Range and natural history
FishBase reports the species from Oregon’s Columbia River drainage and describes a life in creeks and rivers. Adults do not parasitize other fish. The reviewed account reports autumn metamorphosis and spring-to-summer collections of spawning adults. The account’s additional California timing observations reflect older regional literature.
A 2024 genetic and taxonomic study placed the western brook and river lampreys in Occidentis, separate from Atlantic Lampetra. It retained pacifica as a recognized species while identifying further unresolved diversity in western lampreys.
Sources: Occidentis pacifica species summary; Taxonomy and name history
Guide sources
Research reviewed 2026-10-19.
- Occidentis pacifica species summary — FishBase
- Taxonomy and name history — PLOS ONE
