishing both recreationally and a good portion of that was in the charter and tackle industry i have fished a lot of the coasts of west aussie qld and central and northern nsw. so yeah i have a bit of experince in a few fishing styles. but i guess that doesnt qualify me to answer any questions by your measure. so its time to take my bat ball and offensive posts and leave you with it. its not worth risking violence to try and share my knowledge.

Caster I dont know slider from a bar of soap I was posting my reaction and feelings to people like you, deal with it.

[Slider]

My apologies to Fishfeeder - it was Fishhunter I meant in my last post. And thanks Fishhunter for helping to clarify.

Northc - thank you for raising that very good point and I'll do my best to provide an adequate response.

Antipredator behaviour by fishes is not a cut and dried case of abandonning a location as soon as a predator threatens. They would be in a constant state of avoidance behaviour if this was the case. 'Risk assessment' by the fish/school occurs - weighing up the benefits associated with avoidance vs the requirement for that fish/school to feed and breed. The pilchards or anchovy are generally inshore in large shoals for spawning purposes and to abandon the area altogether prior to fertilisation of eggs is of greater detriment to their species than to stay and POSSIBLY be eaten. In saying that, there is definite avoidance behaviour displayed by the baitfish when being predated upon by the pelagics and sharks. The individual fish within the school swim more tightly together and they move away from predators on a local scale as much as they possibly can. On completion of spawning - they're out of there.

The question should also be asked - how long does it take anchovy and pilchards to spawn?

It doesn't take days - is the answer. The reason why these schools appear to be present for days is that it is not the same fish schools that we are seeing each day. Just like many other species such as tailor for instance, schools will move into the same location to spawn as schools before them due to idyllic spawning conditions existing in that location, communication between schools that lets incoming schools know where they are and the benefits associated with having massive quantities of eggs and milt from different schools in the same location which creates maximum recruitment ability and across different gene pools.
Has anyone noticed that these spectacles of inshore baitfish shoals seems always to occur in calm conditions. This is due to the fact that calm conditions causes for there to be minimal current and minimal dispersal of eggs and milt.

And as opposed to nets which take out entire schools in one fell swoop, individual predators, even if in large numbers, will only make a proportionately small indent in the baitfish population - one pilchard/anchovy at a time - and will not prevent successful spawning as would a net. Fish species that have a life history of being netted, see nets as so much of a threat in this regard that they take extraordinary measures to avoid the threat that they have learned that nets pose.

The next question is - how do the pelagics and sharks know they are there?

As indicated by man's ability to attract fish (pelagics in particular) by the use of sound, the predatory species, as do the dolphins, listen for the vocalisations of their prey in order to locate them. If this wasn't the case, the predators would be wandering aimlessly around the ocean in the hope of locating prey which would be so inefficient as to render their species extinct. And the predators love it when the bait is shoaled up inshore as this provides them with the ability to herd them against the shoreline where they can't escape. The pilchards and anchovy don't really want to be in the surf zone as that isn't their choice of spawning location and renders them more vulnerable to predation. They want to be just offshore where currents are minimal and also wave action so as to provide the best possible chance of fertilisation occurring. They end up in the surf because the predators have herded them there which is an indication of avoidance measures in itself. But pelagics are mostly day time feeders and the anchovy and pilchards are mostly night time spawners, so they don't stay in the surf zone and do get their opportunity to spawn.
Of course, the audible and chemical alarm cues that are released by the pilchards/anchovy, acts as an attractant for more predators to arrive on the scene to predate on the bait. This is unfortunate for the baitfish, but this is the trade off that has evolved with the benefits associated with releasing alarm cues outweighing the negatives. However, the jury is still somewhat out on the evolution of alarm cues.

I'll make the point at this stage that it is becoming increasingly apparent that predatory species are not being drawn to spawning schools of anchovy and pilchards inshore as they used to. I have witnessed on several occasions in the last few years when massive shoals have been a stones throw from the beach for days but with no predators in attendance other than MAYBE a couple of sharks, a small school of small mac tuna/tailor or the odd dolphin. Whether this is due to netting or population depletion of the predatory species, I couldn't say. But it is cause for concern.

Now when nets are involved in targeting commercial quantities of fish, they are targeting spawning aggregations - as a rule. These fish, whilst taking extraordinary avoidance measures, must also assess risk. Therefore, they will avoid the area initially, but must arrive at a suitable spawning location quickly or waste the eggs and milt within. So when it would seem logical that they should head offshore for the term of their natural life in order to avoid the beach haulers, they can't, or recruitment would plummet to extinction levels. They must spawn inshore and that coincidentally (not) is where their predominant food source exists. Evolution over millions of years has seen this scenario and pretty well every other ecosystem dynamic, develop in similar fashions. So the species that are targeted by beach haulers will do their best to avoid the nets via learned predatory responses, but at the end of the day must revisit the inshore area where they are potentially vulnerable to "predators" in order to feed and breed. Mullet are a prime example of this situation in that they are demonstrating a tendency to leave the estuary in a directly offshore direction when they once turned immediately left on the eastern seaboard and right on the western. The mullet come back to shore at some point to the north of the estuary to spawn and this year it was more than 25km north after exiting the Noosa River.

However, it would seem that a species can arrive at a point of population decline through overfishing that they will actually alter their migrations to avoid the nets - which is what the mullet are trying unsuccessfully to do. Tailor have been demonstrating this behaviour for several years now with a demonstrated offshore migration that never used to occur. This is particularly the case with mature fish which of all species have demonstrated an earlier and more substantial flight/avoidance behaviour than smaller, younger fish due to learned predatory response. Offshore spawning results in serious ramifications to both the fertilisation of eggs in that spawning is occurring in locations less conducive to successful fertilisation and the ability of larvae to actually reach an estuary where they must spend the first 12 months of their lives. This means that smaller, younger fish become the predominant spawners inshore with the average size of tailor per age now known to be smaller than it once was resulting. This I suspect is caused by younger tailor having less robust eggs than mature tailor, though the actual reason is unknown.

'Risk assessment' is an aspect of research into chemical alarm signals with a number of papers dealing with this scenario with definite outcomes to the experiments in this regard conducted.

And we thought that they were all just gold fish swimming around and around. I think it is extraordinary that fish have these abilities and it has been one hell of a ride for me in discovering that this should be the case. I might point out that much of the above has never been written about before and are largely my own conclusions based on the existing related research into the various circumstances involved and my own observations.

[Slider]

I'll take this a step further because it's not just fish that are involved in this issue.

