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Types of Sharks
Types of Whales
To most people, sharks are considered the villains of the ocean, animals with whom none wants to cross paths.
Perhaps for that reason, declining shark populations receive less than adequate attention.
The Food and Agricultural Organization (FAO) promoted one of the earliest shark conservation efforts, developing an International Plan of Action for the Conservation of Sharks. It was built on the principle of states voluntarily creating shark management plans for their territorial waters.
Despite this early conservation effort, over the past decade shark populations continued to decline. The latest Atlantic Shark Study, for example, notes:
"The release of the first ever IUCN Red List of Threatened Species assessment of northeast Atlantic sharks, rays and chimaeras reveals that 26 percent are threatened with extinction and another 20 percent are in the Near Threatened category."
Because many shark species swim in oceans that cross state boundaries, devising a workable shark management plan faces many roadblocks. In December 2008, member states of the Convention on Migratory Species (CMS) met to discuss the issue, stating,
"Action is urgently needed to conserve migratory shark populations globally, which according to IUCN data are significantly more threatened than those which do not migrate."
They agreed to pursue another voluntary action plan, this time multilateral in nature, to manage migratory shark populations.
The issue of declining shark populations extends beyond the loss of a couple of species, it possibly means large scale changes in ocean ecosystems.
Their status as predators at the top of the ocean food chain means declining shark populations often correlate with increases in the populations of their preferred prey. A chain reaction sets in with the increased population of lesser predators causing decreases in populations of their (the lesser predators) prey.
Reports on declines in the bay scallop fishing industry, for example, are linked to decreases in the Atlantic shark population. As shark populations declined, the populations of one of their preferred preys, Cownose rays, increased. The cownose rays then began feeding unimpeded on the bay scallop populations.
The report, Why Healthy Oceans Need Sharks documents some of the more common ocean ecosystem changes noted to date. They report,
"Apex predators not only affect population dynamics by consuming prey, but they also can control the spatial distribution of potential prey through intimidation. Fear of shark predation causes some species to alter their habitat use and activity level, leading to shifts in abundance in lower trophic levels. Top predators affect other animals in a cascade effect throughout the ecosystem, ultimately influencing community structure."
Additional InformationThe IUCN/SSC Shark Specialist Group
© 2009. Patricia A. Michaels