Aw. Fast, DISTRIBUTIONS OF RAINBOW-TROUT, LARGEMOUTH BASS AND THREADFIN SHAD INLAKE CASITAS, CALIFORNIA, WITH ARTIFICIAL AERATION, California fish and game, 79(1), 1993, pp. 13-27
Seasonal depth distributions of rainbow trout (Onchorhynchus mykiss),
largemouth bass (Micropterus salmoides), and threadfin shad (Dorosoma
petenense) were measured during August 1976 through January 1978 with
vertical gill nets. Bass occupied shallow, warm water with mean depths
mostly < 5 m during the summer, but migrated into deeper waters > 15
m during the winter when the lake destratified. Trout had the opposite
pattern and were found in deep, cold water > 20 m during the summer,
and in shallow water < 10 m during the winter. Shad depth distribution
s did not have a distinctive pattern. Changes in the diffuser during 1
977 caused some minor changes in reservoir oxygen and temperature valu
es, but had no apparent effect on fish depth distributions. Fish depth
s were more readily explained by considering thermal preferences and p
redation, with depth selection by bass apparently providing the main f
orce effecting depth selection by shad throughout the year, and winter
depth selection by trout. Trout and bass typically selected temperatu
res and depths closest to their fundamental ecological niche temperatu
res, but shad never did, apparently in response to predation pressures
from bass and trout, especially bass.