SPECIES PROFILE: LAMPREY
Lampreys have all but disappeared from water bodies and people’s minds all over Europe. But they still exist, and in a few regions, they are still being caught and eaten. An ancient tradition lives on.
What sort of strange creatures are these? With their elongated body and fin-like dorsal and caudal fringes, they resemble eels, yet they lack a compact bony gill cover. Instead, they have seven separate openings on each side of the front part of the body, through which the respiratory water flows out of the body after passing the gills. In the early Middle Ages, the dark spots of these openings were interpreted as eyes, which, in conjunction with the single nasal pit (there is only one nasal opening instead of two) and the two real eyes, led to the equally bizarre and misleading name neunauge (nine-eye) in German. When the actual situation was clarified around 300 years ago, the name neunauge had already become so deeply ingrained in common usage that it was simply retained. Since then, these creatures have been subject to two fundamental misinterpretations. First, they do not have nine but only two eyes, and second, they are not fish at all, as many people still believe today.
Despite their eel-like appearance, lampreys do not belong to the fish category, as they lack several characteristics typical of fish. While their primitive cartilaginous skeleton suggests a certain evolutionary closeness to sharks and rays, a simple look at the front of the head reveals that they lack jaws. Instead, there is a rounded sucker mouth, equipped with hundreds of horn-like teeth that surround a razor-sharp rasping tongue. This is why zoologists classify lampreys particularly not with fish but rather in a completely different group, the jawless (Agnatha) or Cyclostomes (Cyclostomata, from the Greek kýklos – circle, stóma – mouth).
The English name ‘lamprey’ is likely derived from the Latin word lampetra, which loosely means stone-licker (Lat. lambo – to lick, petra – rock, stone). Some lamprey species attach themselves to stones to graze on the algae that grow there. For the ancient Romans, this behaviour was so striking that they referred to lampreys as lampretae, from which the English words lamprey, the Italian lampreta, and the French lamproie have evolved over centuries.
Contemporaries of the dinosaurs
Lampreys are considered quite primitive representatives of vertebrates, essentially living fossils. The oldest fossil finds are about 360 million years old, dating back to the late Devonian period. Some researchers even suspect that the oldest traces of these creatures date back over 500 million years to the Cambrian period. Even if that is not the case, lampreys are one of the most ancient vertebrate groups on our planet, having swum in the waters during the time of the dinosaurs and survived at least four major extinction events since then. The modern diversity of lampreys probably only emerged in the Cenozoic era during the last 10 to 20 million years. To which talents these animals owe their extraordinary survival ability, persistence and longevity over millions of years is hard to say. However, the specialised parasitic feeding behaviour that some species of Cyclostomes still practice today might be involved. They attach themselves with their toothed, funnel-shaped suction mouth to fish and other aquatic hosts to suck their blood and rasp off flesh, skin, and scales from the bones.
There are currently 38 known living species in the jawless group (Petromyzontiformes) worldwide, with two smaller families living in the Southern Hemisphere (Geotriidae, Mordaciidae) and one large family in the Northern Hemisphere (Petromyzontidae). In both the north and the south, the occurrence of lampreys is mainly restricted to temperate regions because their larval stages cannot survive the high water temperatures of the tropics. About half of the 38 species live parasitically in adulthood, feeding on the blood and tissue debris of their victims and to which they cling with the teeth of their suction mouth. The other half are ‘vegetarians’ and only eat algae and aquatic plants, which they rasp off of stones and other hard structures.
Years-long larval stage
All lamprey species go through a larval stage in the early phase of their life known as ammocoetes (English) or querder (German), lasting several years. Some species even spend the majority of their lives in the young ammocoete stage. These larvae differ significantly from the adult animals in appearance and lifestyle. They have a worm-like shape and are practically blind, but can perceive light and shadow. Additionally, they lack the characteristic suction mouth, which develops only at the end of their larval period during metamorphosis into the adult form. Ammocoetes feed exclusively on plankton and suspended particles, filtering them from the water in a manner similar to mussels. The term querder is derived from the Old High German querdar, from which the word köder (bait) eventually emerged. Our early ancestors had noticed that the spawning aggregations of lampreys, where often hundreds of animals gather, attracted numerous predatory fish. The lampreys passionately engaged in reproduction are equally enticing and easy prey for them. In countries such as Great Britain, lampreys are still commonly used as bait for fishing.
