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  B. A Unique Glimpse Into Deep Sea Fish Populations

Narrator: This is Science Today. Over the last fifteen years, ocean scientists at the University of California, San Diego's Scripps Institution of Oceanography have been studying fish populations living in the vast, muddy plains on the ocean floor more than 13 thousand feet deep. Researcher David Bailey says their first-of-its-kind study gives researchers a unique glimpse into fish populations unperturbed by human influence.

Bailey: What we did is look at an environment where the fish numbers are not being changed by fishing and what we showed is that the numbers of fish are getting driven by changes in their numbers of their prey.

Narrator: In fact, the researchers found a threefold increase in fish abundance in the deep sea driven by food available to the animals, such as dead plankton and carcasses of fish, mammals and crustaceans that fall to the bottom of the ocean. Bailey says this is called a “bottom-up control”.

Bailey: Because it's driven from the bottom, driven by food availability, whereas what people thought was going on previously was it was top down, which is changes in the numbers of predators drive changes and everything else.

Narrator: For Science Today, I'm Larissa Branin.