By Carl Safina
Atlantic Bluefin tuna might be the best studied marine fish in the world. But counting Bluefin in the wild is difficult. They can live several decades and reach 1,500 pounds, and they migrate across the ocean. It’s been particularly difficult for western Atlantic Bluefin. (Eastern Atlantic and western Atlantic tuna are named for where they mainly spawn. Eastern in the Mediterranean; western in the Gulf of Mexico.)
Problems arise because the two populations overlap to feed, only swimming their separate ways when it is time to reproduce. Therefore, many individuals caught by U.S. and Canadian fishermen are really eastern fish, born in the Mediterranean and headed there if they survive to breed. They look the same. It all creates confusion.
You might think that scientists would assess the strength and abundance of each population on their spawning grounds, where they are separate. That’s not what they do.
What they do is count how many have been caught all over the ocean, then try to tease apart what fish probably belonged to which breeding population. Long story short: they can’t.
So a recent estimated growth in the population of western-spawned fish is based partly on confusion with eastern-spawned fish. The western fish might be increasing, holding steady, or declining. The methods used are not highly reliable.
Some people like it that way. At any rate, a recent estimate that western fish are increasing should be regarded with cautious optimism. Cautious because the methods stink. Optimism because the western fish have been depleted for decades and are under a supposed “rebuilding plan.”
So what do the scientists have to say? They say: let’s let fishermen catch a lot more. Twenty-five percent more than they were allowed in recent years. Two and a half times what they calculate would let the population grow.
Is that a scientific conclusion? Of course not. Catching more is an economic conclusion. A short-term one.
Millions of dollars were spent to “improve the science,” but the results spawned disagreement regarding what a healthy population of western Atlantic Bluefin looks like. Nineteen years into a 20-year recovery plan, and the scientists are unable to advise policymakers on whether or not the plan has been successful.
They did, however, agree that the current western population size is somewhere between 45% and 69% of what it was in 1974, when it was already so depleted that in 1975 the U.S. government considered listing the fish under the U.S. Endangered Species Act.
This year, the scientists also compared the current population size to the population in 1950. They say there are just 18% as many Bluefin in the water now. Given that conclusion and the current confusion, it’s reckless to recommend a catch limit that is 2.5 times higher than would prevent further population decline.
The scientists do agree that during the “rebuilding period” 2003 was a hugely successful year for Bluefin reproduction. The years since have not been nearly as good. For nearly a decade, scientists have been advising policymakers to protect these 2003 fish. Now that those fish have finally reached the size/age where they can be most fecund in breeding—it’s irresponsible in the extreme to want to increase the mortality on them by 25 percent. These fish could live and reproduce for another 25 years, and the plan is to kill them, much faster!
International policymakers will convene in Marrakesh, Morocco starting November 14th to negotiate Bluefin catch limits for the next few years. It is now up to them to decide whether they will let this depleted population continue to grow, or whether they will increase allowable catch knowing that even current catch levels will cause the stock to decline.
Scientists do agree that a catch limit of 1000 metric tons would allow the western Atlantic Bluefin population to continue to grow, which would actually enhance future opportunities for fishermen. It is time to fully commit to population recovery by setting a catch limit of 1000 mt.
We’ve learned from their cousins in the eastern Atlantic that if catches are kept at the right levels Bluefin can – and will – come back. Doing so will be good for the fish and the fishermen – and would lead to real recovery and future opportunities for both recreation and wealth for the next (human) generation.