Winter Feeding as an Overwintering Survival Strategy in Young‐of‐the‐Year Winter Flounder

Abstract

AbstractFor fish, the first winter of life can be a period of high mortality prior to recruitment. When resources are limiting or when fish are unable to feed due to low temperatures, starvation can often lead to size‐dependent overwintering mortality. Larger individuals are typically better able to survive starvation because they have a higher percentage of energy reserves and a lower metabolic rate per unit of body mass than small individuals. Alternatively, fish that can feed during the winter are able to maintain their lipid stores and reduce their chance of starvation. The aim of this study was to examine the overwintering mortality and physiology of young‐of‐the‐year (age‐0) winter flounderPseudopleuronectes americanusin relation to body size. Size‐dependent mortality was investigated with 17 years of length‐frequency data. In addition, I sampled the diet and whole‐body crude lipid content of 309 age‐0 winter flounder over the course of 1 year. Samples were taken in three estuaries in the northeastern USA during October–April. Whole‐body crude lipid content ranged from 4.7% to 12.4% of dry weight. Larger age‐0 winter flounder did not have higher lipid stores, and the age‐0 fish did not exhibit size‐dependent overwintering mortality. Age‐0 winter flounder fed on amphipods and polychaetes throughout the winter, and their whole‐body crude lipid content was maintained through the fall and winter. The physiology data lack temporal replication, but the spatial coherence in results (i.e., consistency among the three estuaries, representing two different stocks) suggests that the consumption and energy allocation patterns are real and that age‐0 winter flounder follow an alternative overwintering survival strategy.