In European waters, three species in particular – sea lamprey, river lamprey, and brook lamprey – have historical, ecological, and regional economic significance even today. In spite of some similarities, river lamprey (Lampetra fluviatilis), brook lamprey (L. planeri), and sea lamprey (Petromyzon marinus) show differences that are evident not only in their body lengths but also in their lifestyles and distribution. While brook lampreys grow only to a maximum of 15 to 20 cm, sea lampreys can reach lengths of up to 1.2 metres. River lampreys fall in between at about 50 cm, but on average, most specimens of this species hardly exceed 30 or 40 cm. River and sea lampreys are anadromous migrants that, like salmon, migrate to the sea after metamorphosis and return to fresh water years later to spawn. The migrations of the brook lamprey, on the other hand, are confined only to fresh water. This species, which occurs only in the upper reaches of Western European rivers north of the Pyrenees and the Alps, does not feed after metamorphosis. The animals only spawn and then die. A life-cycle comparable to that of mayflies.
However, the suspicion has recently grown stronger that brook and river lampreys might be ecotypes of the same species, much like river trout and sea trout. Where both forms coexist, they spawn together, and occasional crossbreeding produces viable offspring. Even with genetic methods, it is not possible to clearly differentiate between species. The only significant difference is in their migratory behaviour. Whether they are two separate species or just one remains an intriguing question that still requires definitive clarification.
High conservation status in the EU
The most widespread and economically important species is the river lamprey, which used to be found in nearly all larger rivers in Europe and adjacent marine areas and is still present in some regions. There are no records for the eastern Mediterranean, the catchment area of the Black Sea including the Danube, and the northern parts of Scandinavia. River lampreys were popular food fish in the Middle Ages, but their populations gradually declined due to water pollution and the destruction of suitable spawning areas. For this reason, this endangered species was included in the EU Nature Conservation Programme under the Habitats Directive.
The life cycle of the river lamprey largely follows a family-typical pattern. Adult lampreys lay their eggs in nests that they dig in the sandy or gravelly beds of clear rivers. After hatching, young larvae are carried downstream by the current until they reach soft sediments, where they bury themselves so deeply in the silt that only their heads stick out. There they live for several years as filter feeders, filtering detritus, plankton organisms, and organic suspended particles from the water. The anatomical differences of the ammocoetes compared to the adult animals include a gill gut, which is used for feeding. However, the water flows extremely slowly through the feeding apparatus of the ammocoetes, which is why they require particularly nutrient-rich water to meet their needs. While mussels and other invertebrate suspension feeders often make do with less than 1mg of organic solids per litre, ammocoetes need at least 4mg/L. In the course of metamorphosis, which takes several weeks, the gill gut is transformed into gills and the previously non-functional eyes become functional. Moreover, the typical suction mouth of the mature animals with hundreds of tiny teeth develops during the metamorphosis.
Parasitic modus vivendi in the oceans
The metamorphosed river lampreys are now ready for life in the sea and migrate downstream with the current. They remain there for a minimum of three to four years, preferably in the shallow coastal areas, where they live parasitically. They occupy host animals, anchoring themselves to their bodies with the teeth of their suction mouth. The lampreys then scrape away skin and muscle tissue from their victims with their sharp rasping tongues, mixing everything into a nutritious slurry that they suck up along with blood and tissue fluids. Once they are sufficiently satiated, however, they leave their food source. For large and strong host animals, these ‘vampires’ are unpleasant but usually harmless. Especially as the lamprey carefully conceals its attacks with highly effective substances in its saliva (anticoagulants) that numb pain and inhibit blood clotting. Although the round suction mouth leaves characteristic scars on the surface of the body, the victim animals typically survive. Only sick and weakened animals are at serious risk. Occasionally, it may also happen that a lamprey penetrates the abdominal cavity of a prey fish, injuring internal organs and killing it.
