Effects Of Ammonia And Nitrite Toxicity On Yellow Catfish Pelteobagrus Fulvidraco

In this paper, the toxicity of ammonia and nitrite were studied in different developmental stages of the yellow catfish (Pelteobagrus fulvidraco), and the chronic impact of ammonia levels on growth performance of juvenile yellow catfish. And we explained firstly the effects of ammonia and nitrite toxicity on yelllow catfish at high, medium, and low dissloved oxygen. Through the results of the blood biochemical parameters, stress response and energy metabolism pathway were understand in yellow catfish.The 96 h median lethal concentration (96 h LC50) tests were conducted using four different sizes of yellow catfish to provide primary information on the sensitivity of this species to elevate ammonia or nitrite, and to determine if the sensitivity is mediated by size. The results showed that the 96 h LC50 of fish weightedⅠ0.034±0.002 g,Ⅱ0.296±0.049 g,Ⅲ3.516±0.946 g and IV32.958±5.748 g to un-ionized ammonia were 0.37 mg/L,0.54 mg/L,0.71 mg/L and 1.03 mg/L, respectively, and nitrite were 69.03 mg/L, 97.18 mg/L,133.55 mg/L and 195.96 mg/L, respectively. These results indicated that the susceptibility of this fish to ammonia or nitrite reduced with increasing size, and existed in certainly correlations between them (P<0.05).Through 96 h the water aquatic acute toxicity test, the acute toxic effects of ammonia and nitrite on yellow catfish were studied at high dissloved oxygen (10.77±0.40) mg/L, medium dissloved oxygen (6.89±0.33) mg/L, and low dissloved oxygen (3.45±0.54) mg/L. The results showed that the 96 h LC50 of un-ionized ammonia and nitrite to the yellow catfish were 0.54 mg/L, and 97.18 mg/L respectively at medium dissolved oxygen level. While they were exposed to high dissolved conditions, the 96 h LC50 of un-ionized ammonia and nitrite were increased to 0.74 mg/L and 137.69 mg/L respectively. When they were exposed to low dissolved conditions, the 96 h LC50 of un-ionized ammonia and nitrite were respectively decreased to 0.34 mg/L,54.22 mg/L respectively. No matter at what dissolved oxygen conditions, ammonia was much stronger than nitrite in toxicity to yellow catfish. So ammonia in toxicity to the yellow catfish is one importent factor in duration of aquaculture. At the same time, yellow catfish tolerated much higher concentrations of nitrite or un-ionized ammonia under high dissloved oxygen. At last, the way that could improved the yellow catfish endurance to nitrite and un-ionized ammonia was also advanced in this study to increase the survival of the yellow catfish farming.The effects of sublethal ammonia were determined with respect to the stress on growth, food intake and blood parameters of the yellow catfish juveniles. The health of catfish were respectively kept in ammonia concentration (3.36 mg/L,6.72 mg/L,13.44 mg/L,26.88 mg/L, and the control group. Four hundred and fifty fish in good health and condition were evenly distributed among fifteen 280-L circular fiberglass tanks, and the exposure time was 56 d. The results showed that un-ionized ammonia had significantly effected on growth, feeding and blood parameters for the yellow catfish juveniles, but not significantly different on the body composition (P>0.05). With the increase of un-ionized ammonia, feeding rate was significantly decreased and feed efficiency reduced, which having slowly growth and higher mortality. Plasma ammonia concentration significantly increased (P<0.01), and the treatment group blood ammonia concentration was much lower than the surrounding total ammonia (TAN). However, plasma urea nitrogen levels were not difference signifficantly in all experimental groups. Alkaline phosphatase (AKP) activity and cortisol levels increased quickly in two concentration group (A3, A4), although increased in the low concentration group compared with the control group, but not significantly different (P>0.05). Glucose (GLU) concentrations generally showed a decreasing trend of two high concentration group (A3, A4) decreased rapidly. Alamine aminotransferase (ALT) and aspartate aminotransferase (AST) activity tended to increase overall, the more obvious in the high un-ionized ammonia concentration, the greater the tendency of its increase. Therefore, it was not appropriate for yellow catfish juveniles in the high concentration of ammonia, and should be maintained at less than 6.72 mg/L.