Tench (Tinca tinca) are an invasive fish native to Europe and Western Asia. They are a member of the minnow/carp family Cyprinidae and were introduced to the U.S. as a food and sport fish.
Tench was illegally introduced by an unlicensed fish farm in the 1980s to the Richelieu River, a tributary of the St. Lawrence River. It is currently found in the Columbia watershed in British Columbia and is well established in the U.S. Mississippi River Watershed. There is concern Tench may spread further south on the St. Lawrence River and eventually enter Lake Ontario and other Great Lakes.
Tench inhabit weedy/muddy water bottoms. They have high reproductive rates, long lifespans and can survive in low-oxygen environments. They are generalist predators whose diet includes fish eggs, snails and other benthic invertebrates which puts them in direct competition with many native fish species. Tench have the ability to diminish aquatic food-webs, increase water turbidity, and introduce non-native parasites into the Great Lakes. Early detection of Tench is extremely important in preventing its spread into the Great Lakes basin.
Tench can grow up to 18 inches in length and weigh up to 10-12 pounds.
Tench have dark olive to pale golden coloring and a white bronzy belly and bright red/orange eyes. They have a terminal mouth with a barbel at each corner. Fins are dark-colored and rounded, with no spines.
You can help stop their spread by learning how to recognize Tench and keeping an eye out for this fish. Help find tench by joining our Invasive Species Surveillance Volunteer Network
Search for Tench in the St. Lawrence River between Cape Vincent and Massena, NY. Pay special attention to waterbodies near farming ponds. Golden colored Tench varieties are popular aquarium species.
Do not use Tench as bait. Never release unwanted pets or dump unused bait into waterways, doing so may spread invasive species.
Title photo by Alan Butterworth www.bugwood.org
Side by side photo retrieved from Invadingspecies.com
Tench in hands photo by Sunci Avlijas www.bugwood.org
Eurasian Tench (Tinca tinca): the next Great Lakes invader, by Sunci Avlijas, Anthony Ricciardi and Nicholas E. Mandrak
Intentional Introduction of Tench into Southern Quebec, by Pierre Dumont, Nathalie Vachon, Jean Leclerc, Aymeric Guibert
La tanche, Quebec ministry of forests, wildlife and parks
Tench, Ontario government