BEAVER DAM EFFECTS ON DOWNSTREAM AQUATIC
INVERTEBRATE COMMUNITIES




Christie Deloria
School of Science and Natural Resources
Lake Superior State University
Sault Ste Mane, Ml 49783 USA



Abstract. The effects of a beaver dam on downstream aquatic
invertebrate communities were evaluated in the Hurricane River within
the boundary of Pictured Rocks National Lakeshore, Ml. Samples were
collected during a three week period in July and August from one upstream
control site and three downstream sites using a Surber sampler.  Drift net
samples were also collected at the upstream control site and one
downstream site. ANOVA/Tukey results showed similar mean densities
between the upstream control site and the two downstream sites with
similar habitats.  The downstream drift net results showed significantly
greater numbers (p<.05) of Ephemeroptera than the upstream site. It was
observed that the beaver dam decreased amounts of sediments
downstream thereby creating improved invertebrate habitat. Therefore,
the beaver dam did appear to have an effect on the overall downstream
aquatic insect communities.


Selected References

Clifford, H.F., G.M. Wiley, and R.J. Casey. I 993. Macroinvertebrates of a
beaver-altered boreal stream of Alberta, Canada, with special
reference to the fauna on the dams. Can. J. Zool. 71: 1439-1447.

McDowell, D.M. and R.J. Naiman. I 986. Structure and function of a benthic
invertebrate community as influenced by beaver (Castor canadensis).
Oecologia, 68: 481-489.