CORVALLIS A new study of marine ecosystems suggests that the preservation of biodiversity is more than just a lofty goal - it's an absolute necessity to keep the system healthy and prevent both local or regional extinction of multiple species.
The population balance between various fish species, their competitors and their predators are all essential to the proper functioning of the ecosystem, the study showed, and overfishing of any one species can have ripple effects that destabilize the whole fishery.
The study was conducted by marine zoologists at Oregon State University and published this week in a professional journal, the Proceedings of the National Academy of Sciences. It was done on coral reefs in the Bahamas, which allowed the type of experimental manipulations that are usually impossible to do in a marine ecosystem.
"The research showed that all fish species within a food web are connected with one another, and the removal of any one species can cause whole populations to break down," said Mark Hixon, an OSU professor of zoology. "This is especially true when you take away the predatory species, which are a key to the natural balance and health of marine ecosystems." The study is particularly relevant to the global problems now being experienced in many commercial fisheries, Hixon said, because many of the fish species most commonly targeted by fisheries are marine predators.
In particular, this study confirmed the operation in a marine ecosystem of a concept that has long been recognized with animals in terrestrial ecosystems that of "density dependent mortality." Basically, when a species population size is low, the mortality rate will also be low predators tend to target species that are more abundant. And when a species population is high, the mortality rate will increase, as predators take advantage of the easy availability of food.
Other than the interaction between prey and predator, Hixon said, there is
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Contact: Mark Hixon
hixonm@bcc.orst.edu
541-737-5364
Oregon State University
21-Aug-2002