Mediterranean Grouper

Collaborators: Dr. Mikel Zabala, Dr. Bernat Hereu and Dr. Christine Linares – University of Barcelona

In the Mediterranean Sea, overfishing has driven Mediterranean grouper stocks below sustainable levels and has even eliminated them from much of their range. The Medes Islands Marine Reserve was established in the early 1990s near L’Estartit, Spain, in order to provide refuge for some of the last remaining Mediterranean groupers. Researchers from the University of Barcelona and the Fisheries & Conservation Biology Lab at MLML have been studying population trends and movements of Mediterranean groupers, seabreams, and other fished species in the Medes Islands Marine Reserve in order to determine if the marine reserve has been successful in increasing populations of fished species.

Using SCUBA techniques, we caught about 20 Mediterranean groupers underwater, by hand feeding baited hooks to selected male and female groupers. Once fish were caught, we brought them by hand to the surface, anesthetized them, and surgically implanted sonic transmitters in their peritoneal cavities. We then placed receivers around the marine reserve to determine site fidelity and movements of individual fish. We have also tagged two other species of commercially important fishes in the Medes Islands.

In the first year of the project, we documented that Mediterranean groupers did not leave the marine reserve. Thus, the increase in numbers of groupers seen at the reserve is due to increased productivity in the reserve, and not migration. Our work has changed the understanding of the value of the Medes Island Marine Reserve for conserving populations of Mediterranean groupers. Resource managers now know that there is not a large migration through the reserve, but that the reserve is working to increase grouper numbers. This will change the perspective on the value of marine reserves around the world.

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