Next: Crayfish in northern Wisconsin
Up: Species invasions and deletions
Previous: Species invasions and deletions
Figure 3:
(A)Generalized representation of changes in fish populations
in the North American Great Lakes. (B) Generalized food web of the
Great Lakes. (From [5]).
|
|
Refer to Figure 3 for a diagram illustrating these
changes in the fish community of the Great Lakes.
- Native fish assemblages dominated by lake trout, coregonids
(whitefish and chubs), and perch.
- Construction of Welland Canal (1829) allowed lamprey (in the
1920s) and alewives (in the 1930s) (both marine) to colonize. Rainbow
trout were introduced in about 1912.
- Overfishing, combined with predation by lampreys, dramatically
reduced populations of lake trout, coregonids, and perch.
- Elimination of piscivorous lake trout led to population explosion
of introduced alewives and smelt, almost eliminating native
populations of planktivores (coregonids and perch).
- Lake trout were reintroduced in 1955 after the development of
effective chemical control for lampreys.
- Massive stocking of several species of salmonids in the 1970s led
to decreased alewife populations. Populations of native planktivores,
especially coregonids and perch, rebounded.
- The result is a fish community whose dynamics are dominated by
introduced species - lamprey, salmonids, alewives, and smelt.
- Lampreys and alewives were previously anadramous. The Great Lakes
populations spend their entire lives in freshwater.
Next: Crayfish in northern Wisconsin
Up: Species invasions and deletions
Previous: Species invasions and deletions
Kent Holsinger
2007-10-30
