Preventing Conflicts With River Otters
River otters are often blamed for preying on wild game fish, particularly trout. Nevertheless, studies indicate that the bulk of the river otter’s diet consists of non-game fish species.
However, river otters—particularly families containing young pups in spring—occasionally cause severe problems in fish hatcheries and private ponds. Otters also den under houses, decks, and other structures near water, and the smell of their droppings and discarded food remains can be unpleasant.
To prevent conflicts or remedy existing problems:
Eliminate access to feeding sites and other areas. Because river otters have heavy bodies and aren’t jumpers, a 4-foot high fence constructed with 3-inch mesh wire can keep them out of an enclosed area, such as where fish or aquaculture activities are concentrated (Fig. 4). Because river otters are strong, fences should be sturdy and extend 6 inches below the surface to prevent otters from pushing under the fence. Alternatively, include a wire apron on the animal side of the fence to prevent otters from entering from underneath.
A double-wire electric fence, with wires set 6 and 10 inches above ground will also deter river otters. Such a fence can stand alone, or supplement an existing perimeter fence. A single wire can be used around docks and houseboats.
River otters are resourceful and will thoroughly investigate fence lines to find a way into a food source. They are known to use abandoned animal burrows as routes under fences. So, inspect fences regularly to make sure river otters have not dug or pushed their way under or worked their way over them.
Provide fish with hiding places. Give fish safe places to hide by constructing sturdy hiding places on the bottom of ponds using cinder blocks, ceramic drain tile, wire baskets made from leftover galvanized fencing, or upside-down plastic crates held in place with heavy rocks. In larger ponds, attach a group of cut conifer trees to a heavy anchor on the bottom of the pond.
Eliminate access to convenient denning sites. Close potential entries under porches, houses, sheds, and other structures with ¼-inch mesh welded-wire (hardware cloth), boards, or other sturdy material. Aluminum flashing, or aluminum or stainless-steel hardware cloth is recommended in saltwater areas since galvanized materials quickly corrode.
Eliminate noxious odors. Commercial odor-eliminators can be used to remove the smell of otter droppings and other debris under structures. Such products are available through hospital supply houses, drugstores, pet stores, and from the Internet using the keywords “Pest Control Supplies.” If the smell is really bad, the beams and other areas under the structure may have to be cleaned with a bleach solution (1½ cups of household bleach in 1 gallon of water). Be very careful of fumes.
However, river otters—particularly families containing young pups in spring—occasionally cause severe problems in fish hatcheries and private ponds. Otters also den under houses, decks, and other structures near water, and the smell of their droppings and discarded food remains can be unpleasant.
To prevent conflicts or remedy existing problems:
Eliminate access to feeding sites and other areas. Because river otters have heavy bodies and aren’t jumpers, a 4-foot high fence constructed with 3-inch mesh wire can keep them out of an enclosed area, such as where fish or aquaculture activities are concentrated (Fig. 4). Because river otters are strong, fences should be sturdy and extend 6 inches below the surface to prevent otters from pushing under the fence. Alternatively, include a wire apron on the animal side of the fence to prevent otters from entering from underneath.
A double-wire electric fence, with wires set 6 and 10 inches above ground will also deter river otters. Such a fence can stand alone, or supplement an existing perimeter fence. A single wire can be used around docks and houseboats.
River otters are resourceful and will thoroughly investigate fence lines to find a way into a food source. They are known to use abandoned animal burrows as routes under fences. So, inspect fences regularly to make sure river otters have not dug or pushed their way under or worked their way over them.
Provide fish with hiding places. Give fish safe places to hide by constructing sturdy hiding places on the bottom of ponds using cinder blocks, ceramic drain tile, wire baskets made from leftover galvanized fencing, or upside-down plastic crates held in place with heavy rocks. In larger ponds, attach a group of cut conifer trees to a heavy anchor on the bottom of the pond.
Eliminate access to convenient denning sites. Close potential entries under porches, houses, sheds, and other structures with ¼-inch mesh welded-wire (hardware cloth), boards, or other sturdy material. Aluminum flashing, or aluminum or stainless-steel hardware cloth is recommended in saltwater areas since galvanized materials quickly corrode.
Eliminate noxious odors. Commercial odor-eliminators can be used to remove the smell of otter droppings and other debris under structures. Such products are available through hospital supply houses, drugstores, pet stores, and from the Internet using the keywords “Pest Control Supplies.” If the smell is really bad, the beams and other areas under the structure may have to be cleaned with a bleach solution (1½ cups of household bleach in 1 gallon of water). Be very careful of fumes.
This information was provided by the Washington State Department of Fish and Wildlife, Russell Link, and Michael Holmquist
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