Every angler is aware that when searching for predatory fish, that to find the birds (terns, gannets) is to find the fish. The reason why this is true is due to the fact that the seabirds are entirely reliant on the predator fish to herd the baitfish to the ocean surface where they can be accessed by the terns, gannets, shearwaters, albatross, frigates, boobies etc. Without the predator fish the seabirds starve irrespective of how healthy baitfish stocks are. Terns in particular need the predator fish, because unlike gannets that can dive from heights and swim and catch prey in shallow/ish water, the terns don't dive and take their prey from the surface.
Terns tend to roost at river mouths where exposed sand banks and built up sand provide a suitable roosting location. Unfortunately for the terns, pretty well every river mouth in SEQ is netted from 400m to the north of the estuary. The netting causes area avoidance by the predator species which can be in tens of kilometres from the estuary mouth. This then requires the terns to fly greater distances to feed than they historically have had to. This compromises not only the ability of the terns to feed themselves, but also their ability to feed their chicks. This is not only due to the distance for them to reach the predatory fish, but also the fact that they can't feed multiple times per day and rest between fishing ventures due to the distance required for each fishing venture. For migratory terns that need to 'fatten up' prior to embarking on migrations to northern Asia, this loss of feeding ability causes greater mortality rates of terns during migrations.
Dolphins are also affected by netting for similar reasons. Dolphins that habitually inhabit inshore areas find that their food source is not always present inshore and are forced to move offshore or to wherever the prey species have gone. Turtles are dramatically affected due to their mating usually occurring in inshore areas and nesting of course on the beaches. These energy consuming activities require sustenance that is derived from fish that aren't necessarily where they are supposed to be.
So if netting in itself affects seabirds, dolphins and turtles, then netting in combination with fish stock depletion is a double whammy that inevitably leads to population declines irrespective of whatever other measures are put in place to reduce their mortality rates associated with commercial nets and shark nets.

[Slider]

This might be of some value from an angling perspective:

While chemical alarm cues are a trigger for conspecifics (same species as the fish emitting the alarm) and heterospecifics (other species that are preyed on by the same species) to avoid the area that they smell the chemical, that same chemical is naturally an attractant of natural predators of that species. So, if, for instance you are using lures to target barramundi, you could 'lace' the lure with a prey chemical to add to the efficiency of the lure. This could be done by perhaps adhering a piece of mullet skin to the lure or soaking the lure in a bucket that has dead and damaged mullet in it. These mullet would have to be freshly dead as the chemical has a 'shelf life' and the skin of the mullet must be damaged in order for the chemical to be most effective. It can be expected though that if soaking the lure, that the chemical would wash off the lure very quickly and it might be something that would need to be done prior to each cast. Plastics might be more effective in this regard, but it is up to the imagination as to how one could adapt this to a given circumstance and lure type. However, I must state that the killing of baitfish for this purpose alone is not something I can condone, but if the baitfish is used as bait as well, then I guess we'd all feel better about it.

Also, if using livies for bait, then to leave a bucket with holes in it with the livies in it, in the water beside the boat, would allow alarm vocalisations to penetrate the water and draw the barra to the area being fished. Similarly, the bucket (with holes) that has freshly dead and damaged mullet in it that is being used to soak the lure being used, was left in the water beside the boat, then the chemicals would penetrate into the water and also draw barra from downstream into the area being fished.

These methods of course can be adapted to suit the target species and the type of baits available.

Further, if you are using lures or bait and are catching fish, then it is possible that the chemical that is released by these fish during the fight can remain on the lure or hook/s. Therefore it might be adviseable to rinse the lure/hooks after each landing to ensure the chemical isn't still present on the next cast and consequently spook the fish you are trying to catch.

On lacing the lure with chemical alarm - another method of extracting the chemical for use at a later date would be to freeze the water that is in a bucket in which the baitfish have been damaged and thaw as required.

To give some idea of how much skin of the baitfish is needed to be effective in spooking or attracting - 1 square cm of skin can permeate 56000 litres of water and be detectable by fish and elicit a response. At that rate it easy to understand how a few tonne of damaged fish in a net can permeate the volumes of water required to spook fish over quite a large area.

[Slider]

In a similar vein, it has been demonstrated to work that putting a mobile phone in a waterproof container, dropping it over the side of the boat and making it ring, will attract reef fish. Perhaps an electric toothbrush would be a more cost effective method of achieving a similar result or even an aerator.

[bondy99]

Slider,

Sounds like you should be doing a PhD from what I've been reading. Good reading and lateral thinking.

Cheers, Peter

[Slider]

Thanks Pete, lateral thinking comes from growing up as an angler, watching these things every day of my life and then applying the science to that knowledge base - becomes an exercise in logic.

So now to the nitty gritty of how nets stuff shore based angling:

All fish when trapped in a net emit alarm vocalisations by drumming muscles against their swim bladder and chemical alarm signals via their urine - proven facts. The fish that have their skin damaged due to rubbing against the net and scales removed emit another type of chemical alarm signal - the one that protects them from uv and heals wounds - proven fact.

Fish outside the net that hear the alarm vocalisations become startled and also emit alarm vocalisations and chemical alarm via their urine - hypothesized by myself, but supported by secondary evidence of 'secondary transmission' in fishes and a logical conclusion based on observations of flight responses by myself of these fish. Secondary transmission could well continue through fish further afield and is likely - due to observations by myself of fish flight responses at distances many kilometres from the netting site.

The alarm vocalisations cause an initial flight response from all fish other than some juveniles and benthic species (flathead, sole, shovel nosed sharks) and fish with no history of predation by beach seine nets within hearing distance of the netted fish (proven fact) and a likely flight response by those in receipt of the audible secondary transmission, but on a reducing scale with distance from the netting site as dictated by 'risk assessment' - conclusion by myself based on secondary evidence of learned predatory responses in fishes and observations of flight responses in fish distant from the netting site by myself.

Chemical alarm cues which stay in the water for days and which move with tidal and wind currents causes fish to both flee on receipt of the chemical cues and to stay away for the length of time that the chemicals are active - area avoidance - proven fact.

Area avoidance is documented to conventionally last for about 1 week and my observations are that this is fairly accurate, but depends on haul size, ocean conditions, food availability, the species netted and the species avoiding the area.

I mentioned earlier in the thread that 1 square cm of skin extracted from a fish has been proven on at least 2 occasions by different scientists and with the skin from different species, to permeate at least 56000 litres of water and to cause flight responses in all fish tested. These experiments were carried out without any actual predator involved and without alarm vocalisations from fish being predated upon or urine expelled chemical alarm and without any actual mortality to any fish. And there have been no 'negative' test results.

Based on that, let's imagine a scenario where there are tonnes of fish in a net that are all emitting alarm vocalisations and urine expelled chemical cues and who all actually die - a normal netting scenario.

Then there is the secondary chemical alarm emitted by the damaged fish. Now if the average size of the legal fish - let's say mullet - trapped in the net is 35cm, which could have a damaged skin surface area on one flank of let's say 10 square cm for arguments sake, and there are perhaps 500 damaged mullet in the net - for arguments sake. Then that chemical cue alone and without the other alarm signals playing any role whatsoever, can permeate a moving water volume of 2.8 million litres of water.

