Migration, Markets, and Mangrove Resource Use on Kosrae, Federated States of Micronesia

Population Characteristics of the Mangrove Crab Scylla serrata (Decapoda: Portunidae) in Kosrae, Federated States of Micronesia: Effects of Harvest and Implications for Management1

“…Although our analysis of spatial variation in attrition rates indicates that harvest is a major source of mortality of mangrove crabs on Kosrae, exactly how much harvest contributes to attrition is difficult to resolve with the available data. Measures of attrition rates and catch-per-unit-effort among the four sites mutually suggest that harvest effects are not negligible and are likely to be substantial (see also Naylor et al 2002). Moreover, the similarity between our estimates of catch-perunit-effort and those reported for populations of S. serrata in South African estuaries considered to be too small to support a commercial fishery (0.50-0.95 crabs trap À1 night À1 [this study]; 0-1.67 crabs trap À1 night À1 [Robertson 1996]) suggests that the crab population on Kosrae might not be able to sustain increased, or perhaps even current, levels of harvest.…”

“…Recent socioeconomic studies show that despite apparent declines in catch-per-uniteffort and harvest effort (households engaged in harvest and number of trips per month) during the 1990s, export of crabs for sale and as gifts actually increased substantially, by factors of 8 and 2.5, respectively, from 1997 to 2000 Drew 1998, Naylor et al 2002). Anticipated economic and human population trends are likely to increase demand for this valuable resource, as well as place greater pressures on the mangrove forests that provide key habitat for the species (Naylor et al 2002, Hauff et al 2006). Such trends, and a general sense among Kosraeans that mangrove crabs are becoming increasingly scarce, have raised concerns regarding the sustainability of current harvest levels and persistence of mangrove crabs as a viable and valuable resource.…”

“…Mangrove crabs have historically been the focus of an artisanal fishery on Kosrae, with almost all crabs being captured by removal from burrows by hand or with simple tools, by ''torch fishing,'' which entails walking the reef flats at night during low tides seeking crabs and other target species, with baited lines and more recently with baited traps (Perrine 1978, Smith 1992. Most households on Kosrae harvest crabs from nearby mangrove forests, but larger-scale family-based commercial fisheries emerged in the 1990s in Tafunsak and Utwe, where they are said to have substantially increased harvest rates (Naylor et al 2002). Before this study, there was no restriction on mangrove crab harvest, but a minimum size limit for retention of 6 inches (152 mm) was enacted in 2000.…”

“…Before this study, there was no restriction on mangrove crab harvest, but a minimum size limit for retention of 6 inches (152 mm) was enacted in 2000. In contrast to many fisheries on relatively longlived, large crustaceans in North America, Australia, and elsewhere, in which harvest is restricted to males, female crabs-including those bearing eggs-are commonly retained on Kosrae (Naylor et al 2002).…”

Ecosystem Services, Well-Being and Deltas: Current Knowledge and Understanding

“…Migration can cause degradation of ecosystem services through migration to forest and other frontiers, particularly when migrants are unfamiliar with new agroecosystems and risks (Winkels 2008). Migration can also cause the degradation of ecosystem services through the investment of remittances in capital-intensive enterprises such as shrimp farming or cash crops (Adger et al 2002;Naylor et al 2002). At the same time, shocks to ecosystem services directly affect migration, with evidence from Bangladesh, for example, showing that crop failures induce additional temporary migration, but there are 'significant barriers to migration for vulnerable households' (Gray and Mueller 2012 p. 6000).…”