The following is a summary of a study being conducted by the Office of Fish and Wildlife Health and Forensics on contaminants in river otters.
Research on Contaminants in River Otters in New Jersey
Fish-eating wildlife may accumulate a variety of organic compounds and heavy metals and thus are good indicators of contaminant levels in the aquatic environment. Monitoring efforts in New Jersey to date have focused on avian species - the bald eagle and osprey - and reproductive effects in some eagles nesting in the Delaware estuary have been attributed to high PCB concentrations in prey (Clark et al. 2001).
Dietary mercury levels of 2 ppm were lethal to otters in a controlled feeding study, and behavioral or reproductive effects may occur at lower dietary concentrations (O'Connor and Nielsen 1981). Mercury concentrations in fish approaching or exceeding 2 ppm have been measured in fish from some parts of the state (Horwitz et al. 1999). Mink are very sensitive to the effects of PCBs, which first became apparent in the 1970s when reproductive failure in ranch mink was attributed to a diet of contaminated Great Lakes Fish (Auerlich et al. 1971).
Controlled feeding experiments with PCBs have not been conducted with the river otter, a species closely related to mink. However, declines in otter populations in some parts of the world have been linked to environmental contaminants (Mason 1989). In field studies in North America, a negative correlation has been reported between baculum length and testicle size in juvenile male otters and tissue PCB concentrations (Henny et al. 1996). We currently have no data on contaminants in fish-eating mammals in New Jersey.
In 2005, the Office of Fish and Wildlife Health and Forensics will be conducting a study of contaminants in river otters in New Jersey. Funding to cover the costs of chemical analysis of otter tissues is being provided by the Department of Environmental Protection's Office of Natural Resource Restoration.
1) Gather baseline information on contaminant concentrations in river otters in New Jersey
Otter carcasses will be collected from cooperating trappers during the 2005 season. Livers will be collected and analyzed for mercury, PCB congeners and chlorinated pesticides. Depending on the number of samples collected and the availability of funding, some liver samples may also be analyzed for dioxins/furans and polybrominated diphenyl ether. Female fertility will be assessed by counting corpora lutea in ovaries. Baculum length and testicle size will be measured in males. Age will be determined by counting dental annulations. The data will be statistically analyzed to look for correlations between contaminant concentrations and corpora lutea counts in females and baculum length and testicle size in males.
Auerlich RJ, Ringer RK, Seagrin HL, Youatt WG. 1971. Effects of feeding coho salmon and other Great Lakes fish on mink reproduction. Canadian Journal of Zoology. 49:611-616.
Clark KE, Stansley W, Niles LJ. 2001. Changes in contaminant levels in New Jersey osprey eggs and prey, 1989 to 1998. Bulletin of Environmental Contamination and Toxicology. 40:277-284.
Henny CJ, Grove RA, Hedstrom OR. 1996. A field evaluation of mink and river otter on the lower Columbia River and the influence of environmental contaminants. Final Report to the Lower Columbia River Bi-State Water Quality Program (Portland, OR). National Biological Service, Forest and Rangeland Ecosystem Science Center, Corvalis, OR.
Horwitz RJ, Valinsky DJ, Overbeck P, Kiry P. 1999. Phase II assessment of total mercury concentrations in fish from rivers, lakes and reservoirs in New Jersey. Report No. 99-7R prepared for the New Jersey Department of Environmental Protection and Energy, Office of Science and Research.
Mason CF. 1989. Water Pollution and otter distribution: a review. Lutra 32:62-67.
O'Connor DJ and Nielsen SW. 1981. Environmental survey of methylmercury levels in wild mink (Mustela vison) and otter (Lutra canadensis) from Northeastern United States and experimental pathology of methylmercurialism in the otter. In: Chapman JD, Pursley D (eds) World furbearer conference proceedings. Frostburg, Maryland, pp 1728-1745.