A Word from the Watershed: The Weird and Wonderful Pacific Lamprey
By Corrie Aiuto
Pacific Lamprey are amazing animals. An eel-like, boneless, parasitic fish, they are resilient, older than the dinosaurs, and have a fascinating life cycle. They also live in our watershed. In January the Upper Nehalem Watershed Council (UNWC) was happy to host Christina Wang of the U.S. Fish and Wildlife Service at the Vernonia Public Library to speak about Pacific Lamprey. We at the UNWC can’t stop talking about her presentation or these crazy fish.
There are approximately 40 species of lamprey around the world. Four species are native to our watershed: Pacific Lamprey, Western River Lamprey, Western Brook Lamprey, and Pacific Brook Lamprey. Some species are anadromous, meaning they return to fresh water to spawn like salmon, and some spend their whole lives in fresh water. The Western Brook and Pacific Brook are an example of resident fresh water lamprey. The infamously invasive sea lamprey, which decimated trout populations in the Great Lakes, is thankfully not found in our rivers.
Lamprey, though they look like eels, are actually fish. They have no scales, and are boneless, having cartilage instead. They have no paired fins on their sides (as goldfish do), only dorsal fins and a caudal fin. They have holes for gills, blue eyes, and depending on species they can be 4-33 inches in length. They are also jawless, having a powerful suction cup mouth with teeth used for feeding, anchoring, and climbing. Lamprey cannot jump and have no swim bladder, so they must constantly swim or use their mouths to anchor themselves. They also use their months to climb over waterfalls, attaching to a rock, and then propel forward with a quick stroke of their tail.
Lamprey biology is ancient. Fossils dating 360 million years old show a recognizable lamprey, its body and form essentially unchanged and they are estimated to have emerged 450 million years ago. That makes lamprey hundreds of millions of years older than the dinosaurs, sturgeon, salmon, and humans. Their survival strategies are so successful that they lived through at least four mass extinction events on Earth.
The life cycle of Pacific Lamprey is one of many transformations and long journeys. Their range spans the upper Pacific Rim from Mexico to Japan.
When it is time to spawn, adult lamprey migrate upstream to build nests, or redds, in habitat similar to what salmon prefer, with gravel bottoms and slower currents. However, rather than returning to native streams to spawn as salmon do, lamprey follow the pheromone signals of live baby lamprey in the larva stage, called ammocoetes. Because of this, an Oregon lamprey can eventually spawn in Russian freshwater, following the scent signals of existing larva. Spawning usually occurs between March and July, depending on how far they must travel. Both males and females build the nests, using their powerful sucking mouths to move rocks into a circular shape for the eggs. Spawning males also use their mouths hold the female while mating and can mate with multiple females in a single spawning event. Female Pacific Lamprey are especially productive and can lay up to 250,000 eggs. After spawning, the adults die with 3 to 36 days.
The eggs hatch in about three weeks. The tiny ammocoetes drift downstream until they find a low flow area with loose silt and gravel where they burrow down beneath the surface. They look and behave much like earthworms; sightless, toothless, they grow to be 8 inches long. They filter feed, pushing their mouths up above the silt to catch passing particles and help mix oxygen and nutrients into the silt. There they stay, hiding in the streambed, for anywhere from 2 to 10 years.
Juvenile lamprey, also called macropthalmia, stop feeding, grow eyes and teeth, develop their suction mouths and the ability to swim freely. They turn silver and, between July and November, begin their outward migration to the ocean. During this journey they can feed parasitically, preying on larger fish.
When they reach the sea, lamprey quickly swim away from shore, and have been found at depths over 4,800 feet where they feed and survive as parasites. They prey on pollock, hake, salmon, flatfish, rockfish and many others. Much of their life and behavior during this time is unknown. Some adults return to fresh water to spawn as quickly as 6 months, while others stay at sea for over 10 years.
Adult lamprey are preyed upon by sharks, sea lions, birds, and many other marine mammals. They are calorie dense, which means they are an important food source for many predators and their presence brings some relief to salmon and other fish listed under the Endangered Species Act.
When lamprey at sea begin their migration to freshwater, they undergo one final transformation. Returning to fresh water streams in the spring and summer months, they typically stay there for about a year, to “overwinter.” They stop feeding completely, become sexually mature, and shrink in size, losing almost one third of their body mass.
Lamprey hold cultural significance to indigenous people. They were a primary food source for thousands of years, prized for their rich, fatty meat and used in tribal celebrations. Harvesting them was relatively easy, using hands or hooks to pluck them from rapids and waterfalls where the lamprey were climbing over, attached to the rocks.
Lamprey populations have declined significantly due to human activity. Culverts and dams prevent their upward migration, dewatering, dredging, and chemical spills kill ammocoetes, and loss of floodplain habitat impacts spawning. The Columbia River Inter-Tribal Fish Commission comprised of the Umatilla, Warm Springs, Nez Perce, and Yakama Nation tribes began working on conservation and drafted a plan in 2008. Since then they have gained partnerships with other tribes, local, state, and federal agencies and a few watershed councils. There is even a new lamprey exhibit at the Oregon Zoo to educate visitors about their biology and importance. The goal is to spread awareness, restore habitat and access to habitat, and reduce threats as much as possible to ensure lamprey thrive into future generations.
The UNWC thanks Christina Wang for her captivating presentation. If you want to learn more about Pacific Lamprey visit the U.S. Fish and Wildlife Service at https://www.fws.gov/pacificlamprey/mainpage.cfm.
Be sure to join us at Vernonia Lake on Saturday, March 7th and 14th from 11:00 am to 2:00 pm for our family-friendly volunteer tree planting event. We will provide all necessary tools, refreshments, and even give away trees to our volunteers to take home! Bring waterproof boots and sack lunch and we will see you there.
Originally published on 3.5.20 in Vernonia’s Voice.