28th October 2021
Happy Sustainability Day! Today is the day that we celebrate caring for our natural environment and raise awareness about sustainability issues on a global scale. Thankfully, in this modern era, more and more people are becoming aware about the need to live more sustainably, but there is also a lot of confusion surrounding sustainability and conservation... What actually makes something sustainable? How can we determine if a resource is being used unsustainably? And with such enormous declines, is it even possible to sustainably fish sharks and rays?
What is 'Sustainability'?
In recent years, we have realised that we cannot continue to exploit our natural resources (known as "ecosystem services") without consequences! In the case of some resources like gas and oil, these resources are truly finite and will eventually just run out. Other resources, like trees or animals, can replenish themselves, but are also at risk of being overly depleted if they are not used sustainably (Yulianto et al, 2018).
There is often confusion about what sustainability actually is and what this means in a practical context. Making resources sustainable does not mean stopping any use of that resource at all. Sustainability actually means that a resource is exploited in a manner that will mean it is not destroyed or depleted to such a degree that it might disappear in the near future. This can mean that we plant trees to replace those we use for paper and furniture, or can mean eating foods that are farmed without destroying the natural habitat.
Sustainability:
avoidance of the depletion of natural resources
in order to maintain an ecological balance
For sharks and rays, this means ensuring that they are not extracted at such a high rate that they cannot replenish their populations. If they are not correctly managed, at best, fisheries could collapse, at worst, an entire species could be driven to extinction!
Shark Fishing is Currently Unsustainable
Shark fisheries are big business all over the world right now. The majority of this is for shark fin soup, which is a delicacy on the Asian market However, sharks are also fished for trophies or to protect ocean users, for their meat, or for other products that are used in both traditional and Western medicines (Yulianto et al, 2018).
Currently, the global extraction of sharks is dramatically unsustainable. So much so that some species have been depleted by as much as 90%! (Pacoureau et al, 2021)
How Do You Make a Shark Fishery Sustainable?
In order for a fishery to be sustainable, scientists must consider many different aspects which keep the stocks healthy: How big is the natural population? How old are the animals they when they breed? How many litters can they have in their lifetime? What is their lifespan? All together, this information is known as the '"life-history strategy" for that species. If we cannot answer all these questions, it is very challenging to determine how to make a fishery sustainable because we cannot know how this species will react to exploitation (Prince, 2005; Simpendorfer & Dulvy, 2017; Yulianto et al, 2018; Ferretti et al, 2020).
Maximum Sustainable Yield:
the maximum level at which a natural resource
can be routinely exploited without long-term depletion
When we have sufficient information about a species, the first stage is to consider the "maximum sustainable yield" of that stock. This means calculating how many fish can be extracted each year before a critical threshold is reached, at which point the stock will collapse (Prince, 2005; Simpendorfer & Dulvy, 2017; Yulianto et al, 2018; Ferretti et al, 2020).
We can then implement "catch limits" (aka Total Allowable Catch (TAC)) to ensure we do not overexploit fish stocks. This means that a certain amount of fish are allowed to be landed during a certain time frame. This does not only benefit the fish, but also the fishers because it means they can earn a livelihood not just now, but also in the future because the fish will not disappear as a result of overexploitation (Prince, 2005; Simpendorfer & Dulvy, 2017; Yulianto et al, 2018; Ferretti et al, 2020).
Total Allowable Catch (TAC):
the catch limit set for a particular fishery over a year or a fishing season,
usually expressed in tonnes, but sometimes set in terms of numbers of fish
Yet, we cannot only consider numbers when determining how to keep fish stocks healthy because not all fish are equal in the population. For example, extracting mature females, (which are capable of producing many young) can be foolish, because we will lose the ability to replenish the stocks. Similarly, removing very small, young individuals will mean that we reduce the amount of "recruitment" into the mature population, which can also lead to depletion. So, it is important to consider which individuals should and should not be fished, by implementing "size limits" on individual fish which can be caught (Prince, 2005; Simpendorfer & Dulvy, 2017; Yulianto et al, 2018; Ferretti et al, 2020).
