Sea Cucumbers Going Down in the Seychelles: Will MPAs Help?

Over the last century, increasing demand for marine invertebrates has led to overexploitation by fisheries. As a result, conservation of sea cucumbers, which play critical ecological roles as nutrient recyclers and filter feeders, is becoming increasingly important. Although there are few marine protected areas (MPAs) explicitly designed to protect sea cucumbers, protective regions already established for other species can still help populations recover. To determine the effects of protection on sea cucumber populations, Cariglia et al. (2013) examined a network of long-established MPAs in the Seychelles islands. They conducted scuba studies to count and identify various species in sites both inside and outside the MPAs and grouped them by economic worth. After performing statistical analyses, they found that 76% of all observed individuals were found within the MPAs and that within protected areas, there were both higher species abundance and a greater probability of encountering economically valuable species. The authors also analyzed habitat types and found that species preferred different types depending on whether they were in fished or unfished areas. Although the Seychelles MPAs were not specifically designed to protect sea cucumbers, they were nevertheless effective in facilitating recovery. —Posted by Katie Huang

Cariglia N., Wilson S.K., Graham N.A.J., Fisher R., Robinson J., Aumeeruddy R., Quatre R., Polunin N.V.C., 2013. Sea cucumbers in the Seychelles: effects of marine protected areas on high-value species. Aquatic Conservation: Marine and Freshwater Ecosystems 23, 418–428. http://goo.gl/srYH1K

Cariglia et al. counted the number of sea cucumbers in 21 sites throughout the Seychelles, nine of which were within long-established MPAs. In each site, they examined 16 circular count areas via scuba and identified the species observed. They then grouped species by economic worth to determine whether encounter rates of cucumbers of various consumption values differed. Since habitats can also influence distribution, they recorded benthic regions such as sand, rock, and coral by recording the percentage cover using visual estimation. To analyze their data, the authors performed statistical analyses that calculated the probability of encountering sea cucumbers of various economic values and assessed the effects of habitat and management types on distribution.

Although the distribution of sea cucumbers was highly variable, protection from fishing was an important indicator of whether sea cucumbers of all economic values could be found in the area. The authors found that 76% of all observed sea cucumbers were found within the MPAs, and that the probability of encountering cucumbers within protected areas was twice as high as that in fished areas. Highly valued sea cucumbers were also 10 times more likely to be seen in MPAs. In one highly protected area, medium and high valued cucumbers were significantly more prominent than in the greater MPA areas, where the probability of finding them was 20%. In contrast, lower value cucumbers were seen in approximately 50% of MPA counts. In terms of habitat, the authors found that high and medium value cucumbers were associated with rock and coral while low value cucumbers preferred sand in protected areas and rock in unprotected regions. These preferences have important implications for MPA design, as previous studies have found that habitat requirements can change according to individual development and also depending on the time of day. Thus, MPAs should incorporate various habitat types to account for the differing needs of sea cucumbers in order to create effective protection. The authors also suggest that the size and location of MPAs should be tailored towards the biology and behavior of sea cucumbers, which may require additional research. Since protected regions can also affect gene flow and have spillover effects, a series of interconnected MPAs may be most effective in replenishing depleted stocks. As exploitation continues, MPAs are increasingly vital in helping restore invertebrate populations and should incorporate effective management practices to ensure recovery.

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