Examining Food Web Dynamics in Washington Lakes

Crayfish Collected in Diablo Lake

Juvenile Native Char Captured During Sampling on Diablo Lake

Flushing Stomach Contents from Rainbow Trout

By Western Fisheries Research Center December 5, 2022

The WFRC Ecology Section examines how environmental variability, human activities and infrastructure influence food web interactions and species performance in freshwater and marine ecosystems. They have extensive experience in quantifying aquatic food web processes as they relate to growth, survival and production of key species of interest, especially resident and anadromous salmonids.

Scientists from Western Fisheries Research Center have been examining the food web dynamics in Ross and Diablo lakes, Washington. Both lakes are reservoirs in the North Cascade mountains of northern Washington state that were created by dams on the Skagit River and part of the Skagit River Hydroelectric Project. They are also located inside North Cascades National Park.

The field work featured in these images is part of a food web analysis that will be used to help guide hydroelectric operations into the future. Specifically, our scientists are evaluating the potential impacts of the prolific but invasive redside shiner on the productivity of native trout. In addition, they are helping determine whether the lakes will support passage of anadromous salmon and steelhead: evaluating prey availability, predation and competition in the food web.

The images provided illustrate many aspects of this field work, including:

Four nets submerged in a stream to capture drifting invertebrates — Collecting drifting invertebrates, such as immature aquatic and adult insects, with drift nets in a tributary to Ross Lake for an investigation into food availability for native fish and limitations to their growth.

Researcher holding a crayfish collected in Diablo Lake — A native crayfish collected in Diablo Lake for an investigation into food availability for native fish and limitations to their growth. Crayfish are invertebrate prey for salmonids and provide useful representative stable isotope values for benthic members of the food web. Crayfish can exclude minnows from using interstitial refuges (i.e., rockslides, etc.), thus exposing minnows to more predation risk by salmonids.

Juvenile native char in a viewing box — A juvenile native char captured during electrofishing sampling on Diablo Lake. Fish are weighed, measured, sampled for age, and finned clipped as part of the investigation into food web limitations on growth and survival of native fish in these reservoirs.

Researchers performing gastric lavage on a rainbow trout — Flushing stomach contents from a rainbow trout from Ross Lake for an investigation into food availability, limitations to growth, and predation by larger trout on juvenile salmonids.

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