• SharkieSophie

Can Shark Fishing be Sustainable?

Updated: Apr 26

The dramatic declines in the populations in recent decades, has lead to sharks and their relatives being considered one of the most threatened groups in the world today. Currently as many as 300 species of "elasmobranchs" (sharks, skates, rays and chimaeras) are considered to be threatened with extinction! One of the most significant drivers of these declines is the overexploitation of sharks in fisheries. So, if these fisheries are so devastating, is there any way to exploit sharks sustainably? How could that ever be possible?


Shark longline fishing (Image source: www.takepart.com)

It is indeed possible that shark fisheries could be sustainable... In fact, when 102 shark scientists and conservationists in America were asked whether they believed this to be true, a resounding majority stated that it is possible and there are already examples of sustainable shark fisheries in the world today (Shiffman & Hammerschlag, 2016).


Scientists' opinions on shark conservation methods (Shiffman & Hammerschlag, 2016)

So why do leading experts feel this way? There must be something to it if shark-lovers who have devoted their entire lives to the cause are making such statements... So where are these sustainable shark fisheries?


The locations of sustainable shark, skate and ray fisheries (Simpfendorfer & Dulvy, 2016)

There are several countries around the world which already have sustainable shark fisheries, including the United States of America and Australia. In a recent assessment performed by scientists in the USA, 10 fisheries which target different species of sharks were considered to have never been "overfished" or currently experiencing "overfishing".


Amazingly, this even included the both the Pacific and Atlantic American fisheries for the IUCN-listed vulnerable spiny dogfish (Squalus acanthias). This means that these shark fisheries have not yet suffered stock collapse and are currently not being extracted at a higher rate than they are able to reproduce, so their populations are stable. At this rate, this should mean these fisheries can continue to be exploited at this rate for the foreseeable future (Ferretti et al, 2020, IUCN, 2021).


Shark fisheries in the USA which are not considered over-fished (GOM = Gulf of Mexico) (Ferretti et al, 2020)

Similarly, assessments made by Seafood Watch, the National Atmospheric and Ocean Organisation (NOAA) and the Marine Sustainability Council (MSC), have recently stated that several shark fisheries in the USA can be considered sustainable. Whilst the three agencies disagreed in their findings to some degree, one of more of them stated that even the Atlantic and Pacific fisheries targeting the endangered shortfin mako (Isurus oxyrinchus) and the vulnerable (ironically named) common thresher shark (Alopias vulpinus) are actually sustainable (Shiffman & Heuter, 2017).



But should we be fishing sharks at all? Wouldn't it be better for their conservation if they were never fished? Well, on the contrary, as many as 90% of the scientists that were asked in that American survey, actually stated that sustainable fisheries would be preferable to the blanket banning of shark fishing and that sustainable exploitation should be the primary goal for shark conservationists! (Shiffman & Hammerschlag, 2016).


Scientists' opinions on shark conservation methods (Shiffman & Hammerschlag, 2016)

This is because, it is becoming increasingly clear that blanket bans are very rarely successful, as they just push activities underground. Basically, if we ban shark fishing entirely, it will just happen illegally. It is almost impossible to police every single corner of the ocean, especially in less-developed nations, with limited resources. Therefore, it is preferable to work alongside shark fishing communities, to come-up with management strategies for threatened species which are also fair to local people who rely on shark fishing for subsistence and for their livelihoods.


So what needs to be in place to ensure that shark fisheries are made sustainable and stay that way? The experts surveyed in America agreed for the most part that there must be strict bans on extracting endangered species, and that this must-go hand in hand with international trade limitations like listings with CITES (The Convention on the international Trade in Endangered Species of Wild Fauna and Flora). This would mean that species considered threatened with extinction should not be fished and should also not be traded internationally. Many also strongly agreed that fisheries should have strict quotas, meaning there is a limit set on how many sharks can be fished. Many also agreed that there should be closures of the shark fishery in critical habitats and at specific times, meaning there would be no fishing allowed in shark nurseries or during mating seasons. This would ensure that the population would not be overexploited. Around 50% of those surveyed stated that they did not agree with nationwide bans on commercial shark fishing, but many agreed there should be specific no-take areas, like marine reserves, where shark fishing is banned (Shiffman & Hammerschlag, 2016).

Level of support from surveyed scientists for different shark conservation measures (Shiffman & Hammerschlag, 2016)

So with all these brilliant methods for making shark fishing sustainable, why is it not just easy to make all shark fisheries sustainable right now? One of the greatest challenges facing shark conservationists is limited knowledge. We cannot plan how to make fisheries sustainable if we do not know details about their "life-history" - How long do they live? What age do they reach sexual maturity? How many pups do they have per litter? Where are their nursery habitats? etc.. It is only when armed with this knowledge that we can determine how rapidly a shark population might recover when being exploited by fisheries (Ferretti et al, 2020).


Shark fisheries in the USA yet to be assessed for over-fishing (GOM = Gulf of Mexico) (Ferretti et al, 2020)

Another massive problem is determining what the natural population of sharks should be. How many sharks would there be if we had never fished them? (known as their "baseline abundance"). The problem is that we simply do not know for many species, as nobody thought to count the sharks before they started fishing them. This means that the only way we have of tracking the population of sharks is through monitoring their "relative abundance" - this means assessing whether the population has declined or increased since we last counted them? This can allow us to check we are not overexploiting a shark stock... but for many shark fisheries we simply do not even have this information. For dozens of commercially exploited shark species, we have no idea whether the population is declining, and there have been no assessments to determine if they are overfished (Ferretti et al, 2020).


In the case of sustainable fisheries, knowledge is power! The more we know, the better chance we have of designing management strategies which will be successful.


"With strong science-based management, most shark species have the potential to support sustainable fisheries"

- Simpfendorfer & Dulvy, 2016



Knowledge is also power on the part of the consumer! If you would like to eat shark products responsibly (or any fish, for that matter!), you can choose to buy products which include a logo proving they were sourced from sustainable fisheries. You have the power to demand change, by only buying products which have been sustainably sourced!



References

Ferretti F, Jacoby DMP, Pfleger MO, White TD, Dent F, Micheli F, Rosenberg AA, Crowder LB & Block BA (2020). Shark fin trade bans and sustainable shark fisheries. Conservation Letters, e12708, DOI: 10.1111/conl.12708. Access online.


Shiffman DS & Hammerschlag N (2016). Preferred conservation policies of shark researchers. Conservation Biology, 30, 805–815. Access online.


Simpfendorfer CA & Dulvy NK (2016). Bright spots of sustainable shark fishing. Current Biology, 27, R83–R102. Access online.


By Sophie A. Maycock for SharkSpeak.

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