Otters and Water Pollution

Why is Water Pollution a Problem?

Because otters are semi-aquatic (they spend much of their life in the water) and find most of their food in the water, they are at risk of being harmed by water pollution. In New York State in the 1800's and early 1900's, many waterways became very polluted. The Hudson River was a major commercial river used for travel and trade as well as an outlet for many people's waste. Since that time the river has been cleaned up dramatically. In the 1970's, legislation like the Clean Water Act helped to revive many waterways in the United States. There are still many pollutants that remain in New York rivers, however, including mercury, cadmium, pesticides and organochlorine compounds.

The Hudson River Otter Stewardship Program is involved with contaminant studies that are being done by the New York State DEC. Currently, scientists are most concerned with the effect of PCBs, or polychlorinated biphenyls, on mink and otter.

Polychlorinated Biphenyls (PCBs)

The term polychlorinated biphenyls refers to a group of 209 different chemical compounds. PCBs were used primarily for lubrication and insulation in electrical equipment. For 30 years PCBs were used and released into the Hudson River until they were banned in 1977. Although they are no longer used, PCBs are still at a level of concern in certain areas. To learn more about PCBs in the Hudson River, visit www.epa.gov/hudson.

Most of the PCBs that were released sank to the bottom of the river where they have bound to the sediments. In the Hudson River, the sediments are constantly being mixed due to tides and currents so that the contaminants continue to be available to bottom dwelling organisms like insects and mussels. This mixing is also believed to cause PCBs from the sediments to be re-released into the water column where they are made available to fish.

PCBs and Otters

This build up of PCBs can cause a problem for organisms low on the food chain, but PCB levels increase dramatically higher up on the food chain. This is because of something called biomagnification, or the multiplier effect. As big fish eat smaller fish and insects, along with all the energy they get from that meal, they also get all the PCBs that their prey has stored up over its lifetime. Take a look at this diagram and you can see that otters can take up a very large amount of PCBs because they are eating fish that already have concentrated levels of the pollutant in their bodies.

New York State DEC is concerned with the bioaccumulation of PCBs in river otter in the Hudson River area. It is not known if PCBs are harmful to otter, but studies have been done on mink and the European otter showing negative effects caused by PCBs. It was found that mink, a close relative of the river otter, that were fed a diet of PCB contaminated fish had a lower birth rate and lower survival of kits per litter than those with no PCBs in their diet. This, along with studies showing that European otter no longer live in areas that are contaminated with PCBs, has led scientists to believe that a diet high in PCBs might be harmful to the American river otter.

What studies have been done?

New York State DEC is in the process of carrying out a study on mink and river otter in the Hudson River Watershed. For more information on mink and otter studies in the Hudson River area, see the NYS DEC Hale Creek Field Station website. Distribution studies are being conducted on mink in the upper Hudson River drainage using track boards. Little is known, however, about the mink distribution in the lower areas of the river. As for river otters, the only distribution information that DEC has for the Hudson Watershed is that gained from trappers.

This is where you can help!

If we can locate where otters are living in the Hudson River Watershed, scientists can take scat samples that will be used in uninvasive contaminant studies. From scat samples, we can find out what an animal is eating, how many animals live in an area, and any pollutants in their diet. Tests will be done not only for PCBs but also for other industrial organochlorine compounds, industrial metals, and pesticides.