Ecosystem impacts of the introduction of bycatch reduction devices in a tropical shrimp trawl ﬁshery: Insights through simulation
Maria Isabel Criales-Hernandez a,∗ , Luis O. Duarte a,b , Camilo B. Garc´a c , Luis Manjarr´ s a ı e
Laboratorio de Investigaciones Pesqueras Tropicales, Universidad del Magdalena, AA 1690 Santa Marta, Colombia bDepartamento de Oceanograf´a, Universidad de Concepci´ n, Casilla 160-C, Concepci´ n, Chile ı o o Universidad Nacional de Colombia, Departamento de Biolog´a, CECIMAR/INVEMAR, AA 1016 Santa Marta, Colombia ı Received 28 January 2005; received in revised form 22 September 2005; accepted 17 October 2005
Abstract ECOSIM simulations of the introduction of bycatch reduction devices (BRD) to a tropicalindustrial shrimp ﬁshery resulted in moderate to strong positive changes of biomass of selected bycatch functional groups, depending on the position of the BRD in the trawl net. The highest increases in biomass after 20 years of simulation were predicted in the scenario with 12.70 cm × 30.48 cm football-shaped steel ﬁsheye BRD positioned with its center 15 meshes to the outside of top center and 30meshes from the opening of the bag. In general, results are encouraging both in terms of protection of selected functional groups and in socio-economic terms. Croakers, a group that in the Ecopath base model was heavily impacted as part of bycatch in shrimp trawling, show signiﬁcant rebuilding of biomass without substantially affecting shrimp yield at the base ﬁshing effort level. Similarrebuilding was also observed in other economically relevant groups, such as snappers. Predicted biomass increments are conducive to larger captures by the long-line and artisanal ﬂeets operating in the area. The results stress the potential beneﬁts of the implementation of BRD and encourage its testing in Colombian waters. They also stress the need for careful choice of functional groups to be protected.© 2005 Elsevier B.V. All rights reserved.
Keywords: Bycatch; Tropical ﬁsh; Fisheries management; Simulation; Ecopath with ECOSIM; Caribbean Sea; Colombia
1. Introduction Ecosystems subject to active ﬁshery exploitation typically suffer changes in structure and function. Most often expressed as changes in their food webs. Consequently, ecosystem responses to exploitation are usually complex(Jennings and Kaiser, 1998; Hall, 1999). In this context, the main concern is to assess the extent to which the ﬁshery is jeopardizing the long-term viability of both affected populations and ﬁshery yield. From a conservationist point view, the goal is to maintain biodiversity and ecosystem integrity despite exploitation, as to maintain ecosystem functioning into the future (Pauly
∗ Correspondingauthor. Present address: Area de Evaluaci´ n y Producci´ n ´ o o Secundaria, Instituto del Mar del Per´ , Esquina de Gamarra y General Valle u S/N Chuchito Callao, Peru. Tel.: +57 5 4303368x248/+51 1 4296069x263. E-mail addresses: firstname.lastname@example.org, email@example.com (M.I. Criales-Hernandez).
et al., 2002). Thus, new approaches at the ecosystem scale have been invoked for ﬁsheriesmanagement, with a change of paradigm from building “sustainable” ﬁsheries to “rebuilding” of biomass within ecosystems (Pitcher, 2001). The upwelling ecosystem in the Caribbean off Colombia (Fig. 1; Cabrera and Donoso, 1993; Andrade, 2000), sustains industrial shrimp trawling (Via˜ a et al., 2004), semin industrial long-lining (boats of intermediate size and autonomy between the industrial and theartisanal ones (Ar´ valo e et al., 2004) and artisanal ﬁsheries (Correa and Manjarr´ s, e 2004a). These ﬁsheries are mainly targeting shrimps, lobsters, pelagic and demersal ﬁshes (Manjarr´ s, 2004). e The industrial shrimp ﬂeet exerts particular pressure on the demersal community of the area not only due to the extraction of relatively substantial amounts of shrimp (annual catch during 2000 of...