The Science of Shark Finning
Filed under: Discovery,News & Resources
The global appetite for shark fin soup is one of the most serious threats to sharks around the world, driving several shark populations to the brink of extinction. Nearly 100 million sharks are killed annually for their fins, teeth and liver oil, 73 million of which are used for the shark fin trade. Declines of close to 90 percent of entire shark populations are not uncommon today, largely owing to this practice.
(From SeaWeb) – Sharks play an important ecological role as top marine predators stabilizing ocean ecosystems across the world. As apex predators, sharks serve a crucial role in the top down regulation of ecosystem dynamics. Many sharks are considered keystone species because they have a disproportionately large impact on different elements of their habitat given their relatively low biomass. Small shifts in shark populations disrupt the delicate balance between species across the entire ecological spectrum. Removing this critical piece from the puzzle will set off a chain reaction, the consequences of which are complex, sometimes unpredictable but undoubtedly ecologically significant.
Sharks are believed to be naturally rare, slow-growing, late-maturing, long-lived species. They also have low reproductive rates and long gestation periods, signifying that they cannot replenish their populations as quickly as they are being depleted, making them extremely vulnerable to overexploitation and slow to recover from overfishing. The United Nations Food and Agriculture Organization (FAO) estimates that more than 40 percent of highly migratory oceanic sharks are overexploited.
Because the fins only constitute 2 to 5 percent of the shark’s total body mass, fishermen opt to catch and fin the shark and discard the shark to be able to store high quantities of fins aboard their ships. The Food and Agriculture Organization’s Code of Conduct for Responsible Fisheries considers finning a wasteful practice for failure to utilize the entire catch and the multiple potential products derived from sharks, including the significant protein source. Some scientists believe that the most efficient and practical way to regulate shark finning is to implement fin-attached laws, requiring that all sharks be landed whole with their fins naturally attached. The possession of detached fins would be considered illegal, and therefore a punishable offence, thus discouraging the practice of shark finning. Finning bans also facilitate species-specific data collection and promote data collection standards important for population assessments and management decisions. Several shark-finning hubs have already set bans on the possession of fins detached from the body, including Australia, Brazil, Costa Rica, Oman, South Africa and the United States. These nations are now calling upon other countries to adopt similar bans in recognition of the high percentage of illegal, high seas international exploitation. These are significant steps in helping shark populations recover, since Brazil, Costa Rica and the United States are among the world’s top exporters of shark fins to Hong Kong, the largest market for shark fins in the world.
In recognition of the need to transport fins and carcasses separately for storage purposes, the majority of existing shark finning bans use a fin-to-carcass weight limit as the primary regulatory framework. The U.S. National Marine Fisheries Service (NMFS) developed the most common fin-to-carcass ratio in the early 1990s. Based on commercial fishing conditions, the NMFS endorsed a 5:95 ratio of fin weight to dressed (gutted and beheaded) carcass weight. Scientists recommend the inclusion of a 2:98 fin weight to live (whole body) weight stipulation, underscoring the importance of distinguishing between dressed and live sharks as the head and internal organs of a shark account for a significant proportion of its total weight. Exceeding these ratios would effectively enable two-thirds of all landed sharks to be finned within the legal parameters.
The scientific community also advocates using commercial quotas, trip limits, and limited access in commercial fisheries to reduce shark finning. These restrictions are theoretically established according to the maximum sustainable yield principle, providing the largest economic benefit without surpassing the species’ biological limitations to replenish itself. Appropriate quotas require significant research to provide adequate estimates of sustainable catch rates. Many countries require regular stock assessments to: 1) prevent overfishing of shark resources; 2) encourage management of shark resources throughout their range; 3) establish a shark resource data collection, research and monitoring program; and 4) increase the benefits from shark resources while reducing waste, consistent with the other objectives. Shark data collection and reporting, however, is notoriously inaccurate and insufficient.
Many species of sharks are highly migratory, moving regularly between jurisdictions and marine habitats (i.e. open ocean to continental shelves) occupied by different fisheries. Furthermore, much of the shark fin industry is supported by illegal, unreported and unregulated fishing (IUU), leaving large gaps in the data. The practice of finning therefore impedes the collection of accurate scientific data and the provision of essential management advice. Because scientists cannot collect, weigh, track and identify every individual shark, mathematical models are often used for population estimations to determine fishing quotas. However, these models are only as good as the data that feeds them. According to the International Union for the Conservation of Nature (IUCN), as many as 25 percent of pelagic (open ocean) shark populations are data deficient, lacking sufficient information to assess their status based on life history traits, suggesting their vulnerability and mortality from fishing trends. Thus, many models used to compute sustainable catch allowances are scientifically incomplete and inaccurate.
In the absence of bans or other regulatory mechanisms, the high and growing demand for shark fins will inevitably result in further declines and, eventually, the likely collapse of populations of sharks around the world.
