Overfishing has left many shark species vulnerable.
Sharks are found worldwide from the equator to the polar oceans, from the deep ocean
depths to shallow nearshore waters, and even some distance from the ocean in a few of
the world's rivers. Sharks vary greatly in their size and form depending upon the habitats in
which they live. Most species of sharks are active swimmers and are sleek, streamlined
animals. But some lead a more sedentary lifestyle (like nurse sharks, Australia's
wobegong and others) and do not need to swim actively to pass water over their gills as do
most other sharks. With a few specialized exceptions, sharks are opportunistic feeders and
predators on fish, invertebrates (squid, octopus, crabs and others), and sometimes on
marine mammals (like seals and sea lions). Whale sharks and basking sharks, which can
grow to lengths of over 40 feet and weigh over a ton, feed only on microscopic plankton!
Because most species of sharks are predators and occur where people fish, sharks are
often caught incidentally by recreational and commercial fishermen. A number of species
are known to form aggregations or schools based on age, sex or reproductive status,
which almost certainly contributes to their vulnerability to exploitation by fishing. Sharks are
particularly susceptible to overfishing because they grow and mature slowly, are relatively
long-lived, and produce small broods. Although many of the larger inshore and pelagic
sharks may live for more than 20 years, they may not attain reproductive maturity until their
teens or later. Depending on the species, broods typically contain fewer than ten pups and
a number of species produce no more than two young in any given brood. Moreover,
mature sharks may not reproduce each year. This combination of low reproductive
potential, behavioral characteristics which have served sharks well for their survival over
millions of years, and the potential for exploitation and overfishing, has caused major
concerns for conservation biologists and fishery managers. In past years there have been
fisheries directly targeting some sharks, either for food (for example, sharkfin soup), as
sources of vitamin A (before it was synthesized chemically), or for industrial purposes.
These directed fisheries in past years were largely unregulated, and some sharks were
overfished to the point that fisheries on them became uneconomical after shark
populations declined. The collapse of former fisheries for shark clearly demonstrated the
need for management of this resource. Currently, shark fishing-commercial and
recreational-in the United States is highly regulated to help conserve shark populations
and maintain the health of our marine ecosystems.
Brown, S.T. (1999). Trends in the Commercial and Recreational Shark Fisheries in Florida,
1980-1992, with Implications for Management. North American Journal of Fisheries
Camhi, M., Fowler, S.L., Musick, J.A., Bräutigam, A., and S.V. Fordham (1998). Sharks and
their relatives-Ecology and Conservation. IUCN/SSC Shark Specialist Group. IUCN, Gland,
Switzerland and Cambridge, U.K.
Hart, T.J., and P.J. Hart (1983). Fisheries Ecology. AVI Publishing Company. Westport. CT.
Hoese, H.D., and R.H. Moore (1998). Fishes of the Gulf of Mexico, Texas, Louisiana, and
adjacent waters. Texas A&M Press, College Station, TX.
Weber, M.L., and S.V. Fordham (1997). Managing shark fisheries: Opportunities for
international conservation. TRAFFIC International and Center for Marine Conservation.
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