Influence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessment

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dc.contributor.authorBallesta Artero, Irene Mariaen
dc.contributor.committeechairJiao, Yanen
dc.contributor.committeememberOrth, Donald J.en
dc.contributor.committeememberSiegried, Kate Andrewsen
dc.contributor.departmentFisheries and Wildlife Sciencesen
dc.date.accessioned2014-01-14T09:00:12Zen
dc.date.available2014-01-14T09:00:12Zen
dc.date.issued2014-01-13en
dc.description.abstractIn natural sciences, frequentist paradigm has led statistical practice; however, Bayesian approach has been gaining strength in the last decades. Our study assessed the scalloped hammerhead shark population on the western North Atlantic Ocean using Bayesian methods. This approach allowed incorporate diverse types of errors in the surplus production model and compare the influences of different statistical estimators on the values of the key parameters (r, growth rate; K carrying capacity; depletion, FMSY , fishing levels that would sustain maximum yield; and NMSY, abundance at maximum sustainable yield). Furthermore, we considered multi-levelpriors due to the variety of results on the population growth rate of this species. Our research showed that estimator selection influences the results of the surplus production model and therefore, the value of the target management points. Based on key parameter estimates with uncertainty and Deviance Information Criterion, we suggest that state-space Bayesian models be used for assessing scalloped hammerhead shark or other fish stocks with poor data available. This study found the population was overfished and suffering overfishing. Therefore, based on our research and that there was very low evidence of recovery according with the last data available, we suggest prohibition of fishing for this species because: (1) it is highly depleted (14% of its initial population), (2) the fishery status is very unstable over time, (3) it has a low reproductive rate contributing to a higher risk of overexploitation, and (4) the easiness of misidentification among different hammerhead sharks (smooth, great, scalloped and cryptic species).en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:2141en
dc.identifier.urihttp://hdl.handle.net/10919/24819en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectSphyrna lewinien
dc.subjectlogistic production modelen
dc.subjecttypes of erroren
dc.subjectlikelihooden
dc.subjectBayesian approachen
dc.titleInfluence of the Estimator Selection in Scalloped Hammerhead Shark Stock Assessmenten
dc.typeThesisen
thesis.degree.disciplineFisheries and Wildlife Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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