Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper
| dc.contributor.author | Vincent, Matthew Timothy | en |
| dc.contributor.committeechair | Jiao, Yan | en |
| dc.contributor.committeemember | Smith, Eric P. | en |
| dc.contributor.committeemember | Murphy, Brian R. | en |
| dc.contributor.committeemember | Walter, John F. | en |
| dc.contributor.department | Fisheries and Wildlife Sciences | en |
| dc.date.accessioned | 2015-05-10T06:00:19Z | en |
| dc.date.available | 2015-05-10T06:00:19Z | en |
| dc.date.issued | 2013-11-15 | en |
| dc.description.abstract | Estimation of natural mortality within statistical catch-at-age models has been relatively unsuccessful and is uncommon within stock assessments. The models I created estimated population-dynamics parameters, including natural mortality, through Metropolis-Hastings algorithms from Gulf of Mexico red-snapper Lutjanus campechanus data. I investigated the influences of assumptions regarding model configuration of natural mortality and selectivity-at-age parameters by comparing multiple models. The results of this study are preliminary due to parameter estimates being bounded by uniform priors and thus a potential lack of convergence to the posterior distribution. Estimation of a natural-mortality parameter at age 0 or a Lorenzen natural-mortality parameter could be confounded with selectivity-at-age-1 parameters for bycatch from the shrimp fisheries. The Lorenzen natural-mortality curve was calculated by dividing the parameter by red snapper length at age. An age-1 natural-mortality parameter might not be estimable with the currently available data. Values of the natural-mortality parameter for ages 2 and older appear to be slightly less influenced by assumptions regarding selectivity-at-age parameters. We conducted a simulation study to determine the accuracy and precision of natural-mortality estimation assuming the selectivity-at-age-1 parameter for bycatch from the shrimp fisheries equaled 1.0 and a Lorenzen natural-mortality curve. The simulation study indicated that initial abundance-at-age parameters may be inestimable within the current model and may influence other parameter estimates. The preliminary simulation results showed that the Lorenzen natural-mortality parameter was consistently slightly underestimated and apical-fishing-mortality parameters were considerably underestimated. The estimation of natural mortality within a statistical catch-at-age model for Gulf of Mexico red snapper has many caveats and requires additional investigation. | en |
| dc.description.degree | Master of Science | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:1697 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/52244 | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | red snapper | en |
| dc.subject | Lutjanus campechanus | en |
| dc.subject | natural mortality | en |
| dc.subject | statistical catch-at-age model | en |
| dc.subject | stock assessment | en |
| dc.subject | population dynamics | en |
| dc.title | Estimability of natural mortality within a statistical catch-at-age model: a framework and simulation study based on Gulf of Mexico red snapper | en |
| dc.type | Thesis | en |
| thesis.degree.discipline | Fisheries and Wildlife Sciences | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | masters | en |
| thesis.degree.name | Master of Science | en |
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