COUNTING LIVING AQUATIC ANIMALS IMMERSED IN WATER

摘要

Apparatus for counting living aquatic animals, such as salmon parr and salmon smolts, whilst they are immersed in water, comprises one or more narrow passageways 11 through which the animals are constrained to pass in a predetermined direction. Light is directed horizontally across the or each passageway towards an array of light detectors 29 which are arranged to produce a signal corresponding to the height of the shadow of each animal as it passes. The peak of each signal is detected at 32 and, after stabilisation by a pulse former 33, the peaks are counted at 37, to indicate the number of animals that have passed through the passageway(s). The passageways can be interchanged with passageways of different cross-section to suit fish of different sizes or shapes, and a grading screen can be placed over the entrance to the passageways to restrict the size of fish that can enter the apparatus. IMAGE