It is proven that any fish of the same species (mullet) or another species that has the same predator (net), will flee the area on contact with this chemical laced water alone.

It is also proven that when more than 1 alarm cue is involved, that the flight reaction by the fish is vastly stronger than a single cue on its own. But there is actually a fourth cue involved with nets in that the sight of fish fleeing an area (physical alarm) will elicit flight responses by conspecifics and heterospecifics that have a common predator.

The end result, I am 100% certain, is the avoidance of an area by all relevant species other than flathead, sole and shovel nose and some juveniles that will be at least in single digit kilometres from the netting site for at least a period of days. But it can be much worse if the hauls are big, conditions calm and the nets are regular - as they are.

To summarize and leave out my hypothesized conclusions: Netted fish emit alarm vocalisations and chemical alarm cues which cause the area avoidance of species that have a history of being netted and hear and/or smell the alarm cues. That sentence can't be questioned - it is pure fact. But there is no doubting that there is more than that going on and I stand by my assertions which will eventually be proven in total.

I accept that there will be plenty of people who think the above is absolute horse shit and that I am being blinded by my 'agenda'. But the facts in this eqasion are what they are and can't be ignored. And that my hypothesis is that of a person without scientific qualifications which can be deemed to render the hypothesis worthless. But is it?

Fisheries must at least look at the facts involved and they should investigate my hypothesis, cause it just might be right. To not do anything and continue to punch out the line "the fishery is sustainable" is simply turning the other cheek to a situation that has potentially great ramifications to fish stocks, seabird, dolphin and turtle populations and to the billion dollar recreational fishing industry. The precautionary principle demands that they at least investigate. To simply use commercial catch statistics as a gauge of fishery health is fraught with danger due to the very real potential of hyperstability - which I believe is occurring in fisheries everywhere.

I am not advocating the banning of netting across the board. I am of the belief that some areas need to be set aside for species repopulation and affected commercial fishers adequately compensated for their loss of employment. No doubt every rec fisher would like their 'back yard' to become net free, but that is of course impossible. Selecting areas where netting is banned should occur on the basis that those areas be of real and tangible benefit to species and which allow fishing related tourism to prosper in those areas. Economic viability for the remaining commercial net fishers is of paramount importance also.

[brucem32000]

Very Interesting. Makes me think! 1st driff, lots of bites & quite a few in the boat. 2nd drift, still bites, but not quite as many. 3rd drift, nothing!

Could it be those fish you caught were yelling on the way up, "DONT TOUCH THE FISH STRIPS, THEY are LOADED with *!!#%^&**)**HOOKS!!!"

Think about it . Could be!

Bruce............

[Slider]

Not as silly as it sounds Bruce - hooked fish vocalise alarm signals and some species might (probably do) react to that. Many experienced snapper fishers keep fish they've caught in a holding tank due to the fact that released fish seem to spook their mates. Tailor schools, I know from lots of experience, can easily spook when using metals if you drop a fish while it's still in the gutter - and this spooking seems to happen more every year that passes. But if you catch and release a tailor, there doesn't seem to be a problem. But if you have a hundred guys in a gutter at Fraser and fish being dropped all over the place, they don't spook. This would be because the bait presence causes the fish to weigh up the risks and decide they're hangin for the feed. I'm sure there would be any number of examples that people on this site have noticed in their angling experiences - like trying to get big bream to bite that you know are there but won't touch a baited hook. Then there's the well known theory that fish begin to recognise lures that are used a lot in an area and begin to avoid them with newly introduced lures out performing the tried and tested. It's all about learned predator responses and associating trauma with negative stimuli. Bit like a dog won't do something twice if it's belted after the first time.

[gunna]

Now if only that pesky sounder in the boat knew the fish language lol.

[brucem32000]

Not silly at all Slider. At least no more so than the Wright Bros saying that they would make that pile of wood,wire & paper, FLY!!

Now, all we need is a, recording of a fish sa.. no, "drumming",.... "Try that red plastically looking one, tasts real cool!"

Yea... Bruce

[fisher28]

you must have done a lot of reading and researching to come up with all that,and im sure it'll keep your post count up too:)!i agree with a lot of what you said and some i disagree with.in regard to river mouths i think loss of habitat for mullet is a huge problem,more and more little creeks just get lined with concrete and turned into rain drains.do you think recreational cast nets and bait nets are a problem or add to the problem of fish stocks?

[bondy99]

you must have done a lot of reading and researching to come up with all that,and im sure it'll keep your post count up too:)!i agree with a lot of what you said and some i disagree with.in regard to river mouths i think loss of habitat for mullet is a huge problem,more and more little creeks just get lined with concrete and turned into rain drains.do you think recreational cast nets and bait nets are a problem or add to the problem of fish stocks?

Governments shouldstop the practice of allowing canal developments, not only does it destroy mangrove habitat which is also primary nursery grounds for most fish, crustaceans and molluscs there is also a good chance of creating acid sulfate soil disturbance.

[Slider]

Yes Fisher28, there's been a hell of a lot of reading involved, a hell of a lot of fishing in netted areas and non - netted areas and a hell of a lot of just watching and observing. There's probably easier ways of getting the post count up though.

There is no question that habitat destruction is potentially a factor in adding to fish population depletion of many species. However, the damage that has been done in that regard, can't now be undone. But the fact that fish populations have bounced back in areas where nets have been banned indicates that nets are more detrimental than is the habitat loss. It would appear that the fish can adapt in this regard with man made structure also providing some habitat to compensate to some degree for that loss. The banning of netting in Sydney Harbour - our largest concrete jungle and our most polluting city - and the documented return of fish here is a very good case in point. The anecdotal and scientifically documented success of some RFH's in NSW in repopulating fish stocks also demonstrates beyond doubt that nets are the 'big one'.

Similarly, coastal and estuarine algal blooms may well be a factor in this equasion. It is my belief that we should be trying to do more about these than we currently are due to the potential of them becoming worse over time as human pops continue to increase. I have certainly tried hard to have this occur via newspaper articles, QFM articles and by contacting any scientist and government department that might be able to play a role. However, I think I have achieved next to nothing due to there not being a suitable enough desire for any preventative measures to be put in place and a lack of awareness about the seriousness of the situation - or perhaps an awareness that little can be done. This disappoints me greatly. The fact that probably little can be done, means that attempts at fixing this issue is not a means of returning fish pops on its own and that leaves the banning of netting in some areas as the only real and worthwhile means of achieving that aim.

Cast and drag nets obviously can't be of any help in maintaining fish pops. But they do not cause area avoidance on anywhere near the scale that commercial nets do. I rarely use them myself and wouldn't miss them if they were banned. But I'm not going to be the one calling for them to be banned and as yet I haven't seen any evidence that this is necessary. Should RFH's be established, then there probably isn't any necessity either. They certainly don't get used very much in the areas that I am proposing to be RFH's due to the surf.

