Seasonal growth potential of Oncorhynchus mykiss in streams with contrasting prey phenology and streamflow

The growth of any organism depends on habitat conditions, food availability, and their seasonal interactions. Yet in vast literature on Pacific salmon (Oncorhynchus), the seasonal interaction between habitat conditions and food availability has received relatively little attention. We examined juvenile O. mykiss rearing, physical habitat, and resource phenologies in two Mediterranean coastal streams – one perennial, cool, and shaded; the other intermittent, seasonally warm, and sunny. We used a bioenergetics model to investigate the timing and magnitude of growth potential for drift foraging O. mykiss during the spring and summer in both systems. Growth potential peaked at least two months earlier in the intermittent stream than in the perennial stream. By early summer (June), growth potential had declined in the intermittent stream, whereas growth rates were peaking in the perennial stream. However, the mid-July lipid content of juvenile O. mykiss in the intermittent stream was nearly ...