The best available biological information for the silky shark, Carcharhinus falciformis, was used to produce a demographic analysis for the silky shark population off the southeastern U.S. Monte Carlo simulation was used to vary natural mortality (M), fecundity (mx), age-at-maturity (tmat) and longevity (tmax) to account for some of the uncertainty in these vital rates. Demographic analyses were run 1000 times to allow estimation of 95% confidence intervals. Under the scenario of natural mortality only, results indicated the silky shark population would grow at a rate of 4.5 %/year (R0 = 2.038, G = 16.223, and r = 0.044). Adding the latest available fishing mortality estimate (F) for large coastal sharks resulted in a population decreasing at a rate of 4.8%/year. Finally, to incorporate the hypothetical effect of gear selectivity on fishing mortality, length frequencies for silky sharks caught on longlines off the southeastern U.S. were used to estimate gear selection at various ages. Demographic analyses that consider hypothetical gear selection, when compared to analyses using constant across-age mortality models, suggest that gear selectivity and the resulting fishing mortality-at-age may be an important influence on demographic model output, and should be considered where possible when using demographic analyses as management tools.
| Identifer | oai:union.ndltd.org:nova.edu/oai:nsuworks.nova.edu:occ_stuetd-1082 |
| Date | 01 January 2000 |
| Creators | Beerkircher, Lawrence R. |
| Publisher | NSUWorks |
| Source Sets | Nova Southeastern University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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