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U.S. reservoirs hold billions of pounds of fish – Daily Democrat

A reservoir in Marion County, Oregon. (Dan Meyers/Unsplash)

After humans built dams on most of the world’s major rivers for nearly a century, man-made reservoirs now represent a huge freshwater footprint on the landscape. Yet these reservoirs have been underexplored and overlooked for their potential for fisheries production and management, a UC Davis study shows.

The study, published in the journal Scientific Reports, estimates that U.S. reservoirs contain 3.5 billion kilograms of fish. If managed properly, these existing reservoir ecosystems can play an important role in food security and fisheries conservation.

“There is a large amount of fish stock in U.S. reservoirs that is being overlooked, despite its value being comparable to fish harvests from fisheries around the world,” said lead author Christine Parisek, a doctoral candidate in the UC Davis Ecology Graduate Group and the Department of Wildlife, Fish and Conservation Biology.

States with the most reservoir fish

For the study, the authors analyzed, digitized, sequenced and classified reservoir data collected by the U.S. Army Corps of Engineers between the 1970s and 1990s, after dam construction dwindled from its heyday in the 1940s to the 1960s. The data includes fish biomass and production rates from 301 reservoirs in the United States.

Southern U.S. reservoirs hold 1.92 billion kilograms of fish. Reservoirs across the US hold an estimated 3.43 billion kilograms of fish.

Most states show reservoir reserves of at least 100 million kilograms (220 million pounds). The top five states with the largest stock, or total weight, of reservoir fish are Texas, Arkansas, Oklahoma, Florida and South Dakota.

When the total weight is adjusted by the amount of reservoir surface area available in the state – similar to a per capita measure – Louisiana, Indiana, Alabama, Maryland and Illinois score the highest.

The study also shows that the large abundance of fish in U.S. reservoirs is of great importance to the global carbon cycle, as fish play an important role in carbon flux, food webs, nutrient cycling and energy transfer.

Managing amidst challenging realities

The authors emphasize that the study is not an argument for prioritizing reservoir building over protecting and restoring naturally flowing rivers. The study states: “The ecological impacts of dams have been overwhelmingly negative and represent one of the leading causes of freshwater biodiversity loss at all scales.”

The study suggests unrealized opportunities to better manage both natural and built ecosystems given the realities of reservoir survival, climate change and the serious challenges facing native fish.

“We should be able to walk and chew gum,” says fish ecologist and senior author Andrew Rypel, director of the UC Davis Center for Watershed Sciences and professor in the Department of Wildlife, Fish and Conservation Biology. “We should be able to decommission and remove some dams, and manage others for food and as important habitats.

“In a worst-case scenario where the salmon become extinct and the native fish disappear, this fishery may be all we have left. It is worth having the foresight on how to manage these well and how to use these ecosystems to create value for the environment and for people.”

Other authors include co-first author Francine De Castro, Jordan Colby and Steven Sadro of UC Davis, and George Leidy of consulting firm AECOM and Stillwater Science.

The study was funded by the National Science Foundation, UC Davis Center for Watershed Sciences’ Bechtel Next Generation Funds, University of California Agricultural Experiment Station, and the California Trout and Peter B. Moyle Endowment for Coldwater Fish Conservation.