Sea lampreys do not typically attack humans. These ancient, jawless fish are not programmed to target large, warm-blooded mammals. While their appearance and feeding habits on fish might seem concerning, direct and intentional attacks on people are not characteristic behavior. Their primary goal is to find and parasitize fish, not humans.
Understanding Sea Lamprey Biology
Sea lampreys (Petromyzon marinus) are aquatic vertebrates with an evolutionary history spanning over 340 million years. They possess an eel-like body, lacking jaws and a bony skeleton, instead having a cartilaginous structure. Their most distinctive feature is a large, round, suction-cup-like mouth, lined with numerous sharp, keratinized teeth arranged in concentric rows, and a rasping tongue. Adults typically measure between 12 and 24 inches, though some can reach up to 47 inches.
They are native to the Atlantic Ocean, including its northern and western shores, the western Mediterranean Sea, and the Black Sea. Sea lampreys exhibit an anadromous life cycle, migrating from saltwater to freshwater to spawn. In regions like the Great Lakes, where they are an invasive species, some populations have adapted to complete their entire life cycle within freshwater environments. Their life cycle involves distinct stages: larvae that filter-feed in stream sediments for several years, followed by a metamorphosis into parasitic juveniles that migrate to open water, and sexually mature adults that return to rivers to reproduce and then die.
How Sea Lampreys Interact with Their Environment
Adult sea lampreys are parasites that feed on the blood and bodily fluids of other fish. They attach to their host using their powerful suction-cup mouth, creating a tight seal. Once attached, they use their sharp teeth and rasping tongue to abrade the host’s scales and skin, creating an open wound. To facilitate feeding, they secrete lamphredin, an anticoagulant that prevents the host’s blood from clotting, allowing them to continuously draw fluids.
This specialized feeding apparatus and behavior are adapted for aquatic prey, specifically fish. Their sensory systems are attuned to chemical signals released by fish, which guide them to potential hosts. The parasitic phase can last between 12 and 18 months, during which a single individual can consume a significant amount of fish. Their biological design and instinctual drives are geared toward locating and feeding on fish, not warm-blooded mammals like humans.
Human Encounters and Safety
Reports of sea lampreys attaching to humans are rare and almost always accidental, not intentional attacks. Sea lampreys are not predators of humans, and their feeding mechanisms are not designed for attacking large, warm-blooded animals. Any such incident typically occurs when a swimmer is in areas where lampreys are present, and the creature might mistakenly latch on due to confusion or if it is handled.
If a sea lamprey accidentally attaches, it will likely detach once it realizes the host is not a fish. While not life-threatening, an accidental attachment can be painful due to their suction and teeth, and the wound carries a risk of infection if not properly cleaned. If an attachment occurs, it is advisable to remain calm and gently try to detach the lamprey, avoiding forceful pulling that could worsen the wound. Afterward, thoroughly clean the affected area with soap and water and seek medical attention if signs of infection develop.