Science vs Super-trawler; The Margiris docks in South Australia today

The second largest fishing vessel ever built, the controversial Margiris super-trawler is estimated to haul up to 18,000 tonnes of baitfish from Australia’s southern fisheries.

Independent MP Andrew Wilkie says the ship’s owner, Gerry Geen, was improperly allowed to remain at a meeting on March 26 where the quotas were finalised.

He has been quoted as saying the quota is “not worth the paper it’s written on”.

Professor Jessica Meeuwig, Director of the Centre for Marine Futures at Oceans Institute, University of Western Australia discusses the science behind the issues.

To put forward a reasonable case for increasing the exploitation of Australian ‘small pelagic’ fish by a factor of 10, we need to have a reasonable amount of information about the species and the number of them out there”, says Professor Meeuwig.

“We are mislabelling, and thus misunderstanding, the target species. Blue mackerel, jack mackerel, Peruvian jack mackerel and redbait are repeatedly referred to as ‘small pelagics’, ‘forage fish’, and ‘baitfish’.

Such labeling conjures teeming schools of Peruvian anchoveta and Atlantic herring associated with the highly productive waters of South American and South African western margins and of the North Sea.

Such species share a set of life history characteristics, such as high growth rates, low maximum age, and high reproductive output, pursuing the quintessential ‘live fast, die young’ strategy. While such characteristics increase their resiliency to exploitation, it should be noted that they have been insufficient in preventing their over-exploitation in the face of highly efficient industrialised fishing such as that represented by super trawling.

The problem is that the Australian ‘small pelagic’ ‘baitfish’ proposed for targeting by the super trawler do not share these resiliency characteristics. Our ‘small pelagics’ are typically twice as large in maximum length as typical forage species (63 vs 33 cm), have a maximum life span 60% longer (21 vs 13 years), feed higher up the food chain, and grow 30% more slowly (0.17/year vs 0.62/year).

Indeed, these characteristics make them statistically more similar to reef fish such as baldchin groper that are recognised as over-exploited and it is unclear how the recommendations from the Forage Fish Task Force apply to non-forage species. We should not be treating these animals as a highly productive resource on which we experiment with super trawlers, but rather as valuable wildlife in Australia’s low productivity southern oceans.

Our population estimates are highly uncertain. In setting a total allowable catch of approximately 18,000 tonnes (again, a 10-fold increase over previous years’ landings), the Government is relying on its ability to determine the unfished biomass, effectively counting fish.

The estimates are generally based on old information, inferred from other species. It is thus likely that biomass estimates (and thus associated quotas) are much more uncertain than is currently reported.”

There are many other reasons not to allow super trawling including concerns over bycatch in substantially larger nets, low economic returns (reportedly of $1/kg) for a valuable resource, uncertainty around the effects of a warming ocean on fisheries productivity, and dependencies of other wildlife on these species. But even at the most basic level, the scientific case is not strong enough.

The world’s fishes are at a fraction of their natural abundances. We are basically mining the oceans of fish. The move to supertrawler fishing is symptomatic of this, as highlighted in the documentary ‘The End of the Line’.

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