Added 30/12/2012 to assert the exclusive rights of the copyright owner: Copying of these of these documents and computer programs is allowed for private study and research purposes only. Copying for other purposes is not allowed unless express permission is obtained from the copyright owner. An updated analysis for peer review and publication is currently in preparation.


Download below a spreadsheet that implements the statistical analysis suggested by the “Hidden truth behind the quota …” poster (First published on TT here) ... and republished below.

The results are not exactly the same: the analysis here calculates a 2002 jack mackerel spawning mass between 25,000 tonne and 35,000 tonne depending on which egg-incubation model is used.

Nevertheless, these numbers are seriously lower than the 140,000 tonne given as the “best-estimate” by the fishery scientists and the IMAS 2011 study.

The simple message is that the statistical analysis presented in the IMAS study is badly flawed. The bootstrap histograms for the P0 parameter are bimodaI, showing undue influence of a single high egg-density outlier on the estimation of mean egg abundance.

I doubt there is a single statistician, economist, biologist or social scientist in Australia – those people who use statistics in their day job – who, looking at these diagnostics, would support the results of the IMAS analysis, let alone base the quota for the jack mackerel fishery on it.

Approving the proposed TAC of 10,100 tonne, when the recommended precautionary quota should be no greater than 2,250 tonne (and most likely less), would be like legislating that pi = 3.

If you haven’t already done so, email your State Senators now, before it’s too late, and tell them the plain truth: that the ‘statistics’ behind the quota is wrong. Senators will vote on what the Margiris is allowed to trawl for on Monday. Please contact them today.

“All that is necessary for the triumph of evil is that good men do nothing.” (Edmund Burke)

Download, Statistical analysis for deriving estimates of jack mackerel spawning biomass, 9 Sept 2012:

• And, from the Anonymous Reads Alot ... Download, The Hidden Science Behind the Quota: ... That’s the recommended and precautionary estimate that the authors of the “general background” didn’t want to you to calculate for yourselves. This is the value they ignored, the value they don’t want you to know. What’s the impact? The AFMA used the 140,000t to set a recommended biological catch of 10,600t of jack mackerel (that 7.5% of the spawning mass) – the total allowable catch (TAC), aka quota, is 10,100t. This quota, supported by the 7 scientists, is 42% of the precautionary estimate of 24,000t of jack mackerel spawning biomass. That’s double the maximum 20% exploitation rate internationally recognised as sustainable and set by the AFMA’s Harvest Rules.

• George Monbiot: “When the British government first started gathering data, sail trawlers were beginning to be displaced by steam. After 500 years of trawling, the ecosystem was likely to have been gravely depleted. Even so, the researchers found that when fishing effort was taken into account, fish populations declined not by 30 or 40% in the 118 years following 1883, as the scientists advising fishery managers had assumed, but by an average of 94%. In other words, just one-seventeenth of the volume of fish that existed in 1889 survived into the first decade of the 21st century. Fish stocks, they found, collapsed long before the amount of fish being landed declined: the landings were sustained only by ever more powerful boats, with ever more effective gear, scouring ever wider expanses of sea.  Haddock, they found, had fallen to 1% of their former volume, halibut to one-fifth of 1%.” Read more here