Bioaccumulation of P-32 in bluegill and catfish

Bluegill and catfish were fed P-32 at a constant feeding rate per body weight to determine the bioaccummulation factor (BF/sub r/) for P-32 in muscle relative to water. The fish were maintained in flow-through tanks at two feeding levels. The bluegill accumulated P-32 for 51 days, followed by depuration for 28 days. The catfish study had to be teminated after 11 days. Fish were analyzed in triplicte for P-32 and phosphorus at intervals of 1 to 8 days. Additional aquaria experiments were performed to determine the effects of water temperature, feeding rate, and type of food (worms vs. pellets) on P-32 uptake, and to observe P-32 uptake from water by unfed fish (including fish with blocked esophagus). A simple calculational model was used to determine the phosphorus turnover constant from the specific activity in tissue relative to food. This ratio at steady state approaches the BF/sub r/BF ratio (where BF is the phosphorus bioaccumulation factor) if P-32 transfers rapidly from water to food. The bluegill showed a weight gain of 0.2 %/d, a phosphorous turnover constant in muscle of 0.43 %/d, and a BF/sub r//BF ratio of 0.081 at the higher feeding rate, and 0.05 %/d, 0.34 %/d, and 0.064 at the lower feeding rate. Hence, respective P-32 BF/sub r/ values are 6000 and 4000 at a phosphorus BF of 70,000. The BF/sub r/ values for catfish were approximately twice as high. The aquarium experiments suggest that the higher factors are due to a much higher phosphorus intake, higher water temperature, higher retention from pellets than from worms, and possible higher retention by catfish than bluegill under the same conditions. 36 references, 15 figures, 22 tables