PERFORMANCE-CHARACTERISTICS OF A FISH MONITOR FOR DETECTION OF TOXIC-SUBSTANCES .2. FIELD TRIALS

Following on from the laboratory trials described in the previous paper in this two part series [Baldwin I. G., Harman M. M. I. and Neville D. A, (1994) Wat. Res. 28, 2191-2199], the field trials presented here sought to determine whether the established performance could be sustained in operation and to identify factors which may cause false responses. The study used data collected at two field test sites over a one year period. The main factors causing false responses were associated with physical disturbance: entry into fish monitor rooms and interruptions in water flow. Sudden changes in water conditions resulting from influences of extreme high tides were also identified as causing responses at one site. There was no evidence of normal changes in river water conditions causing false responses, nor was there any evidence of the occurrence of contaminants at either site. After taking into account responses resulting from the factors mentioned, the false response rate was found to be at or below that estimated from laboratory trials (1 in 3 months).