Effect of dietary Mirex and PCBs on calcium and magnesium metabolism in rainbow trout, Salmo gairdneri and coho salmon, Oncorhynchus kisutch; A comparison with great lakes coho salmon

Abstract

1. 1. Dietary Mirex (50 mg·kg −1 dry weight of feed) or PCBs (500 mg·kg −1 dry weight of feed) significantly lowered serum Ca 2+ concentrations in yearling coho salmon ( O. kisutch); lower organo-chlorine levels and a mixed diet of Mirex and PCB were without effect. There were no significant changes in serum Mg 2+ concentrations. 2. 2. There were no significant changes in muscle or skeleton Ca 2+ content in salmon, although fish fed Mirex- or PCB-contaminated diets for 10 weeks had elevated skeletal Mg 2+ concentrations. 3. 3. Spawning female Lake Erie coho salmon had significantly lower serum Ca 2+ levels than comparable fish from Lakes Ontario and Michigan and serum Mg 2+ levels in spawning Lake Erie fish of both sexes were significantly lower than in comparable fish from Lake Michigan. Significantly higher serum Ca 2+ levels were found in the females in spawning coho salmon in Lakes Ontario and Michigan but not in fish from Lake Erie. 4. 4. The hypocalcaemia evident in feral coho salmon from Lake Erie cannot be related to organochlorine content but may be a factor in the poor growth of coho salmon in Lake Erie compared with those in Lakes Ontario and Michigan. 5. 5. None of the contaminated diets had significant effects on the Ca 2+ or Mg 2+ levels in serum, muscle or skeleton of rainbow trout ( S. gairdneri). 6. 6. Dietary Mirex (50 mg·kg −1 dry weight of feed) or PCBs (500 mg·kg −1 dry weight of feed) significantly elevated muscle water content in trout but not in salmon and significantly lowered muscle lipid content. 7. 7. HSI values were significantly elevated in PCB-fed salmon and trout and weight gain was significantly lower in trout fed the high Mirex or PCB diets.