Incidental catch (bycatch) in fisheries is one of the major threats to marine mammal populations worldwide. The harbour porpoise (Phocoena phocoena, Linneaus 1758) is one of the most common cetaceans in northern Europe. Previous studies have reported high bycatch numbers of harbour porpoises in gillnet fishing operations in the North Sea and Skagerrak Sea. With the aim of disentangling the driving factors behind bycatch of harbour porpoises, I looked at the relationship between occurrence of harbour porpoise bycatch and properties of fishery and porpoise density. Parameters of fishing effort, gear characteristics and operations of 951 sets of strings of cod and pollack bottom set gillnets were collected by an on-board observer programme in the Swedish Skagerrak and Kattegat Seas during 1995-1997. Porpoise density data was generated from satellite tracking locations of 116 individuals from 1997 to 2016. Generalised linear models with binomial distribution were applied to identify the relationships between the occurrence of porpoise bycatch and seven explanatory variables extracted as soak time, string length, net height, mesh size, net bagginess, water depth and porpoise density. During the observer programme, a total of 21 porpoises were bycaught during 10,174 km*h of observed fishing effort. The total bycatch was estimated to be 2.6% of the population abundance at that time, i.e. above the maximum sustainable total anthropogenic removal (1.7%). Soak time, string length and water depth were identified to be positively related to bycatch occurrence. The findings provide guidance for bycatch mitigation measures in terms of adjusting fishing operations, improving gear and establishing separate management units. Modelling can be used to predict possible spatio-temporal high-risk hot spots for harbour porpoise as well as other marine-living species to optimise future monitoring efforts.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-02-12T17:34:13Z No. of bitstreams: 1 robsonhenriquedecarvalho.pdf: 3308952 bytes, checksum: 15b338c6950df1516539e069a54dbee2 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-02-26T12:21:34Z (GMT) No. of bitstreams: 1 robsonhenriquedecarvalho.pdf: 3308952 bytes, checksum: 15b338c6950df1516539e069a54dbee2 (MD5) / Made available in DSpace on 2016-02-26T12:21:34Z (GMT). No. of bitstreams: 1 robsonhenriquedecarvalho.pdf: 3308952 bytes, checksum: 15b338c6950df1516539e069a54dbee2 (MD5) Previous issue date: 2014-02-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A costa brasileira é área prioritária para conservação das tartarugas marinhas, pois cinco das setes espécies de tartarugas existentes no mundo podem ser encontradas no Brasil, estando todas ameaçadas de extinção. As ameaças para esses animais incluem: Ocupação da costa, poluição, doenças e principalmente capturas incidentais em artefatos de pesca. Resgatar a sabedoria popular de pescadores e o conhecimento local é essencial para a conservação desses quelônios. O Objetivo desse trabalho foi apresentar e comparar o conhecimento de pescadores sobre tartarugas de três cidades do sul do Espírito Santo. O estudo foi realizado nas cidades de Anchieta, Piúma e Guarapari, ES, Brasil. As informações relacionadas ao conhecimento local e interação entre as pessoas e tartarugas marinhas foram coletadas através de entrevistas utilizando questionário semiestruturado. Foram entrevistados 44 pescadores e 7 marisqueiras, sendo 19 pescadores em Piúma, 5 pescadores e 7 marisqueiras em Guarapari e 20 pescadores em Anchieta. A tartaruga-de-couro é mais conhecida em Piúma e a verde a mais conhecida em Anchieta e Guarapari. As características que permitem diferenciar os animais são formas do casco e cor e os animais são conhecidos por vários nomes populares. Em Piúma e Anchieta foram citadas altas taxas de captura em rede e consumo de carne de tartaruga. As atitudes em relação as tartarugas marinhas e o conhecimento sobre a reprodução desses animais são diferentes em cada cidade devido a fatores como: Cidade que reside e arte de pesca. Os resultados desse estudo indicam que a conservação de quelônios marinhos requer conhecimento das práticas diárias de comunidades locais e as peculiaridades envolvidas na relação entre os pescadores e as tartarugas marinhas, além do levantamento dos impactos causados pelas práticas diárias. / The Brazilian coast is a priority for conservation of sea turtles, because five of the seven species in the world and they can be found in Brazil and all of them are endangered. The threats to this animal include: Occupancy of the