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LABORATORY AND FIELD EXPLORATION OF NATURAL AND SYNTHESIZED REPELLENTS FOR SEA LAMPREY (PETROMYZON MARINUS)
István Imre1, Richard T. Di Rocco1, Nicholas S. Johnson2, Grant E. Brown3
1Biology Department, Algoma University, 1520 Queen St. East, Sault Ste. Marie, ON, P6A 2G4, Canada
2 USGS, Great Lakes Science Center, Hammond Bay Biological Station, 11188 Ray Road, Millersburg, MI 49759
3Biology Department, Concordia University, 7141 Sherbrooke St. West, Montreal, Quebec, H4B1R6, Canada
The Great Lakes Fishery Commission has encouraged the development of alternative control methods that are effective and environmentally benign. One of the recently suggested approaches involves chemical alarm cues that could be used as natural repellents for the behavioural manipulation of migratory phase adult sea lamprey populations for control purposes. In a series of laboratory and field experiments, we investigated: 1) whether the behavioural response of photoreversed animals to natural repellents is similar to animals held at natural photoperiod, 2) whether injured conspecific and predator cues function synergistically or additively to induce an avoidance response, 3) the optimal concentration of PEA HCl (a putative predator cue) to induce an avoidance response, 4) new predator cues that have shown promise in other species, 5) the response of sympatric fish species to the range of conspecific and predator cues identified so far, 6) whether migratory sea lamprey show sensory adaptation when continuously exposed to sea lamprey whole-body extract or PEA HCl, 7) the efficacy of individual predator cues and the optimized mixture of injured conspecific and predator cues as a chemical barrier in a natural stream, and 8) whether conspecific damage-released alarm cues and predator cues can be used to induce emigration of sea lamprey ammocoetes in a semi-natural laboratory environment. Our findings revealed that there was a significant avoidance response to both sea lamprey extract and PEA, irrespective whether we used photoreversed or non-photoreversed animals. The behavioural response to PEA HCl did not differ significantly between photoreversed and natural photoperiod animals. However, the avoidance of sea lamprey extract was significantly stronger in natural photoperiod, as compared to photoreversed animals. We conclude that the use of reversed photoperiod subjects is suitable for studies examining the presence/absence of avoidance in response to novel chemosensory alarm cues, or the change in the magnitude of antipredator response. Studies investigating the natural magnitude of antipredator response should use natural photoperiod experimental subjects. We found that the combination of conspecific and predator cues (sea lamprey whole body extract plus PEA HCl) functions in an additive manner, suggesting that using a combo of a predator and a conspecific cue does not provide any additional benefit over using either cue by themselves. Migratory sea lamprey showed an increasingly stronger avoidance response with an increase in the concentration of the PEA HCl they were exposed to. We found that sea lamprey response did not significantly differ from deionized water control at PEA HCl concentrations at or below 2x10-9 M. An exploratory experiment found that the amino acid ι-lysine (a human saliva component) and ι-serine, (an amino acid that induces a temporary avoidance response in migrating coho salmon (Oncorhynchus kisutch)) do not induce an avoidance response in migratory sea lamprey. In a daytime experiment, age 1+ hatchery rainbow trout (Oncorhynchus mykiss) exposed to deionized water control, sea lamprey extract, their own species specific extract, human saliva and PEA HCl did not change their distribution in the stream channel in response to any of the above stimuli. Migratory common white suckers (Catostomus commersonii) exposed to the same suite of stimuli during the day (2014) and at night (2015) in two separate experiments showed significant avoidance of their own extract and sea lamprey extract but not PEA HCl or human saliva. Migratory sea lamprey maintained their avoidance response to PEA HCl (a putative predator cue) and sea lamprey whole-body extract (a conspecific damage-released alarm cue) even after being continuously exposed to them for up to 6 hrs and up to 4 hrs, respectively. Two in-stream experiments demonstrated that fewer sea lampreys entered the tributary and side of a river scented with sea lamprey tissue extract. Unexpectedly, sea lampreys did not avoid the tributary and side of the river scented with PEA HCl. A final laboratory experiment found no difference in the avoidance response of sea lampreys to PEA HCl mixed with river water versus PEA HCl mixed with water from Lake Huron. As such, the lack of sea lamprey response to PEA HCl in the stream is unlikely to have been caused by the presence of the river water. Rather, the difference may be attributed to the complexity of the physical environment. Finally, we found that labelling ammocoete habitat as ‘risky’ with regular release of chemosensory alarm cues over several days did not induce emigration from the experimental arenas in a seminatural laboratory experiment performed in the fall. In conclusion, sea lamprey whole-body extract and human saliva hold promise at this time as repellents to be used for behavioural manipulation of sea lamprey populations in the Great Lakes. Future studies should elucidate the active ingredients of the sea lamprey whole-body extract and human saliva. Future studies should also investigate the effectiveness of PEA HCl as a repellent in other natural water bodies.