Examining the daily feeding rhythms of amago Oncorhynchus masou masou using self-feeding systems

Knowledge of circadian feeding rhythms in farmed fish species can help farmers determine the optimal feeding times to maximise feed consumption and minimise feed wastage. This study examined i) the circadian feeding rhythms, ii) the inter-day variability in feed demanded and iii) feed wastage of amago, Oncorhynchus masou masou, fed using self-feeding systems. Three replicate groups of 16 fish were held under a 12:12 light:dark cycle at 16 degrees C for 56 days. After a 28-day self-feeder acclimation period all three groups had become competent self-feeders and the treatment period ran from day 28 to day 56. Under the experimental light and temperature regime utilised amago appear to be visual self-feeders, actuating self-feeders almost exclusively during the light phase (99.9% of actuations). All three groups exhibited a distinct diurnal feeding rhythm within the light phase and demonstrated significant (P < 0.05) crepuscular peaks in feed demand. In addition, one group also displayed a significant peak at midday. Daily ration varied both within and between groups but no clear rhythmicity was observed in these variations. Feed waste was very low (always < 2%) for each group. The results of this study suggest that farmers can optimise daily feed consumption by feeding amago exclusively during the light phase, specifically at dawn and dusk, with a possible extra meal at midday. (C) 2011 Elsevier B.V. All rights reserved.

了解养殖鱼类的昼夜摄食节律有助于养殖者确定最佳投喂时间，以实现饲料消耗最大化和饲料浪费最小化。本研究考察了（i）昼夜摄食节律，（ii）饲料需求的日间变异性以及（iii）使用自动投喂系统投喂的山女鳟（Oncorhynchus masou masou）的饲料浪费情况。将三组每组16条鱼的重复样本在16℃、12小时光照∶12小时黑暗的周期下饲养56天。经过28天的自动投喂器适应期后，三组鱼都能熟练使用自动投喂器，处理期从第28天持续到第56天。在所采用的实验光照和温度条件下，山女鳟似乎是视觉自动摄食者，几乎只在光照阶段触发自动投喂器（99.9%的触发行为发生在光照阶段）。三组鱼在光照阶段都呈现出明显的昼间摄食节律，并且在饲料需求上表现出显著（P<0.05）的晨昏高峰。此外，一组鱼在中午也显示出一个显著的高峰。日投喂量在组内和组间都有变化，但在这些变化中未观察到明显的节律性。每组的饲料浪费都非常低（始终<2%）。这项研究的结果表明，养殖者可以通过只在光照阶段（特别是在黎明和黄昏）投喂山女鳟，并可能在中午增加一餐来优化每日的饲料消耗。（C）2011爱思唯尔有限公司。版权所有。