by Sharon Young
Worldwide shark populations are in grave peril. Of 547 species of sharks and rays evaluated by the The World Conservation Union (IUCN) in 2006, 19 are considered critically endangered and 25 endangered. One-fifth of all sharks and rays are considered to be threatened with extinction, and there is insufficient information on nearly 100 others to evaluate their status.
Many of these endangered and threatened species swim in U.S. waters. Even the common skate is no longer common in the United States. Although listed as endangered by the IUCN in 2000, its population plummeted to critically endangered in 2006.
One of the threats to shark populations in the United States comes from overexploitation by commercial fisheries. Sharks are uniquely vulnerable among fish because their life histories more closely resemble those of whales. They are long lived, and, like whales, they are slow to reproduce and have very few young. What's more, most are highly migratory. Sharks caught on one side of an ocean basin are often from the same population being exploited on the other side, which can create conservation crises. For example, Canada proposed listing the porbeagle shark, which the IUCN lists as declining and vulnerable to extinction, on its version of the U.S. Endangered Species Act. But even though American porbeagle sharks are from the same population found in Canada, the United States gives them no special protection.
Sharks are targeted by commercial longline and driftnet fishing boats as well as by purse seine fishing boats, which use large nets to encircle groups of fish. Shark meat is eaten in restaurants worldwide and, in the Far East, shark fins are popular for soup and other dishes. There is also an incidental by-catch of sharks by fisheries targeting other fish species, and most of these sharks are discarded as waste.
Sharks in U.S. waters are also caught by recreational fishermen and in a growing number of shark tournaments. The National Marine Fisheries Service (NMFS), which manages most shark species, has stated that in the eastern Gulf of Mexico alone, shark tournament fishing has grown from half a dozen tournaments in 1973 to as many as 70 today. The greatest conservation concerns are about species for whom there is a large commercial market. This includes large sharks such as mako and blue sharks, and small sharks such as skates and dogfish.
The Status of Sharks
Many sharks are distributed worldwide, but their status varies in different locales. Although the United States has not granted protected status to most shark species, international bodies have expressed concern for a number of species found in U.S. waters. In New England alone, The U.N Food and Agricultural Organization lists six of the 15 commonly caught shark species as declining and of significant concern.
A 2003 study by Dalhousie University, published in the journal Science, estimated that all recorded shark species, with the exception of makos, have declined by more than 50 percent in the past eight to 15 years. Some species, such as hammerhead and thresher sharks have declined by as much as 80 percent. The Pew Charitable Trust's Global Shark Assessment predicts collapse and extinction of several species of sharks if current levels of fishing mortality remain the same. Study after study indicates that we should be very concerned about the fate of sharks, which play a critical role in coastal food webs. Despite concern by international bodies, there are active commercial and recreational shark fisheries in the United States, and there is resistance to more restrictive management.
East Coast Sharks
At least 73 species of sharks inhabit the waters of the U.S. east coast, including the waters of the Gulf of Mexico and the U.S. territories of Puerto Rico and the Virgin Islands. The NMFS places sharks in one of five categories for purposes of managing fisheries that may interact with them. Large coastal sharks, which are the frequent targets of fisheries, are considered overfished by NMFS. This category contains 11 species including sandbar, blacktip, tiger and hammerhead sharks. A recent NMFS report found that fisheries have been exceeding established quotas for this group in the Gulf of Mexico and South Atlantic. A second category, pelagic sharks, contains five species, including thresher, Porbeagle, shortfin mako, and blue sharks. All sharks in this category are considered "fully fished" and can sustain no further fishing pressure. The category of small coastal sharks is also considered "fully fished." This category contains four species, including bonnethead, blacknose and sharpnose sharks. In this category too, fisheries in the Gulf of Mexico have dramatically exceeded the 2006 quota.
A fourth category is referred to as "prohibited sharks." The 20 species in this category are so imperiled that it is illegal for fishermen to possess them. This category includes whale sharks, basking sharks, sand tiger sharks, and dusky sharks among others.
The last major category on the east coast is deepwater/other sharks. This category contains 33 poorly understood species such as lantern sharks and gulper sharks. Spiny dogfish are IUCN listed as endangered.
West Coast Sharks
Less is known about west coast sharks than those of the U.S. east coast. However, there are conservation concerns for most of the sharks targeted by commercial fisheries. According to the NMFS, the most common targets of commercial fisheries on the west coast of the U.S. are various thresher sharks, shortfin mako and blue sharks. In the north Pacific, spiny dogfish are the most commonly targeted species. In the western Pacific, around Hawaii and the territories of Guam, Midway and other atolls, tiger, sandbar and Galapagos sharks, which are coastal in nature, may be caught by fisheries that are primarily targeting other fish species (such as tuna and billfish.) Many of the shark species targeted by fisheries are considered to be overfished and likely declining.
Summary
A 2004 meeting of IUCN specialists on the status of sharks in North and Central American waters concluded that fishery restrictions helped improve the status of some species in the United States, such as black-tipped sharks. Others, such as sand tiger sharks which produce only two young every two years, continue to decline despite protection. The report highlighted the continued vulnerability of sharks to overfishing. In 2007, the IUCN's Shark Specialist Group found that the status of sharks continues to deteriorate. They recommended that all thresher sharks be listed as threatened with extinction globally. Shortfin mako sharks, a favorite target of fishermen, were also considered threatened with extinction. Although commercial fisheries are the primary threat to sharks, pressure from recreational and tournament fishing adds to the peril facing a number of species of large sharks.
Sharon Young is The HSUS' marine issues field director.
Updated June 4, 2007
