3.5.1.9 Invasive Species

or accumulated stress, and those contents were almost entirely the remains of crayfish (HDR 2022b).

3.5.1.9 Invasive Species

Several types of aquatic invasive species (AIS) are present in Wyoming, including fish, pathogens, plants, and mollusks (WGFD 2017c). The most notable AIS in Wyoming is currently the New Zealand Mudsnail (Potamopyrgus antipodarum) and whirling disease (WGFD 2010), both of which affect salmonids. The New Zealand Mudsnail was recently discovered in the Casper Region (WGFD 2019c). These AIS can impact native species through competition, disease, changes in food resources, and direct mortality. For example, the New Zealand Mudsnail can form dense colonies where it spatially outcompetes native insect communities, which are a primary food resource for young trout and other native species (National Park Service [NPS] 2017). It also consumes large amounts of algae, which reduces a food resource available for native fish and aquatic invertebrates. Whirling disease is caused by a microscopic parasite (Myxobolus cerebralis) originating from Europe that can infect trout and salmon (NPS 2020a). The parasite feeds on the fish’s cartilage and cause skeletal deformities, a blackened tail, and a whirling swimming behavior and can eventually lead to mortality.

In the Platte River Basin several AIS are present including curly pondweed (Potamogeton crispus) observed downstream of Seminoe Dam, rusty crayfish (Orconectes rusticus) observed in Wagon Hound Creek, a tributary to the North Platte River downstream of Casper, Asian clam (Corbicula fluminea) observed in the North Platte River and the Guernsey Reservoir near Guernsey, and Brook Stickleback (Culaea inconstans) observed on the North Platte River upstream and within Seminoe Reservoir (WGFD 2022c).

Curly pondweed was introduced to the U.S. in the 1800s and quickly spread. It is currently found in the Miracle Mile section of the North Platte River, downstream of Seminoe Reservoir. The rusty crayfish are native to the southern U.S. (NPS 2017) and introduced to Wagonhound Creek (a tributary of the North Platte River) through the use of bait buckets. Rusty crayfish can outcompete native crayfishes and destroy native plant communities. Rusty crayfish have not spread due to repeated chemical treatments (WGFD 2017c, 2019).

Asian clams were discovered in the Columbia River in 1938 and are now widespread throughout the U.S. (WGFD 2017c). Asian clams cause damage with biofouling at power generation and water supply facilities. Asian clams are found in the Laramie River upstream of the town of Laramie and in the North Platte River downstream of Guernsey Reservoir.

The Brook Stickleback was introduced through bait introductions or accidentally through aquaculture and are widespread through the Platte River Basin, including the PathfinderSeminoe Reservoir drainage (WGFD 2017c). Other invasive species, such as zebra mussels (Dressena polymorpha), quagga mussels (D. bugensis) and Silver Carp (Hypophthalmichthys molitrix) are present in neighboring states and present high risk to introduction in Wyoming (WGFD 2017c).