Out-Muscling the Mussels

Out-Muscling the Mussels

Zebra Mussels have quickly moved to the forefront of AIS management in South Dakota. We now have 3 waterbodies in the state where this particularly troublesome AIS can be found. Zebra mussels were discovered in Lewis & Clark Lake and the Missouri River below Gavins Point Dam in 2015. A mussel population was also discovered at McCook Lake in May of 2016. While the spread of Zebra mussels into McCook Lake was alarming, it was not unexpected.


Since the initial discovery of Zebra mussels in Lewis and Clark Lake, they have been rapidly spreading throughout the lower portion of the lake and downstream through Gavins Point Dam. Downstream spread is inevitable since larval Zebra mussels, called veligers, are free floating and move wherever the current takes them. McCook Lake is an oxbow lake in Union County with a water table tied directly to the Missouri River. In order to artificially maintain the water level in McCook Lake, the lake association and various partners pump water directly from the Missouri River into the lake through an irrigation pump system.  It is likely that veligers were pumped from the river into the lake through that system and matured into the adults that can now be found in the lake.

The speed at which Zebra Mussels have reproduced and spread within Lewis and Clark Lake is a little shocking. In 2015 Game, Fish & Parks staff performed a snorkel survey of boats in Lewis and Clark marina and discovered that about 34% of all boats surveyed in the marina had at least one mussel attached somewhere on the hull or motor with only 5% of those boats being heavily infested (more than 10 mussels). When that same survey was performed in 2016 the percentage of boats with mussels attached skyrocketed to about 84% with 80% of those being heavily infested. Many of the boats surveyed in 2016 had thousands if not tens of thousands of mussels encrusting the hull, motor, trim tabs and anything else that spent time in the water. 


Although there are certainly obstacles to overcome at Lewis and Clark Lake, there were some major successes in AIS management in South Dakota in 2016 that should not be overlooked.  For the first time a Watercraft Inspection and Decontamination (WID) program was up and running in South Dakota. Four WID teams were stationed in each of the geographic regions of the state (Northeast, Southeast, Missouri River & Black Hills) and one team was stationed at Lewis and Clark Lake. These teams inspected boats entering or leaving a lake to make sure that AIS were not attached and introduced to a new lake. Although many inspections were completed, no decontaminations were required and many people were able to learn about AIS and how they can take a few simple steps to prevent the spread to new waters.

The biggest success story in 2016 came from inspecting construction equipment at Belle Fourche Reservoir. Game, Fish and Parks was contacted to inspect 9 large barges that were going to be used for a dredging project at Belle Fourche Reservoir.  Conservation officers and fisheries staff immediately identified many zebra mussels on the equipment and prohibited the contractor from launching them. After nearly a week of work, the equipment was fully decontaminated and allowed to launch into the reservoir. Although many of the mussels on the barge were dead before the inspection, this inspection and decontamination prevented those that may have been able survive from reaching Belle Fourche Reservoir.

New Rules

Throughout the course of 2016 it became evident that some modifications needed to be made to the AIS regulations to better serve boaters, anglers and the ecosystem. In October, Red-swamp cray fish were added to the AIS list. These crayfish are prized as table fare, but can have significant impacts to the ecosystem if they make it into a lake or river. The second change that was made in October was to remove the term “immediately adjacent” from the AIS rules pertaining to plug removal and live bait and fish transport. This term was very confusing for boaters, anglers and Game Fish and Parks staff and it became difficult to understand when and where plugs should be removed. In order to make this easier for everyone to understand, the new regulation states that all plugs need to be removed before leaving the boat ramp parking area. Similarly live bait and fish may not be transported in lake or river water beyond the boat ramp parking area. These changes should help everyone to easily do their part to ensure that they aren’t moving water from one lake to another.

The Game, Fish and Parks Commission made more significant changes to the AIS Regulations in March. These regulations work together as a package not only to protect South Dakota lakes and rivers from new AIS introductions, but also to make compliance faster and easier for boaters, anglers and other sportsmen and women. 

The first new rule will create a list of waterbodies that will be classified as Containment Waters. These are waterbodies that have an AIS of concern in them and require special designation to facilitate management efforts. The next new rule builds off of the containment water list and allows Game, Fish and Parks to create Local Boat Registries at Containment Waters. The Local Boat Registry program will give boaters that participate the freedom to more easily transport and store boats locally in areas with Zebra mussel infestations, while restricting their movement to other waterbodies unless they are decontaminated.

The next two rules also relate to the Containment Water list and require boats to be decontaminated if they are used on a containment water and either have a ballast tank with undrained water (like a wakeboard boat) or are moored in the containment water for more than 3 days.

The purpose of these rules is to ensure that water that may hold mussel veligers and boats with very small mussels attached to the hull are properly cleaned before they are used in a different waterbody.

The fight against Zebra Mussels in South Dakota is still in the early stages. We do have 3 infested waters, but we still have the opportunity to slow or prevent the spread of mussels to other waterbodies. Anglers and boaters are now more aware than ever on how they can slow the spread of AIS in South Dakota and with the new regulations and WID teams out in full force again, 2017 is shaping up to be a year where we have a great opportunity to work together to out-muscle the mussels and keep them from spreading to more South Dakota waters.