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Analysis of Atlantic sea scallop (Placopecten magellanicus) fishery impacts on the North Atlantic population of loggerhead sea turtles (Caretta caretta)
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  • Alternative Title:
    Atlantic sea scallop (Placopecten magellanicus) fishery impacts on the North Atlantic population of loggerhead sea turtles (Caretta caretta)
  • Description:
    "An estimated 619 loggerhead turtles of various age and sex classes were taken annually during 1989-2005 in all components of the US Atlantic sea scallop (Placopecten magellanicus) fishery. We provide here a quantitative assessment of the potential for these takes to jeopardize the continued existence of the US Atlantic Ocean population of loggerhead sea turtles (Caretta caretta). A population viability analysis (PVA) was used to estimate quasi-extinction likelihoods under conditions with and without fishery effects. This PVA used US index nesting beach data for 1989-2005 to estimate the loggerhead population trend ? (mean growth rate) and variance ?2. The starting population (N0) for the exercise was the sum of nesting females estimated from the 2005 nest count in the North Carolina to Florida area. The base model (with fishery bycatch) was developed by using estimates of ? (-0.022), ?2 (0.012), N0 (34,881) and a quasi-extinction threshold of 250 adult females. Quasi-extinction likelihoods were bootstrapped (1000 iterations) under baseline conditions to derive confidence intervals. The ? for each bootstrap iteration was drawn from a normally distributed random sampling of ? values lying within the 95% confidence interval around the original ?. The model was then rerun with the estimated annual fishery mortality of adult females (102 turtles) added back into the population, thus changing the trend (? = -0.019, ?2 = 0.012, and N0 = 34,881). Results of the two models were similar; the quasi-extinction probabilities were zero at 25, 50, and 75 years, and 0.01 at 100 years for both analyses. Median times to quasi-extinction were 207 years versus 240 years, and the number of bootstrap simulations with extinction probabilities greater than 0.05 in 100 years was 258 and 178, respectively. These results suggest that the annual take of loggerhead sea turtles in the US fisheries for Atlantic sea scallops, though detectable, does not significantly change the calculated risk of extinction of the population of adult female Western North Atlantic loggerheads over the next 100 years"--Abstract.

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