Science behind the proposed closures

[flathead_fred]

Im liking this argument guys.

Flick,
Basically without much more detailed stidies of larval ecology and fish movements/habitat utilization, we only have theories as to what the expected outcomes of closing areas to fishing are. MPAs do significantly increase biomass within them. My Orpheus Island trip was one of 6 studies conducted since 2000 of the exact same areas in the Palm Islands, using the same Underwater Visual Census techniques, and there have been consistently more and larger fish found in Green Zones including Plectrompomus sp. and Lutjanus sp. But I pose the question, what good is this to fisheries? Yes we are conserving the habitat for future study/ecosystem services/tourism, but of late there has been a push to quantify the monetary benefits of ecosystems, and there must be a direct linkage with adjacent areas so we can physically see the results.

To confuse matters more, not all seagrass beds, reefs, and mangrove forests created equal. Some are sources and some are sinks for recruits (larvae which will one day enter the adult population and subsequently be caught by rec fisherman). Rather than explain this, ill give you and example. Queensland Grouper larvae are extremely abundant in seagrass beds within estuaries adjacent to the reefs which they are found, but they are less abundant on subtidal rocky areas. This would lead you to presume the seagrass bed is "NURSERY HABITAT" and must be protected at all costs. Molecular studies revealed that almost no adult Grouper were from these larval populations, with most of the population were originated from those larvae found on rocky reefs. They got it wrong. Add to this variation in habitat quality between seagrass beds/rocky reefs and things become even more confusing(based on hydrodynamics, nutrient cycling etc).

Currently a very well respected academic at UQ is studying the effects of habitat mosaics on the nursery potential of these habitats. This unpublished research has so far discovered prawns prefer/survive/grow better in seagrass when it is adjacent to a healthy stand of mangroves without a large gap of open substrate to separate the two. This mosaic is also heavily reliant on the "quality" of these habitats, whether they are degraded of not, as a poor mangrove stand will support a poor prawn population on the seagrass.

These aspects are being considered when zoning areas of Moreton Bay, among others, to select the most valuable habitats to conserve.

I have deliberatley not mentioned anything about declining water quality, habitat degradation, threats of introduced species, impacts on macrofauna (turtles, dugongs) fire weed, CLIMATE CHANGE etc. We all know the story with these, and it will be interesting to see into the future as to how current management will deal with these pressing issues.

Thanks guys,
Mike

[Glind]

I think you have done very well Mike,
All the best with your studies.
Tim

[littlejim]

Lg is still at it. Trouble is it is his sort of logic that seems to be influencing how the spread of marine parks is done.

Recreational fishermen catch fish. Littlejim caught 5 flathead today, there are now five less flathead. He will do this 10 times this year now there are 50 less flathead this year.

LG ate one egg this morning he will do that 300 times this year now there will be 300 less chooks on the planet. he eats a loaf of bread every six days soon the world's supply of wheat will be gone.

the amount of air the blighter breathes is a concern especially when he goes for a run. I think he uses about 20 litres a time. It all adds up there will be none left soon.

With the huge number of US recreational fishermen, who have been at it a bit longer than we Aussies how come there are any fish left in the US.

You can't run marine parks on somebody's gut feelings or logic that taking even a small number of fish affects the total fish stock. All the things above including the fish are being replenished. Somewhere there is a sustainable 'harvest'. That's what we have to stay below. We also need to find out what the fish need to breed and stop jiggering it up. it isn't the cliff face along from Point Perpendicular and it isn't Brook's Rock.

If the marine parks don't fix everything up I hope LG and his friends aren't going to say the reason is that the parks are too small, and that the answer is to multiply it by some factor, and then logically things will get better.

I think we all go along with the idea of some protected areas like the land based national parks, to provide a refuge for fish to breed but it would be nice if they were based on knowledge that fish actually breed in those areas, rather than the basis that they are a popular fishing spot, or 'x' people have drowned there or killed themselves falling down the rocks.

How about providing some more places for fish to breed and grow up?

[Burley_Boy]

Thanks for your input Mike.

I was just thinking.."what good is this to fisheries" and you wrote it! I believe that a managed fishery is of value to humanity while a "dam" stocked full of fish left to themselves are a waste of a resource. Sustainability is the key and true management of the resource.

Lefty....
Why are fish harder to catch close to large population centres... ever tried birdwatching on the M1.
I'd say its harder to catch fish on a Saturday than a midweekventure too. Fish get shy in heavily fished and trafficked areas and I'd be interested in knowing how different the qty of fish was in the area but not based on catch rates!

Go diving in a heavily fished area and watch the fish ignore bait! (Gold Coast Seaway is classic in this regard) And don't tell me there are not fish there.

[fishingmaddad]

When artificial structures become "green zones" doesn't so called science get relegated to the realm of Science Fiction???

