- Hits: 3469
Chapter I – 1
“It's eel season on the Yukon River. Hundreds of thousands, perhaps millions, of the squiggly, squirmy creatures are swimming up from the Bering Sea, a seething mass wriggling quietly beneath the river ice to spawn and die. Like salmon, except for the mystery posed by winter's icy cover.”This came from an article by Joel Gay in the Anchorage Daily News entitled “Eels under Yukon ice turn into cash for villagers,” November 30, 2003.
But wait—although eels may squiggle and squirm, there are no eels in the Yukon River. So what is going on here?
The article continues, “When the eels—Arctic lampreys, to be precise—pass through a village, fishermen rush to the river to dip their nets and ‘eel sticks’ through holes in the ice, pulling the fish out by the hundreds. Baked or canned, eels are considered a rich delicacy.”
Ah ha. Lampreys, not eels. Okay, what is the difference between a lamprey and an eel? And what is a lamprey eel? The last question is the easiest because there is no such thing. People often use the term lamprey eel when they are referring to a lamprey. There are fishes named lamprey and fishes named eel but there is no lamprey eel. Each name is the designation for one of two very distinct types of fishes. Lampreys, however, are often mistaken for eels because both lampreys and eels have long, slender, cylindrical bodies.
Lampreys are ancient fishes. They have been around some 500 million years and they are still with us today. A lamprey is a primitive, jawless fish. Its mouth is a round, sucking disk rimmed with small, tough, toothlike structures. They have no other hard body parts.
An eel has a bony skeleton, fine scales, and a full set of fins, jaws, and gills with one gill opening. Most fishes, including eels, have a mouth formed by hinged upper and lower jaws that open and close. Lampreys and another group of cartilaginous fish, hagfish, have a mouth opening but do not have jaws. A lamprey mouth opening is circular and is tilted downward. It functions, in part, like a suction cup. Lampreys do not have a bony skeleton, or scales, or jaws. They do have gills, but each gill arch has its own porelike opening that is displayed as a series of seven pores along the frontal part of their bodies.
Lampreys come in two versions, anadromous and freshwater. There are about 40 species worldwide, mostly in the northern hemisphere. There are 20 species of lampreys in North America, of which 5 are found in Alaska waters. Of these, the Arctic lamprey and Pacific lamprey may be the best known because they are anadromous, big, and visible. These species are parasitic on other marine fishes. Nonanadromous lampreys are limited to freshwater, where they are smaller in size and more inconspicuous.
Arctic lampreys, in Alaska, are distributed from the Arctic coast in the north, and south to include the Yukon River, Alaska Peninsula, Aleutian Islands, and Kenai Peninsula. The Pacific lamprey distribution overlaps and extends farther south. The Arctic lamprey is found nearly worldwide in northern waters. This fish is typically anadromous but it may have freshwater and nonanadromous forms as well.
Arctic lampreys spawn in the spring in flowing waters over a gravelly bottom. The upstream migration is mainly at night. Males and females work together to excavate a nest or redd. They fan away fine materials with their fins and use their mouths to move stones one at a time. A lamprey grasps and lifts a stone, waves its tail, and uses the current to drift downstream before dropping the stone. They can also use their sucker mouths to attach to a wet surface, such as a rock, if they need to rest in fast water. In spawning, the male uses his sucker to grasp the head of the female and wrap his body around hers and they simultaneously release eggs and sperm. The fertilized eggs sink to the gravel and are not buried. After spawning, the adults die.
Development and hatching requires several weeks. The larva, or ammocoete, looks quite different from adults. They do not have eyes or the disklike mouths of their parents. Instead, they have a small gland on their heads to detect the presence or absence of light, and a small funnel-shaped mouth with no teeth. They burrow into the silt and mud of shallow pools and backwaters of rivers and sloughs and filter microorganisms and organic matter from the sediment. Ammocoetes remain in freshwater for 1 and possibly 2 years to as many as 8 years before metamorphosing into adults. During this rearing period in freshwater, a myriad of other animals feed on juvenile lampreys including river otters and many birds. Fish, such as burbot, inconnu, and northern pike, also feed on the ammocoetes.
Metamorphosis to the adult form is probably in late summer and migration to the ocean begins. Arctic lampreys are parasitic on other fish and this is when the suction mouth comes in handy again. They use suction to attach themselves on their host fish and they use their flat tongue with its rough rasplike surface to scrape through the skin so they can suck the body fluids from the other fish. As the lamprey grows, it detaches and transfers to a larger fish. Their marine lifespan, apparently, is about 1 to 4 years before they migrate back to freshwater.
Arctic lampreys are typically about 15 inches in length, but 24-inch-long individuals have been reported. Some may be up to 2 inches in diameter.
Apparently, some Arctic lamprey populations complete their life cycle entirely in freshwater. These appear to be nonparasitic and individuals rarely exceed 7 inches in length. Nonanadromous lampreys in Alaska waters are small, about 6 inches in length. Nonparasitic lampreys exist primarily in the ammocoetes life stage. These lampreys often live in areas of soft bottom and most filter stream bottom materials for the nutrients they find there. Adults have a nonfunctional gut and do not feed. The ammocoetes life stage may be 8 years long and the adult stage less than a year.
How are Arctic lampreys of interest to Alaskans? The newspaper article says most of it. Subsistence fisheries use this oily, protein-rich fish as food for dogs and humans. Some commercial fisheries may operate and in parts of Asia, lamprey meat is considered a delicacy and will fetch a higher price per pound than salmon. Apparently, some anglers dig through the mud for ammocoetes to use as burbot bait. On the Yukon River, people use chainsaws to cut holes through the ice to catch the migrating lampreys with dip nets or an eel rake made from a spruce pole with a row of pointed nails sticking through at one end. The rake is used to impale the fish. The meat of an Arctic lamprey is extremely rich and oily. People eat lampreys and also feed them to their sled dogs.
Lampreys are different from American eels in another way. There are over 600 species of eels. Nearly all are marine but the American eel is found in Atlantic Ocean coastal watersheds. Pacific and Arctic lampreys are anadromous. American eels are catadromous— just the opposite from anadromous. Mature, adult American eels migrate from freshwater to spawn in the Sargasso Sea in the southcentral region of the North Atlantic Ocean. The feeble, larval American eels, called leptocephalus larva, migrate—actually, they drift—westerly, then northerly in the Gulf Stream until they encounter a river mouth and migrate upstream, where they grow and mature before they return to the ocean to spawn and die.
Lampreys may be considered to be a primitive fish but there is not much about this fish that is simple.
References: Morrow,1980; Mecklenburg et al., 2002; Paxton and Eschmeyer, 1994.