Understanding low success trapping invasive sea lampreys: an entry-level analysis

Abstract

Invasive sea lampreys (Petromyzon marinus) in the Laurentian Great Lakes are the target of binational control. Trapping of adults could be used for control if trap success was higher. At a hydro-generating station on the St. Marys River, we tested whether the probability of trap entry is low (0.2–0.3) because (i) lampreys spend insufficient time near traps to find and enter the trap, (ii) high discharge at trap sites makes attractant flow from traps difficult to detect or trap openings difficult to reach, and (iii) conspecifics impede trap entry. Discharge at the site was manipulated nightly, and the behaviour of lampreys at trap openings was video-recorded. Odds of a lamprey reaching a trap opening and entering the trap were 3.4 and 1.6 times higher, respectively, with every second spent at a trap. The probability of reaching a trap was not lower on nights when discharge was high or when conspecifics were present at the trap opening. Improved trap entry will require manipulation of stimuli other than discharge that affect the time spent at traps.