Research Precedes Offshore Cisco Stocking


Marking Cisco with a Coded wire tag. Credit: USFWS

The cisco (the fish formerly known as lake herring), is known for not only being a historically important commercial fish species, but also an important forage species in the Great Lakes. Many native species such as the lake trout depended heavily on this species in their diets. Throughout the Great Lakes cisco populations have been on the decline due to overfishing and competition with introduced species such as the alewife. Alewife introductions were harmful to Great Lakes cisco populations due to direct competition for food, and harmful to predator populations due to alewives carrying high levels of an enzyme called thiaminase in their bodies, which results in poor egg survival to fish that prey on them. Great Lakes fisheries scientists have placed a high priority on rebuilding cisco stocks due to its value as a prey species for many of the valuable sport and commercially exploited predator species in the lakes, and to possibly increase egg survival in apex predator species in the Great Lakes. In the fall of 2016, US Fish and Wildlife Service fisheries offices in Michigan and Wisconsin banded together to collect eggs from northern Lake Huron to begin pilot efforts to learn how to culture the species, and possibly develop a disease free future brood stock to use for a disease free egg source. Eggs were brought to the Genoa National Fish Hatchery quarantine facility, to be reared for 16-18 months and three fish health inspections to ensure that the fish can be transferred safely to other Service captive brood stock stations. The resulting fry soon outgrew their homes and with more than enough to begin the first brood line, 10,000 4.5 inch cisco became surplus.

This first small lot of fish became a good pilot program to see if expected culture practices would be adaptable to large scale restoration efforts in existing facilities currently used as lake trout production facilities. Methods of mass marking were tried as well as long distance hauling and offshore release methods on this sensitive species of fish. The physiological effects of marking and transportation were also measured to determine whether these methods were suitable in large scale efforts. Results are being compared in order to make recommendations on hauling densities and how to reduce stress through the culture, marking and transportation cycle. Through these preliminary studies, it is hoped that methods used may be beneficial to our sister hatcheries as they begin large scale production efforts in the fall of 2017, for targeted restoration areas in Lake Huron.

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