Fin frenzy: Consequences of shark finning
The majority of shark species are known as apex predators, meaning they are at the top of their respective food chains. some well known species include bull sharks, tiger shark, hammerheads and the great white shark. Unfortunately, a majority of shark species face decline in population due to the act of shark finning, which in many countries is illegal.
What is shark finning
The phrase sharking finning is used to describe the act of capturing a shark, removing the fins and then throwing the shark back into the ocean alive. Shark finners will take most fins from a shark from the dorsal fin to pectoral fins as well as the caudal fin (Tail fin). No matter which fins are taken the shark cannot live without them as they are needed for movement, therefore the shark will eventually die when thrown back into the ocean. Shark finning originated in China during the sung dynasty (968 AD) but can now be found in practice both legally and illegally all over the world. Shark finning primarily supplies the production of shark fin soup, the shark fin itself gives the soup a more gelatinous texture with no extra flavour added. Approximately 73 million sharks are killed annually due to the shark fin trade, with even more being killed illegally through unregulated trading. Shark finning as a whole has impacts and consequences on both individuals and their populations, as well as the environment they live in which in turn can affect us economically.
Impacts of shark finning on individuals and their population
In every species of shark both the dorsal and pectoral fin have a role in the locomotion of the individual and without them they would be unable to move through the water. Some species of shark including Great whites, Mako and Whale sharks need to constantly move to supply themselves with oxygen as they cannot automatically pump water through the gills (Buccal pumping) needing a constant flow of water over them, this is known as “Ram ventilation”. Unable to move they will eventually suffocate. Although the majority of species don’t have this problem they will still be unable to move without their fins, therefore being unable to hunt or escape other predators.
The video below taken from YouTube gives a brief simple explanation of how sharks take in the oxygen they need to survive:
These are problems an individual would face if caught by shark finners, but due to the number of sharks being hunted it not only affects the individual but also the population of the species as a whole. On average approximately 38 million sharks were caught annually between the years 1996-2000. Since 2006 it has been estimated this total has risen to around 26-78 million a year, although this figure may have increased since. Unfortunately, sharks have a K-selection lifestyle possessing a stable population that produce a very small number of offspring, generally with long gestation periods, slow maturation and long lifespans giving sharks a low reproduction rate. Due to the number of sharks being caught the rate of capture is much higher than what their reproductive cycle can handle slowly depleting the population each year. According to a study produced in 2013 the exploitation rate was between 6.4% and 7.9% of sharks killed per year. This is well above the rebound rate (rate of reproduction for species to not decline in abundance) which is around 4.9% per year, providing statistical evidence towards the decline in shark populations. If the population keeps decreasing there is a potential this will cause a bottleneck in the population. This is where the population gets so small that the diversity of genes within a species drastically decreases to the point that most individuals in a species will become very similar to each other to a genetic level. Over the past 50 years the population of some shark species has dropped by a staggering 90%, one example being since 1972 the black-tip population has fallen by 93%.
As well as the shark population shark finning can have a long-lasting impact on the population of other organisms living in the same environment, natural mortality of a species being one factor involved. As shark population’s decline due to over fishing the mortality rate of organism’s apex predatory sharks would normally prey upon would start to decrease, therefore increasing their population over time. This leads to an overpopulation of Mesopredators, smaller predatory fish/marine mammals leading to a decline of other prey species in the same environment. Distribution patterns of organisms can also be affected by the decline in shark species where organisms generally not found in certain locations will be seen in abundance due to the lack of predatory presence. This is seen in a majority of “mesopredator” species expanding their distribution to account for the increased population.
Effect’s on the ecosystem
Recently Impacts on coastal ecosystem habitats due to the decline in apex predatory sharks has been increasingly prevalent. One case study reported in 2007 describes the decrease in 11 different shark species over the past 35 years around coastal areas that fed on smaller elasmobranch species “Mesopredators”. As the apex shark population declined 12 out of the 14 mesopredators examined increased in abundance, one species in particular the Cownose ray “Rhinoptera bonasus” started to prey upon Bay scallops “Argopecten irradians” at an increased rate due to overpopulation. This led to the termination of a century old scallop fishery showing a clear indication of what a decline in shark population can do. This can occur in demersal and pelagic ecosystems as well causing the same effect where mesopredator population increases putting strain on organisms lower down the food chain lowering their abundance, this eventually leads to a decline in diversity as organisms will be forced away by predation or leave due to the lack of prey.
Could ecotourism be the shark saviour?
In recent years Ecotourism has become increasingly popular, being tourism directed towards exotic natural environments. The intent of ecotourism is too support conservation efforts through public awareness and interest in observing wildlife. Shark dives have slowly become a huge aspect of ecotourism creating an income of more than $314 million a year worldwide. This income has been predicted to further increase as shark diving increases in popularity, because of this the profit to be gained from ecotourism may succeed any profit to be made from shark finning. This in turn will push for more developing countries that rely on shark finning towards ecotourism. As of yet scientific research has not recorded any side effects behavioural or otherwise in sharks associated with shark ecotourism, allowing us to safely say ecotourism may be the way forward for shark conservation efforts for now.