Jiasheng Yin

Effects of tank colour on growth and survival of taimen Hucho taimen (Pallas, 1773) larvae

This study was conducted to evaluate the effect of tank colour on growth and survival of taimen Hucho taimen larvae. Larvae (initial weight 0.11xa0±xa00.01xa0g, 21xa0days after hatching) were cultured in the water flow-through system. Fifteen aquaria (200xa0L per aquarium) were randomly allocated into triplicate groups of 500 larvae. The outsides of the tanks were covered in red, blue, yellow, white, or black sheeting. Larvae were fed eight times a day by hand to apparent satiation. The experiment was conducted for 56xa0days. The results showed that the specific growth rate was significantly affected by tank colour, which was higher in the yellow tank than that of the tank (black or red) (Pxa0<xa00.05). The tank colour did not significantly affect survival, condition factor, and feed conversion ratio among all the treatments (Pxa0>xa00.05). The highest feed intake was observed in fish reared in the yellow tank, followed by that of the white, blue, or black tank, and the lowest was in fish in the red tank. In conclusion, the light-coloured tank (yellow or white) was optimum for rearing taimen larvae based on the growth performance.

THREATENED FISHES OF THE WORLD: Hucho taimen (Pallas, 1773)

Taimen Hucho taimen (Pallas, 1773) was once common in China, Russia, Kazakhstan and Mongolia but is disappearing now from its native region. This vulnerable species has considerable ecological importance but there are few data available on its biology. The limited available data on its systematics, distribution, ecology, reproduction and threats are summarized and discussed.

Effects of dietary phosphorus on growth, body composition, and blood chemistry of juvenile taimen Hucho taimen

To determine the optimum P requirements of taimen (Hucho taimen), the present study investigated the effects of diets supplemented with different levels of inorganic P (NaH2PO4) on growth, proximate composition, blood chemistry, and mineralization in juvenile taimen. Triplicate groups of fish (mean initial weight 15.39xa0±xa00.28xa0g) were fed, until satiation, with different diets containing graded levels of digestible P (0.22, 0.40, 0.55, 0.74, 0.90, and 1.07%), for 84xa0days. Weight gain, feed conversion ratio, and protein retention were significantly (Pxa0<xa00.05) improved with 0.40% dietary P, with values 210.69xa0±xa016.08%, 1.13xa0±xa00.11, and 31.73xa0±xa03.34%, respectively. However, no significant increase in these parameters was obtained with increasing dietary P levels (Pxa0>xa00.05). With increasing dietary P levels, P retention and whole-body lipid content decreased from 75.41xa0±xa07.06 to 36.41xa0±xa03.30% and from 3.23xa0±xa00.13 to 2.74xa0±xa00.25%, respectively, whereas vertebrae ash and plasma P content increased from 43.68xa0±xa00.23 to 52.09xa0±xa00.28% and from 2.18xa0±xa00.14 to 3.98xa0±xa00.23xa0mmolxa0L−1, respectively. Using a broken-line regression model that incorporated measurements of P digestibility, feed efficiency, and normal whole-body and vertebrae P content, the dietary requirement of digestible P was determined to be approximately 0.5% for taimen.