Document Type

Technical Report

Publication Date

4-2010

Abstract

Lake trout abundance in Lake Ontario is now at a low level that has not been observed since modern restoration efforts began in the 1970s. However, the continued observations of small numbers of naturally spawned age-2 lake trout in assessment surveys and the appearance of mature lake trout of suspected natural origin, despite low abundance of the stocked population, is encouraging. Changes in stocking policy for Canadian waters in the early 1990s has produced a situation where lake trout along the north shore are concentrated in the west and east and suggests that the lakewide indicators of restoration progress used in the past for this part of the lake are in need of re-evaluation. In addition, this absence of lake trout along the central northern shore may be decreasing ecosystem stability and resistance to invasive species affects. Low lake trout abundance also seems to have positive implications for native preyfish recovery. Concurrent with lake trout declines, native deepwater sculpin (Myoxocephalus thompansonii) have reappeared (Lantry et al. 2007) and their recovery may indicate an enhanced opportunity exists for restoration of extirpated native deepwater coregonines. The results from this study thus far indicate that it would be beneficial to periodically repeat the whole lake survey and the five year interval of the EPA/EC Great Lakes cooperative monitoring cycle seems adequate and presents an ideal opportunity for researchers from this and other programs to share data and sampling infrastructure. Periodic lakewide lake trout assessments will extend annual monitoring of the condition of the lake trout population for the southern and north eastern areas of the lake to the whole lake and provide opportunity for assessment along the north shore. The whole lake surveys will also provide opportunities to calibrate between the annual USGS/NYSDEC standard lake trout assessments along the south shore and the OMNR community index netting occurring in the northeast portion of the lake; and an opportunity for collection of tissue samples for periodic examination of dietary trends and reproductive health.

Comments

Final Study Completion Report United States Environmental Protection Agency Region II - U.S. Geological Survey Interagency Agreement No. DW14942144-01-1

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