Reclusive, primitive and eel-like. The brook lamprey is an ancient and rarely seen fish found in the rivers and streams of several of our woods. It lives most of its life as a larva buried in the silty stream bed before turning into an adult and swimming upstream to spawn - its last act before it dies.
Common name: brook lamprey
Scientific name: Lampetra planeri
Family: Lamprey
Habitat: woodland brooks, streams, rivers, occasionally lakes
Diet: detritus, however they do not feed as adults
Predators: herons, otters and large predatory fish
Origin: native
Brook lampreys have a long, eel-like body and measure between 15-25cm as an adult. They are greenish-grey in colour and have two back fins, along with gill openings on either side of the head. They do not have a jaw; instead they have a round sucker for a mouth. They have one single nostril on top of their head and their larvae begin life with no eyes or mouth.
Credit: Blickwinkel / Alamy Stock Photo
The brook lamprey only feeds when in its larval form, filtering detritus and other organic matter from the water. Once it transforms into an adult, its digestive functions stop and it becomes unable to feed altogether.
Unlike other lamprey species, brook lampreys do not migrate out to sea in order to breed. Instead, they spend their entire lifecycle in rivers and streams.
Adults spawn in the shallow parts of streams from April to June. Both male and females work to build nests, using their sucker-like mouths to pick up rocks and create pits in the stream bed. Several males mate with a female, and eggs are then deposited into the nests.
Eggs hatch within a few days and the young lamprey stay in the larvae stage for around three to seven years. They live buried in the sand and metamorphose into adults during the autumn. This is when they develop eyes and a mouth but stop feeding entirely. A few weeks after spawning the adults die.
Credit: Blickwinkel / Alamy Stock Photo
Brook lampreys are a freshwater species, living in streams, rivers and occasionally lakes.
During spawning, the anal and mouth areas of the brook lamprey turn an orangey red.
As they spend much of their time hiding in sandy sediments, it can be difficult to spot brook lamprey. The best time to see them is during the spawning season, which takes place in the spring. Head to the shallower areas of brooks, streams and rivers and you might just see the spawning clusters in action.
Credit: Blickwinkel / Alamy Stock Photo
The biggest threats to the brook lamprey are habitat loss/degradation and pollution.
The brook lamprey’s skeleton is made up of cartilage, not bone.
