![]() ![]() Physical barriers can pose particular risks to river and sea lamprey that migrate up rivers to spawn. Good water and substrate quality (particularly in spawning areas) is important for all lamprey species, and all species are threatened throughout their range by habitat degradation. River and sea lamprey will then begin their migration to the sea from late autumn onwards. Ammocoetes feed on diatoms and other algae, and bacteria.Īmmocoetes may stay in soft substrate for up to five years (up to eight years for sea lamprey) before they transform into pre-adults. They settle in nursery habitats – areas with fine, soft substrate in well-oxygenated, slow-flowing water. Once hatched, the lamprey larvae – known as ammocoetes – drift downstream with the current. Sea lamprey spawn in much smaller numbers. On reaching their spawning ground, lamprey construct a ‘nest’ in which to lay their eggs.īrook and river lamprey spawn in a ‘ball’, which may comprise up to 50 individuals. They spawn from May to July in areas of pebble and cobble substrate. The sea lamprey is the largest of the three British lamprey species, reaching approximately 1m in length.Īfter spending 18 to 24 months feeding at sea, adult sea lamprey migrate up rivers in the spring and early summer. The dwarf river lamprey is found in Loch Lomond and is so called as it reaches only 25cm in length. Purely freshwater-resident populations of river lamprey are rare in Europe, but one exists in Scotland. Spawning takes place from April to May on pebble/gravel substrates. River lamprey migrate upstream at night and the adults rest in cover during the day. ![]() Autumn migrants are sexually undeveloped, while spring migrants enter from the sea in spawning condition. They migrate from their coastal feeding grounds into freshwater, to get ready to spawn, during the autumn and spring. River lamprey are larger than brook lamprey, reaching 30 to 50cm in length. All of these adults will die after spawning. On reaching suitable gravel areas, these fish hide until spawning takes place from April to June. For example, larvae may drift downstream to sandy/silt nursery areas.Īctive upstream migrations of pre-adults and adults occur through the winter. Unlike other British lamprey species, they don’t feed as adults.ĭespite being wholly freshwater-resident, brook lamprey do undergo limited spawning migrations – though some such movements may be passive. Lamprey are found in temperate waters in both the northern and southern hemispheres.īrook lamprey are an entirely freshwater species and the smallest of the British lamprey, reaching 15 to 19cm in length. ![]() Most, but not all, lamprey species are parasitic on other fish. A round, sucker-like disc surrounds the mouth which, in adults, carries rasping teeth. Lamprey skeletons are formed of strong, flexible cartilage rather than bone. Lamprey belong to an ancient order of vertebrates, the Agnatha or ‘jawless fish’. ![]()
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