Pacific Lamprey’s Big Year

This Pacific Lamprey was seen recently on the South Fork of the Eel. After completing its life cycle by spawning in freshwater after traveling upstream from the ocean, it will die. [Photo by Talia Rose]

While South Fork of the Lamprey River does not roll off the tongue with same ease as South Fork of the Eel, it would be a more accurate name for our local waterway, especially this year when it is enjoying an abundance related to the high pre-drought water flows of a few years back. Older than the dinosaurs, a delicacy to native tribes, and a fussy architect to boot, the Pacific Lamprey is integral to the complex web of life involving endemic and introduced fish species in the inaccurately named Eel.

The renewed abundance of this very old fish is like a happily singing canary in the mine here on the North Coast when the news about so many of our local fish is grim. Because of its role in the food chain, return of the lamprey may be good news for other fish species.

Evolving 450 million years ago around the same time as sturgeon and shark, the lamprey spends most of its life as an ammocoete, or larva, after hatching in fresh water streams. The small, worm-like larvae burrow into the rocky river bottom and filter-feed on detritus and micro-organisms.

River Otter enjoying a meal of lamprey on the South Fork of the Eel [Photo by Talia Rose]

After 2-7 years, the ammocoetes undergo a metamorphosis lasting several months and then journey out to sea as adults, growing up to 30 inches long, where they feed by attaching their jawless mouthparts onto fish and other vertebrates, drawing blood and other body fluids without killing the host.

After 1-3 years at sea, lamprey return to fresh water streams where the female may spend a week or more preparing her “redd” or egg repository, arranging rocks on the stream bed to her precise specifications before depositing up to 100,000 eggs which are later fertilized by the male.

Like most anadromous fish in the Eel, the adult lampreys die after spawning, bringing a huge quantity of nutrients into the Eel River food chain. Unlike Pacific salmon species, it is suspected that lamprey do not necessarily return to the same river in which they were born.

The fact that they are so abundant in the Eel these days could be a very good sign for our river. The Pacific Lamprey is in decline in most of the Pacific Northwest and elsewhere in California due to pollution and flow diversion, and may be choosing the Eel because of its health relative to other waterways.

According to Patrick Higgins, local fish biologist and Managing Director of the Eel River Recovery Project, our lamprey are going through a resurgence that is part cyclical, but also may indicate that a healthy balance of fish species is returning to the watershed.

Besides otter and bear preying on lamprey, Osprey catch them as well [Photo by Talia Rose]

“My hypothesis is that the lamprey are doing better because the Pikeminnow population is depressed,” says Higgins. The invasive Pikeminnow, introduced to the Eel system in about 1979, has taken a toll on the lamprey by feeding on the ammocoetes. “About 20% of the Pikeminnow diet was lamprey ammocoetes when diet studies were done in the late 90s. River Otters appear to be suppressing Pikeminnow through intensive predation, which is likely to have caused a resurgence of lamprey,” says Higgins. [Note: Some scientists have expressed serious reservations about the theory that the Pikeminnow population is suppressed. As one of the commenters says below, “[Lamprey] returns were also very strong to the Klamath and especially to the South Fork Trinity both of which do not have pike minnow. This indicates more of a region-wide resurgence.]

The weather may also play a part in the lamprey resurgence as wet years have typically enabled the downstream migrating ammocoetes to maneuver more successfully past the Pikeminnow in the greater volume of water and increased turbidity. “This is the third year of high abundance of lamprey, which indicates good brood production in 2005-2007; therefore, runs are likely to continue strong for the next several years as a result of high spring flows through 2012,” said Higgins. It remains to be seen how the next cycle from 2020-2024 will reflect the low water times of that drought.

Another factor contributing to renewed lamprey productivity is the recovery of gravel beds in the Eel system. With much of the sand and silt deposited during the 1964 flood now washed to the ocean, there is more suitable clean gravel for lamprey redds. Lamprey, unable to jump like the salmonids, attach their mouths to rocky surfaces to shuttle upstream against the current. This same attachment function allows the parent lamprey to move rocks around precisely, creating an ideal nursery for the eggs.

Juvenile Pacific Lamprey, or ammocoete. [Photo from Wikicommons]

Keith Parker, Yurok tribal member and Humboldt State University graduate student, has been working on genetic diversity of Pacific Lamprey in the nearby Klamath River. Local tribes have long used lamprey as a nutrient-dense food that helps them get through the lean times when salmon are scarce. Lamprey have nearly 5 times the lipid content of salmon, making them a high energy food source. Because the primitive fish is a poor swimmer that hugs the edges of streams where it can attach its mouth when needed in order to make progress, it is harvested from the shore with an eel hook, a short pole with a wire hook at one end.

“Lamprey is what fed our people when there were no salmon,” says Parker. He adds that a healthy abundance of lamprey benefits the entire riparian ecosystem. Like all fish who die in the river after spawning, their corpses deposit rich marine nutrients that contribute to the health of flora and fauna throughout the system. “Core samples of redwood trees taken in the upper reaches of Redwood Creek show marine-derived phosphorus, most likely deposited by lamprey, who account for the largest bio-mass in the Klamath system.”

