军曹鱼(Rachycentron canadum)早期发育阶段的摄食及其影响因子

Cobia (Rachycentron canadum) feeding and its influencing factors at early developmental stages

研究了军曹鱼(Rachycentron canadum)仔、稚鱼的日摄食节律和摄食强度,以及饵料密度、温度、盐度对其摄食的影响。结果表明,发育8d仔鱼(摄食轮虫)、23d稚鱼(摄食卤虫无节幼体)和38d稚鱼(摄食鳗鱼粉状饵料)均表现为明显的昼夜摄食节律,摄食主要在白天进行,白天摄食强度占日摄食强度的68％以上;在白天的摄食中,又以早晨6:00-8:00和傍晚16:00-18:00摄食强度最大:夜间摄食较少或基本不摄食,所以军曹鱼早期幼体的摄食习性属白天摄食且偏于晨昏性类型。在不同饵料密度梯度的试验中,发育8d-11d仔鱼和23d-26d稚鱼摄食的适宜饵料密度范围分别为15 ind·mL-1-20 ind·mL-1和7 ind·mL-1-2 ind·mL-1。温度和盐度对发育21d-24 d稚鱼日摄食强度的影响均表现为抛物线型的变化曲线,摄食的适宜水温范围为27-31℃,适宜盐度范围为28‰-32‰。结果还表明,幼休摄食强度与饵料密度、水温、盐度的关系均适合于用二次多项式来定量描述。

The feeding rhythm and intensity of Cobia (Rachycentron Canadum) and the influences of food densities, temperatures and salinities on larvae and juvenile were investigated. The results showed that an obvious feeding circulation rhythm of 8 d larvae (fed on rotifers), 23 d juvenile (fed on atemia larvae) and 38 d juvenile (fed on non-living food) were observed. Feeding mainly proceeded in daytime, which accounted to more than 68% of the all-day total feeding intensity, and there was little or no feeding in the darkness of night. The feeding intensity during the period of 6:00-8:00 am and 16:00-18:00 pm was maximum. It seemed that the Cobia feeding rhythm was characterized by twilight feeding. The suitable food densities of 8 d larvae and 23 d juvenile were ranged at 15 ind·mL-1-20 ind·mL-1 and 7 ind·mL-1-12 ind·mL-1 respectively in the experiments of different food densities. The curves of the effects of temperatures and salinities on the feeding intensity of 18d juvenile cobia were displayed in the parabola type. The suitable temperature and salinity for juvenile were ranged 27℃-31℃ and 28‰-32‰ respectively. The relationship between feeding intensity and food density, temperature and salinity were well described by a binomial equation.