Since 1979, southern hake (Merluccius australis) has been exploited in Chile from the Bio Bio to the Magallanes regions, between the parallels 41°28.6'S and 57°S. There is evidence of a constant fishing effort and a sustained reduction of the fish population, consistent with a progressive decrease in total annual catches. Management strategies based on the maximum sustainable yield (MSY) and quota assignment/ distribution criteria have not been able to sustain acceptable biomass levels. A non-linear optimization model with two objective functions was proposed to determine an optimal total catch quota for more sustainable exploitation of this fishery. The first function maximizes the total catch over time in response to an optimal assignment of fishing mortality rates per fleet; the second function maximizes the total economic benefit associated with the total catch. The dynamics of the fish population were represented with the equations of a predictive age-structured model. Decision variables were fishing mortality rates and annual catch quotas per fleet, subject to constraints that guarantee a minimum level of biomass escape over a long-term period. The input parameters were obtained from the last stock evaluation report carried out by the Instituto de Fomento Pesquero (IFOP) of Chile. The historical background data of the fishery and the regulatory framework were relevant aspects of the methodology. Five scenarios were evaluated with the two objective functions, including a base scenario, which considered the referential mortality rate as input data as the average mortality rate per fleet from 2007 to 2012. Total economic benefits fluctuate between 102 and USD 442 million for total catches in the range of 108 to 421 thousand tons, which were obtained from maximizing the economic and biological objective functions. Economic benefit/catch ratios were reduced for scenarios with higher constraints on catch limits, and they were more efficient from a biological point of view. Situations with lighter constraints showed in general higher economic benefits and better performance ratios than those with stronger restrictions. The use of optimization models may provide a useful tool to evaluate the effect of regulations for adequate conservation and economical utilization of a limited resource.
SOLDECOCOS es una ONG especializada en desarrollo comunitario y gobernanza en espacios naturales y recursos marinos, cuyo marco de acción son las comunidades costeras y comarcas vinculadas al mar. Desde 2015, desarrolla junto a WWF España la iniciativa Seguimiento y mejora de pesquerías del Golfo de Cádiz, mediante procesos de gobernanza en zonas de alta productividad biológica, siendo el registro fósil de cabo Roche un lugar clave para su interpretación.
Examinamos las redes de conocidos, apoyo social e información ecológica local de los patrones de embarcaciones del puerto de Chipiona autorizadas a pescar en la Reserva de Pesca de la Desembocadura del Guadalquivir (n= 40), en el suroeste de España. El tiempo invertido en cada zona de la reserva mostró una relación inversa con la distancia al fondeadero. Se identificaron tres tipos de barcos en función de que su actividad de pesca la desarrollen de forma preferente, respectivamente, en la desembocadura, el frente costero entre Matalascañas y Mazagón, y los caladeros alejados de la reserva de pesca. Los pescadores mostraron una tendencia significativa al intercambio de apoyo e información con aquellos colegas que no comparten su misma zona de pesca (heterofilia). Los resultados de la encuesta y el análisis de redes entre embarcaciones fueron presentados en un foro cualitativo (n= 21), en el que los pescadores informaron de la práctica del secreto en la actividad pesquera. Discutimos las implicaciones de la estructura de relaciones en la conservación de los recursos pesqueros y en el desarrollo de una visión integrada del ecosistema. Palabras clave: Áreas Marinas Protegidas -Pescadores artesanales de pequeña escala -Apoyo Social -Conocimiento ecológico local -Redes de embarcaciones.Networks of ecological information, social support, and acquaintanceship among the skippers of the boats anchored in the port of Chipiona and authorized to fish in the Fishing Reserve of the Mouth of the Guadalquivir River (SW Spain) were analysed (n= 40). The time spent in each area of the reserve was inversely related to the distance to the anchorage. Three types of ships depending on their fishing activity were identified: boats that preferentially fish, respectively, at the mouth; in the waterfront of Matalascañas and Mazagón; and in fisheries far away from the Fishing Reserve. Data showed that fishermen have a trend to significantly exchange support and information more probably with those colleagues who do not share the same fishing area (heterophily). The results of the survey and analysis of networks between boats were presented in a qualitative forum (n = 21), in which fishermen reported a usual practice of secrecy in the fishing activity. We discuss the implications of the structure of relationships in the conservation of fishery resources as well as the development of an integrated vision of the ecosystem.
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