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Attachment Behavior of Sea Lampreys
in Relation to Substrate Characteristics


Ulrich Reinhardt 1

1 Eastern michigan University
Biology Department
316 Mark Jefferson
Ypsilanti, MI, 48197





Attachment by the oral disk is essential for sea lamprey (Petromyzon marinus, L), passage through high-flow areas during their spawning migration. The first goal of this study was to develop a technique to quantitatively examine the attachment process on surfaces with varying types of grooves. The second goal was to test whether the lampreys would seek out the surface that best promoted attachment and whether they would use attachment to pass over barriers. In the first set of laboratory experiments, the ability to attach depended on the interaction between a surface’s characteristics and the sea lamprey’s oral disk anatomy. The flexibility of the oral disk and fimbriae made the shape of the groove as important for suction maintenance as its cross-sectional area. Wider, rounder grooves allowed for the molding of the fimbriae to close off the intrusion, and thus maintain a tight suction seal. A narrow groove of 1-mm width and 3-mm depth prevented all lampreys from making a lasting suction attachment, despite the small cross-sectional area. For management applications where lamprey attachment is a concern, the procedure and metrics utilized in these experiments would be useful for testing candidate surfaces for passage-enhancing or -blocking structures. In the second experiment of the study, sea lampreys displayed little preference among surfaces with varying levels of texture. Repeating this experiment in a high sheer environment may be needed to clarify if a preference for certain surfaces exists and can be exploited for lamprey management purposes. In a third set of laboratory experiments, lampreys were observed by video and PIT tag recorders when trying to scale a wetted barrier of different lengths and inclination angles. No lamprey was able to pass a barrier of 30 cm vertical height. Lampreys were never seen to attempt to jump out of the water to pass a barrier; attachments to the inclined barrier were frequent, but did not help the lampreys to pass. Lower barriers of between 10 and 15 cm vertical height were passable to lamprey, but the success rate was influenced by barrier angle and lamprey body length. A logistic regression analysis of passage success revealed that any barrier longer than 50% of the body length on a lamprey was impassable. A field experiment validated the laboratory result of limited ability of sea lampreys to scale an inclined barrier. The findings suggest that modifications of the current barrier specifications may be possible: barriers could have a lower crest height, the overhanging lip may not be necessary and an inclined ramp instead of vertical dam may be tested in further studies.