By I Anestis, R.J Neufeld
Water Research, Volume 20, Issue 10, October 1986, Pages 1233-1241, ISSN 0043-1354, DOI: 10.1016/0043-1354(86)90152-1.

Avoidance-preference reactions were studied in rainbow trout (Salmo gairdneri) pre-exposed for 7-20 weeks to potassium dichromate solutions (K2Cr2O7) ranging from 0.01 to 3.0 mg l-1 as Cr(VI). Experiments were performed in a hydraulic channel 9.15 m long by 30 cm wide, partly divided along its length and at a flow depth of 30 cm, combining steep and shallow gradient characteristics. An avoidance threshold value of 0.028 mg l-1 was determined for a population which had not been previously exposed to chromium while avoidance thresholds for pre-exposed fish increase linearly with the level of pre-exposure. Pre-exposed fish exhibited lower avoidance reactions compared to the nonexposed population. Avoidance reactions decreased with increasing level of pre-exposure. Fish exposed to test concentrations matching their pre-exposure level clearly preferred this same concentration over any adjacent lower or higher test concentration. After 7 days of acclimation in clear water fish previously exposed at 0.01-0.8 mg l-1 Cr(VI), behaved similarly to the nonexposed population, indicating functional recovery of chemoreceptive capacity, while fish pre-exposed beyond the 0.8 mg l-1 level did not recover fully within the same 7 day acclimation period. The 0.8 mg l-1 Cr(VI) level is proposed as a critical pre-exposure level for short term recovery of normal chemoreceptive capacity. Times of pre-exposure within the range used for the study had no influence on avoidance reactions.
Keywords: avoidance-preference; Salmo gairdneri; chromium(VI) toxicity; toxic pre-exposure

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