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SynopsisThe feeding habits of Galaxias maculatus (Galaxiidae) and Odontesthes microlepidotus (Atherinidae) larvae and juveniles were studied in an Araucanian lake of Argentina. Fish specimens were grouped, on the basis of the percentage of each food category found in their gut, using multivariate methods. These groups of fishes showed significant differences in average total length. Positive correlations between prey size and fish length were also detected. Diet overlap between juvenile G. maculatus and juvenile 0. microlepidotus was observed. We discuss the interaction between the two species and the role of functional capabilities for prey capture during these early life periods.

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Recibido: 10 mayo 1999; versión corregida: 12 junio 2001; aceptado: 20 septiembre 2001RESUMEN. Se estudió la distribución de larvas de crustáceos decápodos dentro del estuario de Bahía Blanca con el objeto de comprobar la hipótesis de que algunas especies pueden retenerse en el estuario y otras son dispersadas aguas afuera pudiendo reinvadirlo. Se identificaron larvas de 30 especies, encontrándose las mayores abundancias de zoeas de Chasmagnathus granulata (84%) y Cyrtograpsus altimanus (60%). Un gran número de especímenes de estas dos especies se observó entre 120 km y 80 km en la zona interna del estuario con valores de 6.000 ind/100 m 3 ; la máxima densidad se encontró a 110 km (12.441 ind/100 m 3 ) hallándose las cuatro zoeas de Ch. granulata y cinco de C. altimanus. En la boca, las densidades de estas dos especies disminuyeron notablemente. Esta misma tendencia se observó en zoeas de Majidae y Xanthidae. Las zoeas de Pagurus exilis, Pinnotheres maculatus, Pinnixa patagoniensis y Corystoides chilensis fueron poco abundantes y sus densidades se incrementaron en la boca del estuario.ABSTRACT. Distribution of larvae of decapod crustacean was studied in the Bahía Blanca estuary with the objective of testing the hypothesis that some species can be retained in the estuary and other can be dispersal offshore waters and can be reinvaded. Larvae of 30 species were identificated, the most abundance corresponding to Chasmagnathus granulata (84%) and Cyrtograpsus altimanus (60%) respectively. A high number of stages of these species were found between 120 km and 80 km in the inner zone of the estuary with 6000 ind/100 m 3 . The maximum density was found at 110 km (12.441 ind/100 m 3 ). And here was found life cycle of Ch. granulata and C. altimanus. In the mouth of estuary, the density of both species decayed. The same tendency was observed to Majidae and Xanthidae zoeas. Pagurus exilis, Pinnotheres maculatus, Pinnixa patagoniensis and Corystoides chilensis were less abundant but their densities were incremented offshore waters.

0.80) but there was a relationship in the abundance of N. americana for the three sampling stations (ANOVA, n=10, P<0.05) since the highest density of this species was recorded in the inner zone of the estuary. Significant differences in salinity were found between the three sampling stations for those dates when N. americana was present (ANOVA, n=10, P<0.05) but it could not be demonstrated that this variable is related with the spatial distribution of this species in the estuary (covariable, P>0.15)]]>