On NSW RFH's - 209 commercial licenses were bought back by gov using revenue attained by a rec fishing license. I am aware that this measure has not been a cut and dried success in that some fishing pressure has been shifted to areas where netting is still permitted - such as the Hawkesbury. However, despite a reduced overall inshore commercial presence and an increased recreational presence, inshore commercial catch statistics have stabilised or increased since 2001. This indicates to me that the RFH's have worked in not only improving fish stocks within the boundaries of the RFH's, but has improved populations in other areas that can be netted. This surely equates to improved viability for those commercial fishers remaining and no negative impacts to the commercial fishery as a whole - which is the Qld governments greatest fear in banning netting in areas in this state. They have little to worry about in this regard providing suitable havens are established and the tourism benefits associated with having a healthy rec fishing industry would see a return to the state coffers exceeding the current level, rather than a purely downward trend that could be expected from both sectors if the status quo continues.

[oldboot]

I think that the whole concept of the ocean as "the silent world" is most unhelpfull.

Just because we cant hear stuff we assume there is no sound.....all based on our very poor hearing and our even poorer willingness to understand outside of our limited existance.

I have heaps of older fishing books ( back before fishing media was all about selling merchandise), there are plenty of accounts of various sounds from the sea in these old books.

Blokes who before sounders would locate reefs by the shelfish sounds comming thru the hulls of their boats, and of course all the crude culture about the role of sound in fishing...being quiet..lures that make noise and so forth.

If fish were not using sound, why would they have ears?

I know from my work as a sound guy and from working with hearing impared, that generally humans and most animals make sounds consistent with their hearing ability...if a humans hearing is damaged and reduced in range, they tend not to make vocal and mechanical noises outside their hearing range.

so it is reasonable that if you could establish the posibility of a fish's vocalisations by examining its ability to hear.....an ability that may be beyond the comprehension of the majority.

There is evidence that even our own hearing functions far beyond concious hearing.

I think that as things progress, it will be found that like on land, in the sea it will be those creatures that do not make any sound will be the remarkable ones.

On land it is quite rare to find a creature that does not make sounds and some how, use them to communicate.....think how far the calls (the ones we are capabe of hearing) of birds and insects can be heard in air.

Water ( assuming the sounds are taylored to its properties) is a better conductor of sound than air, why would the crustations and fish not be able to communicate over similar or greater distances.


as for net fright and the responses of various fish.
Because fish grow, mature and naturally die over vastly different periods, some fish may not get the chance to learn net or predator avoidance.

The entire lifespan of some baitfish may not extend far beyond a season or two, just long enough for a spawning cycle, where large fish may have many years in which to learn.

A bream for instance at legal size ( from what I have heard) is going to be 4 or 5 years old, they have plenty of time to learn to be hook shy, why not net shy.

I like to draw a paralell between birds and fish, because in physiology and habits thay are not all that far removed. So what do you recon is smarter, a snapper or a parrot.

We expect certain birds to be "smart" because we observe their behaviours in our world.

We know parrots can learn behaviours and even make vocalisations we think are close to ours, crows have proven to be smart enough not to eat the most toxic part of cane toads and experiments have sugested they can count to arround 5, I have even encounted a magpie that had sufficient of a sense of humour to come up behind people and make mobile phone ring sounds.

Why is it so hard to belive that fish can communicate in at least a crude form and learn to avoid places where nets are commonly set.

cheers

[Slider]

Thank you Oldboot for your very constructive and informative post. As you say there are parallels to be found elsewhere in the animal kingdom that do have relevance to the discussion at large. At the end of the day, a fish is an animal and it is animal behaviour that is the focus of this discussion.

I also draw parallels with that of birds, as have scientists studying fish for a long time due to the many similarities that exist. I have been fortunate in this sense in that there is a very healthy bird population all around me at Teewah and some of these have been of great value in trying to understand fish behaviour.
For years I have been feeding spangled drongos which are a bird that migrates to here from southern regions each autumn. The same troop of drongo's turns up each April and I feed them by flicking mince in the air which they catch as they would an insect. Amusingly, the butcher birds and magpies became nearly as adept at catching the mince as the drongos - and I'm not talking lobbing the mince, I mean like slips catches off Brett Lee.
Anyway, there was a situation that was of most note with regards alarm signals. The leader of the troop who is a bastard of a bird that won't let the others feed until he's had a fair few pieces of mince himself, had a trick he often used. He would make a call that would have all the other birds - drongos, maggies, butchies, kookaburras, white faced herons, friars, wattle birds, honey eaters, wrens - bolting all over the place as if to get away from something. The head drongo however would remain sitting on a branch a few feet from me and wanting to be fed. What he was doing was emitting a 'false' alarm signal which is a known behavioural trait of birds which provides the caller with the best opportunities to feed without having to compete with conspecifics or heterospecifics. The fact that all species reacted to the call is of great interest and created an insight for me with regards the fish alarm vocalisations and why tailor for instance would react to mullet vocalisation.
Was also funny that all the other birds would be back within a minute or so after the false alarm and they'd be like grumbling quietly - 'yeah, you got us again, haha'.

[Slider]

There's more .....

Was chatting to my neighbour today who reminded me of a situation that is of great relevance to this and that is water depth.

During my research, I found an endless stream of research papers that dealt with diel migrations of fish in relation to 'net avoidance', which is the vertical migration or movement of fish. The researchers were attempting to find out how to minimise this diel migration when trawler nets are deployed. They were of the belief that the sound of the trawling gear would alert the fish to the presence of the net or that the sound of the vessel itself would. The development of quieter gear was the aim, but it certainly was demonstrated that the fish recognised both the sound of the gear and the sound of the net carrying vessels (trawlers) which was alerting the fish and the fish would swim deeper in order to avoid the nets. Similarly, researchers trying to capture fish or larvae with nets found that they had the same problem.
This brings me to the relevant point, that in shallow water such as the inshore areas of our coastline, the fish can't move up or down to avoid nets, they can only move sideways (away). Therefore area avoidance behaviour of fish inshore can be very different to area avoidance of fish offshore. This I believe would have a great deal of relevance to the grey mackerel commercial fishery also, as the mackerel, I understand, are being located on the ocean floor more and more these days.

He (my neighbour) was also telling me of the redfish (I think he called them) that were introduced to lakes in Victoria that they would fish for down that way. He said that if they caught and released a fish, then it would be almost certain that they wouldn't get any more fish of any variety in that location and would have to move to locate them again. He knew that the rest of the school had been spooked and the other fish also - just like the snapper mentioned earlier in the thread.

