Climate change-informed dietary modeling in Pacific cod: Experimentally-derived effects of temperature and dietary quality on carbon and nitrogen stable isotope trophic discrimination factors.

Stable isotope analysis is a powerful tool for dietary modeling and trophic ecology research. A crucial piece of information for isotopic dietary modeling is the accurate estimation of trophic discrimination factors (TDFs), or the isotopic offset between a consumer's tissue and its diet. In order to parameterize stable isotope dietary models for future climate scenarios, we investigated the effect of water temperature and dietary protein and lipid content on TDFs in juvenile Pacific cod (Gadus macrocephalus).

Critically endangered Rice's whales (Balaenoptera ricei) selectively feed on high-quality prey in the Gulf of Mexico.

Determining the drivers of prey selection in marine predators is critical when investigating ecosystem structure and function. The newly recognized Rice's whale (Balaenoptera ricei) is one of the most critically endangered large whales in the world and endemic to the industrialized Gulf of Mexico. Here, we investigated the drivers of resource selection by Rice's whales in relation to prey availability and energy density.

Effects of Environmental Temperature on the Dynamics of Ichthyophoniasis in Juvenile Pacific Herring (Clupea pallasii).

The effects of temperature and infection by Ichthyophonus were examined in juvenile Pacific herring (Clupea pallasii) maintained under simulated overwinter fasting conditions. In addition to defining parameters for a herring bioenergetics model (discussed in Vollenweider et al. this issue), these experiments provided new insights into factors influencing the infectivity and virulence of the parasite Ichthyophonus.

Energetic Cost of Ichthyophonus Infection in Juvenile Pacific Herring (Clupea pallasii).

The energetic costs of fasting and Ichthyophonus infection were measured in juvenile Pacific herring (Clupea pallasii) in a lab setting at three temperatures. Infected herring incurred significant energetic costs, the magnitude of which depended on fish condition at the time of infection (fat versus lean). Herring that were fed continually and were in relatively good condition at the time of infection (fat) never stored lipid despite ad libitum feeding.

Seasonal cycles in whole-body proximate composition and energy content of forage fish vary with water depth.

Quantifying the nutritional quality of forage fish is integral for understanding upper trophic levels as forage fish are the dominant prey for top predator fish, marine mammals, and sea birds. Many existing reports documenting body composition of forage species are not comparable due to confounding effects. This study systematically assessed the variability in proximate composition and energy content of 16 forage species in southeastern Alaska (57.

Changes in the lipid class and proximate compositions of coho salmon (Oncorhynchus kisutch) smolts infected with the nematode parasite Philonema agubernaculum.

Coho salmon (Oncorhynchus kisutch) smolts infected with the nematode Philonema agubernaculum had 36% lower mean lipid content (1.4%) than nonparasitized coho salmon (2.2%) harvested simultaneously from the same outmigration.