In 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). / Master of Science

Submitted by (edna.saturno@ufrpe.br) on 2017-02-17T14:32:33Z No. of bitstreams: 1 Natalia Priscila Alves Bezerra.pdf: 2116155 bytes, checksum: 25ac05e8bfcb1edeee75fcfaf93d7ec7 (MD5) / Made available in DSpace on 2017-02-17T14:32:33Z (GMT). No. of bitstreams: 1 Natalia Priscila Alves Bezerra.pdf: 2116155 bytes, checksum: 25ac05e8bfcb1edeee75fcfaf93d7ec7 (MD5) Previous issue date: 2013-02-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The hammerhead shark (Sphyrna lewini) has a circuntropical distribution, ranging from coastal and semi-oceanic tropical and temperate regions to and island ecosystems. Located near the equator, the Saint Peter and Saint Paul Archipelago (SPSPA) is a group of small islands where hammerhead sharks are frequently observed. For that reason, the SPSPA was selected for the study of hammerhead shark movements, through satellite tagging, using PSAT (Pop up satellite archival transmitting tag).Three females were tagged, two in October 2010 (TM 1: 250 cm TL e TM 2: 260 cm TL), and one in March 2012 (TM 3: 200 cm TL). Although all tags were programmed to remain attached to the animals, collecting data, for 70 days, TM 1 and TM 2 tags were released prematurely, on the 7th and 5th day of monitoring, respectively. TM3 tag was released at the programmed date. According to the deploy and pop-up information (TM 1 e TM 2) and geolocation (TM 3), all sharks remained in SPSPA surroundings during the monitoring period, diving at great depths, mainly during the night, with the deepest dive of 728 m being recorded for TM 3. TM 1 and TM 2 had a depth preference between the surface and 150 m, while TM3 had a more restricted depth preference (surface to 75 m) during both periods, day and night. The temperature profile indicated that the three tagged hammerhead sharks preferred to be in temperatures between 24° C and above 26°C. Despite the great amount of time spent by all sharks in depths attributed to thermocline in SPSPA, the specimens moved from the mixing layer to the mesopelagic zone. In spite of the relevance of the obtained information for the understanding of the species movement patterns, complimentary studies are yet necessary to elucidate its migratory behavior. / O tubarão martelo (Sphyrna lewini) apresenta distribuição circuntropical, abrangendo desde as áreas costeiras e semi-oceânicas das regiões tropicais e temperadas até aos ecossistemas insulares. Localizado próximo à região equatorial, o arquipélago de São Pedro e São Paulo (ASPSP) é um conjunto de pequenas ilhas onde existe a ocorrência do tubarão martelo. Por essa razão, o ASPSP foi o local escolhido para o monitoramento via satélite da espécie através da utilização do transmissor eletrônico PSAT (Pop up satellite archival transmitting tag). Foram marcadas três fêmeas, duas em outubro de 2010 (TM 1 e TM 2) medindo 250 cm e 260 cm (CT), respectivamente, e uma última em março de 2012 (TM 3) com 200 cm de CT. Embora os três transmissores os três transmissores tenham sido programados para coletarem dados por 70 dias, ocorreu o desprendimento prematuro das marcas do TM 1 e TM 2, após um período de fixação aos tubarões de apenas 7 e 5 dias, respectivamente. De acordo com os dados de marcação e soltura dos transmissores (TM 1 e TM 2) e de geolocalização (TM 3), os três tubarões permaneceram no entorno do ASPSP durante o período em que foram monitorados. Os três espécimes foram capazes de realizar incursões frequentes a grandes profundidades principalmente durante a noite, com o mergulho mais profundo registrado a 728 m, atribuído ao TM 3. Os tubarões TM 1 e TM 2 frequentaram preferencialmente as profundidades entre a superfície e 150 m tanto de dia quanto à noite. Já o TM 3 passou a maior parte do tempo em uma faixa que variou entre a superfície e 75 m de profundidade em ambos os períodos. Os perfis de temperatura indicaram que os três espécimes permaneceram com maior frequência em águas aquecidas, entre 24 °C e acima de 26 °C, no período diurno e noturno. A despeito do elevado tempo de permanência dos três tubarões em profundidades atribuídas à termoclina nas proximidades do ASPSP, os espécimes se deslocaram desde a camada de mistura até a zona mesopelágica. Apesar da relevância das informações obtidas para a compreensão dos padrões de deslocamento da espécie, são necessários ainda estudos complementares para elucidar o seu comportamento migratório.