[fisher28]

oldboot,that is intersting about finding the reefs.i have found many a sandbank using my keel and propellor,lol.

id like to see castnets banned just as the castnetters would like to see trawlers banned i guess.depends which side of the fence you sit on as to who is right in whoevers eyes.would fish stocks be better if we banned or limited recreational fishing and only allowed professionals to fish certain areas?i have been on mesh netting trips for whiting and tunnel netting for mixed fish,but have never been beach hauling.i watched once over at straddie and thought it was great,mainly because all of the fish i saw were well over size.and i just naturally assumed that the place has been netted for so long that if they are still doing it then all is well.

[Slider]

Well, we could close areas off to everyone and there's no doubt that there would be more fish in those areas, but that is specifically what I'm trying to avoid. But in answer to your question fisher28 - the nets are the single largest factor reducing fish populations and this is obviously the case - refer NSW RFH's. So to ban recs, which are demonstrated to not reduce fish populations (refer NSW RFH's) and allow commercial to continue would be a pointless and massively controversial and politically suicidal exercise.

Hyperstability is the term used to describe how nets return a catch rate that appears to be stable, but with increased efficiencies and more shots around smaller schools to achieve that. How can anyone tell if school sizes are getting smaller? "Looks like a lot of fish in that net so must be plenty out there" - when 20 years ago there was most likely much larger schools being netted, but less frequently to achieve a catch stat.

[fisher28]

haha,yeah i dont think we'll see any pro only zones anytime soon,or ever!!i beg to differ a little but you have looked far far deeper than me.i can only go on what i see.anyways keep up the interesting reading and good luck!

[NorthC]

Lindsay,

I have been trying to find more out about the chemical alarms you are hypothesising about - the Schreckstoff you refer to seems to be limited to freshwater fishes and a few non-fish marine species (eg: gastropods). I started looking because I am not comfortable with the assumption you seem to be drawing (correct me if I am wrong) that all fish will produce chemical alarms. For example tough scaled/skinned fish (tailor, mullet, bream) versus soft scaled/skinned fish (pilchards, anchovies, herrings) - I would hypothesise that these two nominal groups don’t produce similar chemical alarms based on their differing physiology and morphology. I have some reasonably good search engines but not a lot of time, but I haven’t yet found Schreckstoff mentioned for a marine fish – if you have a handy reference or two you could point me toward, that would be appreciated.

In the little searching I have done, the following extract was also interesting – in that chemical alarms, for those fish that use them, cause other behaviours as well as area avoidance.

Sensory compensation and the detection of predators: the interaction between chemical
and visual information (Proceedings from the royal society).
Eric J. Hartman and Mark V. Abrahams*

Since its discovery, ostariophysan alarm substance (AS)
has been assumed to function as an alarm signal designed
to alert other shoal members of danger (Von Frisch 1938;
Pfei¡er 1962; Smith 1992; Fuiman & Magurran 1994).
Individuals which sense AS (also called Schrecksto¡ )
respond with a fright reaction which may involve
dashing, freezing, hiding, area avoidance or increased
shoaling (Levesley & Magurran 1988; Magurran 1990;
Smith 1992; Krause 1993).

Thanks
Andrew

[Slider]

I have to say Andrew that I am very pleased that someone is checking up on me and keeping me honest. I do want anyone that has views, observations, scientific material that casts doubt on what I am saying, to post these. If I am making a mistake anywhere, I definitely want to find that out now.
I haven't had any real chance today to look for research articles that I have (somewhere in my pc) that delve into chemical alarm signals in salt water fishes - other than a quick look just now on arriving home from dinner and drinks at one by Brian Wisenden and Doug Chivers - through my Jameson goggles. And to quote - cause I don't know how to extract the relevant paragraph and post -

"Chemical alarm cues are passively released into the public realm by damaged tissue when a predator attacks and captures prey. Animals able to detect and respond to these cues can avoid the most imminent class of predation threat. So ancient and steep is this selection pressure that antipredator responses to conspecific alarm cues is virtually universal among aquatic animals. Protozoans, flatworms, annelids, arthropods, molluscs, fishes and amphibians, all exhibit alarm reactions to conspecific alarm cues".

I take that to mean that both fresh and salt water fish release chemical alarm cues - though I may be misinterpreting.

I have noticed that most experiments conducted into chemical alarm signals in fishes, have involved fresh water fish. This is probably due to the ease with which these fish can be experimented on. However, I know that I do have literature on chemical alarm signals in salt water fish and will post these tomorrow. Earn Grant is certainly of the opinion that chemical alarm signals in salt water fish is the 'official' definition of spooking.

Wisenden and Chivers' reference to molluscs is most interesting - as a completely unrelated matter. Many readers will have noticed how eugaries, (pipi's for the southerners) in the days when there was still a few around, would all lift out of the sand on the same outgoing wave - in their thousands. It always had me tricked as to how they would all know to do this on the same wave. Perhaps it's a chemical cue, perhaps it's a vocalisation. I have heard on the internet, beach worm vocalisations on a hydrophone manufacturer's site. Still don't actually know about the eugaries, but it is interesting.

This afternoon a mate and I went for a quick spin in front of Teewah for tailor over a patch of rocks that I've been watching for a while for signs of life - though haven't seen any. This happened to coincide with 11 pro vehicles with 6 boats that had been following a school of mullet from the 3rd cut and they were about 200m south of Teewah and heading north as we drove down the ramp from Teewah - Doh! As we started throwing the first slugs out, the mullet school appeared in front of us and the pros, knowing that they can't shoot a net within 300m of rec fishers, stopped in a group on the edge of the water about 100m north of where we were fishing. As the mullet went past us, as a school, CRUISING northwards and arrived at the point where the pros had gathered, they scattered in all directions at high speed with about half the school suddenly swimming southwards in a very animated fashion. Now, I can't say that I've seen this before and I can't say with any certainty that the mullet must have seen the accumulation of vehicles and reacted, but it certainly was odd behaviour at a very coincidental point. My mate was and is sure of the fact that the mullet saw the pros due to his experiences of cast netting for mullet in the surf and the reactions he'd seen from mullet in the process. The fact that a boat had been despatched to try and herd the fish about 1 km south of Teewah may be of relevance in that they may have been alerted to a potential threat - see 'net avoidance and diel migration'. My thoughts are that if this is actually the case, then the fish have far more refined attributes than I've ever given them credit for. The pros eventually shot a net at the start of the coloured sand hills to the immediate north of Teewah, but they certainly missed the majority of the school which was still in front of where we were.

