Previous work has demonstrated that survival of largemouth bass Micropterus salmoides
through the first year of life can be size dependent, favoring larger individuals. Because
size, diet biomass, lipid accumulation, and ultimately overwinter survival of juveniles are typically
positively related to age, early spawning is clearly advantageous. However, a true understanding
of which largemouth bass cohorts contribute to the new year-class remains somewhat unclear
because these conclusions have largely been based upon fish collected during summer rather than
fish collected during spring. Conceivably, even earlier hatched cohorts of largemouth bass could
have existed in many of these studies, and these fish may simply not have survived to the summer
collection period. In order to assess this possibility, we quantified first-summer survival of largemouth
bass cohorts collected during 1992 and 1993 in Auburn, Alabama, ponds (which were
2–5 ha each). Our results indicate that it is early-hatched cohorts that likely contribute to the new
year-class. Although we found that early-hatched cohorts were lost between May and July, these
losses were not attributable to age-dependent mortality; instead, sampling biases associated with
avoidance of seines by older, larger young-of-year largemouth bass appear to have driven these
shifts. In addition, because we found that size-dependent cannibalism during summer acted to
remove smaller, later-hatched largemouth bass, early hatching may enhance survival during larval
and early juvenile stages in southern systems (and not just during the winter period). Given this
information, fishery managers may potentially be able to implement harvest regulations that are
designed to protect large, early-spawning adults, thereby increasing the probability of producing a strong year-class by enhancing first-summer growth and, ultimately, recruitment to adult stages.This research was supported in part by National Science Foundation grants DEB-9108986 and DEB-9410323 and Federal Aid in Sport Fish Restoration project F40-R (administered by the Alabama Game and Fish Division to D. R. DeVries)
