Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/61103
Title: Interactions between fish farming, wild fish populations, local fisheries and society: a case study in Catalonia, Spain
Author: Bacher, Kathrin
Director: Gordoa Ezquerra, Ana C.
Canals Artigas, Miquel
Keywords: Aqüicultura marina
Peixos marins
Indústria pesquera
Mariculture
Marine fishes
Fishing industry
Issue Date: 10-Oct-2014
Publisher: Universitat de Barcelona
Abstract: [spa] Esta tesis persigue avanzar en el conocimiento de las interacciones de la piscicultura marina, de carácter multidisciplinar y estructurada en tres áreas: ecología (capítulos 1 y 2), pesca (capítulo 3) y ciencias sociales (capítulo 4). En el área de ecología, se analizó la extensión espacial y temporal del efecto atractor de peces salvajes sobre dos tipos de granjas: atún rojo (Thunnus thynnus) y dorada (Sparus aurata). En ambas el efecto atractor se restringía al límite de las jaulas, variando estacionalmente y en profundidad. Las diferencias entre granjas, permanente en doradas y estacional en atunes, se deben a diferencias en la composición específica asociadas con la localización y tipo de cultivo. El análisis de la variabilidad interna en la comunidad íctica se analizó ya que podría ser un factor distorsionador en la estimación del efecto atractor. Los resultados mostraron que la abundancia de peces en superficie disminuía significativamente en los períodos de no alimentación y durante la alimentación las concentraciones de peces disminuían en función de la distancia al barco alimentador. Por el contrario, la variabilidad de agregación en el fondo dependía exclusivamente del tipo de sustrato. La interacción con la pesca artesanal se evaluó con el fin de conocer si las granjas actúan como zonas de protección o como trampas para los peces salvajes. Los resultados no mostraron beneficio, detrimento o diferencia de la pesca en las proximidades de la granja respecto a zonas distantes (en términos de producción, ingresos y composición de las capturas). El análisis de la percepción de la acuicultura, indicador del escenario de aceptación y de elementos clave para su desarrollo, se realizó sobre cinco grupos de interés (ONGs, pescadores locales, industria de la piscicultura, científicos y administración regional) en el marco regional de Cataluña. Se identificaron cuatro percepciones; dos claramente divergentes y dos de posturas intermedias. Los impactos ambientales no fueron percibidos como de alto riesgo por la mayoría de los actores. Las principales debilidades fueron atribuidas a aspectos económicos (p. ej. la competencia con otros países productores) y sociales (p. ej. la falta de información acerca de la credibilidad de los productos acuícolas).
[eng] The overarching goal of this doctoral thesis was to advance the understanding of the interactions between marine fish farming, wild fish populations, the local small-scale fishery and the society. This thesis was designed as a multi-disciplinary study and is divided into three different sections: ecology (chapter 1 and 2), fisheries (chapter 3) and social science (chapter 4). In the ecological part we examined the spatial and temporal extent of the attraction effect of wild fish at an Atlantic bluefin tuna and a Gilthead seabream farm. At both farms wild fish aggregated closely to the cage structure, revealing an abrupt decline of fish abundance rather than a gradient. The intensity of the cage effect varied according to farm, season and depth. At the seabream farm, the cage effect persisted year round, whereas at the tuna farm, the effect was restricted to summer and spring. The variability of wild fish aggregations within the Gilthead seabream farm was analyzed because it can be a distorting factor in estimating the farm attraction effect. Our findings showed that at the surface, fish abundance was significantly higher during feeding compared with non-feeding periods. Moreover, the distance from the feeding vessel significantly influenced fish aggregations in the water column. At the bottom, substrate type was the dominant factor explaining aggregation variability. The effect of fish farming on the small-scale fishery was evaluated in order to determine whether farms act as protection zones or as traps for wild fish populations. The findings revealed a relevant amount of commercial and recreational fishing effort in farm vicinity. However, the results showed no benefit or difference of fishing in close proximity to the farm compared to areas away from the farm (in terms of yield, income, and catch composition). Yet, farm-aggregated fish are vulnerable to hidden fishing practices inside the farm. The analysis of the perception of marine fish farming in Catalonia was performed with five key stakeholder-groups (NGOs, local fishermen, fish farming industry, scientists and regional administration). Four perceptions were identified; two represented divergent views and two intermediate positions. Environmental impacts were not perceived as a high risk by the majority of the participants. The major weaknesses were attributed to economic (e.g. price competition with other producer countries) and social issues (e.g. lack of credible information about farmed products). Overall, this thesis provides new information about the complex dynamics of wild fish aggregations at marine fish farms and investigates how this attraction effect influences the local small-scale fishery. Moreover, an understanding of the different perceptions on marine fish farming can help to secure a social, economic and environmental sustainable activity.
URI: http://hdl.handle.net/2445/61103
Appears in Collections:Tesis Doctorals - Departament - Estratigrafia, Paleontologia i Geociències Marines

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