Sleepy Greg made mention of 'spray washing' on game fishing boats earlier in the thread and I asked in response if this was the spraying of water on the surface to keep pelagics on the chew. Greg never replied, but my mate, referred to above, used to work on long line tuna boats off North Queensland and knows all about this. He tells me that his boat would spray the water on the ocean surface to draw the tuna in, as the sound that the water makes when it splashes on the surface replicates that made by baitfish avoiding pelagics feeding. They would, at the same time, chum the water with broken pilchards, because if they didn't, the tuna wouldn't respond after a few times of just spray washing. This element goes back to a reference I made to attracting fish with sound and that fish would eventually stop responding to attraction sounds if there was no reward for them when they got there and that the attraction sounds would need to be varied - or I gather you could just 'chum the water'.
Similarly, the Japanese netting yellowfin tuna in the Solomons found that they couldn't find schools to net after a succesful haul - area avoidance. So they started to net schools of baitfish which they promptly dumped over the side of the boat which drew the yellowfin in. The live baitfish (some anyway) emitting alarm vocalisations and chemical cues along with vibrations of damaged fish did the job. Consequently, the Solomons now has a serious baitfish depletion problem along with a lack of yellowfin.

[Slider]

Sorry Andrew I only answered one of your questions. The other answer to varied behavioural responses is this. The experiments conducted on the differing behavioural responses to chemical alarm cues were conducted in a small aquarium or small tank. This means that the fish cannot flee. They are confined to a small space. They only have the option of 'freezing' or hiding behind any structure that the scientist might place in the tank as a variation for the purposes of the experiment. However, there are other experiments and particularly by Brian Wisenden that are conducted in the wild that would be of more realistic value.

It may be beneficial for both of us, given my lack of abilities in extracting relevant parts of research papers and posting if you send me an email and I would then be able to send you the papers of relevance to your questions. ldines@bigpond.net.au

[Slider]

Chemical alarm cues in salt water fishes:

I would if I could - and I've been trying - post the research articles on chemical alarm cues in salt water fishes. So I'll quote the relevant bits.

This from Ferrari, Wisenden and Chivers (March 2010) - "All major groups of aquatic organisms, from protists to amphibeans, show antipredator responses to chemical cues released from injured conspecifics".

From McCormick and Larson (2007) - I won't quote directly from their research as it wouldn't make any sense here in the form in which they were studying - 'trade offs' between food deprived coral reef dwelling goby (asterropteryx semipunctatus) compared to well fed fish in response to chemical alarm cues and the "benefits derived from maintaining chemical alarm cues and the cost of producing them". The goby is a salt water fish that is producing chemical alarm signals.

Holmes and MCormick (2009) studied the "The role of chemical alarm cues in predator learning during early life history in a marine fish" - namely damselfish (pomacentrus amboinensis). They used chemical cues from 7 different saltwater species in this experiment.

There's probably more to be found Andrew, but I'm not sure that it is necessary.

[Slider]

I spoke about the net shot last night and that the pros missed half the school. Well, it seems that we came up for dinner and missed the other 5 nets that were shot immediately after the the net we saw shot. Received a call this morning from a very experienced fisher who has had a house on the Noosa North Shore for over 30 years and has fished this beach for longer than that. He watched the pros shoot the 6 nets, one after the other in a direction leading away from the first net. They do this so they don't lose the fish that are fleeing from the first net. End result was, he estimated about 10 tonne of mullet between the 6 nets. He then fished into the night and again from before first light this morning to as far north as Freshwater and didn't get a bite. But my mate and I did manage 4 choppers with a lot of lures cast prior to the nets being shot and over the only patch of rocks that I'm aware of south of Massouds Rocks near Freshwater.

This situation of 6 different nets being shot in sequence is an example of improved efficiencies that the pros have developed in response to declining catches and area avoidance that their nets cause. This also adds weight to the theory that hyperstability is influencing Fishery assessment of the stock status and their resulting conclusion that the "fishery is sustainable". Today, hopefully, I will have time to outline all the improved efficiencies that the pros have developed over the last 15 years and how they are still able to find fish despite my claims of a reduced biomass and area avoidance.

Just to quote the fellow who rang this morning on his observations over his lifetime of fishing this beach. He said that "30 years ago it wasn't difficult to go down the beach and get a feed of bream, tailor, whiting, dart, tarwhine, but these days you're lucky to get a couple of fish of any species." He asked me "where are the bream? "They've gone" - and they have. I know from my own very lengthy and intense fishing of this beach over the last 39 years that this fellow is right on the money.

[fisher28]

i really think there is more it.if the guys managed to get "about" 10 ton of fish then whoopie for them,its their job,and it sounds to me as though they did well.banning them isnt going to make you catch more fish.

if old mate reckons the bream arent there like they used to be maybe its because of the increased boat traffic from better ramps,maybe the loss of mangroves from better chainsaws and excavators,maybe the fish have been taken by pros and amateurs alike with better boats,better fishing gear,and faster than years gone by.maybe the fish dont like the pollutants washed in by huge storm water networks that werent there years ago.maybe all the bream are hiding in the canal estates that were not around years ago.if the pros can shoot shot after shot then thats progress just like all the other points.it is not just the pros that should get banned or suffer just because they affected someones afternoon fishing.

[Slider]

Maybe all the points you have raised have already been addressed in my previous posts.

Don't get me wrong with regards the pros doing what is their bread and butter. My aim isn't to make them suffer in any shape and my gripe is not with them personally. It is only fair that they be adequately compensated for their loss of livelihood which should mean that they don't suffer - if that situation should arise - and I am proposing methods of obtaining funds that will allow them to be adequately compensated. (though we haven't progressed to that point in the thread as yet, but we will) Several of the K8 license holders have publicly stated that they are ready to have their licenses bought back which says something in itself. It is an unfortunate situation that we have arrived at a point in our country's evolution where we have to look at putting people out of work in order to preserve our natural assets. But I didn't cause that to occur, we as a population did. And if the rec fishery is improved, as the evidence says would occur should rec fishing havens be established in suitable locations, then long term jobs will be created in that sector that are unquestionably sustainable positions.
All I am doing is presenting the evidence as it stands with the aim of having Fisheries look at the situation in an informed manner that results in a sustainable fishery for both sectors. I doubt that professional fishers universally would like for our fisheries to collapse and if I can assist in averting that from happening then my job will have been well done.

By the way fisher28, it's not adviseable to argue a point - ie habitat destruction - in one post and then refute that arguement yourself later - ie canal estates.

[fisher28]

unfortunatly employing ex-pro fisherman isnt high on everyones list.yes i have read that you recommend a payout and thats great,if the k8 holders want to sell then thats good all round but what worries me is the rec fishing havens.except for the k8's that want to sell out,its about better rec fishing,not just saving fish from extinction.

[Slider]

Isn't it wonderful that you can have better rec fishing and save species at the same time? Cause that is what I am proposing amounts to, along with improved employment prospects in the long term and a healthy social environment in which we live. Ah, but there has to be a catch somewhere doesn't there? Well there aint.

[Slider]

Hyperstability:

Which I gave a brief description of earlier in the thread and which amounts to inaccurate stock assessments due to inflated catch statistics eventuating from improved commercial efficiencies and in this case, increased catch per unit effort.

