Entosphenus trudentatus (Richardson, 1836)
The maximum recorded age for Paciﬁc lamprey is 9 years. The maximum weight published for a Paciﬁc lamprey is 500 grams (17.6 oz).
SIZE: Common length for Paciﬁc lamprey is 41 cm (16.1 inches). The maximum recorded length for Paciﬁc lamprey is 76 cm (30 inches).
RANGE: The range of the Paciﬁc lamprey within the North Paciﬁc extends from the Bering Sea coasts of Asia and Alaska, southward to the Yuhuntun River, Hokkaido, northern Japan and southward to Punta Canoas, central Baja California and Mexico. There are some freshwater resident populations existing in Culrus Lake and the Columbia River, British Columbia, the Spague River in Oregon, the Goose Lake in Oregon/California, the Klamath and Shasta rivers and Copco Lake in California.
HABITAT: Adult Paciﬁc lamprey inhabit marine environments in depths ranging from 300 to 2,600 feet (90.9 m – 788.9 m). Pacific lamprey have been recorded at distances of 62 miles oﬀ the west coast of the United States. Adult lamprey spawn in habitats similar to adult Paciﬁc salmon, which includes the upstream end of riﬄes areas in streams with gravel bottoms.
DIET: Paciﬁc lamprey are a parasitic anadromous species that feed on the blood and bodily ﬂuids of other ﬁsh species. They attach themselves to other ﬁsh by using a round, sucker‐like mouth containing several types of specialized teeth that enable them to attach themselves to other ﬁsh.
Paciﬁc lamprey are an anadromous species. Adult Paciﬁc lamprey spend between 1 to 3 years at sea before they stop feeding and begin to migrate into freshwater between February and June of the same year. It is believed that once they return to freshwater habitats, they overwinter and inhabit freshwater for about one year before they spawn. During this overwintering period, they may shrink in size by as much as 20 percent.
Paciﬁc lamprey spawning usually occurs between March and July depending on the geographical location of their native range. It is believed that lamprey larvae release some type of ﬁsh hormone that enables the adults to locate suitable spawning locations. Both the male and female adults participate in nest construction. After the nest is completed, the females of the species then deposit their eggs in the nest and the male lamprey then fertilizes them by releasing his milt over the eggs.
Paciﬁc lamprey populations have decreased in many river drainages, while some populations have become extinct above impassable river barriers on west coast streams and rivers. Paciﬁc lamprey face signiﬁcant threats to their habitat. These threats include ﬁsh passage barriers, inadequate water ﬂows, poisoning from toxic water spills, poor water quality, impacts from dredging operations from mining and water channel maintenance, and stream and ﬂoodplain degradation. During their ocean phase, Paciﬁc lamprey face variable ocean conditions which include prey variability and increased risk of predation.