Collin The Whale

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What happened to SeaWorld????

In the 10 years from 1997 to 2006 Australian commercial tuna catches totalled nearly 60,000 tons.

Worldwide for the same period, the total was almost 20,000,000 tons (Yes 20 million tons)

Who are we kidding??? Is this sustainable??

PM me with your email address if you would like the comprehensive catch figures, and values for Albacore, Bigeye, Skipjack and Yellowfin Tuna for the 10 years 1997 to 2006. (Released in March this year)

Cheers

Mariner

With most fish stocks you can harvest 20- 30 % of the population in a year and be still sustainable. Yes it does have an impact of course. Its wrong to assume that any decline in a fish stock is unsustainable. The maximum sustainable yield is usually regarded as when they are fished down to 30- 40% of their original numbers. Our fisheries managers aim for a somewhat lighter harvest than the MSY from what I have heard. Species with slow growth rates such a orange roughy are more vulnerable to overfishing and the following Wiki article deals with them. STB are fairly slow growing too. In addition they are wide ranging so that their managment is an international issue. Work is underway to reduce quotas to try to get a recovery.

Maximum sustainable yield in fisheries

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fisheries & fishing

In population ecology and economics, maximum sustainable yield or MSY is, theoretically, the largest yield/catch that can be taken from a species' stock over an indefinite period. Under the assumption of logistic growth, the MSY will be exactly at half the carrying capacity of a species, as this is the stage at when population growth is highest. The maximum sustainable yield is usually higher than the optimum sustainable yield.

This logistic model of growth is produced by a population introduced to a new habitat or with very poor numbers going through a lag phase of slow growth at first. Once it reaches a foothold population it will go through a rapid growth rate that will start to level off once the species approaches carrying capacity. The idea of maximum sustained yield is to decrease population density to the point of highest growth rate possible. This changes the number of the population, but the new number can be maintained indefinitely, ideally.

MSY is extensively used for fisheries management. Unlike the logistic (Schaefer) model, MSY in most modern fisheries models occurs at around 30% of the unexploited population size. This fraction differs among populations depending on the life history of the species and the age-specific selectivity of the fishing method.

Unfortunately errors in estimating the population dynamics of a species can lead to setting the maximum sustainable yield too high (or too low). An example of this was the New Zealand Orange roughy fishery. Early quotas were based on an assumption that the orange roughy had a fairly short lifespan and bred relatively quickly. However, it was later discovered that the orange roughy lived a long time and had bred slowly (~30 years). By this stage stocks had been largely depleted.

Edited August 26, 2008 by billfisher

[Dreamtime]

However, it was later discovered that the orange roughy lived a long time and had bred slowly (~30 years). By this stage stocks had been largely depleted.

Unfortunately, as it seems, this type of information always comes too late.

Governments give out quotas based on whos figures?

Then when the populace of a species declines to that of an endangered level, they appear to throw the sword at some other phenomenum - be it Global Warming or the like.

My opinion, whether right or wrong, is that ignorance plays a major part.

Correct me if I am wrong.

Edited August 26, 2008 by Mariner 31

[Guest]

This has gone on long enough and is way off topic You guys want to discuss the pros and cons of the SBT or any other overfished species ??? start your own thread.

Topic closed.

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