Lampreys are ancient, jawless fish that have existed for over 350 million years, predating dinosaurs. This article explores whether these unique aquatic vertebrates pose a threat to humans or aquatic ecosystems.
Lamprey Biology and Habitats
Lampreys possess distinctive characteristics, including a cartilaginous skeleton instead of bones, and an eel-like body that lacks paired fins. Their most notable feature is a suctorial mouth lined with keratinized teeth, which they use for feeding. These creatures spend their initial life stage as larvae, called ammocoetes, burrowed in sediment in freshwater streams, where they filter-feed for several years.
After this larval period, lampreys undergo a transformation into their adult form. Some species remain non-parasitic as adults, relying on energy reserves accumulated during their larval stage, while others develop into parasitic forms. Lampreys are found globally in both coastal and freshwater environments. Many species are anadromous, meaning they migrate from the ocean back to freshwater rivers to spawn.
Risk to Humans
Direct attacks by lampreys on humans are exceptionally rare and do not pose a serious threat. If a lamprey does attach to a human, it is typically accidental, such as during swimming. Their mouth, which is designed for suction and rasping, can cause a superficial bite.
Lampreys are not aggressive towards humans and do not actively seek them out as prey. The human body is not an ideal host for a lamprey, partly due to its warm blood, which differs from their typical cold-blooded fish prey. Therefore, any interaction is unusual and not life-threatening.
Ecological Impact
While lampreys pose minimal danger to humans, certain parasitic species, particularly the sea lamprey (Petromyzon marinus), can significantly harm aquatic ecosystems. The sea lamprey, native to the Atlantic Ocean, became an invasive species in the Great Lakes after gaining access through shipping canals like the Welland Canal in the early 20th century. In their native environment, sea lampreys generally act as parasites, often not killing their hosts. However, in the Great Lakes, native fish species did not co-evolve with this large parasite and are highly vulnerable.
Sea lampreys attach to fish using their suction-cup mouths and then use their sharp, rasping tongues to bore through the host’s skin. They feed on blood and body fluids, secreting an anticoagulant to maintain flow. This parasitic feeding often leads to severe injury, disease, or death for the host fish. A single sea lamprey can consume up to 40 pounds of fish during its parasitic stage.
The extensive predation by invasive sea lampreys led to a catastrophic decline in native fish populations, including lake trout, and caused the collapse of commercial and recreational fisheries in the Great Lakes. This ecological disruption resulted in significant economic damage and job losses in the region. Control efforts have reduced sea lamprey populations by over 90% in most areas of the Great Lakes, allowing for some recovery of the ecosystem and a multi-billion dollar fishing economy.
Interacting Safely with Lampreys
When encountering a lamprey, the safest approach is to leave it undisturbed and avoid any attempt to handle it. While some lamprey species are parasitic, many others are non-parasitic and play important roles in their native ecosystems. Larval lampreys, for instance, are filter feeders that contribute to improving water quality and cycling nutrients within streambeds.
Adult non-parasitic lampreys, often called brook lampreys, do not feed and complete their life cycle in freshwater streams, contributing to the food web as prey for other animals. Therefore, while certain invasive species like the sea lamprey pose substantial threats to aquatic ecosystems, the danger lampreys present to humans remains minimal.