The decline of fishes and fisheries in Lake Champlain: A historic review

In the last 150 years, several fish species have severely declined or become extirpated in Lake Champlain, including Atlantic salmon, lake trout, lake whitefish, American eel, and lake sturgeon.  Habitat alteration, particularly loss of access to spawning areas, was clearly a major factor in some of these declines, but the extirpation of lake trout by the early 1900s and loss of the whitefish fishery are more difficult to explain.  Historically, commercial fishing was small-scale, using shoreline seines and pound nets; gillnetting and offshore fishing were almost unknown.  However, fishing was focused during the spawning seasons of the major target species, and may have had significant population impacts.  Hydrological connectivity of the lake was altered by construction of causeways beginning the mid-1800s; stream habitats were impacted by dumping of sawdust and soil run-off from farming; portions of the lake have become highly eutrophic due to phosphorus inputs; benthos in the main lake has been substantially altered by zebra mussels since the mid 1990s.  Fifteen non-native fish species have become established, and sea lamprey numbers have risen to unprecedented levels.  These biotic and abiotic changes may decrease ecological resilience, particularly to recent invaders such as alewife.