- Adult fishes moved from 6 western Mediterranean marine reserves, where they were most abundant and reached their largest sizes, into nearby fished waters.
- Grouper eggs drifted outside the Cabrera reserve in Spain to surrounding waters.
Western Mediterranean
Fast Facts
Photos
An adult dusky grouper
Photo by Robert Patzner
Photo by Robert Patzner
A Mediterranean fisherman hauls in his catch
Photo by Paolo Guidetti
Photo by Paolo Guidetti
Fishes Move Outside Mediterranean Marine Reserves
In 2003, scientists and fishermen began a collaborative study of 6 well-enforced marine reserves in the western
Mediterranean. Their goal was to determine whether the young and the adults
of dozens of commercial fish species move outside fully protected areas, potentially enhancing surrounding fisheries.
of dozens of commercial fish species move outside fully protected areas, potentially enhancing surrounding fisheries.
They found that across all 6 reserves, average fish biomass was 4.7 times higher and average fish weight was 3.4 times higher inside the reserves than in the surrounding fished areas. Through their video and SCUBA observations, scientists discovered that fish biomass decreased consistently across the reserve borders and into fished areas, indicating that adults were spilling over into fished waters. Data on fishing effort and catches confirmed that fishing boats concentrated near marine reserve boundaries (see example at right), where catch rates were higher.
These marine reserves also appear to be a source of fish eggs that can drift outside and support populations beyond the reserve borders. Greater numbers and sizes of adult fish within reserves can produce eggs and young that are exported to fished areas. For example, at Spain’s Cabrera reserve, grouper eggs decreased in density from inside the reserve to surrounding fished waters (see figure below) where groupers are rare. Such data provide mounting evidence that reserves can benefit local fisheries by protecting important spawning grounds for commercial fish species.
References
1. Crec’hriou R, et al. (2010) Fisheries Oceanography 19: 132–150
2. Harmelin-Vivien ML, et al. (2008) Biological Conservation 141: 1829–1839
3. Stelzenmüller V, et al. (2008) Marine Pollution Bulletin 56: 2018–2026
Visit the PISCO Website
Visit the website of the Partnership for Interdisciplinary Studies of Coastal Oceans to learn more about the Science of Marine Reserves. There you can download our booklets, video series, and high-resolution figures.
