Overwinter growth and survival of age-0 largemouth bass (Micropterus salmoides): revisiting the role of body size

Abstract

How large size affects overwinter growth and survival of age-O fish may vary as a function of food, predation, and energetic condition. During two winters in Ohio, we assessed how these factors affected growth and survival of varying sizes of age-O largemouth bass (Micropterus salmoides) by combining a field survey (N =2 reservoirs) with multiscale experiments (reservoirs, ponds, outdoor pools). In our survey, more small (<100 mm total length) individuals died by spring in one reservoir than in the other. Similarly, when we stocked two reservoirs with marked age-O largemouth bass in fall, mortality of small individuals was higher in one system overwinter, potentially due to differences in predation intensity. In ponds during two winters, size-selective mortality of small largemouth bass occurred in only two of eight ponds, potentially as a function of cannibalism. Varying ration in pools (starved, 0.5x maintenance, or 1.5x maintenance) did not affect survival, even though starved individuals lost substantial wet weight and energy content. Only when predators were present did small individuals die at high rates, although energy depletion may have contributed to predatory mortality. To increase the probability of overwinter survival, managers should seek to improve first-summer growth, reduce winter predation, and increase winter forage.