Optimal energy allocation to ovaries after spawning

For iteroparous organisms in which fecundity is positively related to body size, a trade-off exists between allocation of energy to gonads, thus ensuring some reproductive output, and allocation to somatic growth, thus increasing potential fecundity in the future. This tradeoff can influence several life-history patterns, including when, for organisms that grow after maturity, allocation to gonads begins following the previous reproductive event. White crappie Pomoxis annularis, a spring-spawning freshwater fish, began allocating energy to ovaries in autumn at the expense of continued somatic growth and higher potential fecundity. Within five populations, the amount of early allocation varied between years. We combined dynamic programming with an individual-based model to determine how summer and spring feeding conditions interact to influence when allocation to reproduction should begin. Model results indicated that autumn allocation to ovaries was in response to future spring feeding conditions rather than recent summer feeding conditions. At least a 10% probability of poor spring feeding conditions resulted in ovary investment patterns that matched field observations. The model was unable to explain the inter-annual variation in autumn energy observed in the field. Early allocation of energy to ovaries is probably an evolutionary adaptation to the possibility of poor spring feeding conditions.This research was funded in part by Federal Aid in Sport Fish Restoration Project F69- P, administered jointly by the United States Fish and Wildlife Service and the Ohio Department of Natural Resources, Division of Wildlife