Regional / Seasonal Fishery Closure:
banning fishing of a certain species in a certain space / during a certain time,
to promote the sustainability of fish stocks
We must also consider where we allow fish to be taken. There might be certain sub-populations of a fish species which are collapsing or near to collapse. This might make it sensible to create "regional fisheries closures", so that the population can recover in that area. This method can also allow us to protect critical areas, like "spawning habitats" or "nursery habitats", which are vital for reproduction. Similarly, it might also be wise to implement "seasonal fisheries closures". This means that a certain species may not be extracted at certain times of the year, during spawning season, for example (Prince, 2005; Simpendorfer & Dulvy, 2017; Yulianto et al, 2018; Ferretti et al, 2020).
Sustainable Shark Fisheries Already Exist!
It certainly is not straight forward to ensure a shark fishery is sustainable, but that does not mean it is impossible! In fact, there are already many examples, all around the world, where sharks and ray are already being fished sustainably (Simpendorfer & Dulvy, 2017).
As long as catch quotas are based on sound scientific advice and the fishery is continually monitored, to ensure populations are not declining, there is no reason that many species of sharks and rays cannot be fished sustainably (Simpendorfer & Dulvy, 2017). In fact, many scientists believe that sustainable fisheries will actually contribute to shark and ray conservation! (Shiffman & Hammerschlag, 2016). To learn more, you can check out Can Shark Fisheries be Sustainable?
How Can You Be More Sustainable?
There is no better time than on sustainability day to consider if there is something you can do in your daily life to ensure you are supporting the sustainable fishing of sharks... Obviously you can choose not to eat any products from sharks or rays, like shark fin soup. If there is no demand for these products, there will be no incentive to fish unsustainably.
But don't forget shark fisheries do not only fish for fins. Teeth used in jewellery might not be ethically sourced and it is also quite possible you have eaten shark meat without even realising! In many countries shark meat is not explicitly labelled as such - Look out for any fish called 'catfish', 'dogfish', ''huss' / 'bull huss','flake', 'whitefish', 'rock salmon' or 'gummy', which are often euphemisms for 'shark'.
You might think you don't need to do anything if you don't eat sharks, but that is not the case! it is always important to ensure that all seafood you eat is fished sustainably. This is easy to check because responsibly sourced seafoods will always have a logo displayed on the packaging. If you are lucky enough to live by the coast, you could also choose to support small, artisanal fishers who do not fish on an industrial scale.
But sustainability does not only apply to foods! Believe it or not, shark products are also often used in pharmaceuticals and beauty products! You can ensure you avoid this by choosing not to buy products that contain 'squalene'; a product sourced from shark livers. Vaccinations, face creams, moisturisers, deodorants, sunscreen... you would be amazed how many products this is in! Squalene can be produced from plants as well, so always check the packaging! If something contains squalene, ensure you only buy products that specify the squalene is not sourced from sharks or rays. If we all make more sustainable choices, we can ensure that sharks and rays will be around for the next generations to enjoy for many years to come!
References
Ferretti D, 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, 13, e12708. Access online.
Prince JD (2005). Gauntlet Fisheries for Elasmobranchs – the Secret of Sustainable Shark Fisheries. Journal of Northwestern Atlantic Fisheries Science, 35, 407–416. Access online.
Shiffman DS & Hammerschlag N (2016). Preferred conservation policies of shark researchers. Conservation Biology, 30, 805–815. Access online.
Simpendorfer CA & NA Dulvy (2017). Bright spots of sustainable shark fishing. Current Biology, 3:27, R83–R102. Access online.
Pacoureau N, Rigby C, Kyne P, Sherley R, Winker H, Carlson J, Fordham S, Barreto R, Fernando D, Francis M, Jabado R, Herman K, Liu K, Marshall A, Pollom R, Romanov E, Simpfendorfer C, Yin J, Kindsvater H & Dulvy N (2021). Half a century of global decline in oceanic sharks and rays. Nature, 589:7843, 567-571. Access online.
Yulianto I, Booth H, Ningtias P, Kartawijaya T, Santos J, Sarmintohadi, Kleinertz S, Campbell SJ, Palm HW & Hammer C (2018). Practical measures for sustainable shark fisheries: Lessons learned from an Indonesian targeted shark fishery. PLoS ONE, 11:13, e0206437. Access online.
By Sophie A. Maycock for SharkSpeak
