Influence of sexual maturity on feeding, growth and energy stores of wild Atlantic salmon parr

Abstract

Maturing Salmo salar parr had significantly lower short-term energy stores (indicated by hepato-somatic index) in August, and significantly lower energy stores and growth rate (indicated by RNA : DNA) in September than immature parr captured from the same stream sites on the same date. There were no significant differences in gut fullness or protein concentrations, suggesting that up to early September the main energetic consequences of maturation were a reduction in allocations to growth and short-term energy storage, but not a mobilization of long-term stored energy in the form of proteins. These are the first observations of relative food intake and energy storage for maturing parr under natural conditions, and also the first to assess growth effects on wild fish before completion of the maturation process.