Fisheries interactions of Delphinus delphis in the north-east Atlantic with an emphasis on Galicia, north-west Spain.

Bycatch from interactions with fisherie s remains the biggest global threat to marine mammals. Galicia, north - west Spain, is one of the world’s main fishing regions and a high level of cetacean - fisheries interactions has been reported from on - board observers, interviews with fisheries stakeholde rs and analysis of stranded and by - caught carcasses. Delphinus delphis is the most abundant cetacean in the area and since 1990 necropsies of over 1800 stranded and by - caught Delphinus have been conducted. Life history data (age, maturity, and pregnancy ra te data) from stranded and by - caught cetaceans can be used to construct life tables and to estimate overall mortality and fisheries mortality rates. Age and maturity were determined from stranded and by - caught Delphinus between 1990 and 2009. Males and fem ales reach sexual maturity at 8.5 and 7.5 years of age, respectively, and no temporal difference in age at sexual maturity was observed. Results indicate 13% annual mortality in the Delphinus delphis north - east Atlantic population and necropsy data suggest s that 60% of mortality (i.e. 7.2% annual mortality) is attributable to fisheries interactions, predominantly from pair trawls and gillnets. By - caught Delphinus were found to die significantly younger than non - by - caught animals (p=<0.001) although no sex - r elated difference in bycatch rate was observed (p=0.051). The estimated annual mortality due to fisheries interactions greatly exceeds the 2% limit set by ASCOBANS and the IWC and high bycatch rates are also reported for other countries e.g. the UK, France and Portugal. Although Delphinus delphis in the north - east Atlantic is one continuous population, the high level of bycatch occurring in parts of the range is most likely unsustainable and will be discussed. There is a need to carry out on - board monitorin g, notably in the north - west Iberian Peninsula (Galicia and Portugal), to incorporate cetacean bycatch into fisheries advice and, above all, to start introducing mitigation measures

Evaluación del estado ambiental de la población de delfín común en el norte y noroeste de la Península Ibérica

El objetivo de las Estrategias Marinas es permitir el uso sostenible del medio marino mediante la gestión de las actividades y presiones humanas siguiendo un enfoque ecosistémico. La evaluación del estado de conservación de las especies marinas y su monitorización para determinar si alcanza el Buen Estado Ambiental (BEA) son sus pilares básicos. Para establecer medidas de gestión que permitan a una población alcanzar el BEA, se debe estudiar el estado de la misma y el efecto que diferentes niveles de amenazas antropogénicas pueden tener sobre ella. La creación de modelos dinámicos permite estudiar las posibles trayectorias de una población ante diferentes escenarios. La fuente de información biológica más importante que poseemos es aquella proveniente de los varamientos, que también proporcionan información sobre la causa de la muerte. El análisis de las muestras de individuos varados nos permite calcular tasas de natalidad, mortalidad, estructura de edad poblacional y el impacto directo o indirecto de las presiones antropogénicas (captura accidental, colisiones con embarcaciones, contaminación, etc.). Asimismo, los patrones observados en los varamientos nos dan información sobre la tendencia en la abundancia de una especie y sobre posibles desplazamientos. La abundancia de una población puede ser obtenida mediante campañas de avistamiento y, dependiendo de la metodología empleada, pueden obtenerse estimas relativas o absolutas. Además, la dieta de los cetáceos nos permite estudiar sus preferencias alimentarias y el papel que pueden estar jugando en el ecosistema. Los modelos multiespecíficos (p.ej. Gadget) posibilitan estudiar su interacción con los stocks pesqueros e informar una gestión ecosistémica. En este trabajo se presentan datos preliminares sobre abundancia del delfín común en el N y NW peninsular, tendencias en la abundancia, parámetros biológicos y su estructura poblacional, mortalidad natural, pesquera y ejemplos de puntos de referencia que permitan determinar si la población alcanza el BEA

Cetacean-fishery interactions in Galicia (NW Spain): results and management implications of a face-to-face interview survey of local fishers

Galicia (NW Spain) is an important fishing region with a high potential for cetacean–fishery interactions. Cetacean depredation on catch and damage to fishing gear can potentially lead to substantial economic loss for fishers, while cetacean bycatch raises conservation concerns. With the aim of gathering information on the types and scale of interactions and of suggesting possible management strategies, we conducted face-to-face interviews with fishers in local fishing harbours, in particular to identify specific problematic interactions and to quantify the level of economic loss and bycatch rates associated with these interactions. We found that cetacean–fishery interactions are frequent, although damage to catch and fishing gear by cetaceans was mostly reported as small. Nevertheless, substantial economic loss can result from common bottlenose dolphins (Tursiops truncatus) damaging coastal gillnets and from short-beaked common dolphins (Delphinus delphis) scattering fish in purse-seine fisheries. Cetacean bycatch mortality was reported to be highest for trawls and set gillnets, and probably exceeds sustainable levels for local common and bottlenose dolphin populations. Although interview data may be biased due to the perceptions of interviewees, and therefore should be interpreted with care, the methodology allowed us to cover multiple sites and fisheries within a reasonable time frame. Minimizing cetacean–fishery interactions requires the implementation of case-specific management strategies with the active participation of fishers. For set gillnet and purse-seine fisheries, the use of acoustic deterrent devices (pingers) may prevent cetaceans from approaching and getting trapped in the nets. For trawl fisheries, where bycatch appears to be particularly high at night in water depths of 100–300 m, possible solutions include the implementation of time/area closures and the relocation of some fishing effort to deeper waters.Publicado