Pacific lamprey

Species of jawless fish

The Pacific lamprey (Entosphenus tridentatus) is an anadromous parasitic lamprey from the Pacific Coast of North America and Asia in an area called the Pacific Rim. It is a member of the Petromyzontidae family. The Pacific lamprey is also known as the three tooth lamprey and tridentate lamprey.

Pacific lampreys grow to about as adults. They are anadromous and semelparous. They have slender, elongated bodies with two dorsal fins arising far back on the body. The anal fins are rudimentary and the lower lobe of the caudal fin is larger than the upper lobe and both lobes are continuous with the dorsal fin and the anal fin. Adults living in the sea are a bluish black or greenish colour above and pale below, but those in fresh water are brown. This species is distinguished by having three (or occasionally two) sharp teeth on the supraoral bar above the mouth and three sharp points on each lateral plate. The Pacific lamprey are often found at sea or often far offshore. At sea, depth: near surface to 1,508 m (4,946 ft)

Although the adult and juvenile stages are more noticeable, lampreys spend the majority of their lives as larvae (ammocoetes). Ammocoetes live in fresh water for many years (usually 3–7 years, but at least one species has been recorded for +17 years). Ammocoetes are filter feeders that draw overlying water into burrows they dig into soft bottom substrates. After the larval period, the ammocoetes undergo metamorphosis and take on the juvenile/adult body morphology. Juveniles/adults have a jawless, sucker like mouth that allows them to become parasitic on other fish and sperm whales, attaching themselves with their suckers and feeding on blood and body fluids. The adults live at least one to two years in the ocean and then return to fresh water to spawn. Whether Pacific lampreys return to their natal streams or seek spawning areas based on other cues is not known. They typically spawn in similar habitat to Pacific salmon and trout. Lampreys construct a nest (redd) in small gravel and females can lay over 100,000 eggs, which are fertilized externally by the male. After spawning, the adults usually die within four days. Also, like salmon, the Pacific lamprey does not feed while migrating to spawn. Pacific lamprey numbers in the Columbia River have greatly declined with the construction of the Columbia River hydropower system. Almost no harvest opportunity for Native Americans remains in the Columbia River and its tributaries except for a small annual harvest at Willamette Falls on the Willamette River (tributary to the Columbia River). The Yurok and Wiyot snag lampreys in the surf at the mouth of the Klamath River, often at night, using hand carved wooden "hooks". It is dangerous work. The high caloric count also make lampreys an important piece of the river ecosystem, as other animals also rely on them. The documentary film, The Lost Fish, chronicles how current tribal communities are actively studying, breeding, and working to restore lamprey and lamprey habitats to the waterways of the Pacific Northwest. Pacific lampreys also hold deep cultural and spiritual importantce for many indigenous tribes of the Pacific Northwest. They are seen as essential components of the ecosystem, serving both as predators and as prey. The tribes have traditional tales that discuss the lamprey's ecological and cultural significance. Their presence or absence in specific waterways would sometimes be interpreted as omens.

Pacific lamprey numbers have greatly decreased due to human infrastructure. Damming rivers, channelization, and declines in water quality have impacted pacific lamprey habitat and their ability to live. However, restoration of rivers and streams in Southern California has re established the fish in portions of their historic southern range. The Pacific lamprey recolonized the Santa Margarita River in San Diego County in August 2019 for the first time since 1940, the furthest south the species has currently recolonized, 260 mile (418 km) south of the previous recolonization of San Luis Obispo Creek in San Luis Obispo in 2017. The Santa Margarita River recolonization has been attributed to a rebuilt weir and new fishway at Camp Pendleton which allowed the lamprey to find passage into the river. There have also been concerns over the conditions in which Pacific Lamprey larva will have to endure in the coming century. The main concern is climate change because we could see temperatures in which the larva live in increase to 27 31 °C. The preferred temperature for lamprey hatching is about 18°C, anything more than that could potentially be deadly. Studies have shown that temperatures that exceed 30.7 °C is a deadly for the larva. A temperature of up to 27.7 °C however is manageable for the larva. Depending on the temperature increase, the larva may also exhibit a change in behavior which could lead to its death. PLCI was initiated in 2008 by the USFWS. A notable collaboration has emerged in the Columbia River basin where several organizations and native tribes have come together under the PLCI to implement various conservation methods.