A Pacific lamprey.
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Lampreys are part of an ancient superclass of jawless fish, call Agnatha. This group of fish evolved over 450 million years ago, making them one of the oldest living lineages in the world. Jawless fish are older than dinosaurs and even older than trees and have survived at least four mass extinction events. Today there are two groups of surviving jawless fish, Lampreys and Hagfish. There are roughly 40 species of lamprey living in both the Northern and Southern hemispheres and there are roughly 80 species of hagfish dispersed around the world oceans. Washington is home to three species of lamprey.
Description and Range
Physical description
Lampreys have a long eel-like body, though they are only very distantly related to eels. In addition to not having jaws, lamprey lack a few other physical characteristics that many other fish share. They don’t have bones, scales, paired fins, or a swim bladder. Instead, their skeleton is made of cartilage and they only have two dorsal fins on their back and a caudal or tail fin. They breathe through seven gill pores or pouches on either side of their body.
Size range
Adults: 13–33 inches in length and up to 1 pound — the largest of Washington’s three native lampreys.
Ecology and life history
Pacific Lamprey are an important food resource in both the freshwater and saltwater environments. Many species of birds, mammals, and fish have been documented feeding on lamprey. They have a high fat content and are very calorically dense, containing 3–5 times more calories by weight than salmonids. Since Pacific Lamprey are such a desirably food resource for many species, they act as an important predation buffer for native salmonids. Larvae and juveniles reduce predation pressure on out migrating salmon smolts as lamprey are eaten by the same fish species as well as shore birds that prey on smolts. Returning adults are preyed on by marine mammals, such as sealions and harbor seals as well as river otters and minks in freshwater and can take the predation pressure off returning adult salmonids.
Pacific Lamprey also deliver important marine derived nutrients that increase the health of the freshwater systems. After the adult lamprey spawn and die, the nutrients in their bodies are broken down and recycled into the stream food chain. The nutrients support the growth of the next generation of lampreys as well as salmon and other native species.
Lampreys provide essential ecosystem services throughout their entire lifecycle. As larvae in the streambed, lampreys make habitats more suitable for other species by burrowing in the sediment and making the streambed softer, much like how earthworms do on land. They also breakdown and bring nutrients from the water column to the streambed through filter feeding, again improving the habitat for other species. When Pacific Lamprey return to freshwater as adults and build their nests, they create lower velocity habitat for salmonids and other freshwater species to utilize. They also increase food availability during nest construction by moving rocks and dislodging invertebrates and algae, and when they spawn they release many eggs, some of which provide food to other species. Lampreys are an integral part of both freshwater and marine ecosystems and we have a lot more to learn about these interconnected communities.
Spawning
Both female and male Pacific Lamprey work together to build nests where they lay their eggs. They use their sucker mouths to move gravels and small cobbles to clear an area suitable to deposit the eggs. Most commonly they create roughly a circle shaped depression 1–2 ft in diameter in the substrate. Sometimes the nest can be much larger, and many individuals will work on moving the rocks to make depressions for the eggs. Females may lay up to 200,000 eggs. Eggs incubate for 3–4 weeks depending on stream temperatures before the larvae emerge and disperse downstream to nearby fine sediments. Spawning timing is also temperature dependent. Where water temperatures are warmer, Pacific Lamprey may spawn as early as February and where temperatures are colder Pacific Lamprey may spawn as late as August. Most spawning in Washington occurs from April–July.
Rearing
Larval lamprey (also known as ammocoetes) are eyeless and burrow in fine sediments where they live for up to 10 years. Larval lamprey are filter feeders; they stick their heads out of their burrows and consume drifting detritus and algae that is in the water column. Through filter feeding, larval lamprey play an important role in making nutrients accessible to other species in the stream food web. They also act like an aquatic earthworm by burrowing into the streambed and make the habitat a healthier place for other species. During this freshwater stage, larval lamprey may move downstream volitionally at night to find better feeding habitat or they may be washed downstream during high flow events. Densities of larval lampreys can exceed 100 fish per square yard in optimal habitats.
After years rearing in the stream environment, larval lamprey transforming into juveniles, readying themselves to feed in salt water. At this stage, the lamprey temporarily stops feeding and spends all its energy on transformation, which includes developing eyes and teeth. The teeth are part of their characteristic oral disc that will allow the lamprey to attach and suction on to their hosts in the ocean.
