Missouri River Otter Saga
provide much-needed relief in the Ozarks by adding a full month to the trapping season with no limit. This helps us to direct the most intensive trapping pressure where it is most needed, and it allows a sustainable harvest of otters in other areas where we want otter populations to remain stable.
Our management goal is to use regulated trapping to maintain healthy otter populations within the tolerance levels of both habitats and people.
In the Ozark streams where the problems are the most severe, our goal is to reduce otter populations to the level where we can improve quality sport fish populations.
Thanks to the current high market prices ($40 to $120) for otter pelts, trappers have been very helpful. In the 2005–06 trapping season, Missouri trappers took more than 3,000 otters. In areas where we want fewer otters, trappers have taken as many as 50 percent of the otters each year. Annual survival rates are averaging about 75 percent in areas where our goal is to allow populations to remain stable or continue to increase slowly.
Missouri’s otter population probably peaked at somewhere between 15,000 and 18,000 animals. We documented as many as three otters per mile in some small streams, and their fish populations did decline. Anglers report better fishing recently, however, and complaints about otters have gone down, although we still have a way to go in some areas.
The statewide otter population is now closer to our goal of 10,000. In most streams, densities are about one otter per mile, and our fisheries managers report that fish populations look good.
Reducing their numbers has made otters nicer neighbors. People tolerate them better, and even many anglers admit they don’t mind sharing a few fish with them.
What Otters Eat in Ozark Streams
We have studied otter diets since we began stocking the animals and have found that their most important food is crayfish, which they eat almost exclusively from April until October. Crayfish populations in Ozark streams are among the highest recorded anywhere.
In winter, otters primarily eat fish. They mostly consume long-eared sunfish (35 percent), but also a significant amount of smallmouth bass (12 percent). Goggle-eye and suckers each account for about 10 percent.
Each year we collect otter carcasses from trappers and, among other tests, we determine their age from their teeth. Otters in Missouri are breeding at earlier ages and having more pups in each litter than previously documented. Many female otters are breeding as yearlings, giving birth to first litters near their second year of life. This cuts the generation time in half, and greatly increases the population growth rate.
Six years ago we enlisted two husband-and-wife trapper teams to live-trap otters and implant small radio transmitters in them. This allows us to determine where otters go, how long they live and how they die.
Of the more than 300 otter captures so far, we have documented 97 mortalities. Of these, 78 were trapped, six were shot, two died from bacterial infections, one was struck by a car and another was struck by a train. We couldn’t determine a cause of death for nine of the otters.
What this tracking study suggests is that when food is abundant, there is no other way than trapping to control otters. Without trapping, otter survival rates would contribute to rapid population growth and many more otter problems.