Illustrating the Sea Lamprey Migration; Can We Draw Them In?

The sea lamprey completes its life-cycle after a migration from offshore feeding areas to riverine spawning grounds, guided by a pheromone mixture (bile acids) produced by stream-resident larvae, which appears to aggregate migrants into habitat sufficient to support future offspring. We set out to describe the coastal migration and evaluate whether the addition of larval odor to a Lake Huron tributary can induce river entry. During a two year study, we investigated the movement patterns that compose the coastal migration using 46 acoustic receivers in a fixed array to monitor acoustically-tagged migratory lamprey as they approached, entered or bypassed a stream under two conditions: 1) with greatly reduced larval odor following larvae removal (April-June 2010, n=57, 37.9 % entered); and, 2) after the addition of synthesized larval odor components (April-June 2011, n=75, 54.6 % entered).  To determine if the observed increase in entry rate was related to plume size or desirability, we are building a hydrodynamic model to estimate the river plume proximity based on water chemistry data taken with an AUV, and hydrodynamic data from an ADCP. After associating fish movement patterns and river plume dispersion, we describe a coastal fish migration at an unparalleled level of spatial resolution.