Damage and Damage Identification

The North American river otter, Lutra canadensis

The presence of river otter(s) around or in a fish hatchery, aquaculture, or fish culture facility is a good indication that a damage problem is imminent. Otter scats or toilets that contain scales, exoskeletons, and other body parts of the species being produced is additional evidence that damage is on-going. Uneaten parts of fish in shallow water and along the shore is evidence that fish are being taken. Otters usually eat all of a small catfish except for the head and major spines, whereas small trout, salmon, and many of the scaled fishes may be totally eaten. Uneaten carcasses with large puncture holes are likely attributable to herons. River otters can occasionally cause substantial damage to concentrations of fishes in marine aquaculture facilities. Often the damage involves learned feeding behavior by one or a family of otters.

Economics of Damage and Control

Although individual incidences of river otter damage and predation on fish can cause substantial losses to pond owners and to fresh water and marine aqua cultural interests, their total effects are believed to be insignificant. Given the otter’s aesthetic and recreational value, and its current legal status, consideration of broad control programs are unwarranted and undesirable.

Legal Status

The river otter is listed in Appendix II of the Convention on International Trade in Endangered Species of Flora and Fauna (CITES). Its inclusion in this appendix subjects it to international restrictions and state/province export quotas because of its resemblance to the European Otter. Moreover, the river otter is totally protected in 17 states. Twenty-seven states have trapping seasons, and four states and two provinces have hunting seasons.