Study On Effects Of Determination And Temper On The Critical Swimming Speed In Juvenile Darkbarbel Catfish.

Critical swimming speed was determined for the darkbarbel catfish (Pelteobag vachelli Richardson) with different duration and velocity increments at water temperature of 25℃. The fish were first tested at the duration of 5,10,15,30 and 60 min at a velocity increment of 15% Ucrit (1.0 body lengths).,and then, tested at a velocity increment of 5%,10%,15%,20% and 30% Ucrit with a duration of 20 min, so as to study the effects of different duration and velocity increment on the critical swimming speed of Juvenile Darkbarbel Catfish. Then the paper is to determine the critical swimming speed of the darkbarbel catfish and reveal the effects of temperature on the critical swimming capacity by selecting the optimum measurement parameters, in three different temperatures (15,22,29℃).The main results were as follows:1,Absolute critical swimming speed (Uα)of the experimental fish decreased from 47.4±0.7 cm-s"1 at 5 min to 39.1±1.5 cm·s-1 at 60min (P<0.05), but the Ua in 20 min group was not significantly different from that in 30 min group.2. The critical swimming speed increased from 44.1±0.6 cm·s-1 in 5% Ucrit increment group to 47.0±0.4 cm·s-1 in 10% Ucrit. increment group (P<0.05). The critical swimming speed in 15% and 20% Ucrit increment group was 45.2±0.2 cm·s-1,46.3±0.8 cm·s-1 respectively. There were no significant differences in critical swimming speed among the groups of 10%,15%,20% Ucrit, but the critical swimming speed in 30% Ucrit increment group was significantly different from that in other groups (P<0.05).3. Under temperature (15,22,29℃),The Uαof the experimental fish was 23.93±0.94 cm·s-1,30.82±0.83 cm·s-1,and 40.81±1.71 cm·s-1 respectively; and the Ur of them was 4.35±0.17,5.60±0.15, and 7.42±0.31BL/s respectively. There were significant differences among the groups (P<0.05), and the temperature and critical swimming speed were positively correlated. The absolute critical swimming speed (Ur) showed a 'line-shape'increase course with enhanced temperature (T). The relationship could be described as: Ur=1.4324 T (N=24, R2=0.9509, P<0.001)The rerults revealed:1. When tested at a duration of 5 min, the Uαof the juvenile juvenile darkbarbel catfish was (47.4±0.76 cms-1), which was higher than the 15 min and 30 min group about 10%,and higher than the 60 min group about 15%, indicating that too short a duration will cause overestimation of the critical swimming speed;2. When tested at a duration of 15 min and30 min, the Uαand Ur did not show significant difference (P<0.05) while the results of this study showed that the Ua in 5% and 30% Ucrit. increment group respectively, which both were lower than the other experimental groups. The proper velocity increment for Darkbarbel catfish was 10-20% Ucrit,too high or too low of a velocity increment would cause underestimation of critical swimming speed.3. The effects of temperature on the critical swimming speed values:the minimum critical swimming speed was at 15℃, the maximum was at 29℃, and without significant differences among the groups. Critical swimming speed continued to show an upward tendency as as temperature rised. The effects of temperature on the critical swimming ability was remarkable.