Grim tale of global shark declines

25 06 2015
Please don't eat me

Please don’t eat me

How do you prevent declines of species you cannot even see? This is (and has always been) the dilemma for fisheries because, well, humans don’t live underwater. Even when we strap on a metal tank full of air and a pair of fins, we’re still more or less like wounded astronauts peering through a narrow window of glass at the huge, largely empty, ocean space. It’s little wonder then that we have a fairly crap system of estimating fish abundance, and an even worse track record of managing them sustainably.

But humans love to eat fish – the total world estimate of legal fisheries landings is something in the vicinity of 190 million tonnes in 2013, up from 18 million tonnes in 1950 (according to FAO). We’re probably familiar with some of the losers of that massive harvest, with species like tunas, bill fishes and orange roughy making the news for catastrophic declines in abundance over the last 30-40 years. And we’re not even talking about the estimated tragedy that is illegal, unreported and unregulated (IUU) fishing.

Back in 1999, the FAO started to report that sharks – the new-ish target of many world fisheries resulting from the commercial extinction of many other fin fish fisheries – we’re starting to take the hit. Once generally ignored by fishing industries, sharks soon became popular target species. Then in 2003, Julia Baum and colleagues famously (and somewhat controversially) sounded the alarm for sharks in the Gulf of Mexico by some claims of major and catastrophic declines of large, predatory sharks. While some of the subsequent to-ing and fro-ing in the literature challenged these claims, Baum’s excellent work was ultimately vindicated.

Since then, more and more evidence that sharks are in trouble has surfaced, including the assessment of the reported (again, only legal) catch indicated heavy depletion of coastal sharks even by 1975, and the estimate that 25% of all shark and ray species have an elevated extinction risk, mainly resulting from overfishing. Now even the direct fisheries landings statistics are confirming this grim tale.

Just published in Fish and Fisheries, this paper by Davidson, Krawchuk and Dulvy, shows that according to FAO fisheries landings data, the global take in sharks has been declining recently in some 59% of 126 countries surveyed. By itself, this isn’t necessarily an indication of a problem, because since the shark alarm has been raised, some countries at least have put a lot more effort into trying to manage their shark fisheries better. But as I indicated above, fish populations are bloody hard to estimate and it’s even more difficult to predict their responses to fishing. So are many of the newly implemented shark management plans working, or are the landing declines indicative of deteriorating populations from over-harvesting?

Davidson and colleagues’ rather exhaustive survey and correlative (random forest) models suggest that while there is some marginal evidence in some countries that management is lessening fisheries pressure, the two most important (albeit indirect) predators of declining catch were high human population size and extensive shark-meat exports. In other words, it’s the over-harvesting, stupid (d’uh), and not the result of better management.

So why isn’t management stemming the declines? First of all, many countries aren’t even signatory to international fisheries sustainable-management plans, nor do most countries have shark species-specific recovery plans. Finning is also rampant and mostly still legal in many countries. Even the plans that do exist are not being implemented effectively. Davidson and colleagues state that the measures so far implemented:

“… are not yet legally binding, far from comprehensive, lacked clear implementation guidelines, operated with vague wording and lacked compliance monitoring”.

What a surprise! Saying you’re going to manage sustainably and actually doing it are two very different things. It’s reminiscent of shitty management in terrestrial protected areas I wrote about last week.

This doesn’t mean, of course, that we should abandon shark management entirely because it doesn’t work; instead, we should be upping the ante and reversing the poor performance of shark fisheries management in many countries. Otherwise, sharks will continue to decline, and our oceans (and us) will be poorer for it.

CJA Bradshaw



One response

29 06 2015
Dr SA Shepherd AO

Much closer to home, the situation is no better. Whaler sharks are seriously declining in South Australia, and nothing is being done to restrict the catch.


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