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Sea birds impact local fisheries; stocking delayed | Preston Citizen

Sea birds impact local fisheries; stocking delayed

May 19, 2013


Assistant editor

All local reservoirs will be stocked with catchable trout by Memorial Day weekend if a sharp-billed sea bird cooperates with the Idaho Department of Fish and Game.

In the recent past, stocking has occurred soon after ice-off on reservoirs in Franklin County in late March or April. But the double-crested cormorant has made inroads into inland areas across the United States and uses Franklin County as a stopover area along its migration route.

The bird has impacted local fisheries by delaying stocking efforts. Anglers, who traditionally like to fish just after ice-off, have had to wait for planted fish, said IDFG officials.

“Even though we haven’t stocked any trout yet, fishing has actually been pretty good this spring with carry-over trout and things will just continue to improve,” said David Teuscher, regional fisheries manager based in Pocatello. “Early season anglers shouldn’t hesitate to go out now. Catch rates may be down just a little. But the fish that are caught should be in the 13 to 14-inch range.”


During the past several decades, double-crested cormorant populations in North America have increased annually by six-percent. Many of the fish eating cormorants currently using Franklin County reservoirs are stopping for short periods as they migrate from warmer coastal regions north to nesting grounds, according to Teuscher.

“Bird counts taken at Foster Reservoir, northeast of Preston, last Saturday revealed hundreds of birds. In fact they were spotted around every reservoir searching for food. They can eat fish up to 13 inches long, but usually go after those in the six to seven-inch range,” he said.

Teuscher said their favorite food is just-stocked hatchery trout. When these trout are placed in reservoirs they don’t have any skills at avoiding predators and are easy pickings for the birds. In fact, the cormorants will immediately switch from small bass and bluegill to the hatchery rainbows, he said.

“That’s why we have to delay stocking until the birds move on to their traditional nesting areas along the Snake River near Blackfoot, the Blackfoot Reservoir, Montana and points north,” he said.

“This spring’s unseasonably cool temperatures have been a factor delaying the migration. Every spring is different and we have to be flexible.”

The Blackfoot Reservoir is one of the nesting locations. In 2001, IDFG counted 214 cormorant nests on Gull Island on the reservoir.

“In 2009, we counted 634. Each nest represents two adult birds, so about four years ago 1,260 cormorants nested on Gull Island and the number is higher now.”

Idaho Fish and Game employees move towards a group of cormorants on Gull Island in the Blackfoot Reservoir. The sea birds are making inroads into Idaho and causing a delay in fish-stocking efforts.

Idaho Fish and Game employees move towards a group of cormorants on Gull Island in the Blackfoot Reservoir. The sea birds are making inroads into Idaho and causing a delay in fish-stocking efforts.

In past years IDFG has received a number of reports of larger-than-normal flocks of foraging cormorants on Franklin County waters.

“Some of the local fisheries were hit especially hard by cormorant or pelican predation both in 2008 and 2009, Teuscher said.

Treasureton Reservoir is an example. Fisheries biologists monitoring the hatchery trout populations observed very poor survival of 2009 plants in the impoundment.

“Holding catchable rainbow trout for several weeks longer than usual helps reduce bird predation. We play the waiting game to give the newly stocked trout a better chance for survival. We wait until most of the cormorants have completed their spring migration and that usually happens by the end of May. It’s all a numbers game,” said Teucher.

Cormorants are medium-to-large sea birds with dark plumage. Their bills are long, thin and sharply hooked. They are costal birds that have colonized inland waters over the past few years. They are fish eaters, dining mostly on small fish.

They dive from the surface. Underwater, they propel themselves with webbed feet. After fishing they go ashore.

They have waterproof feathers. They dive alone and feed singly, but congregate in large groups, according to Wikipedia.

This story is sponsored by The Preston Citizen Bookstore.

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