Effects of Growth and Reproductive History on the Egg Size–Fecundity Trade-off in Steelhead

Abstract The allocation of energy by females into different components of reproduction is critical and includes trade-offs between egg size and number. In anadromous salmonids, it is unclear whether the allocation patterns are determined by the growing conditions experienced when the fish are in freshwater or at sea or by the female's reproductive history. We collected data on length, egg size, and fecundity from female steelhead Oncorhynchus mykiss that had spent 1 year in freshwater and then 2 (designated 1.2) or 3 years at sea (1.3) before spawning for the first time. We also collected the same data from females spawning for the second time but of the same age as those spawning after 3 years for the first time (1.1S1). The older females were longer than the younger ones, but there was considerable overlap in length. The repeat-spawning fish were shorter than fish of the same age that were spawning for the first time, which reflected the reduction in growth associated with the previous spawning migratio...