Dra. Sobenes-Vennekool, Catterina

We cultivated the Pacific oyster (Crassostrea gigas) simultaneously in three types of cultivation device sets deployed in two sites: a sheltered site and a non-sheltered site in the coast of the central area of Chile. Oysters were cultivated in polypropylene trays, nylon cones and lanterns suspended at 2, 5 and 8 m depth from long-lines. Organism sampling was performed monthly from June, 2014 to May, 2015, measuring temperature, salinity and chlorophyll a. Growth was measured by shell length, wet meat weight and meat yield. At the end of cultivation, there were significant differences in the growth of oysters with higher growth in lanterns at 2 m at Punta Lobería (non-sheltered site). Higher growth was also found at 2 m in Coliumo bay (sheltered site). Better growth seems associated with the stability of salinity and chlorophyll a. This is the first study that demonstrates the viability of oyster cultivation in non-sheltered environments on the coast of central Chile.

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.