Approved for FY26 funding under PLCI project.
The purpose of this project is to evaluate the vertical distribution (burrowing depth) of larval lamprey at locations with different: 1) sediment characteristics (composition, compaction, stratigraphy/layering) and, 2) dewatering exposure/history to inform unbiased sampling approaches and updated guidance on dewatering, dredging, and habitat restoration. Little is known about the vertical distribution of larvae, which likely varies with larval size and microhabitat conditions. Laboratory trials suggest that burrowing depth increases with larval size, but confirmatory data from field studies are lacking. The hyporheic zone (HZ, saturated portion of the streambed) provides important rearing habitat and potential refuge during poor environmental conditions. Larvae survived for at least 22 days in the HZ of one dewatered streambed. Burrowed larvae are within the HZ, but how they use the zone, through selection of burrow depth and microhabitat conditions, and how use could affect their responses to dewatering or habitat restoration, is undescribed. Lamprey in habitats that are dewatered regularly (e.g., via tides), seasonally dewatered via human activities, and rarely/never dewatered likely have different, and undescribed burrowing patterns. Additionally, population/demographic data (occupancy, abundance) may be biased when estimated from electrofishing if larger lamprey are less vulnerable to collection because of increased burrow depth.

Study outcomes include: 1) methods to describe lamprey vertical distribution, and 2) assessments of factors (larval size, stratigraphy, temperature, etc.) that affect vertical distribution in diverse habitats. Outcomes could inform best management guidelines (BMG) during dewatering events, dredging, habitat restoration, and optimized field sampling.