If I were to list all the impacts that humans are having on global elasmobranch populations, this would be a very long post, and I still probably wouldn’t be able to tell you everything. The baseline: humans are having a very negative effect on elasmobranch populations.
Maybe you’re sat here reading this, having seen the title was based on sharks, and are thinking “what are elasmobranchs?”. Elasmobranchs are a subclass of Chondrichthyes and contain 13 orders of modern sharks and rays. There are 9 orders of sharks, and 4 orders of Rays, ranging from the tiniest Dwarf Lanternshark, to the largest Whale Shark. They can live in the warmest of waters and the deepest depths and come in a wide variety of sizes and shapes.
Mankind has always had a fear of sharks, with ancient fishing legends telling tales of man eating beasts circling ships and eating those thrown overboard. Even scientists such as Carl Linneaus classified them as “man-eaters”, describing them as “striking, with teeth of armour and stating that they were likely the ones who swallowed Jonah”. Even today, Great White Sharks are often referred to as ‘Man-Eaters’. In the modern day, films such as JAWS and The Shallows have terrified the world and caused negative connotations to sharks. Strangely enough, shark attacks aren’t that common- in fact in 2017 there were just 88 shark attacks reported globally with only 5 fatalities. Compare that to the average ~400 people that drown each year in the UK alone and it becomes clear that they aren’t that scary after all. In fact, they have far more reason to fear us…
One of the biggest threats to elasmobranchs in modern times is shark finning. The process of shark finning involves the capture of sharks- through targeted fishing, long-lining or bycatch. Once on board the boat, their fins are removed and the bodies are often disposed of overboard. Some sharks are still alive when thrown overboard, and die either by bleeding out, or by suffocation as without their fins, they are unable to move, therefore meaning they cannot get oxygen across their gills.
Sharks aren’t always the main target though, sometimes they are caught as bycatch by fishing trawlers or longlining, where they are either finned, or discarded as a whole without reporting. Approximately 50 million sharks are estimated to die each year as bycatch and longlining. The loss of such a keystone species, who often dominate the top of marine food chains, can have major complications and affect ecosystems on a large scale. Without them, all food-webs can be drastically affected, as sharks keep prey populations healthy and in check. Examples of this can be seen in interactions between tiger sharks and sea turtles. Sea turtles graze on sea grass, and studies have found that tiger sharks prevent turtles from destroying whole sea grass ecosystems by “keeping them in check” and restricting the areas in which sea turtles can graze over certain points of the year. As tiger sharks move to warmer waters for the winter, sea turtles are able to graze areas that tiger sharks previously dominated. In the summer months, the tiger sharks return, and the sea turtles move into shark-free waters to avoid predation. This enables the regeneration of sea grass and prevents over grazing of the ecosystem.
But what is the point of finning sharks? Well, the cartilaginous fin of a shark is believed to have medicinal purposes, increasing sex drive and extending life span. In Chinese culture it is used in ‘shark fin soup’, which ironically has no nutritional value, or flavour – chicken stock is actually added to give it taste! Traditionally, shark fin soup is served at weddings, as a sign of wealth and good fortune.
Shark species vary in price, for example a hammerhead fin can roughly fetch around €27.50 per kg. Fins of larger species such as whale sharks and basking sharks typically sell for more. Range of catchment for finning are estimated from 26-73 million sharks per year, of sharks of all ages, shapes and sizes. With approximately ~95% of traded fins ending up in China. This puts a huge strain on shark populations, some species more so than others. Larger species such as whale sharks typically have large gestation periods, slow growth and a high mortality rate of pups meaning that hunting one could result in hundreds more not being born.
But the tables seem to be slowly turning, shark finning is still high, but people are finally becoming more aware. There are currently 39 species of shark and ray on the ICUN Red list, as critical or endangered species. There is a slow growing realisation that sharks are worth more alive than dead, with the current value of global shark fisheries estimated to be at $630 million dollars. The shark watching industry is worth $314 million dollars, supports 10,000 jobs, and is estimated to grow to $780 dollars within the next 20 years. Countries are now banning shark finning, inputting more legislation, and global awareness to the plight of sharks is increasing. In March 2018, Samoa announced they were making their waters a shark sanctuary in order to protect sharks and ensure the ecological conservation of sharks within the Pacific. This follows other Pacific countries such as Palau, Kiribati, Cook Islands and New Zealand, who have all declared their waters shark friendly.
There is still lots to be done to ensure the safety of such keystone species of our marine ecosystems, but education is becoming a key concept of the prevention of shark finning. For more information about shark finning, or just general information about sharks and what you can do, check out the Shark Trust!
Until next time,