The effects of climate change and eutrophication on cisco Coregonus artedi abundance in Minnesota lakes
Jacobson, P.C.; Cross, T.K.; Zandlo, J.; Carlson, B.N.; Pereira, D.P.
Trends in cisco abundance were examined from 1947 through 2007 in 634 Minnesota lakes. Declines in cisco abundance starting in 1980 corresponded with significantly warmer summer nights and longer growing seasons. The increased warming and longer durations of summer stratification likely reduced thermal habitat to the point where cisco populations are being impacted. Cisco have declined both in lakes that have experienced cultural eutrophication in the Eastern Temperate Forests ecoregion and in lakes that have not experienced significant cultural eutrophication in the Northern Forests ecoregion. Cultural eutrophication since the late 1800s probably set a lower baseline abundance for cisco in some lakes primarily in the Eastern Temperate Forests ecoregion, but recent declines in abundance in these lakes were probably the result of climate change. Also, increased abundances of an important cisco predator, northern pike, may have contributed to the decline.