Use of a flat-bed passive integrated transponder antenna array to study the migration and behaviour of lowland river fishes at a fish pass

The suitability of fish pass designs currently installed in rivers for non-salmonid species is poorly known, particularly in terms of their efficiency. The use of an automated flat-bed passive integrated transponder (PIT) antenna array to study the behaviour of fish at a Denil pass on the Yorkshire Derwent, North East England, is described. The array comprised four flat PIT antennae, each connected to a detector unit. Two antennae were positioned at the downstream end of the fish pass, and two at the upstream end. Each detector unit sent interrogation signals, received transponded signals from tags, and stored the data in a memory chip. Efficiency of the upstream detectors was validated as near 100% using tagged brown trout (Salmo trutta) introduced below the detectors and observed to swim past them. Between 22 May 1998 and 23 June 1998 a total of 284 fish, comprising 11 species with a combined length range of 9-95 cm, were PIT tagged and released downstream of the fish pass. Continuous recording between 23 May 1998 and 31 August 1998 demonstrated the effectiveness of the PIT array at this site, for recording entry to, and successful exit from the pass. A total of 160 separate entries from 36 different fish were recorded at the downstream detectors, and six fish successfully exited from the top of the pass, giving a pass efficiency of 16.7%, based on the proportion of different fish which passed. Overall 12.7% of tagged fish entered the pass, comprising chub (Leuciscus cephalus), dace (Leuciscus leuciscus), roach (Rutilus rutilus), perch (Perca fluviatilis), bleak (Alburnus alburnus) and brown trout. (C) 1999 Elsevier Science B.V. All rights reserved.