Winter energy allocation and deficit of juvenile walleye pollock Theragra chalcogramma in the Doto area, northern Japan

Abstract

Seasonal energy allocation and deficits of marine juvenile fishes have considerable effects on their survival. To explore the winter survival mechanism of marine fishes with low lipid reserves in their early life, juvenile walleye pollock Theragra chalcogramma were collected along the continental shelf of northern Japan over a 2-year period, and energy allocation and deficit patterns were compared between wild and laboratory-starved fish. Contrary to expectations, wild fish generally continued to accumulate protein mass and concurrently tended to reduce lipid mass from late autumn through winter. The most plausible explanation for the continuous structural growth is that juvenile pollock give priority to reducing mortality risk from size-selective predators under quasiprey-limited conditions. Exceptionally, inshore small fish reduced both constituents during a winter. The inshore fish consumed 2.5 times more lipid energy than protein energy in November-December, but protein was more important than lipids as a source of energy in December-January and in FebruaryMarch. However, dependence upon protein reserves was lower for the wild fish than for the laboratorystarved fish, suggesting milder nutritional stress of the wild fish than that observed in the starvation experiment. Moreover, the lipid contents of mortalities in the starvation experiment were mostly <1%, whereas few wild fish had such lipid contents in the field. These results suggest that juvenile pollock are able to avoid both starvation and predation by accumulating protein reserves.

Exploring the Influence of Food and Temperature on North Sea Sandeels Using a New Dynamic Energy Budget Model

“…Many 0group fish use energy to grow rapidly to reduce predation pressure (Anthony et al, 2000), with some maintaining lipid levels just above the minimum required to survive, even when physiologically capable of allocating energy to reserves (Biro et al, 2005). Once a threshold size is reached, sandeels, like many other species, begin to store considerably more lipid (Robards et al, 1999;Post and Parkinson, 2001;Biro et al, 2005;Kooka and Yamamura, 2012). This threshold size corresponds to the minimum length of an overwintering sandeel (Holland et al, 2005), suggesting the onset of overwintering is determined by lipid stores (Robards et al, 1999;Holland et al, 2005).…”

Life history trade-offs in ectotherms impart a pseudo-hormetic response, not hormesis

“…Energy reserves and growth-Trade-off theory suggests that resources are shifted among life history components based on need when resources are limited (Gadgil and Basert 1970;Charnov and Krebs 1973;Stearns 1992). Our study shows that when internal resource budgets are exceeded, ectotherms may increase intake to supplement growing needs (MacKay 1985; Kooka et al 2009). Further, this supplementation may result in a resource surplus that the body can redistribute to growth or potentially other life history components.…”

Energy stores and mercury concentrations in a common minnow (spottail shiner, Notropis hudsonius) associated with a peaking hydroelectric dam

“…Triglyceride concentrations increased in Wapiti and DS2 sites from August to September, yet remained lowest at DS2, indicating that spottail from this location were not accumulating the same critical triglyceride stores as their upstream counterparts in the lead up to winter. The non‐significant trend of decreasing triglyceride slopes across the sites suggest that the observed increases across months may have been preceding the loss of lipid reserves observed in other species in winter (Biro et al, 2004; Kooka, Yamamura, Ohkubo, & Honda, 2009). The overall trend of lower triglyceride concentrations at DS2 relative to sites receiving no or lesser hydropeaking effects is perhaps the strongest evidence from this study that hydropeaking may interact with shore morphology to act as a chronic stressor.…”