After the transformation is complete, juvenile lamprey migrate downstream to the ocean and latch on to a host species to begin feeding. Once attached to their host, they extract blood and body fluids but do not consume flesh. Through fishing and stock assessment data gathering, numerous fish species have been identified as the hosts for juvenile Pacific Lamprey, such as Pacific salmon, flatfish, rockfish, Walleye Pollock, and Pacific Hake. Rarely, Pacific Lamprey have been observed feeding on whales, too. Though not a lot is known about this life stage of Pacific Lamprey, the healed scars on host fish show that many individual hosts survive having a lamprey attached. It is not known how many hosts a single lamprey will attach to or how often they change hosts, but Pacific Lamprey feed in the ocean for 1–6 years. After this time spent growing the ocean, Pacific Lamprey stop feeding and return to freshwater, becoming adults. Unlike salmonids, lamprey do not return to their natal (original) stream, but instead follow scents in the water to spawning grounds. These scents include the smell of pheromones that are released by larval lamprey and signal there is good rearing habitat nearby. Some adults enter freshwater in summer and fall and then overwinter (“stream-maturing”), holding in deep pools and under logs and rocks, before spawning in spring or early summer. Other adults will enter freshwater in the spring (“ocean-maturing”) and will spawn shortly after entering the freshwater.
Geographic range
Pacific Lamprey are native to the North Pacific and can be found from California to Alaska and across the Bering Sea to Russia and Japan. This range is similar to that of Pacific salmonids like steelhead, Coho, and Chinook. Also, like Pacific salmonids, Pacific Lamprey are anadromous, they rear in freshwater before migrating to the ocean to grow and then return to freshwater to spawn. Pacific Lamprey can travel hundreds of miles inland to find quality spawning and rearing habitat. Historically, Pacific Lamprey inhabited large to medium streams across this range. Today, they can be found in a significantly smaller portion of the previously inhabited area due to the construction of dams and other fish passage barriers that that block migration to and from the ocean.
Climate vulnerability
Sensitivity to climate change
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Pacific Lamprey exhibit physiological sensitivity to warming water temperatures. Egg and larval survival is lowest and larval deformations most common at 22°C relative to lower water temperatures. Warmer summer water temperatures (>20°C) have also been found to compound adult body size reductions and accelerate sexual maturation and post-spawning death the following spring. All life stages of Pacific lamprey are likely vulnerable to shifting flow regimes due to reduced snowpack, earlier snowmelt, and shifting precipitation regimes. Warmer water temperatures and low summer and fall flows can affect adult spawning migration timing (i.e., migration occurs earlier in warmer, lower flow years) and/or inhibit adult migrations upriver by constricting channels or causing thermal barriers. Reduced streamflows can also limit or degrade stream habitat for spawning and rearing by elevating water temperatures and/or contributing to larval and nest stranding and desiccation. Lamprey nests, which are constructed in gravel and cobble reaches, may also be vulnerable to scouring via spring flood events.. Climate-driven changes in the marine environment may also affect Pacific lamprey, including changes in host distribution and abundance, but little is known about this part of their life stage. Recent evaluations have found that Pacific lamprey will be more vulnerable to the negative impacts from climate change in rivers that are highly altered by anthropogenic (human-made) changes.
Exposure to climate change
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- Increased water temperatures
- Lower summer/fall flows
- Increased winter flood events
- Altered fire regimes
Conservation
Pacific Lamprey are important to many tribes in the Pacific Northwest. They provide food and medicine and are use in ceremonies. Like Pacific Salmon species, Pacific Lamprey populations have declined rapidly over the past several decades. Tribes across the Northwest were among the first people to notice and call attention to the fact that action was needed to protect lamprey. Since that time, efforts have been made to assess Pacific Lamprey populations and identify threats at a watershed scale. Like Pacific salmonids, there are many factors contributing to these declines, including habitat degradation, passage barriers, dewatering/flow management impacts, and impaired water quality, all of which may be compounded by the effects of climate change. Predation by non-native fish and disease may also contribute to declines, though less is known about these issues. There are still many fundamental research questions and information gaps about Pacific Lamprey and this lack of knowledge and awareness is a threat to lamprey populations. Learning about Washington’s native lampreys and sharing that information with others is a way to help conserve these important species!
Resources
- Pacific Lamprey Conservation Initiative
- Columbia River Inter-Tribal Fish Commission (CRITFC) Lamprey
- The Lost Fish (24 minutes, CRITFC and Freshwaters Illustrated film in cooperation with the US Fish and Wildlife Service)
- Native Lampreys of Oregon (PDF)