Monday, August 29, 2011

Sustainable fishing for Sharks - Heresy?

So - is sustainable fishing for Sharks possible?
Yes of course it is!
The number of Sharks that can be harvested globally: somewhere between one Shark and, say, 200 million!

I'm obviously being facetious.
But, what is, or rather: what should be equally uncontroversial is that in theory, there really is such a magical number. In theory, one should be able to extract less, or about as many Sharks as are being recruited every year and observe other imperatives, see below, and one should be able to fish for Sharks forever.

Please re-read this.
What the paper stipulates is that Shark fisheries can be managed, and that sustainable levels will vary depending on Shark species and their life history, and this principally in regard to their reproductive strategies, i.e whether they are rather K-selected or r-selected. Don't get me wrong: no Shark is really r-selected whereby it produces thousands of offspring like Tuna - but there are still marked differences in number of offspring (2 in intra-uterine cannibalistic Sand Tigers to up to one hundred in aplacental viviparous Tigers) and in life expectancy (= population turnover) that warrant a differentiation.

And in practice?
As always, it is complicated.
I won't bore you with the details, but trying to formulate and then implement the correct fisheries management strategies is exceedingly complicated, highly controversial and of course, fatally politicized.
And so far, it has been an utter fiasco.

Wherever we look, the track record sucks!
Largely thanks to Juerg's widely respected research and to the notoriety it confers to us, we get to increasingly meet some very, very smart (and incidentally, inevitably very cool) researchers.
One of them mentioned recently that what we've been doing to the oceans is veritable protein mining, starting from the bigger most valued fishes all the way ever further down through the trophic levels - and in the end, when everything is all but gone, we throw in a couple of bombs or poison to really get to the very last little bit.
So true - seen it a dozen times with my own eyes from Burma to Indonesia to the Philippines, the ultimate confirmation that small-scale fishing, if perpetrated by too many hungry people, is at least as bad if not worse than the so much reviled commercial exploitation! And as the demand soars ever higher and local waters are depleted, the rich nations are traveling ever further to catch other people's stocks and are increasingly importing Fish from other countries.

Anyway, I'm digressing as usual.
What I wanted to say is that arguably and with probably the exception of some small scale local ventures, there does not exists a single fully sustainable fishery anywhere, not for Fishes and certainly not for Sharks.
Instead, what we see is either a history of whole fisheries crashing, or of fisheries that are but a shadow of what they once were, both in output but also in quality, like the pathetically small Tuna I talked about here, or the Cod that are apparently rebounding but are now much smaller, possibly changed forever.
And since the fishermen have been so effective at killing everything around them, we are already seeing attempts to encroach (and in NSW!) on the paltry few Marine Protected Areas we have been able to establish - remember this post?

Please click for detail.

And of course, overfishing is only one, albeit a major element in a whole array of factors!
The oceanic ecosystems are in terrible shape - and the cause is unequivocally us.

Back to the Sharks.
Alerted by Sheli's comment, I got myself this paper and found the following list of species declines since specific dates in specific bodies of water.
  • Hammerheads 1986 N.W. Atlantic 89%
  • Scalloped hammerhead 1972 North Carolina 98%
  • White 1986 N.W. Atlantic 79%
  • Tiger 1986 N.W. Atlantic 65%
  • Tiger 1973 North Carolina 97%
  • Carcharhinus spp. 1986 N.W. Atlantic 61%
  • Thresher 1986 N.W. Atlantic 80%
  • Blue 1986 N.W. Atlantic 60%
  • Mako 1986 N.W. Atlantic 70%
  • Mako 1950s Gulf of Mexico 45%
  • Oceanic whitetip 1950s Gulf of Mexico 99%
  • Silky 1950s Gulf of Mexico 91%
  • Dusky 1950s Gulf of Mexico 79%
  • Dusky 1972 North Carolina 99%
  • Blacktip shark 1972 North Carolina 93%
  • Bull shark 1973 North Carolina 99%
  • Sandbar shark 1976 North Carolina 87%
Many of the data have been collated by the late Ransom A. Myers and their credibility is thus very high, the more as these are well documented fisheries. But beware: they are merely an indication of what fishing pressure can do to Shark stocks and cannot be simply extrapolated to describe the global rate of decline. Globally, there are no reliable baseline counts, fishing pressure may be locally completely different, data of reported species are often highly deficient, many species are not being targeted and/or cryptic and thus not being reported, there is widespread IUU, etc.
This is why in practice, the controversy about the global numbers is pretty much irrelevant - and yes, I am repeating myself!

