Cormorants: Georgia’s Flying, Feathered Fish-Eaters
Each winter, these birds migrate by the thousands to Georgia lakes and ponds. Are these fish-eaters having an impact on sport fishing?
They come winging south to winter in Georgia and Florida by the thousands. Long lines or “V”s of 4- to 5-lb. birds, often mistaken for geese, migrate north and arrive in big numbers on Georgia impoundments in early winter. They line the standing timber in Sugar Creek on Lake Oconee, they roost in the trees on the island in Big Lazer Creek and they fly by the thousands over lakes Seminole and Eufaula. The birds are double-crested cormorants — named for twin tufts of feathers on their heads during breeding season — and they come searching for fish to eat. Underwater, a streamlined cormorant is something of a guided fish torpedo powered by wide, webbed feet. They can dive to 20 feet and stay submerged 30 seconds to chase and catch fish in their saw-tooth bill. They can eat a pound of fish a day.
Nationwide, they have experienced a population explosion over the past 20 or 30 years. In the 1960s and 70s they were nearly wiped out by the insecticide DDT in the environment. DDT concentrated in the fish cormorants ate. The chemical caused thinning of egg shells that caused the eggs to fail and stemmed reproduction. With the use of DDT banned in the 1970s, the cormorant population has rebounded in spectacular numbers, and in some situations they are causing problems for people who grow fish. Some fishermen are concerned that they may be hurting sport-fish populations.
Greg Grimes owns Aquatic Environmental services, a pond-management company, and he has clients who have experienced problems with cormorants taking up residence and feasting on the fish in their ponds. The problems can be massive, said Greg.
A client in South Carolina had several ponds stocked full of tilapia — until flocks of cormorants descended on the ponds and essentially wiped out the fish population in seven ponds.
Greg recently became a distributor for propane cannons that are used to scare off nuisance birds, cormorants, in this case. He has sold the devices to Georgia pond owners in Bollingbroke and Thomaston who are battling cor- morants, and one to a pond owner in South Carolina. The jury is still out on whether the cannons are effective long- term in scaring the birds off, said Greg.
Cormorants are protected by federal law. A pond owner cannot simply kill a cormorant. If you have a permitted aquaculture business and grow fish, however, you may be able to obtain a special permit from the U.S. Fish and Wildlife Service (FWS) that allows you to shoot cormorants.
FWS food-habit studies done in the Northeast suggest that forage fish comprise 70 to 90 percent of a cormorant’s diet, but they eat what is easi- est to catch which makes them a bird you don’t want to see swimming on your ponds if you are a fish-hatchery manager. At WRD’s McDuffie Fish Hatchery, Manager George Atnip says he has seen a marked increase in the number of cormorants that show up on the hatchery ponds in recent years.
“Cormorants didn’t used to be a problem,”he said. “But in the past three or four years the numbers have increased. Unless you get rid of them, they will stay on a pond until they clean it out.”
The hatchery operation grows fish to stocking size in 32 ponds that range in size from one-half to one acre. To a hungry cormorant, the ponds must look like the restaurant from heaven packed full of just-right-eatin’ size fish.
The hatchery uses noise cannons and other scare tactics to discourage the birds plundering the ponds. As a last resort they also use lethal means.
Gary Burtle with the University of Georgia Aquaculture Unit in Tifton says there is little information on what impact cormorants have on the aqua- culture business in Georgia, but the birds are a problem.
“They are not a fish-farmer’s friend,” said Gary. “They live to eat fish, and they are only deterred by the most extreme methods.”
At Paradise PFA, Manager Charles West has also been battling cormorants on the 68 ponds on the area.
“When we first opened Paradise PFA in 1990, they (the U.S. Fish and Wildlife Service) didn’t want to issue depredation permits for cormorants. We tried scare tactics — scare shells, sirens, even running at them waving our arms. But what happens is they get used to the scare tactics — whatever we can do — and they ignore you.”
When the FWS finally began issuing depredation permits they had to be applied for annually. Today, a blanket exemption is allowed to state hatcheries, but they must file an annual report with the FWS on the number of birds they kill.
“We are concerned about the birds showing up on our intensively man- aged ponds,” said Charles. “If you have a pond that is being managed for a kids’-fishing event and it is full of cat- fish, cormorants can clean it out in a few days. You see a few birds, and if you don’t do something about it they go get their friends and pretty soon you have 50 or 100 birds on a 2- or 3-acre pond and they will wipe it out.”
Charles said that eating a catfish is no problem for a cormorant. The birds come to the surface with catfish cross- wise in their bill. They flip the fish in the air, catch it by the head and it dis- appears head first down their throat.
“When you see them eating 8- to 10-inch catfish, that’s fish anglers won’t catch, so they are having some impact on angler success,” said Charles. “I have seen catch rates drop when cormorants move onto a pond.”
At Paradise, Charles has worked out a compromise on cormorant’s presence on the area.
“We have allowed them to stay on our bigger ponds, but we try to control them in our catfish ponds,” he said.
“The fishermen are concerned about them. They see the birds eating fish. I have found large bream in cormorants that we have killed. They catch what is easy. When the bream spawn in the spring, the cormorants will work the bream beds.”
At WRD’s Richmond Hill hatchery, cormorants attracted to the ponds are dealt with on an as-needed basis.
“We stock fish in the pond at very high density,” said Region Supervisor of Fisheries Matt Thomas. “If they set up on the hatchery ponds, they can cause problems. We raise the Phase II stripers here that we grow up to 6 inch- es. They really like those, and our cat- fish, too. We try to keep them run off using a variety of scare tactics. Since we are in the city limits, we don’t like to use the shotgun.”
Chris Harper is the manager of the Richmond Hill Hatchery. He says problems with cormorants on hatchery ponds are cyclic.
“We are required to file a report on the number of cormorants we shoot,” he said. “Over the past three years (ending Oct. 31) we killed 41 cormorants. This year, however, since Nov. 1 we have killed 16. Sometimes the birds just won’t leave. They will swim from one side of a pond to the other but won’t fly off.
“You have to scare them off early. They seem to send in a scout. If you get one or two and let them hang around, the next thing you know you have 10 or 20.”
On the the bigger water of the intercoastal waterway, Matt doubts cormorants have a measurable impact on sport fisheries.
“I expect they mostly feed on menhaden and finger mullet,” he said. “On a system that big, I don’t think they have any significant impact.”
Cormorants overwinter in Georgia in high numbers on lakes Seminole and Eufaula.
“There is a lot of standing timber in those lake that they use for roosts,” said WRD Region Supervisor of Fisheries Rob Weller. “They eat a lot of fish, but there have been no studies done in Georgia on what they are eating, so there is no way to quantify the loss. Some people might say they are taking prey species away from game species. Others might argue that they could possibly be helping by thinning out the shad population and keeping it dynamic. Shad populations have a tendency to lock up at large sizes that are too big for game fish to eat. If the shad population is thinned, reproduction increases and there are more young baitfish available for game fish.”
While there have been no scientific studies done in Georgia on the impact of cormorants, the upshot on cormorants and sport fish is that with the exception of aquaculture or small- pond situations, cormorants probably have no measurable impact on sport fishing in Georgia. These fish eaters are opportunistic and will certainly eat a bream, crappie, bass or striper if they find fish the right size. Mostly they catch fish that are the most plentiful and easiest to catch. On most Georgia impoundments that means shad. To some extent, several biologists suggested the birds may possibly provide the same benefit as striped bass that have been stocked in large reservoirs to help control shad populations. It is possible on large reservoirs that cormorants may help trim the baitfish population to keep it dynamic and reproducing young, small, baitfish
for game species to feed on.
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