In September of 2015, the Department of Natural Resources (DNR) asked the Menasha lock be closed to prevent the spread of an invasive fish, the round goby, which was discovered in Little Lake Butte des Morts. The goby is one of 192 invasive species found in Lake Michigan. The invasive species barrier at the Rapide Croche lock prevents transmission of any species from the Great Lakes into the lock system and eventually the Lake Winnebago watershed.
The Fox River Navigational System Authority (FRNSA)
- has been and is committed to preventing the spread of the round goby into the Lake Winnebago watershed,
- Ourgoal is to return the Menasha lock to operation,
- We want to build a system that can be adapted to prevent the spread of any future invasive species.
We are working with fish researchers, the DNR, and an independent fisheries management firm to review the most recent scientific research on invasive species barriers and solutions that have worked for other communities in the Great Lakes region. Smith-Root, one of the nation’s leaders in aquaticecosystem management, is designing a plan using a system of electric deterrent barrier and water flow regulation at the Menasha lock to stop the spread of the round goby.
This concept involves building a concrete, U-shaped channel adjacent to and downstream from the Menasha lock. Electrodes would be recessed in the bottom of the channel. This type of a barrier will allow boat traffic to pass through the channel while halting the passage of fish. The barrier delivers a pulsing DC current to fish entering the channel, causing them to turn around and not enter the lock; it also uses a water velocity process to prevent the round goby from moving into the lock channel. The DC current in the water is not dangerous to humans.
Where will the barrier be located?
The barrier will be constructed immediately downstream of the Menasha lock (remember, the Fox River flows north from Lake Winnebago to Green Bay). The lock is located at 82 Broad Street in the City of Menasha. FRNSA leases the property immediately around the lock from the State of Wisconsin.
What changes are planned for the Menasha Lock?
The proposal calls for building a 100-foot long concrete channel, 36 feet wide with vertical walls approximately 13 feet high (2’ will be visible above the waterline). Electrodes will be recessed in the concrete to create a pulsed DC electrical current. A portion of the riverbank on each side of the channel will be filled in to support the concrete channel. The plan calls for installing a generator to use if needed.
The channel is being built for future use in mind if it is necessary to adapt the technology to deter other invasive species.
Is the electric barrier dangerous to humans?
The barrier uses a pulsed field of direct current (DC) in the water that is not dangerous to humans on shore or in their boats. When going through the proposed barrier, boaters must follow a few safety precautions that are normally required for transit through the locks:
- All boaters must wear an approved personal flotation device (PFD)
- When entering the lock, all boat passengers must keep their arms, legs, and metal paddles out of the water.
- No swimming is allowed in a lock or lock channel (there never has been)
- Passengers must not get on or off a boat within locks or the lock channel
What do we know about round goby behavior and the effectiveness of a barrier?
Fish are uniquely sensitive to electrical currents because their muscle control is based on electrical impulses through their nervous system, and because they inhabit a conductive environment. Electrical barriers and guidance systems make use of this sensitivity.
We have reviewed results of scientific reports from researchers from the U.S. Geological Survey (USGS). Based published research, we know these characteristics of the round goby:
- The round goby is a bottom dweller where the current in an electronic barrier would be strongest.
- The velocity of the water in the navigation channel will affect the travel of the round goby. Part of the electronic barrier plan would allow for flushing the locks daily to prevent immature goby from getting through the barrier.
How would changes in water quality affect the barrier?
Design of an electrical barrier system considers the “worst case scenario” of water quality and ensures the system will continue to be effective when poor water quality conditions occur seasonally.
Where are electric barrier systems currently in use?
Use of electricity to guide and block fish is not a new concept. Electrical barriers built in the 1950s and 1960s are still in operation. Electric barriers are custom-designed for each situation and, as such, include a wide variety of barrier geometries, waveforms, and field strengths. In short, the objective of each barrier and guidance system is what drives the system design.
More than 70 Smith-Root-designed electrical barriers and guidance systems have been installed across the globe. In Midwestern states such as Minnesota, Michigan, and Illinois Smith-Root has 28 pulsed DC electrical barriers in operation for multiple years and monitoring shows the barriers operate reliably.
How did the round goby get here?
The round goby is an invasive fish found in the Great Lakes. Several were found in Little Lake Butte des Morts in September of 2015. When they were discovered, the lock system was not open to the Great Lakes and there were no populations of round gobies in Lake Winnebago according to DNR testing. Additionally at this time, there were three miles of dry canal and three de-watered locks between Little Lake Butte des Morts and Kaukauna. It is important to remember the Fox River flows north and it is impossible for fish to travel from the bay of Green Bay to Lake Winnebago through the lock system due to the barrier at the Rapide Croche lock. The round goby were most likely introduced into the system as fishing bait, or on pleasure boats that were not adequately cleaned.
Is the Menasha Lock the main entry point for round gobies?
No. Since the fish was found, there is a verified population in Little Lake Butte des Morts. Currently, there are more than 60 boat access points to Lake Winnebago that are not monitored, and each summer float planes land in Lake Winnebago thus increasing access points for invasive species. We are confident the gobies did not come into Little Lake Butte des Morts through the locks.