Overwinter survival, growth, and energy allocation strategies of age-0 largemouth bass: exploring the influences of latitudinal origin and predation risk

For many temperate fishes, cohort strength is influenced by overwinter mortality and predation during the first year of life.  Populations from different latitudes are adapted to local environmental conditions and early life history strategies have likely evolved that promote overwinter survival.  We assessed the potential for latitudinal origin and predation risk to influence overwinter survival, growth, and energy allocation of age-0 largemouth bass.  Parental largemouth bass were collected from northern Illinois and southern Alabama and allowed to spawn naturally in mid-latitude ponds.  Equal numbers of similarly-sized Illinois and Alabama age-0 bass were marked and introduced into ponds.  Five ponds had adult bass predators and five were predator free; however, predation risk had no influence on any response variable.  Overwinter growth did not differ between populations of age-0 bass; however, Illinois fish exhibited significantly higher overwinter survival compared to Alabama fish.  Survival of Alabama age-0 bass was a function of fall condition and indices of energy stores; however, no such relationships existed that predict the probability of overwinter survival for Illinois age-0 bass.  Bass surviving winter exhibited similar changes in energy stores and condition, regardless of latitudinal origin.  Our results highlight important adaptations that may affect recruitment success and cohort strength.