Natural resource managers are growing increasingly concerned about the risks of aquatic invasive species affecting native habitat and species communities. Two U.S. Geological Service scientists and several generations of graduate and undergraduate students have been working to provide solutions that help managers reduce the likely transport of aquatic invasive species. Dr. Barnaby Watten of the USGS Leetown Science Center and Dr. Christine Moffitt of the Idaho Cooperative Fish and Wildlife Research Unit have been collaborating for nearly 10 years on developing and testing tools for containing and preventing the transport of invasive mollusks.

The collaboration's early studies focused on fish hatcheries, where the source water springs were infested with New Zealand mudsnails. Watten proposed the use of a hydrocyclone to remove invasive snails from hatchery inflow. The hydrocyclone is an instrument with no moving parts that can separate particles based on their specific gravity. Cyclonic separation is widely used in mining and other industrial venues. Moffitt and graduate student Jordan Nielson found that the prototype system installed at the Hagerman National Fish Hatchery in southern Idaho was 100 percent effective in removing the snails from intake waters. The researchers also collaborated on studies to show that use of pressurized CO₂ was effective in treating and disinfecting tank systems that contained invasive mollusks. Nielson received his Masters degree from the University of Idaho, and is now the Aquatic Invasive Species coordinator for the Utah Division of Wildlife Resources where he works with many hatcheries and water bodies to prevent and control infestations in state waters.

Another tool that has been tested in their field trials is a mixed cell raceway system. Watten and colleagues designed this system to retrofit older hatchery ponds that were highly ineffective for removal of solids. They worked with staff at Dworshak National Fish Hatchery in Ahsahka, Idaho who had retrofitted two Burrows ponds with a mixed cell system. In these studies, graduate student Kelly Stockton, Watten and Moffitt, along with undergraduate assistants, and hatchery staff tested the efficiency of this system in removing particles the size of New Zealand mudsnails from the raceway system. They found that particle removal was very complete, and if fish had ingested snails, they could be depurated in a system such as this, as long as snail free water was available to prevent re-infection. An additional benefit to this rearing system is that it maintains high quality water distributed throughout the system, and hatchery managers can rear more fish per gallon of water. In addition to its potential use for invasive mollusks, the rearing system has shown to be a more productive and water efficient rearing system for salmonids. After completing her master's degree, Kelly Stockton is now employed by Marrone Bio Innovations and works with testing of invasive quagga mussels.

Currently, Moffitt and Watten are collaborating on a project evaluating elevated pH as a tool to prevent transport of invasive mollusks and other invasive species in ship ballast and other tank systems. Ballast water discharges are believed to be a major source of invasive species spread and there is need for methods to control and prevent further introductions using disinfection systems that are economical, environmentally safe, and effective. Several authorities are engaged in management of ballast, at the state, regional and international level. New U.S. Coast Guard regulations require that all new and existing vessels meet standards to guarantee treatments are in place to reduce the risks of introducing harmful species with ballast discharge. Moffitt and Watten's research shows that creating an elevated pH with simple compounds such as NaOH can provide an economically feasible method of disinfecting tanks, not harm the equipment and the pH of treatment can be neutralized with CO₂ to achieve an environmentally safe discharge. This project also involves graduate and undergraduate students as active researchers. In September, Watten, Moffitt, and graduate student Amber Barenberg will be conducting shipboard trials in Lake Superior.

Each month, the ONB features articles from Cooperative Fish and Wildlife Research Units across the country. Working with key cooperators, including WMI, Units are leading exciting, new wildlife research projects that we believe our readers will appreciate reading about.