February 28, 2009

Study: Sharks divide by sex

European scientists say the decline in shark populations might be the result of gender segregation among the predatory fish.

Printed in the Proceedings of the Royal Society B journal, researchers said there is a striking level of sexual segregation among the mako shark in the South Pacific Ocean.

The Australian Broadcasting Corp. reported Wednesday that senior author David Sims of the School of Biological Sciences at the University of Plymouth and his team used data collected from a Spanish commercial fishing boat in the southeast Pacific Ocean between December 2004 and March 2005.

The fishing boat caught 264 male and 132 female mako sharks. Researchers said males occurred predominantly in the western area of the survey region and females dominating in the east.

Male sharks, researchers found, dominate highly fished areas and that has led to population declines.

If high fishing activity occurs in key areas where, for example, the majority of a population aggregate for feeding or mating opportunities there is a potential for increased rates of decline, the study concluded.