‘Bad’ science points to cut in mackerel quota


MACKEREL fishermen are bracing for a cut in quotas for 2019 based on data that the fisheries science advisory body itself acknowledges is flawed.

The International Council for the Exploration of the Seas (ICES) wants a huge cut in the mackerel total allowable catch (TAC) for next year, which would amount to 42 per cent for EU – mainly British – vessels.


Historically, prices have often risen to mitigate the effects of reduced quotas for the catching sector, but this might price smaller processors, which are typical of the UK, out of the market.

Shetland Fish Producers Organisation chief executive Brian Isbister said that while politics meant the whole 42 per cent cut was unlikely to emerge, fishermen could expect a reduction of quota which would probably rise again the following year after a re-assessment.

Isbister said that the problem had in part stemmed from the introduction of tagged fish as an assessment tool. But these had unexpectedly shown a 90 per cent mortality rate instead of around 10 to 20 per cent as anticipated. This skewed the assessment, leaving the EU with a share of about 318,000 tonnes for 2019.


While an effort would be made to convince scientists to discount the tagging data, Isbister said it would more likely be reviewed in the following year and adjustments made to the TAC next time around.

Ian Gatt

Isbister added: “[Fisheries] science is now a calculation based on a complex mathematical model which invariably uses limited real time data input. We have a system that generally always errs on the safe side of the safe side.”

According to Isbister, it was felt throughout the pelagic industry that ICES had increasingly abandoned any common sense making its stock assessments, and ignored that fishermen were finding unprecedented amounts of mackerel in the north east Atlantic.


According to Isbister, ICES own assessment options put the spawning stock of mackerel at anywhere from 2.2 to 4.5 million tonnes – a massive variance.

Isbister said it was “bad fisheries management” and gave the industry no stable base to work from.

Scottish Pelagic Fishermen’s Association chief executive Ian Gatt said there was “considerable uncertainty” over this year’s scientific assessment, including concerns how the model uses data from tagged mackerel.

Gatt added: “Tagged mackerel data has only been used in the assessment process in recent times, and because its data shows a much higher biomass reduction, it is at odds from other data in the scientific process and throws doubt on the overall stock assessment. The ICES perception of the stock is also contrary to that witnessed by fishermen on the fishing grounds.

“The assessment is also using updated egg survey information from two years ago, and with new egg survey data available next year, we are hopeful this will ensure a more accurate assessment of the stock. Mackerel scientists will also be forming a working group in the early part of next year to look at the issues with the tagging information and how the data is processed by the assessment model.”


He said the pelagic sector was a “responsible industry”, and would work with the EU, Norway and Faroe to “ensure the best possible science” when assessing the stock.

According to the association’s chief scientific officer Dr Steven Mackinson, ICES itself considers the assessment to be uncertain because of its sensitivity to scientific survey data that are relatively new and vary from year to year.

He added: “This year in particular, there are significant concerns regarding how the assessment model uses data from tagged mackerel, which is leading to lower estimates of stock abundance due to an apparent low survival rate of the tagged mackerel.

“Another important uncertainty, which affects predictions of stock size and catch, is that estimates for the number of young fish due to enter the fishery (recruitment) has not been quantified for 2016 and 2017 due to the data being unavailable at the time of the assessment.”