Characterizing attraction flows at sea lamprey traps entrances*

The sea lamprey (Petromyzon marinus), an invasive species significantly impacting the Laurentian Great Lakes ecosystem, has traditionally been managed using lampricides since the 1950s. However, emerging research highlights adverse effects of these chemicals on native lampreys and other fish species, necessitating alternative removal methods. Trapping is one such method, although current traps are relatively inefficient and predominantly used for monitoring. The flow patterns induced by these traps, presumed crucial for trapping success, remain unquantified.

This study evaluates two common sea lamprey trap designs using Particle Image Velocimetry (PIV) to measure induced attraction flows and internal trap flows with minimal background turbulence at the University of Michigan Hydraulics Lab. Key flow parameters, including velocity and vorticity distributions, were derived from PIV data.

Further, these trap models were deployed in larger-scale raceways at the USGS Hammond Bay Biological Station to assess flow structure alterations under more turbulent, naturalistic conditions. Paired with video observations, this setup examined sea lamprey behavioral responses to the induced flows. This research contributes to understanding the dynamics of attraction flows in sea lamprey traps and the behavioral responses of sea lampreys, aiming to enhance the efficacy of trapping as an alternative control method.