A Further Study of the Reactions of Fish to Toxic Solutions

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Abstract
This paper records some further observations on the reactions of fish to toxic solutions. The method of experimentation resembles that described in a previous paper by the writer (Jones, 1947b). In every case the solution is presented as an alternative to the Aberystwyth tap water, which is well aerated, very soft, of pH 6.8. In experiments with sodium sulphide a supply system is arranged in which dilute sodium sulphide solution, brought to pH 6.8 by the addition of sulphuric acid, is automatically made up as it runs into the observation vessel. Gasterosteus aculeatus L. reacts negatively to a 0.001 N solution almost immediately; at greater dilution the ‘reaction time’ lengthens, at 0.00008 N is about 47 min. Over the concentration range tested the reaction time is always shorter than the survival time. Gasterosteus is positive to 0.04 N lead nitrate. As a positive reaction is also displayed to equivalent concentrations of calcium nitrate, sodium nitrate and sodium chloride it is possible that the osmotic pressure of the solution is its attractive feature. At 0.01 N the positive response to lead nitrate disappears and at 0.004 N is replaced by a very definite negative reaction which is maintained down to 0.00002 N. The minnow (Phoxinus phoxinus L.) is also negative to dilute lead nitrate and will detect and avoid a 0.000004 N solution. Gasterosteus will avoid water more acid than pH 5.6 or more alkaline than pH 11.4. Over the range 5.8-11.2 the fish are indifferent or very vaguely positive. Gasterosteus is negative to 0.04 and 0.01 N ammonia solution, positive to 0.001 and 0.0001 N. The general result with ammonia is thus the converse of that observed with lead nitrate.