Population assessment and management needs of a green turtle, Chelonia mydas, population in the western Caribbean

In this study I estimated survival rates of large juvenile and adult female green turtles (Chelonia mydas) from mark-recapture data from the Nicaragua foraging ground and from band recovery analysis. I used these data to estimate the long-term growth rate of a simulated population to assess the current status of the Tortuguero, Costa Rica green turtle population. I also examined potential changes to current harvest levels in Nicaragua to estimate sustained yield.; Based on band recovery analysis, large juvenile and adult green turtles tagged at Nicaragua turtle fishing sites and adult females tagged on the nesting beach exhibit low mean annual survival probabilities, x¯ = 0.55 (SE = 0.04) and, x¯ = 0.82 (SE = 0.12), respectively. Based on a series of matrix population projections simulations using these survival rate estimates, there is evidence that the Tortuguero population is probably declining. The severity of the threat, however, depends in part on the proportion of large juveniles from this population that are exposed to the Nicaragua turtle fishery. Based on simulations in which this issue was explored, possibly 40% of large juveniles could be exposed to the Nicaragua fishery and still maintain a stable population, provided the survival rate of the remaining large juvenile population is at least 0.90. These results were based on the model with the most optimistic demographic parameters; other models revealed that 0 or 9% may be exposed to the Nicaragua turtle fishery. It is likely that more than 40% of large juveniles from the Tortuguero population are exposed to the Nicaragua turtle fishery because no other major foraging habitat for large juveniles has been identified.; Estimates of sustained yield ranged from 1,027 to 2,912 large juvenile and adult turtles/yr based on the most conservative model (model with the least optimistic demographic parameters). These results suggest that considerable reductions in the green turtle harvest of between approximately 8,080 and 9,970 turtles/yr are needed based on a current harvest level of 11,000 turtles/yr. Potential mechanisms to reduce the Nicaragua harvest include: a closed season, harvest quotas, size and/or sex restrictions, and zoning fishing areas for variable use.