coast, pollution, disease and mostly incidental catches in fishing artifacts. Rescue the folk wisdom of fishermen and local knowledge is essential to the conservation of these turtles. The aim of this present study was to show and compare the knowledge of fishermen on turtles from three cities in southern of Espírito Santo. The study was conducted in the cities of Anchieta, Piuma and Guarapari, ES, Brazil. The information related to local knowledge and interaction between people and sea turtles were collected through interviews using a semistructured questionnaire. Forty-four fishermen and seven seafood were interviewed, where nineteen were fishermen on Piuma, five fishermen and seven seafood in Guarapari and twenty fishermen in Anchieta. The leatherback turtle is best known in Piúma and the Green one is best known in Anchieta and Guarapari. The characteristics to differentiate these animals are shell shape and color and they are known by several common names. In Piuma and Anchieta were cited high rates of capture on fishing net and consumption of turtle meat. Attitudes and knowledge about reproduction is different in each city due to factors such as location and fishing gear. The results of this study indicate that the conservation of marine turtles requires knowledge of the practices of local communities and the peculiarities involved in the relationship between fishermen and turtles, and a survey of impacts caused by everyday practices.

Ce travail de thèse s'insère dans une démarche globale d'acquisition des connaissances sur la tortue verte (Chelonia mydas) dans l'océan Indien occidental et ce afin de disposer d'éléments scientifiques essentiels à la mise en place d'une gestion cohérente et efficace de cette espèce menacée. Dans un premier temps, appliquant différentes modèles statistiques, ce travail a visé à établir des données de référence sur l'abondance des tortues vertes femelles en reproduction et les tendances sur le long terme des principales populations. Dans un second temps, il a consisté à déterminer la structure génétique et les relations qui existent entre les différentes populations de cette espèce. Enfin, la conservation des tortues marines étant étroitement liée aux pressions extérieures, ce travail a tenté dans un troisième temps de caractériser les pressions anthropiques qu'elles subissent, et notamment celles liées à la pêche. L'ensemble de ces résultats a permis de réaliser des avancées majeures dans la connaissance de la biologie et de l'écologie de la tortue verte et de disposer d'une vision régionale fiable de l'état de conservation de cette espèce dans l'océan Indien occidental. Leur compilation a ainsi permis d'identifier des zones régionales prioritaires de protection mais aussi des sites de vigilance plus spécifiques comme celui d'Europa. Enfin cette synthèse met en lumière les priorités de recherche et les approches scientifiques à favoriser à l'avenir pour améliorer les connaissances et affiner les priorités de conservation non seulement des tortues marines, mais aussi de la mégafaune marine en général. / This thesis is a comprehensive work aiming to improve scientific knowledge on the green turtle (Chelonia mydas) in order to provide key scientific evidences needed for the implementation of coherent and effective management measures to protect at the Western Indian Ocean scale this threatened species. In a first step, this work aimed to established baseline data on the abundance of green turtles nesting females and long term trends of some key nesting populations of the region by applying different modelling methods. In a second step, this work determined the regional genetic structure of this species and the relationships that exists between the different populations. Finally, the conservation of marine turtles being closely dependant to external pressures, this work tried to characterize theanthropogenic pressures they face, more specifically those related to fishing activities. All these results allowed unraveling some key gaps on the biology and ecology of the green turtle in the region and led to a global vision of the conservation status of this species in the Western Indian Ocean. The compilation of the results enabled the identification of regional priority areas for protection, but also some more specific threatened sites such as Europa. Finally, this synthesis shedslight on research priorities and scientific approaches to be promote in the future to unlock other keyscientific issues and refine conservation priorities, not only of marine turtles, but also of marine megafauna as a whole.