Observations on Lampreys in the Naknek River System of Southwest Alaska

Heard, William

Available evidence suggests that both anadromous and dwarfed freshwater forms of the parasitic Arctic lamprey, Lampetra japonica, occur sympatrically in the Naknek River system of southwest Alaska. The freshwater form is the more common of the two. Mature, spawning, and spent lampreys of this form are morphologically almost identical with non-parasitic L. lamottenii. Spawning of the freshwater form of L. japonica occurs in May, June, and early July in many streams throughout the Naknek system. Spawning behavior is essentially the same as that reported for other small lampreys. Ripe and spent anadromous adults have been collected in June, primarily from the Naknek River. Limnetic populations of immature adults are evident in most lakes in July, August, and September. During the same time and continuing into fall, some immature adults migrate downstream from Coville, Grosvenor, and Brooks lakes into Naknek Lake. Transforming ammocoetes are most evident in spring and early summer. Although L. japonica parasitizes several species, there is no evidence that parasitism in freshwater is detrimental to any fish population in the Naknek system.

Observations on Lampreys in the Naknek River System of Southwest Alaska

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