[fishingmaddad]

When artificial structures become "green zones" doesn't so called science get relegated to the realm of Science Fiction???

[lefty_green]

"the "lock-it-up" mentality doesn't factor-in , recent and future Bag & Size limits

e.g. IMAGINE IF......
50% was locked-up ,as the "SOLUTION" to increase Flatheads stocks in SEQ

instead of....
the sensible & generally supported approach ,by RecFishos of an INCREASED minsize , DECREASED maxsize , and a REDUCED baglimit

in the future ,I can see a valid case for a 35~75cm min-max, as they are no longer threatened , and demonstrated self-sustaining biomass

Bream , Tailor , Whiting? will also 'probably' have a minor increase in minsize , Snapper maybe a 'local' issue on the GC for a bag reduction , BUT if deemed 'proven without bias''.....so-be-it!!

TURTLES!!...if the go-slow areas, is not slow enough, change the regs to go SLOWER!!!

No off-limit areas needed....simple"

Check out the posts where it was rumoured that snapper bag limits were being decreased from 5 to 2. I think you had a say about it didn't you Col?

"Recreational fishermen catch fish. Littlejim caught 5 flathead today, there are now five less flathead. He will do this 10 times this year now there are 50 less flathead this year.

LG ate one egg this morning he will do that 300 times this year now there will be 300 less chooks on the planet. he eats a loaf of bread every six days soon the world's supply of wheat will be gone."

To compare the catching fish from a wild stock to removing animals from populations bred for the specific purpose of human consumption is ridiculous.

"I will say it - rec fishing has no honestly measurable impact on saltwater fish stocks!

With just a modicum of ecological understanding/study/knowledge this is so apparent it is shocking.
Now to qualify somewhat, yes every fish in it's particular minute that lands in a boat is an impact ,although time qualifies all. Over the next minute/hour/day/week that incredibly minor impact is well and truly nullified, the effort required to impact a reef above it's natural mortality rate from all natural process over say a 6 month period is something that us rec fisho's would need many many extra tools like spears, dynamite, nets to achieve and not without a hell of a lot of effort, if at all possible under bag limit's and without commercial help.

Rec fishing overall is akin to taking 20 plants of grass from a healthy football field yes it impacts as it is done but try and find the next day where you got the grass from, then try in a weeks time the field is dynamic and easily copes with such a small scale take, natural attrition from internal predators/grazers/disease/environment pales the 20 plant harvest into absolute insignificance.

It's a dam scary eat or be eaten world under the water. Even if I rec fished every hour, day and night of my life till the day I died I couldn't equal a take worthy of one second of natural processes on the reef, a second after i died the reef as a whole never even knew I was even there.

Now take a broad shovel and harvest 20 shovel loads of grass, aka commercial net fishers chain and netting an area. Why we as rec fisherman are scapegoats for the commercial sector still amazes me.

Anyone know just how many (by number)and much fish (by weight)just one spanish macerel consumes to reach just 15kg in weight? What about just one large 100kg cod, just 1 black tip reef shark. The list is endless and for us to compete and impact as rec-fisho's is just a laughable propsition, principles of ecology should be taught in all schools IMO.

drivel over

cheers fnq"

Drivel over? You make a good point saying that these larger fish consume a large number of fish during their lives. You would have to agree that natural removal of fish from an ecosystem is very far removed from human interactions. How you can compare natural removal and removal by humans is laughable. Why did fish stocks prosper before european settlement in Australia? There was alot more mackerel and cod eating small fish back then yet the fishing was better then compared to now. Do you truly believe that the additional removal of animals from an ecosystem does not impact on that ecosystem? "rec fishing has no honestly measurable impact on saltwater fish stocks" - and you oject to the greens making unsubstantiated statements? You're just as bad as them in my opinion and such statements leave rec fishers open to criticism by scientists and managers. And, to say that rec fishing is like removing 20 plants of grass from a footy field is drawing a long bow. That may be true for a single fisher - what about the 880,000 rec fishers taking their 20 plants from the footy field? Are you saying that this doesn't impact on the health of the footy field?

"Some propeller injuries must surely be attributed to container ships, vehicluar ferries, water taxis etc"
I agree 100%. However as I said earlier, a particular member of this site said rec fishers have NO impact on turtle mortalities. The fact is they do. You made no mention about the crab pots? Do you agree that turtles are drowned by crab pots?

As I have said before - People on this site criticise the greenies for making statements without evidence, yet have a look at the number of statements made on this site without evidence. The greens look at those statements the same way their statements are viewed on here. They are dismissed as rubbish. Bring in a licence, do research and prove rec fishing has little impact on fish stocks. Put your money where your mouths are.

