Mapping and Monitoring Aquatic Vegetation in Lake Erie for Grass Carp Risk Assessment

Grass carp (GC) are a large invasive herbivorous fish that have been present in the Great Lakes since the early 1980s. Indirect evidence of natural reproduction was first observed in 2012, and a 2015 survey yielded eight verified GC eggs, providing the first direct evidence of GC reproduction in a Great Lakes Basin. GC consume large amounts of plant biomass and have been known to cause decreases in abundance and diversity of submersed aquatic vegetation, which can adversely affect game fish, and macroinvertebrates and contribute to declines in water quality.   Consequently, there is a heightened need to understand the potential ecological effects that a reproducing population of GC may have on the Great Lakes.

We have created a 3 tier assessment tool using object-based image analysis from existing aerial imagery, hydroacoustics, and field sampling with a rake method as a tool for grass carp risk assessment. We aim to identify submersed and emergent aquatic vegetation distribution and species composition within Lake Erie to establish baseline data in the early stages of GC invasion. This study highlights the importance of pre-invasion mapping and surveys to track long term ecological impacts of invasive species.