REPRODUCTION OF WALLEYE IN LAKE-ERIE - ALLOCATION OF ENERGY

An energetics mechanism is proposed to explain the trade-off between c urrent and future reproduction. Surplus energy can be used for reprodu ctive tissue (current reproduction) or somatic tissue (needed for futu re reproduction); therefore, we needed to determine first, when does g rowth of somatic and reproductive tissues occur, and second, how and w hen is energy allocated to reproduction. Walleye were sampled monthly from the commercial fishery in Lake Erie. Morphological attributes wer e recorded from these walleye, as well as the lipid composition of a s maller subsample. Energy for reproduction is acquired in the winter, s pring, and summer before spawning and stored as visceral lipids. Ovari an lipids are largely derived from visceral fat deposits; thus, female s appear to be capital breeders. Females elaborate gonadal tissue only if there is sufficient visceral fat. The circannual endocrine switch to reproduction may occur in midsummer (August) and in October. Female s may discontinue ovarian development during the early winter if there is insufficient surplus energy (visceral fat). Year-class variation m ay be partly explained by the energy condition of the females and the proportion of the stock able to spawn successfully each year.