DART Pacific Lamprey Status and Summaries -- In Development

Lamprey Counted in Adult Fishways

1. Availability of species counts vary by location and year; that is, not all species are counted at all locations.
2. Lamprey Counts: Historically, DART has only offered daytime counts (fish counting hours 1-16) which were identified as Lamprey but not specified as daytime counts. As of 2025-11-14, where available, DART offers up to three mutually exclusive lamprey counts: daytime fishway ladder counts (hours 1-16), nighttime fishway ladder counts (hours 17-24), and LPS (24 hour count in Lamprey Passage Systems).
3. 'Lamprey are particularly difficult to count in conventional fishways designed to pass and enumerate Pacific Salmon (Oncorhynchus spp.). Lamprey move back and forth in the count station window, spending long periods of time in one place and are more likely to pass at night than salmonids. Further, lamprey use a variety of routes to pass over a dam including the navigation locks, the auxiliary water supply, and specific lamprey passage structures. Due to these life history traits, a variety of passage design improvements (e.g., lamprey-specific passage structures, Washington Shore ladder redesign, Bradford Island lamprey orifices, serpentine weir rest boxes) and enumeration techniques (e.g., lamprey optical counters) have and continue to be developed and implemented to improve lamprey passage and enumeration at dams operated and maintained by the U.S. Army Corps of Engineers. In light of the constraints to lamprey passage and enumeration due to their life history, and recognizing the changes that have occurred in the last two decades to improve both measures, it is perhaps most accurate to view the lamprey counts from 2015 as an approximation of passage for the species.' (R. Wertheimer, USACE, personal communication, January 30, 2026)
4. Click on a Project name in column header view adult visual daily counts at the project by date for 2026.

Adult Visual Count Dataset Inventory for Lamprey

Query Notes and Methods

• DART Adult Passage Visual Counts Metadata & Glossary