The winter munchies: feeding throughout winter is common in juvenile Pumpkinseed and improves energy reserves available in spring

Abstract

In warmwater fishes, feeding during winter is often assumed to be negligible; however, there is growing evidence that juveniles will feed opportunistically even at cold temperatures. If fishes are able to effectively digest prey, then feeding during winter could supplement energy reserves and mitigate the risk of winter starvation. We use laboratory and pond experiments to determine whether feeding during winter can supplement energy reserves in a warmwater species. We compared juvenile Pumpkinseed (Lepomis gibbosus) from two cold-climate (native Canadian) and two warm-climate (non-native Spanish) populations raised in a common environment to determine whether winter feeding is more prevalent in populations that typically experience longer winters. Under simulated winter conditions, Pumpkinseed with access to prey readily fed and had greater lipid mass in spring than those without access to prey. Despite similar rates of consumption, winter feeding improved lipid mass to a greater extent in the Canadian populations, indicating that feeding benefitted the cold-climate populations more than the warm-climate populations. All populations of Pumpkinseed overwintering in outdoor ponds also fed regularly, with 88% of individuals collected mid-winter containing at least one prey item. The pattern of loss in energy reserves over time varied dramatically among populations suggesting that pond-specific environmental conditions were important in shaping how energy reserves were used. These results indicate that winter feeding may be more common in juvenile warmwater fishes than previously thought and that supplementation of energy reserves during winter should be taken into account when considering the factors influencing first year recruitment success.