Total allowable catches – why and how?

03 May 2013

Total allowable catches – why and how?

According to the European Union, total allowable catches (TACs) are catch limits that are set for most significant commercial fish stocks. TACs are proposed by the Commission on the basis of scientific advice on the state of the stocks concerned and decided on by the Council of Fisheries Ministers. TACs are set annually for most stocks and every two years for deep sea species. For an increasing number of stocks, TACs are set in line with multi-annual plans.

They are shared between EU countries under a system known as ‘relative stability‘ which keeps national quotas stable in relation to each other, even when the total quantity of fish that can be caught varies with the productivity of the fish stocks.

In the United States, there are 959 fisheries and more than half of them don’t have enough data to know what their status is. Marine scientists return valuable information about what species are in trouble, but it’s translating these findings to the policy side of the issue that remains difficult. Within the eight regional fish management councils in the United States are hundreds of local governing bodies that help to set the quotas for their region. Qu0tas are only introduced slowly.

TACs or fish quota are definitely not always the same as Acceptable Biological Catches: a scientific calculation of the sustainable harvest level of a fishery as determined by federal fisheries biologists. Political and economical reasons are often used to allow a larger catch than is biologically acceptable. Expert advice is frequently ignored, as it sometimes seems to be an inconvenient truth.

And quota can also cause a very serious problem: ‘non-target species’ and ‘surplus’ fish are discarded , sometimes up to a quarter of the total catch. A wasteful practice that damages the stocks the limits were meant to protect.

Sphyrna lewini (scalloped hammerhead shark) Copyright: Peter Verhoog

Of course, there are also quota for the catches of sharks and rays. It is however hard to monitor all catches, and in the last years, there have also been ‘species problems’,f or example the identity confusion between a new, yet unnamed hammerhead shark species, originally discovered off the eastern United States by Nova Southeastern University Oceanographic Center (NSU-OC) researchers, and its look-alike cousin—the endangered scalloped hammerhead shark—may threaten the survival of both species.

“It’s very important to officially recognize, name and learn more about this new species and the condition of its populations through systematic surveys,” professor Mahmood Shivji of Nova Southeastern University states. “Without management intervention to curtail its inadvertent killing, we run the risk that overfishing could eradicate an entire shark species before its existence is even properly acknowledged.” The look-alike species may face the same fishery pressures as the real scalloped hammerhead, which is being fished unsustainably for its highly prized fins.

The same goes for the common skate:. In 2009, researchers from Muséum national d’Histoire naturelle, France, reported on 80 years of taxonomic confusion that has contributed to near extinction for a once abundant north Atlantic skate. Iglésias and colleagues found that two forms, lumped together in 1926 as European common skate (Dipturus batis, Linnaeus 1798), in fact represent distinct species with morphologic, genetic (in mitochondrial genome), and life history differences. As the researchers report, this taxonomic oversight obscured the disappearance of one species, the flapper skate (D. cf. intermedia) because it was confused with the less threatened blue skate (D. cf. flossada).