Midwest Fish & Wildlife Conference 2018

AUTHORS. Mark DuFour, Kelly Robinson, Michael Jones - Michigan State University; Seth Herbst, Tammy Newcomb - Michigan Department of Natural Resources

ABSTRACT. Grass carp, native to East Asia, have been captured in Lake Erie since the early 1980’s. Managers believed these fish to be triploid (i.e., non-reproductive), and escaped from inland waters where they are stocked to manage nuisance aquatic vegetation in some states. Recently, grass carp captures have increased in Lake Erie’s western basin along the Michigan and Ohio shores. Additionally, a high proportion have been documented as diploid (i.e., reproductive) and successful spawning and recruitment has occurred in one major tributary, the Sandusky River, Ohio. At high densities, herbivorous grass carp pose a threat to aquatic vegetation in coastal wetlands - vital to native invertebrate, fish, and waterfowl communities. Although the highest known grass carp densities are in the western basin, sparse captures have occurred across the Lake and the potential for increasing abundance and spread is a concern for the entire Great Lakes basin. As a response to this threat, Michigan Department of Natural Resources initiated a structured decision making (SDM) exercise led by the Michigan State University – Quantitative Fisheries Center. An SDM provides a formal framework to aid management decisions fraught with uncertainty, while incorporating existing knowledge and stakeholder values. To date, the SDM has held three workshops including participants from fourteen state, provincial, and federal agencies and universities with interest in controlling grass carp abundance, spread, and ecological impacts. The SDM process has helped the group distill a problem statement, establish management objectives, select potential management actions, and build a framework to evaluate consequences and tradeoffs of competing management scenarios. In addition, the SDM process has helped identify key uncertainties that inhibit current decision-making, and promote collecting information to improve future management decisions. The framework built during this collaborative process will help agencies adapt management to a developing threat based on continually increasing knowledge.