Influence of maternal habitat choice, environment and spatial distribution of juveniles on their propensity for anadromy in a partially anadromous population of rainbow trout (Oncorhynchus mykiss).

LIBEROFF, ANA; QUIROGA, A.P.; RIVA ROSSI, C.M.; MILLER, J.A.; PASCUAL, M.A.

ECOLOGY OF FRESHWATER FISH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014

0906-6691

This study evaluated the spatial and environmental patterns of anadromy and residency along the Santa Cruz River (Argentina) in a population of partially anadromous rainbow trout (Oncorhynchus mykiss). The aim was to determine the spatial patterns and environmental experience of anadromous and resident offspring along the river and to evaluate the extent to which maternal breeding activity affects their offspring´s habitat availability and condition. We captured young-of-the-year fish along the river gradient during autumn 2009 and 2010, and spring 2010 and determined their maternal origin (anadromous vs. resident) using strontium-to-calcium ratios in the otolith core. Proportion of anadromous offspring, modeled with logistic regression, showed a tendency to increase towards headwater and in areas with deeper channels and larger substrate composition. Fish condition, measured as body length and modeled with linear multiple regression, varied positively with site´s depth, water velocity, substrate size and maternal origin. In addition, substrate size varied predictably with river distance displaying large sections of coarse substrate composition. Results suggest that anadromous females breed predominantly in middle and upper river sections, in areas with coarse substrate which provide availability of large substrate sites to their offspring in order to maintain their growth performance. Given that body size in this system has been related to propensity for anadromy, this study provides evidence of the relationship between maternal breeding activity, their offspring condition and their tactic adoption through definition of rearing habitats. Relevance of this study is discussed in the context of alterations in response to future dam construction in one of the latest free-flowing rivers sustaining anadromous O. mykiss.