written by Christopher Pennuto
Managing invasive species is always a difficult undertaking, whether the species in question is a hardy, deep-rooted shrub, an aquatic plant able to grow from the smallest stem fragments, or a pugnacious invertebrate like the red swamp crayfish (Procambarus clarkii). This medium-sized crayfish “punches above its weight” among crayfish, and it has a foothold in western New York. Dr. Chris Pennuto, his students, and staff from WNY PRISM have partnered with The Park School in a management effort to prevent further spread of this unwanted addition to the regional crayfish community. Though known from just a single location, there are hydrologic connections to the Niagara River watershed.
Like many crayfish, the red swamp crayfish plays important roles in aquatic ecosystems, serving as food for a variety of predators or aiding in the processing of organic matter. It is a commercially and culturally valued resource in its home range where many a recipe centers on its “lobster-cousin” appeal. However, outside of its native range, a host of ecological damage has been documented and linked to red swamp crayfish activity. Thus, it is a priority management species to prevent further expansion in the region.
Dr. Pennuto and team are considering new management actions to give the local crayfish community an advantage. Part of that action is an intensive trapping effort. Last summer, over 200 animals were trapped from the location, with no apparent reduction in the number caught per trap-night.
Discussions are under way to consider adding large fish predators to the site to help reduce the number of crayfish present, but this has potential drawbacks. Most fish predators large enough to consume red swamp crayfish (like large-mouth bass) will also consume a wide variety of other pond inhabitants like frogs, salamanders, and other fish. Introducing native crayfish that might out-compete red swamp crayfish, a tactic called competitive niche replacement, is also being considered. Unfortunately, this also has potential drawbacks. For example, since the native species in question is a close relative of the red swamp crayfish, it is still unclear if they might hybridize and imperil the native species through biotic homogenization. And other tactics like introduction of sterile males, red swamp-specific pathogens or parasites, or chemical additions are all being evaluated. Stay tuned for updates.
Image caption: Red swamp crayfish.
