What science??

[tunaticer]

For the past decade or more we have been bitching about the "lack of real science" behind bag limits, sizes and marine parks. We all tend to agree there is no real defined data to forms the restrictions that are placed upon us.

My question to everyone is what is the real science we want to see and how would that data be collected and collated?

From my point of view, it would be nigh on impossible to get a head count on fish stocks in the wild. We tend to rely on reported captures and professional logs for the most part.
This form of data only relates to what is being brought ashore, not what is released dead or alive, and if it was released alive, what the prognosis of its survival beyond 6 weeks?

Honestly, I do not have a clue how moderately accurate data could be obtained regardless of the millions of dollars that would need to be invested into the study.

Those millions of dollars could well be spent in many other ways to benefit the fishery without the need for huge data collections.

My point of view is all areas along the coast need a break from fishing pressure on a fairly routine basis. I have uttered before that each river and creek right around the coastline needs to have a closed season at some stage and have put forward the idea that every 4th creek or river system around the coastline should have a 1 year closed protection status applied. The following year the next river/creek gets the protection status and every year it rotates to the next in a clockwise rotation around the country.
You may like it, you may not, but it is a suggestion.

I also believe that the trawler industry should have less available zones in which to trawl where real damages to the environment are evident. Shallow bays and rivers should not be exposed to trawl nets that will kill almost everything they scoop up regardless of species. I don't know about deep water trawler damages, but I presume there would be some degradation in areas of the sea floor and its weed beds and structures.
Maybe the time will come where all prawns for sale will be farmed prawns and the trawl industry completely shut??

I do not know what the answer will be but I suspect that the green movement will regain momentum and blanket permanent green zones will grow and grow.

Back to the question.......how would you see data collected that could be used as real science data?

[NAGG]

Quite simply ..... there is no such thing as real science - fish move to where they need to be ...... food & comfort
HTF can you determine a biomass of an open system ?

the only real way that you can obtain a feel is by charter records in addition to recreational records ..... & done over 2 years plus

Chris

[nigelr]

I remember an older, visionary, surfing aquaintance of mine (Dave Jackman) telling me back in the early 70's of his opinion of the effects of housing development on the local drainage patterns and how it he believed it had caused the surf banks to change over the years at DY.
IMHO, siltation, drainage and water quality are major factors often conveniently overlooked when considering these issues.
You want data on a species that lives in the ocean, you get in the water and observe them! Spearfishers may be able to tell you a lot more than you may think.....lol!
Truly, the rec fishing public are only allowed to see what the relevent Govt. Departments want us to see, in order to bring about their desired outcomes.

[Blythy]

I apologise in advance for this long winded reply.

The green zones that have been put in place recently have nothing to do with fishing as such, they are controlled by the EPA not fisheries. The new zones are there to protect habitats not specific fish. IMO these zones have little benefit to the fishery, if not implemented properly, the best response I have received so far concerning them is that “studies have shown that there are more fish in green zones then outside”, well that’s not really a surprise is it, if you take a fish out of the water there is going to be less fish there. What needs to be looked at is sustainable fishing.

There is very strong evidence to back up most size limits, this is perhaps the easiest value to obtain, the size at which the fish matures is determined and the minimum size is set above this value, basically this allows the fish to reproduce before being exposed to the fishery. This is why the min size for jew was increased so dramatically a couple of years ago.

The setting of bag limits is much trickier, the data that is collected from the commercial fishery is not used to get a count on the overall population, it is used to monitor the overall “health” of the population, by comparing catch rates per unit of effort, these trends can give good indications of what is happening are relatively cheap, if the commercial guys are spending twice as long fishing and catching half the fish something is going wrong.

Catch and release studies are the best way to estimate population sizes, it becomes more difficult with migratory species but is still the best way to obtain data. It is done by catching say 200 fish from a known population tagging and releasing them, you then come back and fish within the same population catch another 100 fish and record how many have tags, say 10, so the recapture rate is 10%, you then divide the total number of tagged fish by 0.1 (10%) and you get a total population estimate of 2000 fish. There are adjustments made for tag loss and fishing related motilities that are worked out for each tag type and fish species.

There is a lot of hard work and good science that goes into this, the problems arise with how the science is interpreted. The people that do the science are not the ones that make the policies.

That's enough for now, blythy over and out

[Ozwald]

The other handicap to understanding the science is the massively high prices that fisheries management books go for. Try a search on Amazon.com with fisheries management as the key words and most of the books are $60 -$100. Pretty steep prices for the average bloke wanting to know a bit more.

[finga]

The way it seems to be done now...
The easiest way to count lots of anything over a huge area is to count the number of things in a little confined space and then multiply that known number to give a total number over the entire area.
An example...you want to know the number of fish in the Logan River.
Work out the total volume of the Logan river. Lets say it's 39,764 cubic metres.
So then you find 10 cubic metres of the river (which 10 cubic meters is determined by the outcome you want), count the number of fish in that 10 cubic meters and multiply that by 3,976.4 and that's how many fish are in the Logan river.
Sampling rates and statistics. They only say what the person paying for the count wants them to say.

How should it be done??
By having many defined sampling spots that are monitors at a few times each year and monitor these precise spots over many years at the same time of the year.

In my opinion the biggest cause for concern is waste water or storm water run-off.
The amount of crap that is washed into the riparian zones and eventually into the ocean, or directly into oceans, via storm water outlets is absolutely appalling.

