It’s no secret that wildlife conservation is a controversial issue. Despite the best intentions of all who are involved in the process, the costs associated with nurturing a species to recovery can be too high for some. The management strategies can be complex, the newly-protected habitat vast, and the timeframe for recovery unknown. And though they represent some of the most threatened ecosystems in the world, oceanic environments seem to be extremely difficult to protect. One of the issues with marine conservation has to do with how populations are replenished. Many of our ocean’s animals are free-floating larvae early in their life, and for the most part cannot control where they’ll travel. When these young drifters finally get their act together and settle down, they could be miles away from their birthplace. With all this off-the-grid migration going on, it’s no wonder population recovery can be difficult to predict in marine ecosystems.
In an experiment that is eerily similar to the Finding Nemo-inspired reality show hosted by Maury Povich that I pitched to Animal Planet last month (wait by the phone Maury), Planes et al. designed a study to monitor the larval dispersal of clown fish across multiple Marine Protected Areas (MPAs). What they found was that by using a combination of genetic testing and otolith chemistry they could determine the parents and the birthplace of a given juvenile clownfish. This allowed the researchers to calculate how many offspring were leaving their original reef to live elsewhere, and thus how much a reef’s population contributes to the populations of neighboring habitats. Despite having a larval form that lasts only 11 days, it turns out these clown fish can travel up to 35km before finding an anemone home. This level of dispersal can functionally unite two or more MPAs, since offspring from one area can travel to and help repopulate another area.
The good news here is that we now have empirical evidence suggesting fish disperse between a network of suitable habitats. In areas where multiple coral reefs are in decline, allowing a single reef to recover may have a positive spillover effect on the surrounding reefs’ populations. However, the opposite is also true; if a single reef habitat is overfished or otherwise threatened, this could have a negative effect on surrounding reefs as well. Thus, it seems that an important method of recovery in coral reef communities, namely dispersal and recruitment, is contingent upon the health of neighboring reefs as well.
I find the Planes et al. study beneficial to marine biodiversity for a number of reasons. First, this connection between MPAs may help policy makers better coordinate the design and implementation of protected areas, so that marine populations receive the maximum benefit. Second, the techniques used in delineating parentage in these clown fish appear to be applicable to a wide variety of fish species. Overall, this work appears promising for the future of marine conservation, in that it may help us more accurately understand how to protect endangered populations. And with all the current and future threats to our ocean’s health, maintaining its biodiversity has never been more important.
November 26, 2013