The improved efficiencies of beach haulers on the Noosa North Shore have come in several forms.

Firstly, the pros realised in the early 90's that they were spooking each other's fish with their nets. This because they were working separately with no coordination of timing or location of nets deployed. In the mid 90's, the NNS pros 'teamed up' so that they could coordinate the timing and location of their netting. So instead of various crews working the total length of Teewah and Rainbow Beach and shooting nets indiscriminantly along the full length and consequently spooking fish for the full length, they worked together in an area of the beach only - for instance, the southern end from say Teewah south to the mouth of the Noosa. Successful shots at this end of the beach only, meant that fish would still be available at the northern end the following day. Which is what they do - not even bothering to look closely at the southern end, but travelling at speed to say the start of the camping area 14km north of Teewah and searching for schools from there to Double Island Point. The following day they might look along Rainbow Beach to Inskip Point as the whole of Teewah Beach is now being actively avoided by species with a history of being netted.

As mentioned earlier in the thread, the ability that the various crews working together achieved, was to be able to shoot several nets to ensure that fish weren't missed by a single net only being deployed. Also, a single vehicle can be despatched to search the length of the beaches for schools and radio in any spotted, rather than each netting crew having to do their own searching.

The use of spotter planes/ultralights came into being in the mid 90's also and which could be funded jointly by the various teamed up license holders.

It must be remembered that the area avoidance is largely only affecting the surf zone and near shore area of the beaches and that mullet that are still in the Noosa are oblivious to all of that. These mullet that are yet to spawn are full of roe and milt and must exit the stream to spawn as they have for millions of years. Therefore, they can exit the stream at any time and irrespective of previous nettings on the open beach. So out they come and with the full knowledge of the netters who are camped at the mouth and who have ample warning that these mullet schools are about to exit. Attempts to herd the fish to the netting zone 400m north of the estuary are made so as to try and prevent the mullet from heading due east where they can't be netted until the schools revisit the beach at some point to the north - and this is where the spotter planes come into play in assessing where they will come in.

Then there is the use of transport 4wds that take the catch back to the Lake Cooroibah area from the nets where a Markwells Fisheries body truck is waiting to take the captured fish to wherever it is that the fish go - I'm not going to speculate on where this might be as there are endless rumours that can't be substantiated and Fisheries can easily assess this aspect for themselves and the appropriateness of some of these destinations for this valuable product. The use of the transport vehicles allows the netter's vehicles to remain on the beach and to pursue any fish that might remain (though fleeing) the section of beach being worked.

Then there is Fraser Island which provides another location for a couple of the netters to include in their netting program. These netters can net the southern end of Fraser from Tooloora Ck to Hook Point and also the northern end from Nth Ngkala Rocks to Rooney Point and south to Wathumba. This allows for these netters to continue working separate sections of coastline, spooking each section as they go, but by the time they have finished the sequence of nettings, the fish are returning to the first section netted following area avoidance. The cycle then recommences with very small windows of opportunity available for recs to catch fish before the nets are deployed in each section.

This cyclic manner of netting, combined with the river mullet exiting streams at times that aren't subjected to coastal area avoidance, the teaming up of license holders and the use of spotter planes and transport vehicles, is how the netters are able to return catch rates that defy biomass reductions and area avoidance. A classic case of hyperstability if ever there was one.

[Slider]

I think I've arrived at the point where there isn't a great deal more that needs to be said about fish behaviour around nets. Though, I have really only talked about the basics associated and kept things as brief as humanly possible and left out quite a bit of detail that I would have liked to include. However, I know that the content of this thread has been fairly in depth and many readers will have found it all to be a bit much to absorb, hard to understand, downright boring or just don't have the time availability to fully scrutinise what has been written. But it was essential that I be able to demonstrate that I know what I'm talking about for the benefit of those that are scrutinising what I'm writing.

Then there will be those that simply don't care and feel this all has no relevance to them. But I have a message for those that think along those lines. This subject matter has relevance to every single human being on the planet. All of the world's oceans are netted and all of the world's oceans are overfished by nets. Fisheries authorities around the world are struggling to maintain sustainable fisheries and there are several reasons for that.
The main reason is that they don't know that fish spook around nets, take avoidance measures so as not to be netted by altering migrations and spawning behaviour and recruitment abilities are compromised in the process. The combination of harvesting fish when in spawning aggregations with that of area avoidance causes fish populations to collapse.
Unless area avoidance and suitable stock assessment technologies involving hydrophones is built into every fishery management strategy, then every fishery isn't being managed properly and it is to be expected that there is only one direction for the world's fish stocks to result.

Queensland Fisheries have now been provided with this information and have the opportunity of being the first in the world to adopt measures that will sustain our fishery into the future. The rest of us now also know how it works and have a role to play in ensuring that Qld Fisheries react to the information being provided - free of charge. There are simple measures to be taken and we should be insisting that they are. I certainly will be on their case, but I can't single handedly cause for the appropriate changes to be made and must have the support of the recreational fishing community to achieve these aims. I need numbers of people behind me as Qld Fisheries will do their best to ignore me on my own as they have now for years. And I can understand that nobody likes being told that they're not doing their jobs properly by individuals that don't have the appropriate university degrees. I would argue however, that it's not appropriate that our fisheries be managed by people who have university degrees, but that don't have the experience in the field to apply the outdated and flawed marine sciences that they have been taught.

So, given that this thread has been pretty well done to death - unless somebody would like to further question me on my conclusions and those of the various scientists that have helped for me to draw these conclusions - then I am going to start a new thread on what needs to be done to improve our fishery and beginning with rec fishing havens for Cooloola and Fraser Island. The role I need to play is far from complete and I am not going to let up until it is.

Lindsay Dines

[Slider]

I haven't had any emails from Andrew (North C) asking for further information on all of this and nobody else has been able to seriously question any of the content of this thread. So does that mean that everybody (other than caster, fisher28 and Flatzie) accepts what I have written? Or is it just too hard for most people to grasp and easier to simply let it all go through to the keeper? Or is it a case of apathy and 'none of this affects me, so why worry'?

I ask these questions due to the fact that I can see the level of importance associated with these scenarios and how there are ramifications to all of the world's fished fisheries, recreational fisheries and conservation of a multitude of affected species. Very little of which is currently being addressed in the single slightest shape or form and not whatsoever in Queensland. If you think none of this affects you, then you are wrong.

So Andrew, where are you up to in analysing my hypothesis? And more to the point, where are Qld Fisheries in analysing my hypothesis? The silence is deafening.

