Sea Lampreys

While sampling upstream of Lake Harney, Florida Fish and Wildlife Conservation Commission (FWC) biologists caught a sea lamprey, Petromyzon marinus. Sea lampreys are considered rare in Florida because there are less than ten documented records of lamprey caught from state waters in the last century. Previously, the most recent specimen recorded was collected in 1978. The rarity of sea lampreys is not a concern, however, because this species is a parasite on other fishes. Moreover, there is no evidence that sea lamprey spawn successfully in Florida rivers, so there are no native populations to conserve.

In addition to being parasitic, sea lamprey will scavenge the tissue of dead fish. While scavengers and even parasitic feeders are important for cycling nutrients and energy through an ecosystem, sea lamprey are very destructive to freshwater fisheries in areas such as the Great Lakes and are considered pests and nuisance fish. Juveniles and adults attach themselves to healthy bony fish, sharks, and even mammals by scraping a hole through a host's skin and sucking out body fluids and flesh. An anticoagulant substance secreted by the sea lamprey's buccal glands prevents clotting of the host's blood.

Sea lampreys are also anadromous; they, like Atlantic sturgeon, spend much of their lives in saltwater before returning to streams to spawn. While in freshwater rivers and streams, sea lamprey will deposit their eggs in nests made on gravel substrates. The larvae that hatch from these eggs, called ammocoetes, will feed on organic matter and microorganisms they strain out at the mud-water interface. Over several years of feeding on this diet, the ammocoetes reach only a modest size (less than 6 inches or 152 mm total length). After four to seven years, the ammocoetes undergo metamorphosis and migrate from stream habitats to the sea. In saltwater habitats, sea lamprey live roughly two years and grow as long as three feet (~1 meter) in total length. To complete their life cycle, adults travel up rivers and streams in the spring to spawn, and they die shortly after spawning.

Sea lamprey occur in the northern Atlantic Ocean, off the coasts of North America and Europe. Along the east coast of North America, they are found from the Gulf of St. Lawrence to northern Florida. There are also three records of sea lamprey caught from the Gulf of Mexico, where a relic population possibly existed (Gilbert and Snelson, 1992). Sea lamprey were first observed in northeast Florida in 1897 by Dr. William C. Kendall. Dr. Kendall witnessed individuals in the vicinity of Lake George, a lake on the St. Johns River (Evermann and Kendall, 1900). Only eight verified lamprey were caught from northeast Florida locales during the intervening century. There is no evidence that sea lampreys were any more abundant in Florida's past or that there was once a breeding population in Florida, so it cannot be stated that their population has declined in any significant manner. The rare individuals that are found are probably all "hitchhikers" who parasitized their hosts at northern latitudes and held on during their host's migration to Florida. Dr. Kendall's observations of sea lamprey seem to agree with this theory. His collections were made while he was studying the winter spawning run of anadromous American and hickory shad. During their lifetimes, American shad migrate to and from Canada, specifically to the Bay of Fundy. Lamprey most frequently affix to American shad during the northern phase of this extensive coastal migration.

The phenomenon of sea lampreys "hitchhiking" on Florida's population of  American shad is substantiated on video. The lamprey captured on video was attached to an American shad, Alosa sapidissima, a common winter resident of the St. Johns River. When examined internally, this lamprey exhibited no evidence of sexual maturity, which is consistent with researchers' understanding that this species does not reproduce in Florida.

FWC biologists are investigating whether circular ulcerations observed infrequently on American and hickory shad are actually wounds from lamprey attachment sites. In such cases, it is hypothesized that a lamprey was feeding on a shad during the shad's coastal migration, but that the lamprey detached itself before entering the shad's winter spawning grounds in Florida (from approximately Lake Monroe to Lake Washington on Florida's St. Johns River). Anglers who periodically encounter these wounded fish can now understand the tenacity exhibited by shad that survive a migration from Canada to Florida with a blood-sucking parasite attached.

For additional information contact: Fishcoll@MyFWC.com

Literature Cited
Evermann, B. W., and W. C. Kendall. 1900. Check-list of the fishes of Florida. Report of the Commissioner, U. S. Commission of Fish and Fisheries Part XXV (for 1899): 35-103.

Gilbert, C. R., and F. F. Snelson, Jr. 1992. Sea lamprey. Pp. 122-127 in C. R. Gilbert, editor. Rare and Endangered Biota of Florida. Volume II. Fishes. University Press of Florida, Gainesville.