Sea lampreys are olive or brown-yellow on the dorsal and lateral part of the body, with some black marblings, with lighter coloration on the belly.

[6] The largest European populations of sea lampreys are located throughout the southwestern areas of Europe (north-central Portugal, north-northwest of Spain, and west–southwest of France).

Females deposit a large number of eggs in nests made by males in the substrate of streams with moderately strong current.

Larvae burrow in the sand and silt bottom in quiet water downstream from spawning areas and filter-feed on plankton and detritus.

[1] After several years in freshwater habitats, the larvae undergo a metamorphosis that allows young, post-metamorphic lampreys to migrate to the sea or lakes, and start the adult hematophagous method of feeding.

[11] The lamprey uses its suction cup-like mouth to attach itself to the skin of a fish and rasps away tissue with its sharp, probing tongue and keratinized teeth.

[15] Due to its lifecycle that switches between fresh and salt water, the sea lamprey is adapted to tolerate a wide range of salinities.

In some instances, the sea lamprey has adapted to living exclusively in fresh water, as evidenced by the population in the Great Lakes.

[18] Sea lampreys parasitize other fishes for their diet, including elasmobranchs such as sharks and rays, which have naturally high levels of urea in their blood.

Lampreys are able to tolerate much higher concentrations than most other fish and excrete it at extremely high rates, obtained from ingested blood.

Trimethylamine oxides present in ingested elasmobranch blood aid in counteracting the detrimental effects of high urea concentration in the lamprey's bloodstream as it feeds.

[21] This sequencing effort revealed that the lamprey has unusual guanine-cytosine content and amino acid usage patterns compared to other vertebrates.

The lamprey genome undergoes drastic rearrangements during early embryogenesis in which about 20% of the germline DNA from somatic tissues is shed.

Lamprey introduction along with poor, unsustainable fishing practices caused the lake trout populations to decline drastically.

One group of pheromones serves a migratory function in that when they are made by larvae, they are thought to lure maturing adults into streams with suitable spawning habitat.

Scientists are trying to characterize the function of each pheromone, and each part of the molecules, to determine if they can be used in a targeted effort at environmentally friendly lamprey control.

[29][30] The intent of lamprey control programs is a safer habitat and a healthier population growth for vulnerable native fish species such as lake trout.