[Matthias]

Without proper monitoring you cannot define any changes in a system. It's all well and good to say this and that, but with no data to support a claim it means you could be accused of talking s%#t. The big issue is that the gov has limited resources so changes from the result of scientific evidence might be too little too late. The only way to get things done with such limited resources is to shut the place while studies are carried out. Its a conservative approach but it makes sense to me. - Im not refering to the reef closures which are considered permenant.

Development is the killer for any natural ecosystem- more people + more ecosystem alterations = less biodiversity

If a system is fished out but maintains it's original natural properties (snags, riparian veg etc) it will most likely recover over time, however if the ecosystem supporting the fish is altered significantly it will never recover to its original state. The best things I've seen to minimise impacts from development is stuff like water sensitive urban design, legislation that enforces clearing buffers for waterways etc and education for the public regarding stormwater runoff etc. In alot of the east coast the damage has been done and is unfortunatly irriversable.

Cheers
Pete

[Micadogs]

Hi

I just gave a long winded response to this very question in another thread today:

It can be found here:

http://ausfish.com.au/vforum/showthr...ur-guess/page4

Regards Adam

[Dignity]

The snapper ban this year was imposed based on the fact that in February last year the commercial sectior caught a lot less fish. Strange that considering the weather patterns in February last year were sh!ite. Science is fine providing it is applied without bias which unfortunately rarely happens, I do not know what the answer is but am sure that politics will intervene 90% of the time.

[Damned67]

Accurate data collection/interpretation is the most difficult part.
After that, peer review for publishing in a legitimate (and hopefully ERA A ranked) journal.
If it's not peer reviewed and published, it's not science.

Well, where I am, if it's not peer reviewed and published, it's not worth squat. I don't see why it should be any different when discussing fish stocks etc?

[Camhawk88]

The snapper ban this year was imposed based on the fact that in February last year the commercial sectior caught a lot less fish. Strange that considering the weather patterns in February last year were sh!ite. Science is fine providing it is applied without bias which unfortunately rarely happens, I do not know what the answer is but am sure that politics will intervene 90% of the time.

Yeah this is where science gets dudded. Political gain.
Quantifying a fish stock has been accurately described as 'counting all of the trees in a forest that you can not see and are constantly moving around.'

To get any meaningful analysis you need meaningful data for which there are strict protocols. It seems a lot of peer reviewed science that has a political slant, conveniently overlooks the methodology of the data collection (because it has been deliberately skewed) adn only concentrates on analytical methods references etc. By relying on one seasons data, there is no repeatability in the data- major fail.

Finga's run down on how stocks are quantified is a basic example of how it is done. Note the repeatability of measuring the same place with the same methods over many years. Truely representative data collection can certainly pin down the stock figure to a pretty small bracket and can be very reliable if done correctly.

[tunaticer]

OK, so after 4+ weeks of this thread running the concensus seems to be there is no definitive science or way of effective data collection to suit the task required.
That leads us to how do we effectively manage a fishery where the data is at best a guesstimate?
I think a poll should be had to see what the bag and size limits should be for snapper from our rec angler point of view.

Personally I think there needs to be two bag limits set. I think for guys fishing well offshore (say around 8nm of further) there should be a 10 fish limit per person and inshore should be 5 per person. Min legal sizes should be 35cm fork length as this length can not be tampered with my bending the fish or whatever. Reason for the two bag limits on snapper is the recs must be able to justify the costs involved in travelling so far in a generally larger than inshore fishing boat. I know it can and will cause problems, but by and large the bigger boats generally head further offshore to the deeper grounds than hang around the shallows. Fisheries inspectors should be allowed to check the GPS tracks for the last 24 hours to determine where these fish have most likely come from. GPS chartplotters are almost always on any offshore boat and used almost every time they start moving the boat. If an inspector checks the days track and sees the boat has travelled offshore beyond the 8nm zone he is entitled to the 10 per person. Denial to let the inspectors check the track should incur a fine of some description as an offence.
As a side point I do not fish offshore anymore, had my last offshore run nearly a decade ago.

[Dignity]

It is interesting that us amateurs are busy discussing how we can have a sustainable fishery considering the pressure bought on by the govt but the pros missed out this time around. I am not knocking the pros and I know they need to make a living but it is a mockery to only look at one side of the fishing industry. From what I see at the ramps the amatuers don't bring in that many fish per boat apart from a few regulars.

[fat-buoy]

As an amateur fisherman I for one would support banning taking a particular species for a period. While we all felt a little put out by the snapper ban recently I am sure that we all survived well enough.. so what if it was for a longer period.. lets say 6 months for a particular species..

I think if fisheries etc had a common sense look at what types of fish you are likely to catch out there and didn't ban pretty much everything you will get in a trip then we can all still have a successful trip and come home with a feed.. even if we didn't get to keep a species.

Along with this should be more education on how to get the best chance of a fish returning to the deep after being pulled up and having swim bladder trauma.

This sort of stuff will ensure the best chance of the fisheries surviving the population growth etc... the environmental issues are another kettle of fish though.

My 2 cents worth - feel free to flame me

[Dignity]

fb I saw a segment on some fishing show somewhere about some research being done on methods of releasing fish, there were some surprises about which fish survived no matter which method was used, apparently there were a number of species where the greater population didn't survive, I dont recall which, the show ended up showing the spiking method which I don't like. I favour the weighted line method, I made my own from a heavy weight with an upturned barbless hook on some blind cord. I don't waste time getting the hook out as I cut the line and get the fish back into the water as fast as I can and try and let the fish back down at the same speed that it was brought to the surface. I do hope that most of mine survive.