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DEVELOPMENT OF A PUTREFACTION DERIVED REPELLENT FOR SEA LAMPREY
C. Michael Wagner1, Jason D. Bals1, Eric M. Stroud2, and Thomas Luhring1
1 Michigan State University, Dept. of Fisheries and Wildlife, 480 Wilson Rd., East Lansing, MI, 48824
2 Shark Defense, PO Box 2593, Oak Ridge, NJ 07438
1. Historical anecdotes indicated the sea lamprey releases a chemical (alarm cue) after death that elicits a strong avoidance response (alarm response) in migrants during the annual reproductive migration. We undertook the first systematic study of this phenomenon in both laboratory and field environments to describe the response to the alarm cue and to ascertain its viability as a repellent for use in sea lamprey control.
2. In the laboratory, migratory sea lamprey: (a) avoided the odors emitted by both recently killed and 96 h decayed conspecifics, whether emitted by larvae or adults; and, (b) avoided the odor from a dead confamilial (silver lamprey) but not a distantly related fish (bluegill sunfish). Sexual maturation eliminated the alarm response in females, but not males. Unlike other fishes, the odorant(s) are distributed throughout the body, though appear concentrated in the skin.
3. In both the laboratory and the field migrating sea lamprey exhibited a graduated response to a range of odor concentrations; however, the response increased to full repellency over a relatively small range of concentrations, suggesting and odor detection induces full activity vs. a threat-sensitive response.
4. Adult sea lampreys can be habituated to the odor with 4 h of continuous exposure, though repeated, sporadic exposure over 6 h does not attenuate the response.
5. Larval sea lampreys detect and respond to the odor generated by dead adults. In a laboratory test the rate of downstream drift decreased with increasing water flow and exposure to the alarm cue, suggesting in inhibits larvae from leaving the sediment.
6. In total, these results indicate the presence of a putative alarm cue that induces a strong repellent response over small spatial scales (100 – 101 m) in both laboratory and stream environments. Our results strongly suggest this repellent may be useful in manipulating the movements of lampreys in streams to achieve control objectives (e.g., driving lamprey into the vicinity of a trap).