Sea lampreys are ancient, jawless fish that often spark public concern regarding their potential threat to humans. This article clarifies the behavior of sea lampreys and addresses whether they actually attack people.
Understanding Sea Lampreys
Sea lampreys are primitive fish characterized by their elongated, eel-like bodies and a unique mouth structure. Unlike most fish, they lack jaws and instead possess a large, round oral disc that functions as a suction cup. This disc is lined with numerous rows of sharp, horn-shaped teeth surrounding a rasping tongue. Their skeleton is composed of cartilage.
The life cycle of a sea lamprey begins with a larval stage, known as ammocoetes, which burrows into the sediment of freshwater streams and filter-feeds on plankton and detritus for several years. After this period, they undergo a metamorphosis, developing their oral disc and eyes, and transform into a parasitic adult stage. These parasitic adults then migrate to larger bodies of water, like oceans or large lakes, to begin their feeding phase.
Adult sea lampreys are parasites. They attach to a host using their suction mouth and then use their teeth and rasping tongue to create a wound in the host’s skin. They secrete an anticoagulant, called lamphredin, into the wound to prevent blood clotting, allowing them to feed on the host’s blood and bodily fluids.
Their Preferred Hosts
Sea lampreys are highly adapted to parasitize large, cold-blooded fish. Their natural prey includes various species found in marine and freshwater, such as lake trout, salmon, whitefish, and even sharks in marine habitats.
In regions like the Great Lakes, where sea lampreys are an invasive species, their impact on native fish populations has been substantial. They have contributed to the decline of economically important species, such as lake trout, due to their parasitic feeding. A single sea lamprey can destroy up to 40 pounds of fish during its parasitic phase.
Interaction with Humans
Sea lampreys do not “attack” humans in a predatory manner, nor do they intentionally target people. Humans are not suitable hosts for sea lampreys due to our thick skin, warm body temperature, and lack of appropriate attachment points. Lampreys are adapted to feed on cold-blooded aquatic organisms, which differ significantly from human physiology.
Any reported instances of a sea lamprey attaching to a human are almost always accidental. Such occurrences might happen due to curiosity, confusion, or disorientation on the part of the lamprey, or simply as a brief, mistaken attachment rather than a feeding attempt. While a lamprey attachment can be startling and potentially painful, it is rarely fatal. The primary concern would be the risk of infection if the wound is not properly cleaned. Swimming in waters where they are present remains safe.