Aquatic Invasive Species

Native to the Ohio River Valley, the rusty crayfish (Orconectes rusticus ) is an aquatic invasive species that has spread outside its native habitat into other freshwater sources ranging from Minnesota to Maine.  Detrimental to invaded ecosystems, rusty crayfish out-compete native crayfish and tend to replace the native crayfish population rather than just displace them. This out competition is mainly a result of the rusty crayfish’s larger body mass and greater reproductive abilities (Klocker and Strayer 2004). As rusty crayfish becomes more dominant with in an invaded environment, they can significantly reduce the amount of benthic invertebrates in an ecosystem resulting in the removal of much of the available nutrient resources in the water (Bobeldyk and Lamberti 2008). In addition the fish and bivalve population suffer under the invasion as rusty crayfish preys on small fish and the eggs of many species (Klocker and Strayer 2004).

Bait buckets are the main transport vector for rusty crayfish across state lines.  As the aquatic invasive species becomes a greater problem, programs have been developed to educate fishermen about the dangers of bait bucket transfer. However, this is not enough and the gravity of this problem has led Michael Potts of Duke University to investigate widespread control methods for rusty crayfish. A native of Pennsylvania, Potts became interested in rusty crayfish after discovering “a research article on the effect of the aquatic invasive species in [his] home state.”  As a result of this discovery, Potts proposes to study the effect of trapping and predation on rusty crayfish populations. Potts’ methodology draws upon a previous study conducted by Hein et al.(2006) in Wisconsin’s Sparkling Lake, however while both his and Hein et al.’s methodology are similar, Potts decided to focus his research on rusty crayfish population within dynamic water bodies, mainly rivers and streams, versus closed water bodies such as lakes. According to Potts, he took this focus “because not a lot of work has been done in moving waters (rivers) as far as trying to control rusty crayfish.”For the predation aspect of his proposal, he will use small mouth bass, a predator of rusty crayfish, and set up a control mechanism to maintain the bass’s population. He will then implement wire minnow traps along the river section in distances approximately 15 meters apart and bait it with frozen smelt and the sex, weight and length of captured specimen will be recorded.

While Hein et al.’s study differs from Potts. He stated in his proposal that “due to the similarities in lake and river ecosystems… it is hypothesized that the experiment will result in a significant decrease in rusty crayfish population.” Furthermore when asked about his believe in the future implication of his project, Potts stated that “ [the] methods in the proposal and the Hein et al (2006) study are very sound and could be easily replicated across different types of water systems such as  rivers, lakes, and steams and would significantly decrease the population of rusty crayfish.”

Sources:  Bobeldyk AM and Lamberti GA, Journal of Great Lakes Research. 34:265-275;  Hein CL, Roth BM, Ives RA, Vander Zanden MJ. Can. J. Fish. Aquat. Sci. 63:383-389.

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