According to Parker, an abundance of lamprey also benefits the salmonids because “they are the preferred meal for seals and sea lions, being easier to catch than fish, and less challenging to consume because of their soft cartilaginous skeleton.” When seals and sea have fewer lamprey to take, they take more salmon.

Lamprey numbers have declined since the 60’s. One study counted 380,000 lamprey crossing over the Columbia River’s Bonneville Dam in 1969. That number was down to 11,000 in 2011.

“By building anadromy barriers,” says Parker, “we have blocked the return of energy upstream.” Parker’s current research seeks to identify a correlation between lamprey size and travel distance in the several north coast river systems which will be used to aid the recovery of lamprey throughout its once extensive range.

When a critical species such as the Pacific Lamprey rebounds as it has over the past few years, it is hoped that because of the role it plays in the web of local life, other species will be boosted by its numbers.





  • Thank you for this informative article! Good to hear the Lamprey Eels are doing so well. Also good to hear the River Otters like to eat the invasive Pikeminnow.

    There was a lot of Lamprey (and Shad) activity at Bonneville Dam, when I was there a few weeks ago.

  • I can’t remember the last time I saw eel carcuses in the Eel river when I was a kid back in the 60s there lots of dead EELS back then nice to see they are back in force .Maybe the salmon will do the same .

  • Thanks for an entertaining and educational piece that me feel more aware of the origins of life around here.

  • When i was a kid in the early 70’s you could stomp around in the same place, in the sand next to the river. This would bring many baby eels to the surface, not any more.

  • What a great story and bunch Talia photos 🙂 . The Wildlife Whisperer…

  • “The pikeminnow poplution is depressed”, was he able to say that with a straight face? LOL Apparently they havent been looking for them. Van Duzen is stuffed with them and almost any day if the week you can pull at least 3 from Holmes.

    • Sorry to hear about that.

    • The pikeminnow population is very strong in eel river. It maybe less than it was because they have eaten so many juvenile salmon,steelhead,sucker and lampreys that they don’t have as much food..Mr. Higgins clearly states it is a hypotheses. I hope he is right, but last summer the lower eel and van duzen was packed with pikeminnow.before pikeminnow arrived, it would be packed with baby steelhead and suckers.very few of those now.

  • Honeydew Bridge C.H.U.M.P.

    Dredging the gravel from the river mouth would be helpful.

    ERB should brew a Lamprey Lager.

  • Great article, thanks. Great to hear of the lamprey .
    What’s the state of shad in the Eel River? Does ayone know? I remember standing in the river surrounded by vast schools of them, getting bumped in the legs as they moved upstream back in the 60s

  • This lamprey picture would make a great cover photo for RHBB..

  • The photography tho…. Proper

  • Thank you for this very interesting piece.

  • Concerned biologist

    Overall, a well researched article, on an important species, but be aware of sources that make big conclusions about recovery and reasons for it based on little real data and lots of anetcdotes and speculation. Sounds about parr for the course, but hey, the general public will eat ‘er up if it sounds good. Since streams across the North Coast have (mostly anecdotally) seen relatively large adult returns the last few years, ocean conditions or some other factor common across them is more likely the driving factor than conditions specific to the Eel River like a change in the pike minnow population. Whatever the reason, hope they continue to do well, but expect large yearly fluctuations like salmon. Shad are not native to the Eel River, by the way. Also, ammocoetes don’t have eyes. I second the Eel River Lamprey Lager.

    • Agree with you Concerned. One thing to keep in mind is that unlike salmon, lamprey don’t necessarily return to where they were born, but adults are instead drawn toward pheromones emitted by the ammocoetes. Eel returns were also very strong to the Klamath and especially to the South Fork Trinity both of which do not have pike minnow. This indicates more of a region-wide resurgence, and a very welcome resurgence at that. The Karuk, Hoopa Valley and Yurok Tribes are cooperatively conducting a large adult lamprey tracking study in an attempt to unravel some of the life cycle. Early findings are that adults sometimes spend a year in freshwater before spawning, and can lose 30% of their body weight (give or take) while doing so. It is not known whether this surge in lamprey originates locally, or whether the northcoast is reaping the bounty of other systems such as the Columbia River. Correct on the ammocoetes not having eyes, those are known as macrophthalmia. I’m more of an Eel River IPA person myself…

    • Are the Pike Minnow related to what is commonly called the “Sacramento River Squawfish”? They seem to have somewhat similar characteristics. Just wondering. I would like to see a Lamprey Eel Stout.

  • I am pretty sure I have found the baby ones in the past. But I did not know what they were called. The photos are amazing as well as the story. I love learning fun stuff. Thank you!

  • a great article….do keep giving us in-depth info about out watershed’s diverse fish, flora, fauna, and natural history. As a 45 year resident of the south fork canyon, it’s great to learn more about neighbors who have been living here for 450 million years!

  • Good article Ann. Nice to hear that some species is thriving in these times! I haven’t seen this many lamprey in the river…nearly everywhere… since the late 80’s-early 90’s.

  • Pingback: Pacific Lamprey’s Big Year – Friends of the Eel River

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