WIT Press

The Survival Of Lamprey On Travelling Screens At Potable Water Intakes


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WIT Press


N. Teague & S. C. Clough


Three species of lamprey inhabit British Waters, sea lamprey (Petromyzon marinus), river lamprey (Lampetra fluviatilis) and brook lamprey (Lampetra planeri). All three are listed under the European Habitat and Species Directive (92/43/EEC) and are indicator species under the fish biological element of the Water Framework Directive. There are a number of Natura 2000 sites under which they are afforded protection. Under their aim of conserving habitats and species, the Special Area of Conservation (SAC) site designations require the assessment of consents which may present a risk to lamprey populations and actions to protect them. For many rivers and tidal waters intake screening is required for both migratory life stages; transformers and adults. Lamprey lack both a swimbladder and otolith organs and as such fall within the non-specialist hearing group suggesting that neither low frequency nor ultrasound acoustic deterrents would be effective behavioural deterrents for their protection. There is some evidence however, to suggest that lamprey may be sensitive to infrasound although the use of such a behavioural deterrent is unproven at this time. Bubble screens have been proven to be ineffective for these species and although lights are considered to have potential they are not a tried and tested behavioural screening technology for these species. Intake screening for lamprey is therefore currently restricted to physical exclusion. Physical screening at the intake frontage requires fine mesh screens with low approach velocities which can often be an impractical retro-fit solution for many existing intakes. Lamprey do not have the vulnerable structures of teleosts such as scales, a bony skeleton, operculum, large eyes or a swimbladder which make them a hardy species which do not appear to exhibit significant handling stress. Entrainment and mark-recapture studies show that they exhibit high retention and survival rates on travelling band screens. In combination with