Individual Growth and
Foraging Responses of age-0 Largemouth Bass to Mixed Prey Assemblages during
Winter
S.M.
Micucci, J.E. Garvey, R.A. Wright, R.A. Stein-2003
Environmental
Biology of Fishes: 67(2): 157-168
Abstract:
We conducted an outdoor pool experiment at a
mid-temperate latitude (Ohio, 40°N) to
determine how commonly occurring prey assemblages affect individual foraging
and growth of individually marked, age-0 largemouth bass during winter. The
treatments were low prey, bluegill prey only, macroinvertebrates only, and
bluegill plus macroinvertebrates. Across all treatments, growth in mass (g)
was unrelated to body size. Conversely, small individuals lost more energy
(kJ) than large counterparts in all but the macroinvertebrate-only
treatment. With low prey, overall growth of largemouth bass was negative,
with losses varying among individuals by 30% and 60% for mass and energy
content, respectively. Counterparts in bluegill-only pools also consistently
lost mass and energy, with less variability (15% mass; 30% energy). In the
macroinvertebrate-only treatment, 31% of individuals gained mass, reflecting
the greatest range in mass (100%) and energy (60%) change. With
macroinvertebrates plus bluegill, overall growth was generally negative,
with intermediate variance among individuals. Variation in growth among
individuals typically increased with the frequency that prey occurred in
diets during sampling. Apparently, some individuals were inactive, foraged
infrequently, and consistently lost intermediate quantities of mass and
energy. Others were active and foraged with variable success. Because
activity and growth vary among individuals as a function of prey composition
during winter, prey assemblages during this season will affect patterns of
first-year survival and cohort strength.