C Pond Smallmouth Bass Investigations

Fishery Interim Summary Report No. 07-06

By David P. Boucher

Maine Department of Inland Fisheries and Wildlife
Fisheries and Hatcheries Division
Augusta, Maine

December 2007

Interim Summary Report No. 2 (2007)

Summary

C Pond has a surface area of 173 acres and is located in C Surplus Township in north central Oxford County, Maine. The pond’s outlet forms the Dead Cambridge River, which flows 7.8 miles to Umbagog Lake, the lowermost water body of the Rangeley Chain of Lakes. C Pond supports wild brook trout that provide an excellent early-season sport fishery.

Local anglers first reported the presence of smallmouth bass in C Pond in 2001. That same year, Department biologists conducted fish surveys but did not confirm the presence of bass. Additional reports of bass were received in 2002 and 2005.  Trapnet and scuba surveys conducted in 2005 confirmed the presence of small numbers of adult and juvenile bass. Bass most likely migrated upstream from Umbagog Lake where they were illegally introduced during the mid-1980s. The presence of smallmouth bass could severely impact C Pond’s wild brook trout population.

In 2006 we recommended the construction of a fish barrier on the Dead Cambridge River to prevent the continued upstream movement of bass and other species from Umbagog Lake, combined with an intensive effort to physically remove bass that had colonized C Pond. In 2007, construction of the fish barrier was completed, and we continued field trials to physically remove bass in C Pond through raft electrofishing. In addition, the Dead Cambridge River and its tributaries above the fish barrier were surveyed to determine the distribution of bass below C Pond.

Raft electrofishing proved to be an efficient means of removing large numbers of bass from C Pond over a two-year period. However, young-of-year and yearling bass remained abundant, indicating that some adult bass survived to spawn successfully despite intensive removal work. We concluded that complete eradication of smallmouth bass from C Pond using electrofishing techniques is not feasible, and that this effort should be abandoned.

Despite our failure to eradicate bass from C Pond, the project provided important information on the feasibility of such an effort in a large brook trout pond (173 acres) that bass have only recently colonized. Raft electrofishing could perhaps be used to successfully eradicate bass, or other invasive fishes, in very small ponds (<25-50 acres) with limited tributary systems. This idea should be explored if an opportunity arises, and if staffing and funding are available.

The feasibility of chemically reclaiming C Pond is currently being assessed. Complicating factors include the pond’s relatively large size and the likely need to include the Dead Cambridge River and its tributaries downstream to the new fish barrier (2.8 miles). Regardless of the outcome of the chemical treatment, the fish barrier on the Dead Cambridge River will be beneficial because it will exclude other invasive fish species that may become established in Umbagog Lake in the future.

For more information, please contact:

Dave Boucher, Assistant Regional Fishery Biologist
689 Farmington Road
Strong, Maine 04983-9419
Telephone (207) 778-3322 Ext. 23
Email: dave.boucher@maine.gov