Wednesday, March 14, 2018

Invasive Alewife Spreading In Champlain Basin


Recently, an avid angler noticed an odd fish in his bait bucket and reported it to the Vermont Fish and Wildlife Department.

The species was identified as a mosquito fish (Gambusia affinis) and the Department took quick action to locate the baitfish dealer, dispose of the non-native fish, and ensure that no more shipments from the baitfish supplier were allowed to enter the State.

In a similar recent case, an angler reported a number of suspected alewife (Alosa pseudoharengus) in a fish die off in Lake Carmi, VT in December 2017. The Vermont Fish and Wildlife Department responded quickly, confirmed the species as alewife, and alerted the Lake Champlain Basin Aquatic Invasive Species Rapid Response Task Force. The Department estimated that close to 3,000 dead alewives were observed, a number of which were collected for analysis.

Lake Carmi is a popular recreational destination in Franklin County, Vermont and provides walleye, pike, yellow perch, and smallmouth bass angling opportunities. This warm-water, relatively shallow lake does not provide great habitat for alewife, which prefer deep, cold-water environments.

The alewife is a marine fish species native to the Atlantic Coast, where they migrate from saltwater to freshwater environments to spawn and complete their life cycle. Lake Champlain and Lake Saint Catherine in Rutland Co., Vt are home to the two previously known landlocked populations of alewife in the Lake Champlain Basin. The Lake Saint Catherine population was first identified in 1997, and the Champlain population in 2004. Both populations were likely introduced by humans and are considered be invasive.

The Lake Champlain Basin Aquatic Invasive Species Rapid Response Task Force has recommended actions to contain and prevent the spread of alewife in Lake Carmi, Vermont. Task Force members met to conduct a risk assessment of the situation, and determine potential alternatives for containing the species and preventing further spread to other waterbodies in the region. The Task Force also reviewed potential impacts and evaluated possible management options to determine whether a response action to contain and control the spread of this species is feasible.

The Task Force determined that the best response action to contain alewife in Lake Carmi is to prevent spread of alewife to other lakes through enforcement of existing rules and regulations, and through education about the importance of not moving aquatic species from one body of water to another. Lake Carmi drains into the Pike River, which enters Lake Champlain in Missisquoi Bay. Given the existing alewife population in Lake Champlain, the Task Force found that there is not an immediate need to control the outflow of the Lake Carmi to prevent out-migration of alewife downstream. In addition, the economic expense and environmental impact to non-target species is too great to consider use of a pesticide treatment to eliminate alewife from Lake Carmi.

The Task Force’s Spread Prevention Recommendations include:

  • Increased aquatic invasive species spread prevention education and messaging to the public, anglers, bait shops, and other organizations in the region.
  • Increased education through game wardens to the public about baitfish rules and regulations.
  • Continued support of boat launch steward and greeter programs at Lake Carmi to help inform users of the presence of alewife and how to prevent spread to other water bodies, and ensure signage alerting the public to the presence of alewife in the lake and the need to prevent spread of aquatic species among water bodies.
  • Incorporate alewife into early detection and monitoring programs in the region.

Baitfish regulations for the three jurisdictions of Lake Champlain can be found here: New York; Vermont (page 31); and Québec.

Anglers can assist with reducing the spread of aquatic invasive species by checking their baitfish, reporting any fish that appear unusual, and never moving any caught fish, baitfish, or plants from one body of water to another.

Illustration: Alewife, courtesy DEC.

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