A new study released by researchers from the Wildlife Conservation Society, James Cook University and Lancaster University found that permanent marine-protected areas where fish can thrive and grow old are crucial in order for the effective conservation of marine ecosystems. Whereas previous research focused on the weight of each fish as a measure of ecosystem recovery, the current study looked at the life histories of fish communities and found that, in addition to biomass, much slower changes were necessary for recovery, some taking upwards of 100 years.
"Fish biomass has been the common way to evaluate fish communities, but what our research shows is that it does not tell the entire story," said Timothy McClanahan, co-author of the study, in a press release. "Analyses based primarily on fish biomass produces an incomplete and somewhat misleading scenario for fast recovery from overfishing. What we found was a slow and continuous reorganization of the fish community well past the stabilization of biomass. A full evaluation of marine reserves needs to look at the species and their life histories and, when we do that, we see the importance of protecting ocean wilderness and making permanent and large reserves."
The study used data from more than 300 coral reefs to examine the changes they incurred due to fishing methods and the number of years they were closed to fishing. In addition, they compared the reefs in marine reserves with the remote Chagos Archipelago reef, a fairly untouched marine ecosystem that is off limits to exploitation. The results showed that biomass measures leveled off after a fairly low number of years, whereas other factors such as age, feeding habits and body size continued to change for approximately 40 years. Furthermore, the results predicted that growth rates were to decline for over 100 years.
"The slow growing species in marine reserves could require a century to fully recover, indicated the importance of permanent and large reserves," said McClanahan.
"If you want to protect the longer-lived, slower growing species, you need old, large and high compliance marine reserves," said Nick Graham, a co-author of the study. "The effective protection of the full suite of fish species and life history characteristics will depend on the establishment of large reserves with strict enforcement."
The findings were published in the Dec. 23 issue of the Proceedings of the Royal Society B.
