National Lamprey Survey of Scotland (2003-2005)

Method steps

1. Semi-quantitative, timed electric fishing was used throughout. Surveyors fished over patches of suitable habitat for 5 minutes using smooth DC. Lamprey ammocoetes and transformers attracted from the substrate were captured in dip nets. The numbers of five-minute samples taken from each habitat unit varied with the area of suitable lamprey habitat, more samples being taken from larger habitat units than from small units. Total time fished was recorded. On completion, the area covered was measured in order that a minimum density could be calculated. Lamprey habitat units were scored as either optimal or sub-optimal using the simple two-point key used by Harvey & Cowx (2003). This defines optimal habitat as stable, fine sediment (silt/sand) to a depth of 15 cm or more, in slow flowing well oxygenated water, often with fine layer of organic detritus. Sub-optimal habitat is characterised by a patchy or shallow covering of fine sediment among larger substrates.
   Lampreys were anaesthetised using 2-phenoxy ethanol and were examined on white measuring boards. All lampreys were identified to the lowest possible taxonomic level and measured to the nearest mm. Surveyors were required to complete pro-forma field sheets.