Wildlife2026-10-03

What is eating my pond fish? Muskrats, geese, otters and herons

On an acre-scale fishing pond the animals that cost you something are muskrats (they tunnel into the dam), river otters (they eat the fish, catfish first), Canada geese (they foul the water and the bank) and beavers (they plug the outlet pipe). Great blue herons take fish, but depth and bare banks limit what they get, and turtles and snakes are close to harmless. Muskrats, otters and beavers are furbearers: trap them in season, or out of season under your state's nuisance rule. Geese and herons are federally protected: scare them freely, but killing one needs a federal permit.

What the authoritative sources say

Muskrats

Penn State Extension says burrows start "usually 6 to 18 inches below the surface of the pond or lake" and the signs are "muddy water, floating vegetation, and pellet-sized droppings on rocks along the shoreline." Clemson Extension says "The burrows can breech the dam causing washouts, water loss, and downstream flooding." The barrier Penn State recommends is riprap: "Apply the material in a layer about six inches thick, extending from one foot above to three feet below water level." For removal, Penn State says "Trapping is the most effective method for controlling muskrats that are causing damage." Indiana DNR gives its out-of-season rule: "Resident landowners and tenants can trap or shoot a muskrat that is causing damage on their property without a permit during the closed season." If a burrow has reached the dam, read how a dam, pipe and spillway are built before you repair it.

River otters

The Missouri Department of Conservation otter guide tempers the panic: "Otters do eat fish, but their presence in a farm pond does not automatically spell disaster for fish populations." The exception is catfish: "Channel catfish populations that must be sustained through periodic supplemental stockings are most susceptible to population declines, and are sometimes eliminated by otters." South Carolina DNR puts intake at "about 2½ pounds of food per day." Neither source gives a number of weeks to empty a pond. Missouri describes the sign to look for: "Otters generally leave the heads of catfish intact along the shoreline." On prevention Missouri says "It is difficult to prevent otters from entering ponds and eating fish. Maintaining some aquatic weeds or placing brush piles in the pond will provide cover to help fish escape," and describes an electric fence of "At least four strands, spaced at 4- to 5-inch intervals." South Carolina adds that "No frightening devices are effective for the control of otters." For a cage trap it says "Be sure the trap is at least 48 inches long." Missouri's "Code specifies that damage-causing river otters may be shot or trapped out of season without a permit," but the take "must be reported to a conservation agent within 24 hours." In Indiana, "landowners can contact the DNR to obtain a nuisance wildlife animal control permit."

Canada geese

Penn State says "One adult goose can eat up to four pounds of grass daily, producing 2 to 4 pounds of manure daily." Mowed grass is the draw: "Geese do not like tall plants," and the page lists "fencing, installing a 2- to 3-foot band of rock, or installing a goose grid 6 to 12 inches above the water." The US Fish and Wildlife Service sets the law: "The Canada goose is a migratory bird species that is afforded the protections of the Migratory Bird Treaty Act, Federal regulations, and State laws." Its depredation order "authorizes landowners and local governments who register with the FWS to destroy resident Canada goose nests and eggs on their property from March 1-June 30," while "shooting birds outside of established hunting seasons, require depredation permit(s)."

Great blue herons

Penn State warns herons "may quickly deplete fish populations in ponds" and are "federally protected under the Migratory Bird Treaty Act. This law prohibits hunting, killing, possessing, and selling them." South Carolina DNR names what you can do without a permit: "A permit is not needed to physically or mechanically exclude any fish-eating bird from raceways or water impoundments. Except for threatened or endangered species such as the bald eagle, a permit is not required to harass or scare fish-eating birds." Its design advice is to "Dig deep ponds (3 feet or more) with steep banks to discourage herons and egrets." USDA Wildlife Services adds "Herons and egrets prefer to feed along vegetated banks where they are concealed from their prey," and warns that scare devices fade "as herons and egrets become habituated."

Beavers, turtles and snakes

Clemson says beavers "block pipes and the outfall with sticks, logs, and mud." The Clemson beaver pond leveler, as published by Minnesota DNR, hides the flow behind a caged, perforated intake because "Beavers repair dams in response to the sight, sound, and feel of running water." On turtles, Texas A&M's James T. Davis wrote that "turtles do not seriously affect fish populations. Recent studies indicate that the diets of most turtles contain less than 5 percent fish," and "most of the fish eaten are dead at the time turtles find them." I found no extension source that puts a fish-loss number on water snakes.

