EMBRYONIC AND LARVAL DEVELOPMENT OF BROWN TROUT, SALMO-TRUTTA L - EXPOSURE TO ALUMINUM, COPPER, LEAD OR ZINC IN SOFT, ACID WATER

Freshly fertilized ova, eyed ova and yolk‐sac fry of brown trout, Salmo trutta L., were exposed to each of four trace metals (aluminium: 6000 nmol l−1; copper: 80 nmol l−1; lead: 50 nmol l−1; zinc: 300 nmol l−1) while held in flowing artificial soft‐water media maintained at pH 4.5 or 5.6 and [Ca] 20 or 200 μmol l−1. In continuous exposure from fertilization, survival of ova was severely affected at pH 4.5 and [Ca] 20 μmol l−1, regardless of the presence of Cu, Pb or Zn; Al reduced embryonic mortality and improved hatching success. High ambient [Ca] at pH 4.5 increased egg survival. At ‘swim‐up’, surviving fry exposed to Al or Pb had lower whole body Ca, Na and K content, irrespective of pH or ambient [Ca]. Cu reduced whole body Ca and K content at pH 5.6 and [Ca] 200 μmol−1, and whole body Ca, Na and K content in the other media. Zn reduced whole body mineral content at pH 5.6 and [Ca] 20 μmol l−1. Whole body Mg content was reduced by all trace metals at pH 5.6 and [Ca] 20 μmol l−1, and by Cu at pH 5.6 and [Ca] 200 μmol l−1. Al and Cu impaired skeletal calcification at pH 5.6 at both ambient [Ca]; Pb only at [Ca] 20 μmol I−1. Zn enhanced calcification at pH 4.5 and [Ca] 200 μmol l−1. In the absence of trace metals, low pH reduced body Ca, Na, K content and skeletal calcification at [Ca] 200 μmol l−1. The uptake of Ca, Na and K, measured at regular intervals from hatching was impaired to the same extent by all treatments at pH 4.5, irrespective of ambient [Ca] or trace metal presence. At pH 5.6, irrespective of ambient [Ca], Al, Cu and Pb impaired Ca and K uptake. The rate of Na uptake was reduced by Al and Cu. Al‐treated yolk‐sac fry, exposed to low ambient [Ca] from 200–300° days post‐hatch, suffered high mortalities regardless of pH. Ca, Na and K uptake was impaired by all treatments at pH 4.5, and by Al and Cu at pH 5.6 in a similar exposure period. The development of the early stages of brown trout in the presence of trace metals is discussed in relation to recruitment failure in areas of soft, acid water. Copyright © 1991, Wiley Blackwell. All rights reserved