Do offspring characteristics reflect parental migration variation?

Abstract

Sea trout, Salmo trutta, display a wide range of migratory behaviours, and one aspect of variation comes from freshwater migration distance. The overall aim of this study was to determine if offspring of long- and short-distance migrants exhibited phenotypic differences relating to parental migration distance. For that purpose, we conducted several behavioural tests (dyadic contest, boldness scoring and open field test) and morphological analysis (relative pectoral-fin length) in multiple freshwater systems across the distribution range of the target species in Europe. It was expected that offspring of long-distance migrants would be more active, bold and dominant than those of short-distance migrants and would have longer pectoral fins relative to body length. Additionally, we investigated if boldness varied in relation to latitude. We showed that offspring of long-distance migrants were more dominant in two cases and more active in one case than those of short-distance migrants; however, there was no difference in swimming distance or velocity. Boldness and relative pectoral-fin length were significantly related to site of origin; however, the direction of this relationship differed between systems. Generally, we detected a decrease in boldness with declining latitude. In summary, we have detected variation among juveniles related to location within a stream; however, the drivers and processes behind these are likely more complex than purely parental migratory strategy. Our results can inform suitable management and conservation efforts directed to anadromous Salmo trutta. For example, habitat restoration and removal of migration barriers can increase the possible range of migration distances helping maintain the phenotypic diversity of offspring.