BLUEFIN TUNA – The importance of protection


In the last few weeks there has been a bit of a stir about the suspension of tuna fishing by the Department of the Environment. Since the fishing season opened over four weeks ago, local anglers have landed over nine tonnes of tuna. This year, a local quota increase is being considered, from 13 to 15.5 tonnes, along with a number of new fishing licences. But what is this spat about and why does it matter?

Tuna or Thunnus, gets its name from ancient Greek which means “quickly dart”. They form part of the family Scombridae and are closely related to mackerel. They are warm blooded predators whose life expectancy can reach up to 40 years. They have fusiform bodies with eyes that are flattened against the body to further reduce any drag whilst swimming. As pelagic dwellers, they are exceptionally strong endurance swimmers.

Bluefin tuna, Thunnus thyunns, typically come into coastal regions once a year, to breed. Females become sexually active between eight to twelve years old and can produce in excess of ten million eggs in a single season. Most of these eggs will not survive long enough to reproduce themselves and the combination of these facts makes them very sensitive to over fishing. Further, the larger the females are, the more eggs they produce, which makes preserving the large specimens that little bit more crucial.

As predators, they supress populations of their prey which has been shown to be an important factor in maintaining a healthy ecosystem balance. Much like the re-introduction of birds of prey into the Upper Rock Nature Reserve has helped to control seagull numbers, these fish serve to protect diversity and numbers by limiting dominance of any particular species below it in the food chain.

But, as has become an all too familiar story, these animals are listed as ‘endangered’ on the IUCN Red List. To be clear, the endangered status means that the animal “faces a high risk of extinction in the near future”. Other animals which are rated at this level include the blue whale, the Asiatic elephant, Asiatic tigers and the whale shark.

So, the suspension has been put into place because based on current projections, the local quota of Atlantic bluefin tuna will be met before the season is over. On the face of it, the position doesn’t make a whole lot of sense because ICCAT has increased quotas for all members this year and our Department of the Environment is considering a similar increase in line with these recommendations – surely these factors demonstrate that tuna numbers are back on the rise? Right? Well, not exactly.

Bluefin are the largest species of tuna with the largest individuals historically reaching close to 700kg. The occurrence of these monsters has been steadily declining with increase in overfishing. This is partly because many individuals don’t live long enough to get that big! As we said before, these are also the most reproductively important to stable populations and with their decline also comes a drop in reproductive potential. This makes the population ever more sensitive to overfishing.

A subtler issue is that as the average size within the populations reduces, it allows more individuals to be removed in order to exhaust the quota. For the sake of clarity, imagine the quota is ten tonnes and anglers are catching a half tonne fish each time. The quota would be exhausted after 20 fish had been caught and the standing stock is 20 individuals down. Now, let us assume the same initial starting conditions but this time people are catching 50kg fish. In this example, we are now removing 200 individuals from the standing stock. Assuming a 50:50 of males : females, that’s 100 potentially reproductive females which are no longer adding to the standing stock at every yearly breeding cycle. The problem is as clear as day.

So why has ICCAT raised the quota then? Simply put, the tuna fishing industry in the Eastern Atlantic is very important commercially. In fact, financially, it’s the biggest slice of profit compared with any other commercial fish. The ICCAT quotas are always under pressure to be lifted for this reason. But Gibraltar are not a member of ICCAT! No, we are not, but we do follow their guidelines pretty much as if we were in it.

Last month, the season re-opened, presumably, until the quota is reached or possibly even extended. The question should be why are we allowing the fishing of a species which is categorised as endangered at all? As a final thought experiment, I would ask you to think about how you would feel about India opening trophy hunting season on Bengal tigers or if Japan’s whaling fleet commenced hunts for blue whales. I suspect people would be outraged and rightly so. It is interesting then, that in our own back yard we don’t suffer the same outrage for an equally endangered species. As a matter of fact, we are considering increasing the quota!