Facebook logo Twitter logo YouTube logo Podcast logo RSS feed logo

Cormorant Conundrum

closeup of cormorant's head

Photo: P. Wallack

"It use to be, 'What in the world is that?' But now it's, 'Oh no, not another one of those bleeping cormorants,'" laments Mike Lint, co-president of the Minnesota Fish and Bait Farmers from his fish farming business in West Central Minnesota. "You can scare pelicans off a fish pond, but cormorants are relentless."

Lint's family has been farming baitfish and other fish since 1956 and has watched cormorants move from novel visitors on farmed ponds to extended clans of unwelcome squatters that resist all but deadly attempts to shoo them away.

During the last two decades, Lint has tried to defend his fish from increasing numbers of cormorants with scare tactics, balloons, and even techniques borrowed from airport efforts to manage birds, to no avail. Now (in compliance with federal depredation rulings that are currently under litigation) he buys 20 cases of shells, hires a "pond guard" each fall, and hopes the Minnesota Department of Natural Resources (DNR) will make astute management decisions to relieve conflicts between fish producers and cormorants. Meanwhile, he estimates that these black birds, with assistance from some white pelicans, can consume over $100,000 worth of marketable fish from his ponds in a year.

Minnesota Sea Grant-funded researchers Linda Wires and Dr. Francie Cuthbert, with the University of Minnesota Department of Fisheries, Wildlife, and Conservation, surveyed Lint and 53 other fish farmers in Minnesota. Their intent was to correlate information on bird-related fish losses with the distribution and abundance of cormorants, pelicans, and herons in the state. The resulting report is aiding the U.S. Fish and Wildlife Service (USFWS), DNR and fish producers in Minnesota as they consider the cormorant conundrum.

"Cormorants aren't the only fish-eating birds that visit fish production ponds but they can be a fish producer's biggest problem bird," said Wires. "People seem to hold very polarized opinions about how cormorants should be handled. On one level, it's miraculous that we have cormorants in the state at all given that environmental contaminants and persecution greatly reduced populations by the 1950s. From another perspective, the growing number of cormorants and pelicans aren't making many friends among fish producers and anglers."

Environmental legislation and changes in societal norms, beginning largely in the 1970s, allowed cormorant and pelican populations to rebound. In Minnesota, estimates suggest that there are 8,000-10,000 breeding pairs of each species. Wires and Cuthbert are poised to conduct a statewide census of Minnesota's breeding cormorants and pelicans during the 2004 nesting season.

"Actually, the biggest cormorant conflicts with aquaculture are found in the Mississippi Delta area where vast regions are used for cultivating fish," said Wires. "The USFWS made a final ruling for the expanded depredation order for aquaculture last October. This means that cormorants can be lethally controlled off-site at their winter roosts without a federal permit.

"In Minnesota, fish farmers can legally kill cormorants at their ponds but they are not allowed to shoot cormorants at nesting sites," said Wires. "Although some might argue otherwise, it appears as though a large portion of the problems that fish farmers have with cormorants involve migrating birds. And that isn't really surprising when you understand that the heart of 'fish-farming country' lies along a major migratory flyway that funnels northern birds down the Mississippi River valley. Thousands of cormorants from the Dakotas and Canada get a bird's-eye view of most of Minnesota's fish farms."

Lint agrees. "The effect of cormorants is more visible with the fall migration. The spring migration isn't as bad because by then
we've completed the majority of our harvest so there are fewer fish to feed on, and also because the cormorants already consumed a lot in the fall.

"We can always tell which ponds have a good crop of fish because the birds will be there," said Lint. "At times we try to carry fish over to the next spring. By ice-out, the migrating cormorants will locate these particular ponds and participate in a feeding frenzy until all of the fish are gone."

The major results of Wires' and Cuthbert's report have been distilled into a fact sheet, Minnesota Fish Producers Report on Losses to Birds. Highlights include:

Fish losses to double-crested cormorants were generally considered more severe than losses to American white pelicans and great blue herons.
Fish losses to great blue herons occurred most frequently but were generally not considered severe.
87 percent of fish producers experienced losses to fish-eating birds.
41 percent of fish producers defined their losses as severe.
Concentrations of fish-eating birds were greatest at facilities during the birds' migratory periods.

To order a free copy of the Minnesota Fish Producers Report on Losses to Birds fact sheet, check item A 20 on the products order form, under the aquaculture category.

By Sharon Moen
February 2004

Return to February 2004 Seiche

This page last modified on March 01, 2018     © 1996 – 2019 Regents of the University of Minnesota     The University of Minnesota is an equal opportunity educator and employer.
Facebook logo Twitter logo YouTube logo Podcast logo RSS feed logo
Logo: NOAA Logo: UMD Logo: University of Minnesota Logo: University of Minnesota Extension