Printer-friendlyEnvironment DEC
From the May 2008 issue
Alewife Die-off in Lake Champlain
Thousands of dead fish are appearing on the surface and shores of Lake Champlain, on both the New York and Vermont sides of the lake. The fish are (immature and adult) alewives, a type of herring with a gray-green back and silvery iridescent sides.
Alewives are an invasive species, first found in Lake Champlain in 2005. Their presence became more widely known earlier this year when tens of thousands of dead alewives turned up on the Vermont side of the lake. Historically, alewife populations in the Great Lakes--where they also are an invasive species--have fluctuated significantly.
Water Temperature and Die-offs
Alewives are an invasive species that pose a threat to native fish populations
Alewives are susceptible to rapid drops in water temperature that can occur at the onset of winter and when cold waters from melting ice mix with the somewhat warmer waters below. This is what caused the die-off in Vermont earlier this year and is thought to be responsible for the recent one.
It is possible that the fish died during the winter but were preserved in the cold waters under the ice. Now that the ice is thawing, the dead fish are surfacing. Vermont officials had tested alewives from the January die-off and found them negative for viral hemorrhagic septicemia (VHS).
While large numbers of dead fish are unsightly and possibly odorous, they do not present a widespread health or environmental problem. Gulls, raccoons and other scavengers will consume many of the fish; the rest will decompose.
Preventing Further Invasions
It is not certain whether alewives entered the lake by migrating through the connecting canal systems or as a result of illegal stocking in the watershed. They may have been introduced due to a misguided belief that they would be a good source of food for gamefish.
Anglers should adhere to the following regulations to prevent the spread of non-native fish and ensure healthy populations of native and managed fish:
- NEVER move fish from one waterbody to another.
- NEVER release unused bait fish, even in waters where using them is allowed.
- NEVER move fish overland unless they have been certified as being disease-free.
