Understanding cetacean and fisheries interactions in the North-west Iberian Peninsula
- Autores: Fiona Read
- Directores de la Tesis: Maria Begoña Santos Vazquez (dir. tes.), Ángel Francisco González González (dir. tes.), Graham J. Pierce (dir. tes.)
- Lectura: En la Universidade de Vigo ( España ) en 2016
- Idioma: inglés
- Tribunal Calificador de la Tesis: Ruth Fernández García (presid.), María del Mar Sacau Cuadrado (secret.), Santiago Cerviño López (voc.)
- Materias:
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- Resumen
The North West Iberian Peninsula (north-west Spain and north-central Portugal) is one of the world's main fishing areas and high levels of cetacean-fisheries interactions are reported. The Iberian harbour porpoise (Phocoena phocoena) is a genetically distinct population with an estimated abundance estimate of around 2,357 individuals. Around 60% of stranded porpoises showed evidence of fisheries interactions, and no sex- or age-related differences in bycatch were detected. Combining results of a life table and necropsies suggest that there is between 4.3 and 11% annual mortality in the Iberian porpoise population due to fisheries interactions. However, the estimated pregnancy rate would be insufficient to balance mortality.
Life history parameters and patterns in strandings were determined for short-beaked common dolphins (Delphinus delphis) from Galicia, north-west Spain for the period 1990-2009. The majority of strandings were immature animals and males stranded more frequently than females. Around 40% of common dolphins showed evidence of fisheries interactions, and as with the porpoises, there was high interannual variation in the number of dolphins classified as bycaught. Based on results of a life table and necropsies, there is around 5% annual mortality of common dolphins in Galicia due to fisheries interactions.
Face-to-face interviews with fishers were conducted in local fishing harbours in Galicia to quantify economic loss and bycatch rates associated with cetacean-fisheries interactions. Cetacean-fishery interactions are frequent, although damage to catch and fishing gear by cetaceans was mostly reported as small. Over 1,700 cetaceans were estimated to be bycaught annually in Galician fisheries and highest rates were reported for trawls and set gillnets, as is also reported in strandings and on-board observers.
Overall, in the NWIP cetacean and fisheries have a high overlap in their distribution and exploit the same resources, resulting in a high volume of cetacean-fisheries interactions. Estimated annual mortality attributed to fisheries interactions in the NWIP greatly exceeds the current recommendations and is of serious concern for the conservation of Iberian harbour porpoise. Minimising cetacean-fishery interactions requires the implementation of case-specific management strategies with the active participation of fishers, however conservation actions are needed urgently.
