Taxonomic Variation in the Energy Allocation Strategies of Young-of-the-Year Fishes

Constraints on the survival of young-of-the-year (YOY) fish can be inferred from ontogenetic shifts in energy allocation because trade-offs between growth and starvation dictate YOY energy allocation strategies. These trade-offs are well understood among freshwater species, but are much less known in marine species. We compared ontogenetic shifts in energy allocation of YOY for ten species rearing in the north Pacific and three Atlantic species by contrasting energy density and length. We discerned three distinct strategies: 1) energy density increases with length until a critical point at which the slope increases and asymptotes at a new level, 2) increases with length and after reaching the critical size the slope rapidly decreases to a new level, 3) energy density is unrelated to length. The first strategy is typical of freshwater and pelagic species such as Pacific herring, capelin, walleye pollock, and salmon. The second strategy typifies demersal species such as Atlantic cod, Pacifc cod, saffron cod, gag, and Pacific Ocean perch. The third strategy characterizes flatfish such as arrowtooth flounder, halibut, northern rock sole, and winter flounder. Assuming energy allocation strategies reflect survival constraints, we conclude the relative importance of resource scarcity and predation varies among species.