Barriers to the spread of invasive scud (Apocorophium lacustre) in the Chicago Area Waterway System

Scud (Apocorophium lacustre) is a high-risk invasive species that threatens to spread into the Great Lakes Basin from the Mississippi River Basin. It was discovered in the Illinois River in 2005 but has not spread from there into the Chicago Area Waterway System (CAWS) that connects the Mississippi River to the Great Lakes. Understanding the current limits to scud spread, and identifying ways to reduce future spread, is critical for managers. We conducted three experiments to determine how scud respond to potential barriers for invasion including water quality in the CAWS, an electric barrier, and ranges of CO₂ enriched water that is a proposed barrier in the CAWS. We found that water from the CAWS led to a 20% reduction in scud survival over 96 h compared to Illinois River and Lake Michigan, although overall survival remained high (~65%). Second, we found that the presence of electric and CO₂ barriers at high strength and concentration significantly reduced movement in scud. Specifically, we found that field-strengths 3 times greater than the operating limit of 2.3 V·in and CO₂ concentrations at the EPA limit and higher (>150 mg/L) caused greater scud immobility compared to lower and permissible levels. We conclude that scud has potential to spread within the CAWS to the Great Lakes despite water quality and electric barriers currently in place. Carbon dioxide barriers are unlikely to be effective. Our findings highlight the need for additional management and investigation into strategies which can prevent the spread of scud into the Great Lakes.

Primary Presenter: John Bieber, Loyola University Chicago (jbieber@luc.edu)

Authors:

Colette Copic, Morton Arboretum  (ccopic@mortonarb.org)

Rachel Egly, Loyola University Chicago  (Regly@luc.edu)

Reuben Keller, Loyola University Chicago  (rkeller1@luc.edu)