What we however do know and can say is this.
We know that there are massive Shark fishing operations ongoing in Central America, Africa, Asia, Arabia and in the high seas. It is also plausible to assume that the pressure we are exerting on the prey of Sharks is further contributing to their decline, especially in pelagic environments where prey substitution is not as easy as in, say, coral reefs. We also know that Sharks are a substantial component of bycatch, and this not only by long liners and purse seiners, but very much also by bottom trawlers that are destroying the demersal elasmobranchs.
Principally as a consequence of the overfishing but very likely also as a consequence of the other principal anthropogenic stressors Pollution, Habitat Degradation and Global Warming, vast swaths of Ocean have been deprived of Sharks, as in Asia, the Caribbean, the Pacific Coast of the Americas, the Northern Atlantic, even Australia where the Whitetips and the Grey Reefs have all but disappeared from the GBR - paper here.
In brief, it is I believe perfectly OK to say that we are presently killing way, way too many Sharks, or those stocks would not have crashed!

We also know about the consequences.
No, not this moronic drivel - real science!
There is a brand new paper about top-down effects that is essential reading. In essence, it documents how the loss of apex predators ripples down through the food chain, often in completely counter-intuitive ways. The coral reef example? Hmmm, not totally convinced, as stipulating causality based on a one-off comparison and not long-term monitoring is highly suspect. What if the differences were based on different climatic effects, or a Crown-of-Thorns invasion or the like?
Anyway, concerning Sharks, there is the famous 2007 paper by the same Ransom Myers. Although controversial and to be cited with caveats, it documents the precipitous decline of apex predators, the concurrent increase of mesopredators and the subsequent decline of Bay Scallops and the fishery depending on them in the NW Atlantic.
Please click for detail.

And of course there is more.
The more recent Ferretti et al that I personally like better documents Shark declines and the possible effects on a more global scale. Other papers and reports, some of which rather anecdotal, document how Sharks influence the size, composition and behavior etc of their prey populations locally.
Two anecdotal examples from Fiji: Reef Blacktips are believed to control the population of Reef Octopus and where they have been fished away, the octopi have gobbled up the economically important crustaceans and mollusks; and a coral gardener told me how the Parrotfishes used to ravage his gardens, this until the advent of a few Reef Sharks that kept the Parrotfishes on the move, very much like the Tiger Sharks/Dugongs-Turtles/Sea Grass story in the link above.
But: not all Sharks are apex predators, plus trophic cascades happen only where humans are not simultaneously exterminating the lower trophic levels - meaning that the theory is sound but that in practice, this only happens relatively rarely!

And then, there's this.
Sharks are basically a non-renewable resource.
Yes there are differences in life history whereby the smaller, shorter lived species with higher population turnover rates may be better suited for commercial exploitation - but still, compared to teleost Fishes, many of which are broadcast spawners, the difference is enormous! Sharks are generally slow growing, mature late and have relatively few offspring, meaning that depleted stocks take a long, long time to recover (decades and in some species, centuries) - if at all!
Plus, as the image of the food pyramid suggests, there are only relatively few of them (but check out this: probably true!), especially at the very top, meaning that local stocks get quickly exhausted.

Thing is, we cannot really afford the risk.
Especially in small island states like Fiji, Palau or the Bahamas whose economies are entirely dependent on fishing and on tourism, risking the health of the marine ecosystem is just simply suicidal, see e.g. here.
If the Sharks get wiped out and the reefs habitats degrade as a consequence, the country does not only lose its physical coastal protection and the sustenance of a large part of its population that is critically dependent on fishing; it also risks losing its entire tourism industry as tourists will not travel to islands where the oceans are depleted but choose other islands featuring intact marine ecosystems instead.
Haiti anybody?

Long (sorry...) story short?
Sharks are being overfished, once they're gone they're not likely to come back anytime soon and although we certainly won't end up writhing on the ground gasping for air, the consequences will be dire.

The inevitable conclusion?
We must invoke the Precautionary Principle and stop the killing by enacting and implementing comprehensive Shark protection wherever we can!
Principle #15 of the Rio Declaration states:
In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.
This is also very much reflected in the IPOA-Sharks - but equally very much not being implemented!

