Reef fish don’t care where conservation lines are drawn
In recent years, marine protected areas, or MPAs, have proliferated around the world and in particular in the Caribbean. But no one seems to have told the fish.
A new study in PLoS One uses miniature acoustic transmitters implanted into 19 species of reef fish to suggest that while most fish do stay fairly close to home inside MPAs, plenty of them do not, and travel widely into areas that do not offer the same protections. The research group, led by NOAA scientist Simon J. Pittman (currently based at the Marine Institute at Plymouth University), says that MPAs and other conservation and management efforts should take this information on reef fish mobility into account.
The study involved tracking 184 individual fish caught and tagged between 2006 and 2008 within the Virgin Islands National Park. A network of acoustic monitors deployed around four different protected areas kept track of fish movements over the course of more than three years. A total of 163 of the fish were actually recorded an amazing 2,848,192 times. The fish included little guys like the blue tang, five different species of snapper and three grunt species, and others on up to the nurse shark.
They found that fish travel surprisingly far. Three-quarters of the fish traveled more than one kilometer, and 33 percent of them moved at least five kilometers. Twenty-eight individuals even made one kilometer journeys or greater within a single 24-hour period; three of them made it almost 15 kilometers in a single day. Only 11 fish never made it more than 500 meters from their first position, though the researchers note that they simply could have been out of range of the acoustic sensors and really did travel more widely.
But most importantly, these long-distance voyages meant that the fish crossed boundaries of MPAs with impunity. Twelve of the 18 species engaged in boundary crossing, and 25 percent of individual fish crossed at least once. Some individual fish made multiple crossings between more than just two of the MPAs; one mutton snapper made a 40.2-kilometer journey from one MPA to another through completely unprotected areas. It’s as if the oceans are all connected and fish can go wherever they want! Here’s that snapper’s estimated journey:
Protected areas of ocean probably should better consider exactly how the fish being protected tend to move around. The authors write: “Re-scaling MPAs to more fully encompass ecological neighborhoods for a group of target species could make major advances in achieving conservation goals.” By following physical boundaries along ocean floors more carefully, MPAs might also be more likely to mirror where the fish choose to wander.
If we want to prevent further collapse of reef fisheries, this type of information is going to prove extremely valuable. Simply drawing a line around what looks like a self-contained reef system is a start, but the fish don’t read maps very well. We need to adapt to them, rather than the other way around. - Dave Levitan | May 13 2014
Source: Pittman SJ, Monaco ME, Friedlander AM, et al (2014). Fish with chips: Tracking reef fish movements to evaluate size and connectivity of Caribbean marine protected areas, PLoS One, 9 (5) e96028. DOI: 10.1371/journal.pone.0096028
Image: shutterstock.com, Amanda Nicholls
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