|TABLE OF CONTENTS||Wiyot Tribe Studies Ancient Lamprey|
By Tim Nelson and Stephen Kullman, Wiyot Tribe Natural Resources Department
Photos courtesy of Stephen Kullman
The river we call the Eel got that name when European newcomers mistook abundant Pacific lamprey (Entosphenus tridentatus) for fish they remembered from the Atlantic. In fact, though lamprey are superficially similar to eels, they could hardly be much more distant in origin. Lamprey are among the last surviving examples of the oldest known vertebrates, recognizable in fossils more than twice the age of dinosaurs like T. Rex.
The sheer number of fish in the river is reflected in the name local native people gave the river – Wiyot, meaning abundance. Today it is the tribe that’s known as the Wiyot, while the river we call Eel carries fewer and fewer gou’daw. Although there has been little concentrated study of Pacific lamprey on the Eel River, locals and native people have observed a steep population decline over the past decades. Once a mainstay of traditional diets for tribes along the river, with higher protein and fat content than even salmon, gou’daw are becoming harder to find and even harder to harvest. Lamprey were also a major food source for predators from sea lions to bears and raptors, as well as scavengers like green sturgeon. It has been suggested that the abundant lamprey functioned as a buffer, reducing impacts on migrating salmonids.
Responding to the decline in lamprey, the Wiyot Tribe Natural Resources Department has been working to identify and prioritize barriers to lamprey migration. (Unlike salmon, lamprey cannot jump – but they can climb up a 30’ sheer face using their powerful mouths to cling to the rock.) Unfortunately, we have encountered situations where passage improvements intended for salmonids have unintentionally created barriers to lamprey migration. Fortunately, through better outreach and inter-agency communications, mitigations can anticipate the needs of all species.
The project, funded through a U.S. Fish and Wildlife Service Tribal Wildlife Grant and conducted in partnership with Stillwater Sciences, includes passage assessments and ammocoete surveys within the Eel River/Van Duzen watersheds. Ammocoete [am-uh-seet] are the wormlike, eyeless and jawless larval stage of the lamprey. They live buried in fine substrate or silt for five to seven years, feeding on tiny bits of organic material they filter from the stream. An assessment can include a full longitudinal profile with survey equipment to model potential passage barriers, lamprey specific spawning and ammocoete habitat assessments, and electrofishing (e-fishing) to determine ammocoete presence. While we are still completing data, some patterns are already emerging. We are beginning to be able to characterize Pacific lamprey distribution throughout the system.
Ammocoetes’ long residence in freshwater and their extreme vulnerability to pollution and dewatering may help explain why lamprey numbers have been declining sharply across the West Coast. During the years that pass from the ammocoete to the spawning stage of the Pacific lamprey life cycle, there are numerous threats to the survival of an individual lamprey. The majority of their lives are spent in the river bottom substrate; survival requirements are sufficient water (for oxygenation), suitable sediments (for protection), and food. If these three requirements are met, the survival rate for the ammocoete is high. However, if the area in which the ammocoete is located has been cut off from the river, it can die from either low oxygen levels as water temperatures heat up or suffocation from the pool drying up before rains can reconnect the river system.
Ammocoetes also play an important role in lamprey reproduction. Unlike salmon, lamprey do not smell their way home to the stream in which they hatched. Rather, current research suggests that adult lamprey follow pheromones emitted by ammocoetes. This is a great way to signal the presence of good larval habitat to would-be lamprey parents. But it can mean that a few severe impacts can cut off both the present and the future of a lamprey population.
So what are the real challenges to lamprey success? The big, glaring problem has to do with water quantity. This has been a historically low precipitation year. Combined with an increase in both legal and illegal diversions, many tributaries went dry. Of the water that is remaining, hot temperatures in combination with high nutrient loads cause blue-green algae blooms that can lead to human and wildlife sickness as well as fish kills.
Besides water quantity and quality, lamprey also have to deal with predation from large, non-native fish called Sacramento pikeminnow. Pikeminnow can grow as large as one meter in length. They are known to compete with trout and prey upon young salmonids and ammocoetes as well as adult lamprey. Once established, the non-native pikeminnow further depleted already crippled salmonid and lamprey populations, slowing recovery.
So far it appears that Pacific lamprey are holding to stretches of river or tributaries that have adequate water supply and/or little human impact. There is a lot more work to do but as long as the species exists, the Wiyot Tribe’s Natural Resources Department will continue to work towards reviving the run of Pacific lamprey on the Eel River.
The tribe and its partners will soon be starting a new USFWS TWG lamprey project focusing on the lower Eel River and Humboldt Bay tributaries. The goals of this project will be to develop preliminary long-term monitoring and management plans for Pacific lamprey. This will include conducting a creel survey of “eelers” – interviewing fishers and surveying their catch, and identifying reaches for lamprey monitoring.
Ultimately we hope this work will help identify and overcome major limiting factors to Pacific lamprey success in the Eel River.