THE EFFECTS OF HYPERCAPNIA ON THE GROWTH OF JUVENILE WHITE STURGEON, ACIPENSER-TRANSMONTANUS

Environmental hypercapnia (high dissolved [CO2]) results from high-den sity sturgeon culture in systems using O-2 injection and water re-use. The influence of environmental hypercapnia on the growth of the juven ile white sturgeon, Acipenser transmontanus, (fish initial wet weight, about 4 g) was examined by exposing the fish to different CO2 concent rations in replicate, flow-through aquaria under normoxic conditions ( oxygen tension, above 130 torr P-O2) at 19 degrees C. The fish were fe d ad libitum rations of commercial trout pellets (Silvercup). After 28 days exposure to severe hypercapnia ([CO2], 45-75 mg l(-1); pH 7.0), growth was significantly reduced (P < 0.05) (the final body weight was reduced by about 38%; the specific growth rate (SGR), 1.17) compared to that of sturgeon in normocapnic water ([CO2], 0.52 mg l(-1); pH 8.0 ; SGR, 2.86), presumably due to decreased food consumption. In two sub sequent experiments (initial wet weights, approximately 1 and 3 g), a low water pH (a mean of 7.1, via HCl addition to water) did not signif icantly affect the growth.