Optimal stocking density for juvenile winter flounder Pseudopleuronectes americanus
E.A. Fairchild, W.H Howell-2001
Journal of the World Aquaculture Society, 32(3):
300-308 (from Current Contents)
Abstract :
A 12-wk experiment was conducted to test the effects
of 50, 100, 200, and 300% stocking densities (ventral fish area to bottom
tank area ratio) on growth, survival, and aggressive behavior in 2-mo-old
juvenile winter flounder Pseudopleuronectes americanus. Over the course of
the experiment. there were no differences (P > 0.05) in growth between
treatments at any given week. Survival decreased in all treatments over
time, however, proportionately more fish died in the high (200 and 300%)
density treatments. At the end of 12 wk, the 300% treatment had
significantly lower survival (P < 0.05). There were no differences in the
degree of caudal fin damage between any of the treatments (P > 0.05)
suggesting that aggressive behavior, such as fin nipping, was not affected
by stocking density. However, fish size was inversely related to caudal fin
damage. When fish were sorted by length, the two smallest size categories
(<2 cm and 2-3 cm) suffered the greatest fin nipping compared to each
other (P < 0.001) and all larger size categories (P < 0.001). These
results indicate that 50 to 300% stocking densities do not affect growth or
aggressive behavior in juvenile winter flounder. Although survival was
affected by density, the final yield (weight per treatment) at higher
densities was still greater than at lower densities. Our hatchery
recommendations are to stock at greater than or equal to 200% but to monitor
fish health carefully. Size grading should be employed to minimize
aggression between fish size classes.
(Univ New Hampshire, Dept Zool, Durham, NH 03824,
USA)