[goat boy]

Where do you want it to head now Lindsay? as in for support from the general fishing public?
I've read and digested this thread, I admit I don't understand the science, I'm a simple person but am open to believe that the netting affects in the way you describe it to....I have predominantly beach fished since I was 7 or 8 and am now 36 so I am aware of whats happening on SEQ beaches ( I live right next to a well-netted one!)
I guess I'm also just sick of heading for a beach fish and finding the pro's have spooked everything off bar juvenile fish that haven't learnt yet
What do you want from us to help your cause?

[PinHead]

I haven't had any emails from Andrew (North C) asking for further information on all of this and nobody else has been able to seriously question any of the content of this thread. So does that mean that everybody (other than caster, fisher28 and Flatzie) accepts what I have written? Or is it just too hard for most people to grasp and easier to simply let it all go through to the keeper? Or is it a case of apathy and 'none of this affects me, so why worry'?

I ask these questions due to the fact that I can see the level of importance associated with these scenarios and how there are ramifications to all of the world's fished fisheries, recreational fisheries and conservation of a multitude of affected species. Very little of which is currently being addressed in the single slightest shape or form and not whatsoever in Queensland. If you think none of this affects you, then you are wrong.

So Andrew, where are you up to in analysing my hypothesis? And more to the point, where are Qld Fisheries in analysing my hypothesis? The silence is deafening.

yep.........

[Lovey80]

Lindsay I am a big supporter of yours. While I don't fish your stretch of the woods as often I would like, I think there is a great opportunity here to really promote Rec Fishing in that whole area (Noosa River to the tip of Fraser). As I have stated last year in one of your related posts, the economic opportunity here with making that area a great big RFH and promoting it to Australian and overseas tourists is immense.

I wish you all the best in making this happen.

[Matt_Campbell]

Unless area avoidance and suitable stock assessment technologies involving hydrophones is built into every fishery management strategy, then every fishery isn't being managed properly and it is to be expected that there is only one direction for the world's fish stocks to result.

And I can understand that nobody likes being told that they're not doing their jobs properly by individuals that don't have the appropriate university degrees. I would argue however, that it's not appropriate that our fisheries be managed by people who have university degrees, but that don't have the experience in the field to apply the outdated and flawed marine sciences that they have been taught.



Lindsay
I am one of these people you say are applying outdated and flawed marine sciences because of my lack of field experience. I'd be interested to know how stock assessment scientists could include results from hydrophone experiements into a stock assessment?

Also with regard to this statement:


The combination of harvesting fish when in spawning aggregations with that of area avoidance causes fish populations to collapse.


Doesn't area avoidance, initiated by netters, prevent the harvesting of some spawning fish because they avoid the areas in which the netters are operating?

[Lovey80]

Doesn't area avoidance, initiated by netters, prevent the harvesting of some spawning fish because they avoid the areas in which the netters are operating?

I know it was directed at Lindsay but in the mean time I think that Lindsay has covered this before. In effect, although they are prevented from capture because of area avoidance, it also prevents them from being able to spawn at all. Occurrences of fish taking much wider births when entering the sea from the river keeping them from being able to spawn in the shallow gutters. Thats how I understood it anyway.

[Slider]

Lovey, thank you - I think you are absolutely correct in your belief that this area can be a major international hit in drawing fishing related tourists. We have, permit, golden and giant trevs, bonefish, tailor, the tunas and mackerels, billfish and reefies, World Heritage Listed Fraser Island with humpbacks in Hervey Bay and W.H. nominated Cooloola with Noosa at its southern boundary. The recipe is a voluptuous one to say the least.

It does affect you Greg unless you don't want to catch bream in the Passage into the future.

Matt, please don't take my comments as a personal attack on individuals at FQ - if there was better funding for these things then we'd be up with other countries in this regard - experience in the field or not. And there are certainly better people to tell you about this than I. Miles Parsons from Curtain Uni would be the best I know of in Aus. Rodney Rountree is one that I can think of off the top of my head from Canada.
But, to start with, each of our commercial species needs to be recorded on a hydrophone by people who know what they're doing - Ian Tibbets at UQ for instance - and these vocalisations databased so that the vocalisations are recognised when heard during stock/spawning assessments. Fortunately for us, many of these species have already been recorded elsewhere in the world and thus the listing of these species at the beginning of the thread. Hydrophones can be placed in static positions - let's say in Moreton Bay near reef structure and specifically seeking snapper vocalisations over a period of weeks or months. Or they can be mobile and be dropped over the side of the research vessel at any location or point in time that is deemed to achieve a result for a given species being researched - or multiple species. Assessing the success or otherwise of green zones would be an excellent application for static hydrophones. Hydrophones are particularly useful in ascertaining spawning locations and numbers associated with an aggregation. To be able to literally count the fish in a spawning aggregation (in essence) without tagging or sampling is far removed from our current methods of assessment. If you like, I can send you research papers into stock and spawning assessments from mainly the U.S. and Canada that would be able to provide you with much better info than I possibly could. Ping me an email if you're interested - ldines@bigpond.net.au
With regards to how the pros are able to still catch fish when populations are in decline or avoidance mode - I did spell this out in post number 55 of this thread under the title of 'hyperstability'. In essence, the pros realised they were spooking the fish and worked out how to get around the problem by teaming up and shooting nets together in the same location, or at the same time in locations separated by just a few kilomtres then moving on and working the full extent of their license parameters on a cyclic basis over a week or so period (avoidance length of time before fish begin to return to the surf). Then there was the mullet which exit the river oblivious of previous nettings and don't have the opportunity to avoid nets that their conspecifics and heterospecifics had emitted alarm warnings about. I didn't mention in that post, but did so earlier in the thread (post 27) about 'risk assessment' by the fish - they have to feed and breed and can't be in avoidance mode all of the time and is why they return to the surf around 1 week after a successful haul depending on food availability, ocean conditions, location (flushing effect) spawning readiness, haul size/species, avoiding species and age.
However, I also mentioned in post 27, that fish that have arrived at a point of population decline that is very low, will alter their migrations to stay away entirely from nets. This is what tailor have started to do by migrating offshore, which is well documented and is a prelude to population collapse due to spawning in non - conducive locations, but doesn't seem to be worrying anyone. Also indicative of a population that is dangerously low is the smaller size per age of tailor that is also well documented, but doesn't seem to be ringing any alarm bells either. I do find it rather concerning that in 2004, research conducted into tailor found that these things were the case and that pops were at 40% of virgin with recommendations that size limits be increased to 40cm. It was warned in this paper, that if recruitment levels did not improve quickly, that a collapse could well occur and that a total ban on the species would be required with no guarantee that the species would recover at all. Fisheries increased the size limit to 35cm a few years later with no further restrictions on the commercial sector, no further research and no idea about area avoidance and migratory alterations. If it wasn't for NSW banning the commercial take of tailor other than bycatch, I am firmly of the belief that a collapse would have occurred by now. The fact that Qld and NSW have not coordinated their approach to this species which migrates along both our coastlines, is a matter that should raise many an eyebrow.