Impact of differential energy allocation in Atlantic salmon (Salmo salar) precocious males on otolith–somatic size proportionality: a longitudinal approach

Abstract

We studied juvenile Atlantic salmon (Salmo salar) males that become precociously mature or not at age-1+ to test the hypothesis that differential energy allocation affects the relationship between otolith size and fish size and to validate the use of a back-calculation method to estimate size over 30 weeks. We used a longitudinal approach by repeatedly measuring marked fish and obtaining corresponding otolith radius measurements. Differential energy allocation of mature males did not affect the proportionality ratio between otolith and somatic size. Short-term otolith growth varied with short-term somatic growth, but only weakly with temperature. Some correlation coefficients of the covariation of otolith growth estimated over a longer time interval with somatic growth were significantly greater than the short-term estimate. For mature and immature males, back-calculated lengths accurately estimated the observed individual length on practically all occasions. These results indicate that back-calculation can be used to estimate size for Atlantic salmon with different energy allocation patterns. Variable strength of coupling of otolith and somatic growth depending on time interval suggests that these processes are completed on different time scales.