The effects of water temperature on the survival, feeding, and growth of the juveniles of Anguilla marmorata and A. bicolor pacifica

In this study, we identified the effects of water temperatures on the survival, feeding, and growth of the juveniles of Anguilla marmorata and Anguilla bicolor pacifica which have been commercially cultured in southeastern China in recent years. Twelve groups of each species, each group of 20, were reared in 12 105-l tanks for 45 days at six water temperature levels of 8, 13, 18, 23, 28 and 33 degrees C (one level two groups). The results showed that A. marmorata all died within 10 days at 8 degrees C and most died at 13 degrees C, but survived normally at temperature of >= 18 degrees C. A. bicolor pacifica all died within 9 days at 8 degrees C and 20 days at 13 degrees C, and partly died at 18 degrees C and 23 degrees C, but survived normally at temperature of 28 degrees C and 33 degrees C during experiment. The maximum feeding rates of both species occurred at temperature of 33 degrees C, being 2.23 +/- 0.10 % day(-1) for A. marmorata and 2.41 +/- 0.06 % day(-1) for A. bicolor pacifica. However, the maximum feed conversion rates occurred at 28 degrees C, being 54.79 +/- 7.54 % for A. marmorata and 71.35 +/- 1.85 % for A. bicolor pacifica. The maximum daily weight gains (DWG) of both species, 2.63 +/- 0.12 g day(-1) for A. bicolor pacifica and 1.19 +/- 0.38 g day(-1) for A. marmorata, were also achieved at 28 degrees C with initial and final mean body weights of 5.62 +/- 0.30 g and 11.59 +/- 0.03 g for the former and 4.97 +/- 0.36 g and 7.18 +/- 0.80 g for the latter. The DWG of A. bicolor pacifica was significantly higher (P < 0.05) than A. marmorata at 28 degrees C and 33 degrees C. The specific growth rates of both species were positively correlated to water temperature (P < 0.01). The optimal growth temperature is estimated to be 27.6 degrees C for A. marmorata and 30.1 degrees C for A. bicolor pacifica. We conclude that A. marmorata and A. bicolor pacifica survive and grow better at water temperature of 28-33 degrees C than that of <= 23 degrees C. A. bicolor pacifica are more sensitive to low water temperature (<= 23 degrees C) than A. marmorata, but grow faster. Our results indicate that both species are suitable for commercial aquaculture, however the water temperature should be controlled relative higher. (C) 2013 Elsevier B. V. All rights reserved.