Dra. Sobenes-Vennekool, Catterina

En el presente estudio se evaluó la calidad de un tramo del sistema fluvial urbano Estero Nonguén en la región del Biobío de Chile. Este estero ha sido encauzado en su rivera, con el objetivo de evitar futuros desbordes y afectar a las poblaciones aledañas a éste. Sin embargo, no han sido evaluadas las intervenciones al sistema fluvial para verificar y evitar que se altere el desplazamiento natural de la ictiofauna presente. Para esto, se analizó la presencia de barreras en un tramo del estero mediante indicadores de calidad y conectividad. Para recomendar una alternativa de paso de peces en un sitio identificado con una barrera, se utilizó el método de ponderación lineal. El tramo del río analizado resultó ser de calidad moderada y la conectividad deficiente, lo que implicaría que existirían grupos de peces nativos que no se pueden desplazar aguas arriba ni aguas abajo de la barrera. Para restablecer la conectividad del sistema fluvial, se propone construir como paso un dispositivo de rampa de piedras, que es un sistema de bajo costo, de tránsito sencillo y acorde al ambiente ribereño.

Choosing an alternative species of mussel for the aquaculture industries, will be possible if it has equal or greater yield than the mussel cultivated. This study compares the growth of the chilean native mussel Mytilus chilensis with the non-native Mediterranean mussel Mytilus galloprovincialis and evaluate if environmental variables and cultivation depth affects mussels growth. Mussel were seeded in summer, with the same mean total weight and shell length for both species. At the end of the experiment, shell length (SL), condition index and gonadosomatic index were compared over month, depth and species. Highly significant differences were found in shell length between month and depth and between month and species (p < 0.05). The linear relationship between the gonad weight and wet meat weight in M. chilensis present a higher gonad weight for the same wet meat weight than M. galloprovincialis. It can be concluded that at the end of the harvest size cultivation M. chilensis presents a greater gonad weight, condition index and gonadosomatic index.

The introduction of predatory salmonids such as rainbow trout Oncorhynchus mykiss Walbaum 1792, and brown trout Salmo trutta Linnaeus 1758, has been responsible for declining populations of native galaxiids in the Southern Hemisphere. The empirical evidence of mechanisms of this decline are, however, scarce. Currently, trout are the most common species in Chilean Patagonia. Galaxias platei Steindachner 1898 is the most widely distributed native species in Patagonia and can still be found in lakes that are not invaded by salmonids. We studied the trophic ecology of the two most common trout species (rainbow and brown) as well as G. platei in invaded and non-invaded lakes by analysing their diet and isotopic composition of their muscle tissues (carbon and nitrogen). The results indicated that the presence of trout delayed piscivory in G. platei and led to a slower ontogenetic scaling and lower trophic level. In addition, juveniles of G. platei tended to expand their trophic niche toward allochthonous prey in salmonid-invaded lakes. Trout showed high levels of piscivory, preying mainly on G. platei. The protection of the remaining salmonid-free lakes appears to be a crucial measure needed for the conservation of G. platei.