River lampreys mainly infest fish, often cod or herring. Occasionally, they also prey on marine mammals such as whales or dolphins and sometimes even on people who are swimming unsuspectingly along the coast. Although attacks by lampreys on swimmers are extremely rare, they are certainly unpleasant for the affected individuals, however, not a reason to avoid swimming. The shock is usually greater than the danger since lamprey bites are neither venomous nor really dangerous. Especially as the attackers can easily be removed with a firm grip. However, why lampreys stray and attack humans remains a mystery. One hypothesis suggests that lampreys find certain substances in sunscreen and skin creams particularly attractive, which is why these may serve as a sort of ‘attractant’.
Imminent loss of habitats
After several years in the sea, lampreys become sexually mature. They then stop feeding and migrate back to the upstream parts of rivers. In the course of their return migration, their intestines regress. It has not yet been definitively established whether they return to their original waters. The suction properties of their mouths give them a certain climbing ability, allowing them to overcome small obstacles such as weirs or ramps in the river with ease. In the spawning waters, the lampreys usually go into hibernation before breeding the following spring from February to May. To do this, the males dig spawning pits in the substrate before wrapping their bodies around the females, which attach themselves above these pits. Over the course of several spawning acts, which can last for days, the female lays up to 40,000 eggs, which are fertilised by the male.
The principle of spatially separated life stages (larvae in freshwater, adults in the sea) is a clever biological strategy that prevents competition between various age stages and allows optimal resource utilisation. However, it becomes a risk when one of these habitats is restricted or access to them becomes difficult. Lampreys have also experienced this, as humans have put these creatures that have survived for hundreds of millions of years under serious threat through massive changes to their habitats. Lamprey populations are seriously endangered in many regions of Europe due to the loss of river habitats, overfishing, and pollution. Dams and other barriers block migration routes and cut the animals off from their spawning grounds. Predators such as cormorants and otters reduce the populations, while the dredging of riverbeds kills lamprey larvae in the excavated sediment.
However, building artificial waterways has sometimes created new habitats for lampreys. For example, in North America, sea lampreys have become an invasive pest in the Great Lakes. After the construction of the Welland Canal to circumvent Niagara Falls, sea lampreys invaded the waters and decimated the populations of some fish species found there by up to 95%. As a result, the formerly abundant commercial fishery collapsed in 1950s.
Economic use is possible regionally
Although their mucus is considered toxic, and lampreys can therefore only be consumed after thorough cleaning, their aromatic, fatty meat has been highly valued as a culinary speciality since time immemorial. Roman writings mentioned them as a delicacy as early as 2000 years ago, and in the Middle Ages, lampreys were a staple in noble dining. Around 1550, the Swiss naturalist Conrad Gesner wrote that they were “good and commendable in springtime, the bigger, the better”. It is even said that King Henry I of England was so fond of lampreys that he regularly ate them, against medical advice, even in old age and ultimately died after an excessively sumptuous meal of lamprey. For centuries, a lamprey pie was one of the traditional gifts presented at royal coronations in England. Even Elizabeth II was honoured with such a lamprey pie at her coronation in 1953. It was not until Charles III took office in 2023 that he renounced it.
In many regions of Europe, lampreys are now so rare that they are considered an endangered species and are under strict protection. However, in a few areas, they are still so numerous that they are regularly fished and eaten as a valued meal: grilled, fried, smoked, or marinated in vinegar and set in jelly. In Sweden, Finland, and Latvia, they are virtually part of the culinary heritage, as shown by the traditions upheld in Västerbotten, Sweden. The Nakkila municipality in Finland and the small commune of Sainte-Terre in France feature lampreys in their municipal coats of arms, and in Latvia, river lampreys are available in supermarkets. For the small Latvian town of Carnikava, located north of Riga, the tradition of lampreys is so important that it was included in the list of Protected Designations of Origin (PDO) by the European Commission in 2015. Pursuant to Government Ordinance No. 587/2006 in Portugal, only sea and river lampreys may carry the trade name Lampreia. Arroz de lampreia (rice with lampreys) is one of the most important and popular dishes in Portuguese cuisine. Lampreys are also a traditional speciality along the Atlantic coasts of Spain and France: Lamproie à la bordelaise is a classic of French regional cuisine.
Manfred Klinkhardt