The brook lamprey (Lampetra planeri) is the smallest of the British lampreys (4), and has two dorsal (back) fins which are in close contact (2). It is grey-blue to green in colour and during the spawning period the areas around the mouth and the anal opening become rusty red (5). Brook lampreys are also known as 'pride' (6). Lampreys are some of the most primitive vertebrates alive today, they are known as cyclostomes, which means 'round mouths' and refers to the fact that they are jawless, having instead a round sucker-like mouth. A further primitive characteristic is that the skeleton consists of cartilage and not bone (2). Lampreys are similar in shape to eels, and have a series of uncovered round gill openings (known as gill pores) on the sides of the head and a single nostril on the upper surface of the head (4).
The adults spawn in May and June, and the eggs are deposited into depressions in the riverbed. As in river lampreys, a number of males mate with one female (5). The larvae (known as ammocoetes) live for three to seven years in the sand or mud, and filter organic matter from the water for nourishment (5). As they mature they develop eyes and the sucker-like mouth, and as sexual maturity is approached they stop feeding entirely. A few weeks after spawning the adults die (5). Unlike river and sea lampreys this species does not migrate out to sea, but spends the whole life-cycle in fresh water (it is not anadromous) (4).
The brook lamprey has declined in some areas of the UK but is relatively widespread and common in parts of England. In Scotland it is generally absent north of the Great Glen (7). In Europe it extends from Sweden to France (6), and has declined in parts of this range (7).
A number of areas have been proposed as candidate Special Areas of Conservation (SACs) for the brook lamprey. The areas chosen support healthy populations and reflect the geographical range of the brook lamprey in the UK as well as the range of habitat features required by the species (7). Although this should help to improve the conservation status of this primitive fish in the UK, it has been noted that further measures will be required to maintain the species (7). Draft Action Plans have been produced for the three lamprey species found in the UK in order to guide their conservation (2). The Life in UK Rivers Project is helping to conserve this species.
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