Studies of external ＆ internal factors affecting to the fish demand-feeding.

为了验证影响鱼类食欲的因素，利用1999年初虹鱼的摄食节律，对外部因素(光)和内部因素(生物钟)进行了研究。在前一年取得的成果的基础上，增加了另一个外部因素，即食物供应。然后，分析了影响鱼类摄食节律的因素。试验一用虹鱼24尾，体重105.52±4.04g。鱼被单独饲养在鱼缸(46L)中，每个需求喂食器都被设置在其中。实验方案如下：(1)明暗循环(12小时光照：12小时黑暗)+恒定进食(MM)；(2)食物循环(12小时进餐：12小时禁食)+恒定光照(LL)。记录并比较在(1)和(2)条件下的需求喂养。结果表明，虹鳟鱼的摄食周期与摄食周期同步。无论是在光照阶段还是在进餐时间，它们都表现出更高的活性。然而，需求取食的活动模式是不同的，表现出与光暗周期明显同步，而不是快速进食周期。这一结果表明，食物也是一个重要的外部因素，与光-暗周期一样，尽管表现出不同的同步方式。在LL和MM条件下，研究了生物钟对需求摄食节律、自由奔跑节律表达的影响。结果表明，虹鲑鱼的自由奔跑节律出现率较高(95%)。这一结果提示存在与食物周期同步的生物钟。这些结果表明，外部因素(光和食物的可获得性)和昼夜节律内部因素(生物钟)的每日循环都影响彩虹鲑鱼需求摄食节律的表达。

To demonstrate the factors affecting to fish appetite, studies of external (light) and internal factor (biological clock) were performed using demand-feeding rhythms of rainbow trout in the initial year, 1999. Based on the results obtained in the previous year, another external factor, food availability, was added. Then, factors affecting to the fish feeding rhythms were analyzed.1. In the first experiment, 24 rainbow trout were used (B.W.105.52±4.04 g). Fish were kept in tanks (46L) individually in which each demand-feeder being set. Experimental regimes were as follows : (1) light-dark cycle (12hr light : 12hr dark) + constant meal (MM), and (2) food cycle (12hr meal : 12 fast) + constant light (LL). Demand-feeding was recorded and compared under these conditions of (1) followed by (2). The results showed that rainbow trout synchronized to LD and food cycle. They displayed higher activity at either light phase or mealtime. However, activity patterns of demand-feeding were different, showing distinct synchronization to light-dark cycle rather than meal-fast cycle. This result suggests that food is also an important external factor as the same as light-dark cycle despite showing different way of synchronization.2. Involvement of biological clock for the expression of demand-feeding rhythms, free-running rhythms was studied under LL and MM conditions. The results demonstrated higher appearance rate of free-running rhythms in the rainbow trout (95%). The results suggest the existence of biological clock synchronizing to food cycle.3. These results demonstrate that daily cycles of both external factors (light and food availability) and circadian internal factor (biological clock) are affecting to the expression of demand-feeding rhythms in the rainbow trout.