And there is more: the precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those taking the action!

Which brings me straight back to the issue of sustainability!
Yes it is quite possible that Sharks can be fished sustainably.
But that implies that stocks are healthy and not depleted (beware of shifting baselines!), that TACs are no higher (I hear that the ideal number is 30%) than recruitment, that the fishery is not fraught with collateral ecological impacts like e.g. bycatch or the habitat degradation caused by bottom trawling, that reporting is accurate, that IUU is accounted for, that quotas are set in concordance with the ecosystem approach, that the whole animals are being landed and utilized (no finning!), etc etc.

And for once, we would be in a better position.
For once, it would not have to be us doing all the leg work in order to prove that the Shark fisheries need to be closed - according to the Precautionary Principle, the onus of proof that Shark fishing can be sustainable and should be thus allowed to resume would lay squarely with the fishing industry!
But let there be no doubt about the following.
As much as I love them and as much as I deplore it when they are being killed: Sharks are not sacred Fish.
For good or for bad, they are a source of protein and some people want to eat them and yes, they are also a rather useless ingredient in an Asian soup. But then again, at least two religions frown on us eating pork - what would we say if they came and tried to tell us what to eat and what not. Criticizing culinary preferences, cultural or not, is just not a good strategy for furthering conservation - advocating strict sustainability is.

Right now, we must advocate Shark conservation and as long as Sharks are being killed in huge numbers world wide, those sanctuaries are certainly the best way of trying to create a resemblance of balance.
But if in the future there will be uncontroversial proof that harvesting specific quotas of specific Sharks in specific waters is fully sustainable, then I believe that we will have to accept that those quotas be extracted.

Can we all agree on this?


Dom@DiveAdvice said...

Wow - yes agreed - thanks for the breakdown - understand its complex but you have probably done the best job I have seen at explainibg it to the layman.

CristinaZ said...

Very much agreed.
Get to the point of protecting sharks without loosing credibility by using inflated numbers and facts.
Thank you as always for the great information, which I try to move forward and share with even more people.

Anonymous said...

very good summary of a large and complex problem.
i mostly agree and i would only like to add an idea. fisheries enhancement through aquaculture. basically, giving the sharks a hand on the slow breeding side of the problem.
i know, complex, expensive and we still don't really know how to do it for most species of sharks, and yet i wonder if its not more realistic than implementing a reduction of 50% or more on shark landings worldwide.

DaShark said...

Thanks anonymous.

Yes, again, sound in theory.
In practice? As you say, probably extremely difficult and expensive.

Plus, the slow growth and breeding cycle means that depending on species, one would have to wait several to many years before being able to harvest, this whilst having to catch an inordinate amount of bait for feed.

The best comparison is probably that to fattening Tuna.
Like many other aquacultures, it is fraught with grave ecological impacts - but at least, the animals grow very quickly so it makes sense economically.

With Sharks, alas, I remain very doubtful.

Anonymous said...

i'm afraid i disagree about the nature of the problem,
technically speaking tunas and sharks couldn't be any further in terms of aquaculture.
while tunas spawn massive amounts of eggs and eat only the best quality fish almost non-stop (thus the ecological impact that you so rightly speak about), sharks are the "cleaners" of the seas and spawn in small numbers.
so for example, you could feed them freshwater fish like tilapia raised on plant based feeds avoiding the ecological impact and simply have larger nurseries to cater for the low numbers of pups.
in addition, once sharks are born they are very easy to care for and feed, in comparison with a minute tuna larvae that is choosy about what zooplankton is gonna have for the next year for dinner.
i think its simply a matter of getting some research done on conditioning, mating and spawning induction, which is expensive (due to the size of the research facility needed for a shark) and takes time but if we have done so for hundreds of species, many of which have much less economical value than sharks i don't see why we can't with them.
i think that is simply one of those long term ecological projects that have to be done in conjunction by universities and large public aquariums backed up by some gov money.
then again with the current economic climate large projects like this one are practically out of the question, but where there is hope....

DaShark said...

I was talking about Tuna fattening, not raising them from eggs - is that even possible?

The Tilapia idea is good of course - but how about this: take all the $$$ and instead of building artificial enclosures and catching breeding stock etc, use it to establish some really big MPAs.

Wait for stocks to recover there & then go & fish sustainably.