Incidental Capture of Juvenile Fish from an Artisanal Fishery in a Coastal Lagoon in the Gulf of California FELIPE AMEZCUA* Instituto de Ciencias del Mar y Limnologı ´a, Universidad Nacional Auto ´noma de Me ´xico, Unidad Mazatla ´ n, Joel Montes Camarena, Mazatla ´n, Sinaloa 82040, Me ´xico JUAN MADRID-VERA AND HUGO AGUIRRE Instituto Nacional de la Pesca, Centro Regional de Investigaciones Pesqueras de Mazatla ´n, Avenida Sa ´balo Cerritos, Mazatla ´n, Sinaloa 82010, Me ´xico Abstract.—Fishing gear used in artisanal penaeid shrimp fisheries in the southwestern Gulf of California usually consists of the trawl net, gill net, and suripera net. These net types are known to capture a high quantity of fish bycatch and are likely to cause high levels of juvenile fish mortality. However, juvenile bycatch mortality has not been documented in previous studies. The aim of this work was to study the effect of a local artisanal shrimp fishery on the juvenile fish community in the coastal lagoon of Santa Maria la Reforma, Sinaloa, Mexico. Length at first maturity was estimated for the seven most abundant species; based on this information, a generalized linear model and a Bayesian approach were used to estimate the probabilities of juvenile fish capture for different types of fishing gear. We found that the three net types captured juveniles, even those of species maturing at small lengths, and were likely to impact the recruitment of the analyzed species, as the probability of juvenile capture by the nets ranged from 0.20 to 0.90. However, the species for which sexual maturity was attained at a smaller length were less vulnerable to the fishing gear types analyzed. The gill net and trawl net had the highest probabilities of capturing juveniles in general, whereas the suripera net showed a high probability of capturing juveniles belonging to certain species. Incidentally, the suripera net is the gear used most frequently in the area to catch shrimp. Fishing is an important human activity in estuarine zones, and consequently a large number of juvenile fish from species that use these zones as nursery areas is captured. Although fishery regulations (e.g., minimum legal sizes) may preclude the retention of juveniles, fishing practices can impact prerecruits if fishing gear is nonselective or if certain life history stages are vulnerable to incidental capture by fisheries targeting other species (Blaber et al. 2000). The survival of these stages is crucial to the success or failure of subsequent year-classes (Campana et al. 1989; Bailey and Spring 1992). Despite many advances in understanding the effects of fishing on the ecosystem, the direct and indirect effects of fishing on juveniles of some fish species remain poorly understood. Because many of these species have little or no economic value, they have been given a low priority for research (Pope et al. 2000). Even if the adults are target species, research on juveniles is somewhat scarce. This is particularly true in the coastal lagoon of Santa Maria la Reforma, Sinaloa, Mexico (southeastern coast of the Gulf of California), which is one of the most important fishing grounds in the region. The main fishing activity in this lagoon consists of artisanal penaeid shrimp fisheries that capture the yellowleg shrimp Farfantepenaeus californiensis, crystal shrimp F. brevirostris, blue shrimp Litopenaeus stylirostris, and whiteleg shrimp L. vannamei. The shrimp fishing season usually lasts from September to March of each year. The number of fishermen varies each season, but approximately 2,100 registered fishermen using about 1,000 boats operate in the area. Studies on the effect of the penaeid shrimp fishery on the fish community in the study area are scarce (e.g., Pe ´rez-Mellado and Findley 1985; Balart et al. 1992; Amezcua-Linares 1996; Madrid-Vera et al. 1998; Aguilar-Palomino et al. 2001; Madrid-Vera et al. 2007), even though it is known that a high percentage of the incidental take in this area consists of fish smaller than 20 cm (Garcı ´a-Caudillo et al. 2000). It was estimated that during 1996, the shrimp fishery generated nearly 200,000 metric tons of bycatch in the area (Garcı ´a-Caudillo et al. 2000). Although awareness of the negative effects of the shrimp fishery has increased, studies that calculate the magnitude of the effects on juvenile finfish do not exist. Thus, it is important to develop methods for assessing the vulnerability of fish species, because these methods will help predict (1) the impact of fishing on certain * Corresponding author: famezcua@ola.icmyl.unam.mx Received January 24, 2006; accepted January 25, 2008 Published online March 9, 2009 245 North American Journal of Fisheries Management 29:245–255, 2009 Ó Copyright by the American Fisheries Society 2009 DOI: 10.1577/M06-022.1 [Article]