Pacific Lamprey

Young, or larval, Pacific lamprey filter-feed from burrows in the river bottom. As adults in the marine environment, Pacific lampreys are parasitic and feed on a variety of fish, including Pacific salmon, flatfish, rockfish and pollock, and are preyed upon by sharks, sea lions and other marine animals. Adult Pacific lamprey do not eat once they return to freshwater.

Migration Behavior 

Pacific lamprey undertake extensive freshwater and marine migrations. Within rivers they can travel distances up to 870 miles (1,400 km) upstream of the Pacific Ocean and to elevations of 6,900 feet (2100 m). In the Pacific Ocean individuals have been observed migrating 3,100 (5,000 km) from the Bering Sea to the Columbia River. They have been caught in depths ranging from 300 to 2,600 feet, and as far off the west coast as 62 miles in the ocean.

Lampreys belong to a primitive group of fishes that are eel-like in form but lack the jaws and paired fins of true fishes. Pacific lampreys have a round sucker-like mouth, no scales and gill openings. Identification of lampreys depends largely on the number, structure structure
Something temporarily or permanently constructed, built, or placed; and constructed of natural or manufactured parts including, but not limited to, a building, shed, cabin, porch, bridge, walkway, stair steps, sign, landing, platform, dock, rack, fence, telecommunication device, antennae, fish cleaning table, satellite dish/mount, or well head.

Learn more about structure and position of teeth found in adult lamprey. Adult Pacific lampreys are characterized by the presence of three large anterior teeth and many smaller posterior teeth on the oral disc. As ammocoetes, or larvae, Pacific lampreys are difficult to distinguish from other lampreys.

Pacific lamprey adults are typically between 1.5 to 2.5 feet long. They stop feeding once returning to freshwater and can lose up to 1/3 of their length before spawning.

Pacific lampreys spawn in similar habitats to salmon; in gravel bottomed streams, at the upstream end of riffle habitat, typically above suitable young larvae habitat. 

Spawning occurs between March and July depending upon location within their range. The degree of homing is unknown, but adult lampreys cue in on the smell of larval lamprey and other reproducing adults, which release pheromones that are thought to aid adult migration and spawning location. Both sexes construct the nests, often moving stones with their mouth. After the eggs are deposited and fertilized, the adults typically die within three to 36 days after spawning.
 

Larval stage

Embryos hatch in approximately 19 days at 59° Fahrenheit (F). Larval lamprey drift downstream to areas of low velocity and fine substrates where they burrow, grow and live as filter feeders for two to seven years. During this time, they feed primarily on algae. Several generations and age classes of larvae congregate in high densities that form colonies.

Juvenile stage  

As their larval stage ends, a miraculous transformation occurs. Juvenile Pacific lamprey grow eyes and a mouth full of teeth. Their brown skin turns silver, they become parasites and eat their first meal as they migrate downstream to the ocean. Pacific lamprey juveniles attach to fish and marine mammals to get nourishment. They live in the ocean for up to five years and may travel across the entire Pacific Ocean before returning to fresh water as adults to spawn. 

Metamorphosis to the juvenile phase occurs gradually over several months, usually beginning in summer and is complete by winter. As developmental changes occur, including the appearance of eyes and teeth, the juveniles leave the substrate to enter the water column. Moving downstream, they emigrate to the ocean between late fall and spring where they mature into adults.

Adult stage

As adults in the marine environment, Pacific lampreys are parasitic and feed on a variety of marine and anadromous fish including Pacific salmon, flatfish, rockfish and pollock. They are preyed upon by sharks, sea lions and other marine animals. Individuals from this species have been caught at depths ranging from 300 to 2,600 feet, and as far off the west coast as 62 miles in ocean haul nets.

After spending one to three years in the marine environment, Pacific lampreys cease feeding and migrate to freshwater between February and June. They are thought to overwinter and remain in freshwater habitat for approximately one year before spawning. During that time they may shrink in size up to 20 percent. Most upstream migration takes place at night. Adult size at the time of migration ranges from about 15 to 25 inches. After spawning, males and females die, and their bodies provide valuable marine-derived nutrients for other aquatic residents. 

Pacific lamprey can live between seven and 11 years. 

Pacific lamprey use different habitats during different life stages, and including both riverine and oceanic environments. Young lampreys can be found in burrows in sandy river bottoms. In the Pacific Ocean they can be found at depths down to nearly a mile.