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The Global Status of Sharks

Hunter S. Thompson once wrote “It was the Law of the Sea, they said. Civilization ends at the waterline. Beyond that, we all enter the food chain, and not always right at the top.” While he was talking about piracy and salvage in the Florida Keys, there is an ecological attractiveness in this statement that cuts to the core of our relationship with the ocean and sharks in particular.

When we dip our heads below the waterline we enter a world where sharks reign and mold ecosystems as they have for much of the 400 million years or so since their evolutionary radiation. This was far before the evolution of flowering plants and trees (about 83 million years ago) and sharks were also around before, during, and following the entirety of the existence of dinosaurs. Sharks are ancient, able, and astoundingly amazing creatures. They prowl the water column with unmatched prowess and an acuteness beyond our experience, including a sixth electrical sense, and play an essential ecological role similar to the wolves of Yellowstone or other top predators in managing and controlling ecosystem function.

great white_Terry Goss_The Forever Engine
Great White Shark (Carcharodon carcharias): Under various synonyms (maneater, white death), the Great White Shark has long been a focus for negative media attention, generated by its sometimes lethal interactions with humans. As a consequence of this typically exaggerated threat to human safety and an almost legendary “Big Fish” status, the species is targeted as a source for sports-fishing, commercial drumline trophy-hunting (for jaws, teeth and even entire specimens preserved), sporadic human consumption or merely as the piscine whipping-boy of individuals pandering to shark attack paranoia. All of these activities have greatly increased since the “JAWS” media phenomenon of the mid 1970s, not only to the detriment of C. carcharias but also in encouraging targeting of other, less high-profile species. Photo Credit Terry Goss/The Forever Engine

Although there are a few species of shark that definitely exist at the top of the food chain, most shark species are relatively small and exist as both predators and prey along the scale of species’ relationships. Those that get the most attention are the sleek, fast, and large predatory sharks—Tigers, Makos, Hammerheads, and Great Whites. However, shark species range from the Dwarf Lantern Shark (Etmopterus perryi) which is only about 8 inches long to the Whale Shark (Rhincodon typus), which is the largest fish in the world and typically reaches a length of over 30 feet.

In 2014, IUCN completed a global Red List assessment of each of the 465 species of shark and 576 species of the closely-related rays, skates, and chimaeras. This assessment concluded that 74 species of shark are classified as threatened species (Vulnerable, Endangered, or Critically Endangered) and when combined with the other cartilaginous fish they are at a substantially higher risk of extinction than most other vertebrate groups. Additionally, despite an enormous amount of heavily publicized research on several popular shark species like the Great White, scientists still lack even the most basic quantity of data to assess the conservation status for over 45% of shark species. What we do know is that sharks are some of the slowest species to reach sexual maturity and exhibit some of the longest gestation times and maternal investment in the animal world (often 2-3 years), which has serious consequences for their conservation potential.

heterodontus_Richard Ling
The Port Jackson Shark (Heterodontus portusjacksoni). Perhaps the cutest shark you’ve ever seen, this abundant shark is endemic to Australian waters.  Although caught in commercial fisheries in substantial quantities most are returned to the water alive. Photo Credit Richard Ling

Throughout the world there are three main hotspots of biodiversity loss for sharks and rays: the indo-pacific triangle between the Philippines, Indonesia, and Eastern Papua New Guinea; the Red Sea; and the Mediterranean. However, several other areas like the Panama Canal region, the Ecuadoran coast, Western Madagascar, and the Great Australian Bight each have high levels of shark irreplaceability should local species be lost. With the notable exception of the US and Australia, threat hotspots occur in the waters of the most intensive shark and ray fishing and fin-trading nations (read the full study by Dulvy et al. here).

The high value of shark fins is a present threat that may drive the extinction of many species, especially the prized shark-like rays (sawfish, wedgefish, and guitarfish). These are species that don’t fit into the typical image of a shark and generally remain unrecognized by the media and the public. Despite their anonymity they are well known to shark finners who can get top-dollar for the fins of these species on the international market.

giant guitarfish_Brian Gratwicke
Whitespotted Wedgefish (Rhynchobatus djiddensis) The restricted coastal habitat, limited life history characteristics, susceptibility to capture in various gear types, and ever growing demand place coastal rhynchobatids amongst the worlds most vulnerable cartilaginous fishes. Photo Credit Brian Gratwicke

The threats to sharks and rays extend far beyond over-exploitation for shark-fin soup. Most shark species exhibit high habitat specificity and small ranges and are also threatened by overfishing and the degradation of coastal ecosystems through pollution that results from unsustainable or reckless commercial, residential, and infrastructure development. Unfortunately, people also kill sharks out of perceived threat of risk to people, misguided attempts to protect aquaculture or fisheries, or plainly, just for fun.

It’s clear that sharks face many of the same threats that plague other flagship  species of wildlife crime—poaching, over-exploitation, habitat loss, persecution, and black market values that are compounded by relaxed or non-existent laws and consequences in many places around the world. The survival of many shark species will be a direct result of the ability of individuals, diverse communities, and governments to recognize and halt the loss of sharks and their relatives, a tall order for a large, open, and mostly unregulated ocean.

While it may seem that shark conservation is at Point Nemo there is a swell of international support to curb shark landings and restore marine ecosystems with an abundance of sharks. This process starts with shark researchers and The IUCN Red List of Threatened Species. The global conservation assessment of shark, ray, and chimaera species allows conservation organizations, individuals, businesses, and governments to take stock of the world’s shark populations and work to improve conditions for shark survival and reproduction.

pristis pristis_Simon Fraser University
Largetooth Sawfish (Pristis pristis): While international trade sawfishes is banned under the species’ listing on Appendix I of the Convention on International Trade of Endangered Species (CITES), illegal international trade may still exist due to the high value of their products. Photo Credit Simon Fraser University

Shark conservation can only succeed if shark finning is converted into a sustainable practice. Already, the Chinese Government has banned shark-fin soup at their official banquets, a move that may drastically reduce the global demand for shark fins and has led to menu changes all throughout China. For instance, organizations such as WildAid are enlisting the help of notable people and communities to change the culture of demand for shark-fin soup, using some of the same social tactics that encouraged people to quit smoking.

The conservation of sharks and the repopulation of the world’s oceans and estuaries will take decades, but it is possible if we embrace the science behind the IUCN Red List.

hammerhead_Barry Peters
Scalloped Hammerhead Shark (Sphyrna lewini). This species of shark occurs in waters around the globe. it’s fins are highly prized for soup and it is estimated that as many as 2.7 million of its fins are sold in the shark fin trade each year. Photo Credit Barry Peters

 

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Craig R. Beatty

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Comments

  1. Atoplopc
    la libertad canton cangrejera , El Salvador
    August 18, 3:13 pm

    linda información de las especies de peligro de extinción