Theme D: Developing optimal release strategies
34. Trochus niloticus TRANSLOCATION: PROSPECTS IN ENHANCING DEPLETED PHILIPPINE REEFS
Roger G. Dolorosa, Alastair Grant and Jennifer Gill
School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, England, UK
rogerdolorosa@yahoo.com
The introduction of Trochus niloticus to many isolated islands in the Pacific has expanded its limited distribution range, and it has become an important resource in some of those areas. By contrast, the species is now threatened in the Philippines where it is endemic. Although trochus fishing is now prohibited, uncontrolled exploitation continues, further pushing its remaining populations to the verge of extinction. Trochus have limited mobility and a short larval period so that population recovery in overexploited offshore reef areas could be impossible even after fishing intensity is reduced. Trochus enhancement through the release of hatchery produced juveniles may not be feasible because of high cost and low survival rates. But the translocation of wild trochus appears promising with high survival rates and high growth rates at some sites. Trochus reintroduction to a network of well managed marine reserves is therefore a potential option to revive the country’s depleted reefs. Trochus plays an important role in the food chain and its revival can further enhance reef biodiversity. The success in reviving trochus population by translocation may pave the way to similar conservation strategies for other reef invertebrates.
Figure 1. Scatter graphs (left hand side) between the monthly growth rate (mm mo-1) and median (measured as the mid-point between the sizes at tagging and recapture or sizes at previous and succeeding recapture) shell diameter (mm). On the right hand side are the projected diameters (mm) at age (year) of trochus in the three sites obtained using the von Bertalanffy growth formula.
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