海洋鱼类仔鱼在早期发育和饥饿期的巡游速度

CRUISING SPEEDS DURING EARLY DEVELOPMENT AND STARVATION OF MARINE FISH LARVAE

本文运用红外光源和录象系统首次对大西洋鲱(Clupea harengus L.)的两个地理种群:苏格兰西海岸和波罗的海鲱、大西洋鳕(Gadus morhua L.)和欧洲江鲽(Platichthyslesus L.)由人工授精来源的卵黄囊期仔鱼以及苏格兰西海岸鲱的较大仔鱼(36和60日龄)在早期发育和饥饿期的巡游速度作了测定。仔鱼巡游模式的发育和完善符合种的发育和生长过程。卵黄囊期仔鱼在卵黄囊耗尽前后仍不能建立外源性摄食,或较大仔鱼在停食后,其巡游速度都有增快的倾向,一般均在抵达“不可逆点”(PNR,即the point-of-no-return)前两天左右达到高峰值。所记录到的平均[一次游泳过程或1000毫秒(ms)间期]和最大(20 ms间期)巡游速度的高峰值分别为1.1—1.2和2.3—3.4BL/s(体长/秒,鲱),1.7和5.7BL/s(鳕)以及1.6和4.1BL/s(江鲽)。此外,本文还对饥饿仔鱼的巡游速度和摄食生态的相互关系作了初步探讨。

Cruising speeds were measured using a video recording system and an infra-red emitting diode as light source during early development and starvation of the yolk-sac larvae of Clyde and Baltic herring (Clupea harengus L.), cod (Gadus morhua L.) and flounder (Platichthys flesus L.) and older larvae (36 and 60 days old) of Clyde herring. The mode of cruising swimming in yolk-sac larvae was developed and established before the first feeding stage. The pattern of the change in the speeds during early development and starvation was similar in all experiments. The cruising speeds increased during early development and initial starvation and tended to peak shortly (about 2 days) before the PNR (the point-of-no-return, when 50% of larvae, although still alive, are no longer strong enough to feed), and then declined gradually during further starvation. The highest recorded mean cruising speeds, (over a swimming course or over 1000 ms) and maximum cruising speeds (over 20 ms) were 1.1-1.2 and 2.3-3.4 BL/s (body lengths/s) for herring, 1.7 and 5.7 BL/s for cod, and 1.6 and 4.1 BL/s for flounder, respectively. The effect of growth on the speeds was very marked if expressed as cm/s, e.g. the highest maximum cruising speeds were 3.5, 4.0 and 4.4 cm/s for yolk-sac, 36 and 60 days old larvae of Clyde herring respectively, tut there were some decrease when specific speeds (BL/s) were used. In general, the mean cruising speeds of fed larvae following yolk absorption were higher than the highest mean cruising speeds during starvation period of unfed larvae, but the maximum cruising speeds were still lower than the highest maximum cruising speeds during starvation period of unfed larvae. In addition, the relationship between cruising speeds and feeding ecology were also discussed.