The effect of size on the mechanical properties of the myotomal-skeletal system of rainbow trout ( Salmo gairdneri )

Abstract

The length and mean cross-sectional area of the myotome of rainbow trout, Salmo gairdneri , scale isometrically with total length (L, cm) and L 2 respectively for fish from 5 to 35 cm in length. The net maximum force, (F, kN·m −2 ) developed by a single twitch of the in situ myotome on one side of the body, and measured normal to the hypural complex increased as; F=1.05×10 −3 ·L 2.6 , and maximum lateral velocity (W, m·s −1 ) at the hypural plate as; W=0.29 L −0.47 . Maximum power (P, W) increased as; P=7.64×10 −5 ·L 3.06 . Acceleration rates predicted from these data do not agree well with observations. In addition, except for small fish, predicted maximum speeds differed from those calculated from minimum twitch times of excised muscle blocks and stride length, the popular method for estimating maximum speed. It is suggested that temporal summation of twitches must occur in larger fish. This could provide forces matched to inertial loads which are important in fitness-critical maneuvers.