Thursday, October 25, 2012

Juvenile Pacific Lamprey in Puget Sound Streams

Pacific lamprey (Photo: R. Tabor)
Pacific lamprey
Pacific lamprey (Lampetra tridentata) are native to the Pacific Ocean and are a vital component of native fish communities. They are also used for food, medicine, and ceremonial purposes by some Pacific Northwest tribes.

Pacific lamprey are anadromous--they live in both fresh and salt water. Adults live in the ocean where they feed on the blood and bodily fluids of marine mammals and fish. After about 2 years in the ocean, they return to freshwater streams to spawn, constructing nests in small gravel where they lay their eggs. Eggs hatch after several weeks. The blind larvae--called ammocoetes--live in fine sediment on the bottom of the stream and filter-feed on algae and detritus. After 4 to 6 years as an ammocoete, Pacific lamprey metamorphose to a second juvenile life stage called macropthalmia. During this stage, the juvenile lamprey migrates out to the ocean and begins a parasitic lifestyle as an adult, growing to about 2 feet in length.

Like salmon, the abundance and range of Pacific lamprey have been reduced. To improve their distribution and abundance, the U.S. Fish and Wildlife Service (FWS) and its partners are working to address threats to Pacific lamprey, restore habitat, and fill in large data gaps. Here in the Puget Sound area, we lack basic information on lamprey, including presence and absence of these fish in our local rivers. To remedy this, the U.S. Geological Survey partnered with the FWS in 2011 to look at lamprey caught in traps designed to capture juvenile salmon.

During the spring of 2011, juvenile lamprey were captured at 18 trap sites located throughout the Puget Sound area, including Hood Canal. Pacific lamprey were identified in 13 of these 18 watersheds. Color patterns and pigmentation on their tails were used to identify ammocoetes to species. No eyed juvenile (macrophthalmia) Pacific lamprey were captured in the traps. We suspect these ocean-bound juveniles move downstream at times outside of our trapping period.

Trap locations within Puget Sound (Mike Hayes, USGS)
Trap locations within Puget Sound
One interesting find was that of "dwarf" adult lamprey. These fish measured less than 300mm in length--an adult fish is typically over 500mm long. Why so short? Do they spend less time in salt water? Or do they remain and mature entirely in fresh water? We hope to find the answers next field season!

For more information on FWS Pacific lamprey activities:

Lamprey coloring book:

Pacific lamprey fact sheet:

Follow Luna the Lamprey's return voyage from the ocean:

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Follow Luna's tweets (@LunaLamprey) on Twitter
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