Overexploitation of Species

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Overexploitation of species affects the loss of genetic diversity and the loss in the relative species abundance of both individual and/or groups of interacting species. Overexploitation may include over fishing and over harvesting.

Historically, humans have fished the oceans, which never seemed to pose a problem due to their abundant resources. Gear (fish trap, gill nets, electrofishing) and vessel efficiency modifications have caused a significant decrease in fish populations. In particular, increasing human populations have placed increasing demands on the sea as a source of food. The overall catch has decreased fish stocks in many areas of the United States, as catches in each area exceed the maximum number of fish that these fishermen are allowed to take.

Incidental by-catch from fisheries operations also contribute to the decline in aquatic biodiversity. By-catch is the accidental capture of unmarketable or restricted commercial fishing species, which takes place during fishery operations. By-catch can include marine mammals, sea turtles, seabirds, and sharks. For example, sharks are a by-catch product in tuna and swordfish fisheries operations. The World Wildlife Fund documents that the number of sharks discarded in Hawaiian-based tuna and swordfish operations increased by 2500 between 1991 and 1999. Most of the time the entire shark is discarded at sea with the exception of their fins, since shark fins in demand as they are considered a delicacy in Asian culture.

Freshwater populations have also been affected by overfishing. For example, Lake Erie trout populations have also suffered as a result of overfishing and environmental stress. In addition, overfishing has caused the extinction of blue pike and the decline in whitefish, walleye, and sturgeon populations.

Humans are responsible for removing about 8% of the total primary production from aquatic ecosystems annually. Each year, we harvest and consume more than one fourth of the annual fish production of ocean upwelling regions and tropical marine shelves. In addition, we remove about 35% of temperate shelf region productivity. Over harvesting to this extent can greatly affect the biodiversity of many important aquatic ecosystems and local industry and the economy. For example, over harvesting was one of the key factors contributing to the former decline in the Chesapeake Bay native oyster population. If exploitation is allowed to continue at increasing rates, not only will aquatic ecosystems experience a loss in biodiversity, but also the composition of species within specific habitats could change, causing severe shifts in species dominance and survival ability.

Additional Resources:

Biological Indicators | Aquatic Biodiversity | Statistical Primer

Overexploitation of Species

To learn more about the major threats to aquatic biodiversity please select from the following:

Additional Resources:

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