Legal frame, as the cited agencies state it. Rules differ by state; check yours.
Animal	Status	Out of season
Muskrat	Furbearer, trapping season	In Indiana a landowner may trap or shoot a damaging muskrat "without a permit"
River otter	Furbearer, trapping season	In Missouri no permit is needed on a pond, but the take must be reported within 24 hours; in Indiana you need a DNR control permit
Beaver	Furbearer	In Pennsylvania you need "a license from the Pennsylvania Game Commission"
Canada goose	Migratory Bird Treaty Act	Scare freely; register to destroy nests and eggs March 1 to June 30; permit to capture or kill
Great blue heron	Migratory Bird Treaty Act	Exclude or scare without a permit; USFWS permit to shoot

What pond owners on the Pond Boss forum do

The forum's most read wildlife threads are "How Do I Get Rid Of A Snake In Pond" and "Great Blue Heron," and one otter thread is titled "HELP HELP OTTERS!!". esshup (Moderator, Ambassador, Field Correspondent) set two Conibear 110s and had a muskrat the next morning. Theo Gallus (Moderator) describes the set: you open the trap, set the trigger and place it underwater in front of an active hole. teehjaeh57 (Chairman) warns that muskrats arriving to eat your cattails trade a cattail problem for a muskrat problem.

The forum agrees that otters are serious and disagrees on what to do about them. Dave Davidson1 (Moderator) says "An otter will eat all the fish it can catch, and it can catch a lot." ewest (Moderator, Hall of Fame 2014) found piles of bass and bluegill scales on the bank. scott69 (Lunker) caught his on beaver dam crossings in the stream below the pond, and adirondack pond (Ambassador) credits an electric fence with keeping them out.

The forum has mostly given up on herons. swampstalker, who ran nine commercial fishing ponds, says there are no permanent solutions; Double-Camp (Lunker) strings monofilament between stakes. For geese, JMAC (Lunker) reports a 10 foot unmowed buffer worked, and h20fwlkillr adds a caution, that cattails may encourage geese to nest. Bill Cody (Moderator) calls turtles a clean-up crew that takes dead, sick and weak fish, and ewest identified a feared moccasin as a speckled kingsnake worth leaving alive.

Where the tiers differ

The forum treats an otter as an emergency and the agencies treat it as a catfish problem. A bass and bluegill pond that reproduces will absorb a visit; a stocked catfish pond will not. Heron appetite is the number that circulates without a source. Vendor pages say a pound of fish a day; no agency source I read gives a daily figure. Goose manure is quoted as ten geese to a cow by Bill Cody and twenty to a cow by ewest; Penn State's "2 to 4 pounds of manure daily" is the sourced figure. Penn State says egg addling "requires a U.S. Fish and Wildlife Service permit"; the FWS now says registration under the depredation order replaces the permit for resident geese in the lower 48, with state law still applying.

Numbers from the cited sources
Measure	Value	Source
Muskrat burrow entrance	6 to 18 inches below the surface	Penn State
Riprap against muskrats	About 6 inches thick, 1 foot above to 3 feet below water level	Penn State
Otter intake	About 2½ pounds of food per day	South Carolina DNR
Pond depth against herons	3 feet or more, steep banks	South Carolina DNR

What to do

Read the sign first. Scale piles and intact catfish heads point to an otter, muddy water and shoreline droppings to a muskrat, stabbed but uneaten fish to a heron, and sticks and mud in the riser to a beaver.
Check your state's season and nuisance rule, then call the state wildlife office or USDA Wildlife Services. A local trapper in season is the cheapest route for furbearers.
For muskrats, trap at the active holes, then riprap the dam face. Trace the rim in the PondTools surface-area calculator (also standalone); it takes a surface area in square feet, or the outline you trace in the app, and the shoreline of that outline is what you price a 4 foot stone band from.
For otters, add brush piles or leave some weed beds, and if you depend on stocked catfish, fence or trap. Do not expect decoys, noise or repellents to work.
For geese, stop mowing to the waterline, haze with a dog, and register for nest and egg destruction if a pair sets up. Do not shoot outside season without a permit.
For herons, keep the banks bare and steep, keep the water deep, string lines, and accept some loss. Do not shoot one.
For beavers, guard the riser intake or install a leveler, then remove the beaver in season or under permit.
Leave turtles and non-venomous snakes alone unless they bother anglers.