Movement of muskellunge in the St. Croix River system

Proposals to install fish barriers in Minnesota’s large rivers near the Twin Cities to prevent upstream expansion of Asian carp (silver carp Hypophthalmichthys molitrix, bighead carp H. nobilis, grass carp, Ctenopharyngodon idella and black carp Mylopharyngodon piceus) prompted a study to evaluate movement or riverine fish throughout this system. A stationary acoustic receiver network was deployed in the Minnesota, Mississippi and St. Croix rivers in 2013 to determine fish passage through the lock and dam systems and study movements and habitat preferences for several native fish species. Six muskellunge (Esox masquinongy) were captured from the St. Croix River in November 2014, implanted with transmitters equipped with temperature and depth sensors (donated by Muskies Inc.) returned to the St. Croix River and tracked for two years. All muskellunge traveled at least 15 river miles. Five of the muskellunge traveled into Pool 3 of the Mississippi River for brief period (typically 1-3 days) and returned to the St. Croix River. One muskellunge left the St. Croix River, passed thorugh Lock and Dam #3 in Red Wing, Minnesota, moved into Pool 4 of the Mississippi River and returned to the St. Croix River after 30 days. Four of the muskellunge generally preferred the lower St. Coroix River (>75% of detections). All of the muskellunge had recorded depths greater than 40 feet (12,2 m) with on exceeding 70 feet (21.3 m). Although the results are preliminary our study shows that placing a barrier at the mouth of the St. Croix River could restrict muskellunge movement between the St. Croix and Mississippi Rivers. Therefore, any barrier constructed to prevent upstream expansion of Asian carp should be tested to ensure that it does not interfere with movement of native fishes such as muskellunge. Continued research will evaluate the importance of fish movements between the St. Croix and Mississippi rivers.