By Wes Ashe, Fisheries Resource Biologist, Belgrade Lakes Region

Fish invasions are often overwhelming to native ecosystems – altering the species assemblage, changing the insect community and forage base, and devastating native fish populations. Most of the time, fish invasions are obvious. Growing to gargantuan sizes, northern pike have forever altered the Belgrade Lakes. Voracious smallmouth bass have taken over northern portions of the Kennebec River and impacted wild brook trout and landlocked salmon populations. White catfish have saturated the lower Kennebec and Penobscot Rivers and likely far outnumber native catfish in some of those reaches. But sometimes fish invasions are subtle and go unnoticed for years, even decades. 

In 2017, MDIFW Fisheries Biologists were assessing illegally introduced black crappie in Savade Pond (Windsor), a 62-acre water at the headwaters of the West Branch of the Sheepscot River. Using a 16-foot electrofishing boat along the weedy shoreline, quick pulses of electric current momentarily stunned Savade fishes in the shallow water. Not too long into the collection, a beefier looking sunfish splashed to the surface and was quickly scooped up. The fish wasn’t a crappie. It wasn’t a native pumpkinseed or redbreast sunfish either. After a minute or two of inspection and disbelief, biologists confirmed the fish species as a bluegill. Bluegill don’t belong in Maine waters, and despite their small size and unintimidating features, they are highly invasive.

read full story: https://www1.maine.gov/wordpress/insideifw/2020/05/19/an-undetected-fish-invasion/?fbclid=IwAR15AV6zNuHrCqk4YhzYBfZKzzNfLDUXj5dPuOPl3rtCoy3dLyUkcBhncRA