Examination of Exhaustion in Larval Pacific Lamprey (<i>Entosphenus Tridentatus</i>) Through Variations of Temperature, Flow, and Cover

Abstract

Pacific lampreys (Entosphenus tridentatus) are culturally and ecologically valuable throughout the western coast of North America. The larval (ammocoete) stage of the Pacific lamprey spends three to eight years burrowed in the sediment as a filter feeder, and is an essential contributor to many of the Northwest’s freshwater ecosystems. Larval lamprey may be vulnerable to warming waters caused by climate change as well as seasonal dredging and salvaging events that dislodge lamprey from sediment, as they prefer cooler water and are relatively poor swimmers in comparison to other fish such as salmon. In this study, we observed how lamprey may become exhausted by these conditions by analyzing the burrowing behavior of 63 larval Pacific lamprey after exposure to treatment combinations of temperature, flow, and burrowing ability. We found that larvae that were unable to burrow during treatments exhibited signs of exhaustion, and that lamprey exposed to warmer temperatures moved more quickly than lamprey in colder treatments. Metrics for turbulent flow did not show differences between groups, and there did not appear to be significant interactions between combinations of temperature, flow, and cover. These results suggest that lamprey may be able to tolerate warming waters resulting from climate change for shorter periods of time, and that an inability to burrow into substrate may quickly lead to exhaustion regardless of turbulent flow presence. These findings may aid in management actions for conservation efforts for Pacific lamprey, including summertime salvage events.