Shifting gears: enzymatic evidence for the energetic advantage of switching diet in wild-living fish

Abstract

Large variations in the activity and scaling patterns of enzymes involved in anaerobic metabolism exist and appear to be related to species differences in the locomotory habits of fish. Here, we show how the scaling of muscle lactate dehydrogenase (LDH) activity is highly variable in fish, not only among species, but also among populations of yellow perch (Perca flavescens) and lake trout (Salvelinus namaycush) exhibiting large differences in the scaling of fish activity costs. These differences in LDH scaling properties were significantly related to differences in diet ontogeny. Scaling coefficients and adjusted R2 values of LDH versus body size relationships were both threefold higher in fish that do not make important diet shifts among planktivory, benthivory, and piscivory than in those that do. We argue that fish activity and related glycolytic potential are reset to lower values whenever fish are able to switch diet to larger prey while growing; we implicate the burst component of foraging (mostly attacks) as being responsible for changes in activity costs. Our results suggest that anaerobic power requirements in fish are highly plastic and adapted to local and recent food web conditions. We discuss these findings in relation to optimal foraging theory and the energetic basis of prey-size selection.

Dimensions of diet segregation in grey seals Halichoerus grypus revealed through stable isotopes of carbon (δ13C) and nitrogen (δ15N)

“…Other considerations include availability of prey and the subsequent costs associated with pursuit, capture, handling and digestion. In fish, diet shifts with increasing body size are thought to reflect the limiting factor of gap size and the increasing foraging cost of consuming relatively smaller prey (Sherwood et al 2002). That is, a shift in diet is made when the costs outweigh the benefits of feeding on a particular prey or prey-size class (e.g.…”

“…That is, a shift in diet is made when the costs outweigh the benefits of feeding on a particular prey or prey-size class (e.g. Jones et al 1994, Sherwood et al 2002. This, in turn, leads to lower energetic demands, with respect to minimizing time and activity costs spent in burst swimming and pursuit of prey (Sherwood et al 2002).…”

“…Jones et al 1994, Sherwood et al 2002. This, in turn, leads to lower energetic demands, with respect to minimizing time and activity costs spent in burst swimming and pursuit of prey (Sherwood et al 2002). Typically, this diet switch is made in the direction of larger prey, but the underlying operative is decreased foraging costs.…”

Diet and divergence of introduced smallmouth bass (Micropterus dolomieu) populations

“…A de-pauperate prey field can limit or prevent the ontogenetic diet shifts that a predator typically exhibits as it increases in body size and can result in slower individual growth rates Sherwood et al 2002); preliminary work suggests that the diet of Provoking bass is lacking in large-sized prey (Orendorff 1983). Water temperatures are also important in determining individual growth in bass and should be examined as a possible driver of divergence .…”

Ecological and socioeconomic implications of a northern range expansion of black sea bass, Centropristis striata

“…However, when examining Kadj for all regions together, I did find a general decrease in feeding, and a shift in diet from predominantly squid and fish to crabs, occurred between 28-36 cm total length, when a decrease in Kadj was also observed. Sherwood et al (2002) found that prey switching often occurs when condition starts to decline, suggesting that these diet changes may be necessary to overcome energetic bottlenecks.…”