In a document “Re-analysis of mean daily egg production in jack mackerel” posted to the AFMA website (here) scientists from IMAS have reanalysed the data in Neira (2011).

Their conclusion is “there is greater agreement between methods about the lowest plausible biomass than there is about the best estimate”.  The “best estimate” here refers to the 140,000 tonne which was the original estimate of jack mackerel spawning mass given Neira (2011); “lowest plausible biomass” refers to the results using the “better … more logically consistent and precautionary” estimates of biomass recommended by SARDI (Ward et al. 2011).

That is, after peeling away the scientific jargon, the “lowest plausible” biomass estimates should have been used to set the jack mackerel quota.

These are precisely the methods given in the document “Statistical_Analysis_for_deriving_estimates_of_jack_mackerel_spawning_biomass_9Sep2012.xls” posted to TT (here). The re-analysis by IMAS was only carried out after this TT analysis had been made public at 4:40 am on 10 September, the IMAS document was created after this at 2:41 pm on 10 September and lodged on the AFMA website at 6:07 pm on 12 September. The document was also misfiled by AFMA under the August document directory, and not the September directory.

The re-analysis report, strangely, does not include biomass numbers but only estimates of mean daily egg production (P0). However, it is easy to convert these to biomass using the method given in the re-analysis report; these are given in the table. The “lowest plausible” numbers are only reported here, as those obtained using the other analysis techniques, and that originally used in Neira (2011) give physically incoherent results as shown in the 9 September analysis.


The estimation of biomass is used to calculate a maximum allowable TAC (Total allowable catch) or RBC (recommended biological catch) which is 7.5% of the biomass estimate. The quota cannot exceed this value. The table shows that the quota for jack mackerel East, based on the data from the re-analysis, should not exceed 1,500 tonne.

This value is low as bias-corrected (bootstrap) values which are calculated using the recommended approach of SARDI are not given in the re-analysis document. A bias corrected estimate is approximately 1,800 tonne – stillless that 80% ofthe current TAC of 10,100 tonne!

This report by IMAS confirms that the science behind the quota was unsound, and the use of incorrect methods of analysis in the Neira (2011) led to the false outcome that a TAC of 10,100 tonne was precautionary.The current TAC of 10,100 tonne is almost 50% of the average biomass estimate – if the quota had been taken up, the jack mackerel fishery would have been devastated.

This result should and could have been known months ago. More recently, when IMAS and SARDI reproduced the results of Neira (2011) they failed to spend the extra 30 minutes testing the results against the SARDI recommended approach.

There are some hard questions for AFMA to answer:

1. Why didn’t they have such a simple re-analysis carried out BEFORE they used the Neira (2011) report to set such an absurdly high and irresponsible TAC? Surely they have in place such checks?

2. Why didn’t they immediately inform their own Minister, the Hon Joe Ludwig about the implications of the report for the jack mackerel quota, given that the report was lodged on the evening of Wednesday 12 September at the height of the “supertrawler” debate?

In fact, even though AFMA posted the report to their website as an official document, they didn’t inform anyone, let alone Parliament, of its implications.