Are We Fishing Down the Food Web in Lake Simcoe?

Session: 56. - Science for a Healthy Lake Simcoe

Erin Dunlop, ON Ministry of Natural Resources, Trent University, [email protected]
Daisuke Goto, University of Toronto, [email protected]
Don Jackson, University of Toronto, [email protected]

Abstract

Analysis of marine commercial catch data has revealed a serial depletion of oceanic fish stocks over time, resulting in fisheries focusing on increasingly smaller species closer to the base of the food chain. This effect of “fishing down the marine food web” can be observed when the trophic level of the catch declines over time, raising concerns about the ecosystem impacts of commercial fishing.  In this study, we make use of catch records from Lake Simcoe dating back to the 1860s, to examine if similar trends are observed in an inland system.  We measured two commonly used ecosystem indicators, the mean trophic level of the catch and the fishing-in-balance indicator, and compared trends between a historical period dominated by commercial fishing activities, and a more contemporary period where commercial fishing ceased and emphasis on recreational fishing increased.  We found evidence that trends occurred in the opposite direction between commercial and recreational fishing time periods, and that indicator responses were affected in a directed way by the presence of invasive species during the past 20 years.

1. Keyword
fisheries

2. Keyword
fishing

3. Keyword
invasive species