Fish stocks depleted, but there's hope

Andy Rosenberg. (Bruce Bottomley Photo)

On a Friday night when many students were hailing the weekend, dedicated members of the Dalhousie community shuffled into the Ondaatje Auditorium for a lecture.

The lecture, however, was not your run-of-the-mill STAT 1060 or PHIL 1010, but the inaugural Ransom A. Myers Lecture in Science & Society—a series established in memory of the world-renowned Dalhousie marine biologist who died last year.  Fittingly, the first speaker of the series was Dr. Andy Rosenberg, a good friend of Myers’ and the man he once described as “the expert in fisheries science.”

Dr. Rosenberg, who has worked extensively in both the policy and science worlds of fisheries, and is a fellow of the American Association for the Advancement of Science, quickly proved his credentials as an expert on the subject we were all there to hear about: the future of fisheries.

He began with a couple of incisive questions Dr. Myers had posed during his career: How depleted are the world’s fish stocks?  What’s the carrying capacity for fish in the ocean?  What is the threshold for overfishing?  Before Myers came along, these questions had only been posed indirectly – but he had a knack for identifying issues that were not only scientifically important, but also crucial to policy and the wider society.

Shepherding us through a series of graphs, Dr. Rosenberg made a convincing case for one of Dr. Myers’ most controversial conclusions: the world’s fish stocks are indeed substantially depleted.  Here in Nova Scotia, for example, the biomass of Atlantic cod is down to a mere two or three per cent of what it was in 1850.  Not only that, but some so-called recovery programs around the world have not actually been reducing overfishing to a level below the sustainable harvest rate.

So the problem is clear enough – but Dr. Rosenberg believes the solution could prove complicated.  Crucially, a change in the incentive system—which currently rewards fishermen for catching as much as they can—will be on the cards.  Instead, what’s needed is a system that rewards conservation and penalizes overfishing.  Of course, that may be easier said than done.

Dr. Rosenberg finished by reminding us that, as far as ecosystems are concerned, the distinctions we make between the services they provide—recreational, medicinal, culinary, and so on—are not at all clear-cut.  All have an ecological impact, and all are affected in turn by ecological changes.  What we need is a way of connecting the management of different services, and a more holistic approach to maintaining the world’s oceans.