The survival and growth of six species of freshwater fish, in tapwater and diluted and undiluted effluent from sewage percolating filters

Abstract

The survival and growth of rainbow trout, Salmo gairdneri Richardson, stone loach, Noe‐macheilus barbatulus (L), bullhead, Cottus gobio L., three‐spined stickleback, Gasterosteus aculeatus L., minnow, Phoxinus phoxinus (L), and roach, Rutilus rutilus (L), have been studied in water of three qualities—Birmingham tap water, 50% and 100% settled effluent from filter beds. Predicted toxicities (the sum of the proportions of the 48‐h LC50 of individual poisons to rainbow trout) were compared with the observed toxicity in 50% and 100% effluent. The behaviour of each species offish and the rates of mortality over an exposure period of 210 days are given together with cumulative growth rates (as a percentage of the initial weight). The Mean Percentage Change in Weight (MPW) and Mean Growth Rate (MGR) for each group offish was calculated from the initial mean wet weight and the mean weight of surviving fish at the end of the first and second intervals. The Mean Production Rate (MPR) over the experimental period was also calculated and was used as a holistic measure of the rate of total tissue elaboration or utilization, or loss in biomass due to mortality. The Condition Factor (K) also reported was calculated from the body weight and length and was used to examine (a) the effects of water quality, and (b) the timing and duration of maturation of the gonads. The latter was further used as a measure of the energy status of the fish.