[lefty_green]

I will say it - rec fishing has no honestly measurable impact on saltwater fish stocks!

Tailor. Drivel over? I think not

[billfisher]

Quote Lefty Green:
"To compare the catching fish from a wild stock to removing animals from populations bred for the specific purpose of human consumption is ridiculous.
How you can compare natural removal and removal by humans is laughable. Why did fish stocks prosper before european settlement in Australia?"


I have news for you lefty-green fish stocks are prospering in Australia after over 200 years of white settlement. Zero human impact is not a legitimate goal. Before that the aborigines had an impact too. There is nothing unatural about humans being part of the ecosystem.

Experts state that the GBR was being harvested at 1% of its sustainable yeild before the costly and unpopular GBRMP. The Park authoratory might as well be managing the moon for all the good it does.

[lefty_green]

Quote Lefty Green:
I have news for you lefty-green fish stocks are prospering in Australia after over 200 years of white settlement. Zero human impact is not a legitimate goal. Before that the aborigines had an impact too. There is nothing unatural about humans being part of the ecosystem.

Fish stocks are prospering? Why do we need size limits? Why do we need bag limits? What about tailor?

[billfisher]

Why do we need size and bag limits? You are joking aren't you?

We need them to ensure the sustainability of the fishery while allowing the socially and economically valuable pastime that is recreational fishing to continue. What we don't need is over zealous and capricious large scale lock outs.

[lefty_green]

Why do we need size and bag limits? You are joking aren't you?

We need them to ensure the sustainability of the fishery while allowing the socially and economically valuable pastime that is recreational fishing to continue. What we don't need is over zealous and capricious large scale lock outs.

If fish stocks are prospering why do we need bag and size limits. I would have thought if stocks were prospering bag and size limits wouldn't be needed? Why do you think there aren't bag and size limits on some species? Maybe because there is less angling pressure on these stocks therefore they are prospering??

I think you have just hit the nail on the head billfisher. Rec anglers do have a significant impact on fish stocks. It becomes less significant with the addition of bag and size limits BUT if stocks could sustain the level of angling pressure being exerted on them at present then bag and size limits wouldn't be needed. Am I wrong?

[Luvinit]

Flathead_Fred,
You're right, this debate (I prefer that term to argument) is quite enjoyable and it's bringing out many good points.
A few years back now i did a mathematical modelling subject at Uni. The focus of the subject was maths but I chose to model a predator/prey ecosystem mathematically and looked at harvesting of each.
The key finding was that these ecosystems usually reached an equilibrium position (sometimes it was an oscillation about an equilibrium point).
Various rates of harvesting would move the equilibrium point but so long as the harvest rate remained constant the equilibrium point remained constant. There was of course an unsustainable harvest rate which would put the ecosystem into continuous decline.

Obviously all of us want to ensure we dont harvest so much that the system goes into continuous decline, but to take the perspective that all harvesting is unsustainable is utter BS.

In harvesting the predators, there was actually a harvest rate that raised the overall population, this was because by removing the mature predators it allowed more prey for the sub-mature predators so they grew more quickly and the overall population increased to above it's natural level.

Now I did not model the harvest rate based upon population density so the effect of fewer fish making them harder to catch and therefore automatially decreasing the harvest rate (a real world factor that is actually self-limiting)

I havent kept the paper, it was few years ago now.

1. to try to exclude all humans from the ecosystem is fundementally flawed and impractical
2. to claim that humans only have a detrimental effect is also false
3. to claim that any harvesting will eventually lead to a decline is utter BS.

What I and every fisho i have ever spoken to, wants is SUSTAINABLE management. lets get some unbiassed research into that.
Without the backing of detailed research (only because its not available yet) lets ask the people who are actually interacting with the ecosystem in question. Thats fishos. They actually have a wealth of knowledge and everyone I've ever met wants to preserve the environment to be enjoyed, not excluded from it.

[lefty_green]

There was of course an unsustainable harvest rate which would put the ecosystem into continuous decline.

In harvesting the predators, there was actually a harvest rate that raised the overall population, this was because by removing the mature predators it allowed more prey for the sub-mature predators so they grew more quickly and the overall population increased to above it's natural level.

Good post Luvinit - did you model what would happen if there was continuous high effort exerted on animals at or just below the minimum legal size. Its interesting that you should mention that removing larger predators is a good thing. Dont they spawn more eggs per animal? Why are slot limits used on flathead?

[scaly]

If fish stocks are prospering why do we need bag and size limits. I would have thought if stocks were prospering bag and size limits wouldn't be needed? Why do you think there aren't bag and size limits on some species? Maybe because there is less angling pressure on these stocks therefore they are prospering??

Talk about drawing low bows How about factoring in recruitment, fecundity etc- Where do you get your theory that fish stocks are in trouble