T. Ryan Gregory and Chris M. Wood
Canadian Journal of Fisheries and Aquatic Sciences 55(7):
1583-1590.
Abstract
Variation among individuals in specific growth
rate
(SGR), feeding, and two measures of swimming performance
and their possible interrelationships were investigated in juvenile
rainbow trout (Oncorhynchus mykiss) kept in groups on
either satiation or half-satiation rations. Maximum sustainable
velocity
(Ucrit) was measured as an index of aerobic
swimming performance and stamina (fatigue time in a fixed-velocity
test at 6 body lengths ·s-1) as an index of anaerobic
performance. Individual performance in both of these tests was found
to be significantly repeatable. Trout fed on
half-satiation ration exhibited significantly lower mean values of
SGR and body size and higher levels of aggression-related
fin damage, but no significant differences in stamina, relative or
absolute Ucrit, glycogen content, or plasma cortisol.
However, in these fish, there was a significant negative relationship
between SGR and relative Ucrit, a significant positive
relationship between SGR and stamina, and a significant positive
relationship
between SGR and total daily meal. None of
these relationships were seen in fish fed to satiation. Plasma cortisol
and tissue glycogen stores were not related to SGR.
These results indicate that under the intensified competition of
restricted
ration, there are trade-offs between growth,
feeding, and different types of swimming performance.