Disruption of energy metabolism and smoltification during exposure of juvenile atlantic salmon (Salmo salar) to low pH.

Juvenile Atlantic salmon were held for 76 days at pH 4.7 during the period when the final stages of smoltification normally occur. Control salmon (pH 6.5) had significant increases in weight, length and liver somatic index which were not observed in those held at low pH. Condition factor decreased in both groups but to a significantly greater extent in the low pH group. After 15 days levels of ADP and glucose were higher and AEC, CP and glycogen were lower in muscles of salmon exposed to low pH. These qualitative differences were maintained until the end of the experiment. ATP and total adenylate concentrations in muscle were lower after 62 days of exposure to low pH compared to controls. The levels of ATP, total adenylates, AEC and glucose were consistently higher in livers of salmon exposed to low pH than those of controls. There were no differences in liver concentrations of AMP, CP and glycogen between the two treatments or with time of exposure within each treatment. The results suggest that exposure of juvenile Atlantic salmon to low pH increased gluconeogenesis and decreased food intake to the detriment of growth.

The disposition of cadmium and zinc in Pandalus montagui.

Cadmium uptake rates in various tissues of Pandalus montagui exposed to sea water containing 37 micrograms Cd/L for 14 days ranged from 0.002-0.06 microgram/dry tissue/hr. During depuration for 57 days, the levels in most tissues decreased slightly, but continued to rise in the hepatopancreas indicating Cd redistribution. Exposure to 65 micrograms Zn/L produced no substantial change in Zn content of the tissues. An increase occurred in eggs and hepatopancreas during the first six days of depuration. During exposure to Cd and Zn combined (40 micrograms Cd/L + 70 micrograms Zn/L), tissue Zn levels responded as with Zn alone. In the presence of Zn, Cd concentration was doubled in the hepatopancreas, depressed by one-third in the carcass, and did not change in the other tissues. Increased amounts of Zn (up to 410 micrograms Zn/L) had not effect on the Cd levels of the tissues except that the Cd level in the hepatopancreas was depressed, although the level was still greater than in the case of exposure to Cd alone. The possible role of metallothionein is discussed.