Written by: Andrew Goode, vice president of U.S. programs for the Atlantic Salmon Federation
In what has the potential to be Maine’s single largest restoration project for sea-run alewives, the Atlantic Salmon Foundation recently completed a Denil fishway (a design developed in 1909 by a Belgian scientist, G. Denil) at the outlet to Pushaw Lake in Maine’s Penobscot watershed. The Orvis Conservation Fund provided a small grant for this work and has previously provided funding for the ongoing large dam removals on the main stem of the Penobscot.
A low head dam built decades ago at the outlet—to maintain water levels for camp owners—combined with poor fish passage on the main river dams had extinguished this huge run of river herring a long time ago. Just 11 miles from the main stem of the Penobscot River in the lower-central portion of the Penobscot watershed, Pushaw Lake is 5,051 acres, with a maximum depth of 28 feet. Little Pushaw Lake, at 411 acres, is located approximately 5 miles upstream of Pushaw Lake.
The Maine Department of Marine Resources estimated the restoration potential of alewives into the Pushaw Lake system at 1.3 million adults, making it the highest priority restoration lake in the entire Penobscot watershed. A run of this size will have broad benefits to other fish and birds of prey, such as bald eagles and osprey. It will also result in a tremendous transfer of nutrients from the marine to the freshwater environment that could beneficially impact all of the aquatic food webs in the Pushaw Lake ecosystem.
Quite possibly, the restoration of alewives will help in the restoration of Maine’s endangered Atlantic salmon populations. Alewives benefit multiple salmon age classes including fry, parr, smolts, and adults. Historically, the upstream alewife migration coincided with the downstream migration of smolts, so these herring serve as a “prey buffer” to the smolts. Alewives are also repeat spawners, so they again act as a prey buffer leaving the river as adult salmon are coming in.
Over the past four years, ASF has opened up 8,800 acres of prime spawning habitat for alewives in the Penobscot River. Over time, this should lead to more than two million alewives returning as the main stem’s dams are taken down as part of the Penobscot River Restoration Project. (Which Orvis has been supporting for years.)
This past spring, Maine DMR stocked 30,000 adult alewives in to Pushaw Lake to “prime the pump.” In the fall, massive schools of juveniles were documented moving out of the lake on their way to the Gulf of Maine. We expect to see the lucky survivors back in the Penobscot in 2016, where they will only have to pass through the soon to be built Milford Fish Lift on their return to Pushaw Lake.