Autumn lipid reserves, overwinter lipid depletion, and high winter mortality of rainbow trout in experimental lakes

Accumulation of lipid reserves is considered important for the overwinter survival many animals. Fish are thought to deplete lipids until they reach a critical minimum below which starvation mortality occurs, meaning that lipid-dependent selective may be strong pressure leading life-history evolution favouring accumulation and storage. Much our current knowledge comes from either laboratory studies or field not well controlled, but rarely directly estimated evaluate mortality. Here, we studied patterns storage, depletion, subsequent single strain rainbow trout (Oncorhynchus mykiss) stocked into experimental lakes differed in productivity experienced same local winter conditions. Productive produced with higher content steeper allometric slopes contrast low food lakes; however, these field-based values were all substantially lower than those determined lab. Surviving emerged poor condition, close expected needed survival, comparison survivors higher-productivity lakes. As expected, was lipid-dependent, fish nearing 90% about 60% high Importantly, estimates (∼70%) modelling (0% 14%) this species. These results, though populations, suggest an even stronger previously thought, creating tight population bottleneck young cohorts likely promoting strategies favour energy storage at expense somatic growth.