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
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 Management
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. Washington, DC.
Florida Museum of Natural History Web site with links to major
shark related sites
National Marine Fisheries Service Marine Recreational Fisheries