Overview of Damage Prevention and Control Methods
- No practical habitat modification has been found for effective control of otters.
- Hog wire fences
- Electric fences
- No frightening devices are effective for the control of otters.
- No repellents are available for the control of otters.
- No toxicants are registered for otters.
- Air rifle (.22 caliber) or 12-gauge shotgun
- Body gripping traps
- Foothold traps
- Cage traps
- Cable restraints
Damage Prevention and Control Methods
No practical habitat modification has been found for effective control of otters.
Fences with 3‐ x 3‐inch or smaller mesh wire can be an economically effective method of preventing damage at sites that are relatively small, or where fish or aquaculture activities are concentrated. Fences are more economical for protection of small areas where research, experimental, or propagation facilities, such as raceways, tanks, ponds, or other facilities hold concentrations of fish. Hog wire‐type fences also have been used effectively, but these should be checked occasionally to ensure that the lower meshes have not been spread apart or raised to allow otters to enter. Electric fences also can be used, but they require frequent inspection and maintenance.
Electric fences usually are impractical for protecting individual ponds, raceways, or tanks. They have greater utility as a supplement to barrier fences along the perimeter of an aquaculture facility. Use at least 4 strands that are separated by 4 to 5 inches, with the lowest strand 4 inches above ground.
No frightening devices are effective for the control of otters.
No repellents are available for the control of otters.
No toxicants are registered for otters.
Shooting of offending otters usually will prevent continued losses. Otters are inquisitive and often swim within close range for a small rifle or shotgun. Use extreme caution to avoid ricochet when shooting a rifle (.22-caliber) at objects surrounded by water. Shotguns (12-gauge) may be used and have lower risks of ricochet. Check local, state, and federal laws and permit requirements governing shooting, the use of lights after dark, seasons, and possession of carcasses or parts of otters to ensure that all activities are legal.
The trapping of river otters is prohibited in 21 states and 1 Canadian province. Check local regulations before attempting to trap otters.
Check state regulations for restrictions on setting body‐gripping traps on land. Conibear® (Nos. 220 and 330) or similar body-gripping traps are best placed beneath the water surface or partially submerged where runs become narrow or restricted. A No. 220 body‐gripping trap is the optimum size for otters when partially submerged at crossings over dams, main runs in ponds, and locations where otters frequently leave the water.
Body‐gripping traps also are effective in trails made by otters that connect pools of water or that cross small peninsulas. The trap should be placed at a height that blends it with the surrounding vegetation to catch an otter that is running or sliding. After ice forms on the surface of streams and lakes, some trappers bait the triggers of body‐gripping traps with whole fish.
A No. 330 Conibear® trap is most efficient for blind sets on beaver runs, dam sets, or toilets.
Poor catches around the belly rather than the neck or chest occur, however. Only hard‐hitting magnum traps in this size should be used. Traps should be set to slide or entangle in deep water whenever possible so that a poorly caught otter drowns quickly. Spread the trigger wide and use a stainless‐steel wire filament stretched between the tips of the trigger to give a more consistent, lethal strike.
Use padded‐jaw (No. 1½) and double‐longspring (No. 11) foothold traps to capture river otters. If a No. 1½ padded‐jaw trap is used, the 4‐coil‐spring configuration is best. A standard No. 1½ padded‐jaw with 2 coil springs may not hold a large otter.
Make sets in narrow trails and pullouts where shallow water forces otters to walk rather than swim. Place traps in shallow edges of trails leading to otter toilets or other areas that are frequented by otters. Cover foothold traps set on land trails and peninsula crossings with damp leaves and other suitable covering. If a lethal set is desired, attach a foothold trap to a 16‐gauge slide‐wire that leads to water at least 4 feet deep.
Cage traps 12 x 12 x 48 inches or larger are effective for capturing otters. Use 72‐inch cages with double‐doors. Place on land, partially in water, or in floating sets. Hancock‐style traps are effective also but otters may damage their teeth by biting the cage. Bait traps with fresh fish or crayfish. Live‐bait is preferable where legal.
Cable‐restraints are neither the most efficient, nor the most convenient devices for capturing river otters, and should not be the first choice for control. A good cable‐restraint is made with 3/32 aircraft cable, a sliding lock, several swivels, and No. 9 wire. Cable‐restraints set for otters often capture other animals. If non‐target species are a concern, place cable‐restraints in the water to reduce non‐target capture. While cable‐restraints may cause moderate injuries to otters, most can be released unharmed.
Secure the cable‐restraint to a tree that is at least 12 inches in diameter, or to stakes anchored in the soil. Otters that are trapped will not stop fighting. The loop of the cable‐restraint should be 5 to 6 inches in diameter and set to close quickly. Set restraints at the bottom of otter slides, cross overs, or other trails used by otters. Position cable‐restraints with the bottom of the loop at least 4 inches above ground level. Use sticks and grass to narrow the trail and encourage otters to pass through the restraint. Otters damage cable‐restraints; do not reuse them after a capture. Cable‐restraints are not legal for capturing otters in some states.