Characterization and Development of Repellant and Attractant Pheromones to Control Invasive Bighead and Silver Carp

New management tools are needed to control the highly invasive asian carps that are rapidily populating the Mississippi River watershed. Numerous species of fish have an alarm pheromone that is produced by cells in the outermost epidermal layer of fish skin which when released during injury by a predator induces a fright reaction in conspecifics (same species) which may include freezing, heightened swimming, or rapid escape from the area. Because of the effectiveness of alarm substances as a repellant, the use of alarm substance extracts has been proposed as a chemical barrier to prevent movement of the Eurasian ruffe (gymnocephalus cernuus) between the Great Lakes to the Mississippi River (Maniak et al. 2000). Such methods may also be useful in protecting stream tributaries on the Missouri, Mississippi, and Ohio Rivers, or repelling Asian carps from areas identified as critical habitats for endemic fish such as paddlefish (Polyodon spathula). Alternatively common carp produce chemical attractants to induce aggregating responses and such chemical signals may be useful as lures to facilitate capture.

The long-term goals of this research is to determine if conspecific skin extracts elicit alarm reactions in bighead and silver carp resulting in avoidance reactions, and to use skin extract solutions to protect critical habitats. Alternatively, we will seek to determine if chemical attractants responsible for schooling responses can be used to lure Asian carp to facilitate their capture in the wild.

Conspecific skin extract solutions induced significant avoidance reactions at all concentrations tested with juvenile big head and silver carp. The fish usually responded within 30 seconds of the onset of extract injection into the chamber and maintained avoidance of the area until the conclusion of the ten minute stimulus period. Silver carp displayed an increase in swimming movements and tended to dash about, whereas bighead carp moved from the area in tight schools, often remaining at the opposite end of the chamber. Similarly, juvenile carp avoided skin extract that had been aged at room temperature for 24 hours, frozen for 24 hours, then allowed to thaw overnight at room temperature prior to use in the tests, thus the extract may be sufficiently stable for field use. In pond mesocosm studies adult bighead carp appeared to avoid the side of the pond to which the skin extract had been applied. When fish were similarly exposed to the skin extract in a 24 foot concrete raceway, they avoided the area where the pheromone was applied, but were unaffected by the application of well water. Hypoxanthine-3(N) oxide is a chemical that has been implicated as an alarm pheromone in minnows. During free-field studies we found that juvenile bighead and silver carp were reactive to this chemical, but only at concentrations higher than would be expected for a pheromone. The alarm pheromone in minnow skin extract has been reported to originate in epidermal club cells. From histological examination of juvenile Asian carp skin, we determine the presence of club cells in both species.

Juveniles of these species are commonly found in large aggregates in the field and chemical cues might, in part, facilitate such interactions. Aggregating pheromones have been shown in other species included the common carp, a distant relative of bighead and silver carp. Studies will be conducted to determine if juvenile Asian carp produce and aggregating pheromone which that might be used as an attractant in the control of these invasive species. Field studies will be initiated to determine the effectiveness of skin extracts to repell Asian carp in the wild.

	Contact: Edward E. Little USGS, Columbia Environmental Research Center 4200 New Haven Rd Columbia, Missouri 65201 573/876-1817 elittle@usgs.gov (see also: Related Science Project from CERC)