The effect of estuarine fisheries on juvenile fish observed within the Guadalquivir Estuary (SW Spain)

• Published in: Fisheries research Vol. 76; no. 2; pp. 229 - 242
• Main Authors: Sobrino, I., Baldó, F., García-González, D., Cuesta, J.A., Silva-García, A., Fernández-Delgado, C., Arias, A.M., Rodríguez, A., Drake, P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2005; Elsevier
• Subjects: Agnatha. Pisces; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Brackish; Decapoda; Discards; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fundamental and applied biological sciences. Psychology; Glass eel fishery; Guadalquivir Estuary; Juvenile fish; Shrimp fishery; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Europe; Spain; ANE, Spain, Andalucia, Guadalquivir Estuary; Spain, Andalucia, Guadalquivir Estuary; Discards; Guadalquivir Estuary; Shrimp fishery; Glass eel fishery; Juvenile fish; Brackish water environment; Estuaries; Offshore discharge; Fishing; Macrura; By-catches; Crustacea; Vertebrata; Fishery; Guadalquivir; Arthropoda; Pisces; Glass eel fishery: Shrimp fishery; Decapoda; Invertebrata; Shrimp
• DOI: 10.1016/j.fishres.2005.06.016
• ISSN: 0165-7836

We assess how estuarine (glass eel and white shrimp) fishing activities may be affecting the recruitment of young stages of marine fish species to the Guadalquivir Estuary. We estimated the spatio-temporal abundance of fish species throughout the last 50 km of the estuary during two annual cycles (May 1997–April 1999), by catching monthly samples using 1 mm mesh size at five sampling sites. At the same time we also estimated the fishing effort (boats fishing per day) in the different estuarine zones. During the second year, we also studied the abundance of larvae and juveniles of marine fish species in discards. The number of marine fish that use the estuary as a nursery ground decreased from 23 in the outer estuary, to 18 in the inner zone and there was a marked decrease in their density upstream (from 72, 322 to 702 individuals 10 5 m 3, on average). Moreover, we found considerable temporal changes in fish density, with minimum values during the colder months (the glass eel fishing season). A highly significant correlation (Spearman rank correlation coefficient, R = 0.73; P < 0.01) was observed between fish community composition and fishery discards during the second year of our study. In general, the fishing effort targeted at glass eels was greater than that targeted at white shrimp. The mean number of fish juveniles (per kilogram of target species) observed in the discard of both fishing activities was considerably higher in the outer estuary. Both fishing activities affect the nursery function of the estuary.