Factors Influencing Trapping Success of Adult Sea Lampreys in the Great Lakes

Mass trapping may be a useful control method for invasive Great Lakes sea lampreys if enough adults can be removed to reduce reproduction. To be trapped, individual sea lampreys must first encounter, then enter, and then be retained in traps. Trap success may be increased by gaining a better understanding of factors influencing number of encounters and probabilities of entry and retention. In this study, sea lamprey behavior at traps was quantified using video at five traps in three streams during five seasons. These behavioral data were used to test factors influencing number of encounters, entrance rate, and retention rate. The influence on daily trap catch of number of encounters, and entry and retention rates was also tested. Trapping success was ultimately improved by the application of a synthesized male mating pheromone, which increased encounters in late season and entrance rate throughout the season. Discharge had a relatively small effect on number of encounters, while trap and water temperature variables were relatively important factors influencing probability of entry and retention. At one trap, where behavior was quantified for the entire migration season, trap catch was influenced primarily by number of encounters rather than retention or entrance rate.