Swimming Performance And Swimming Behaviors Of Schizothorax Dolichonema Herzenstein And Schizothorax Wangchiachii Fang

Schizothorax dolichonema Herzenstein and Schizothorax wangchiachii Fang were both endemic fishes in the upper reaches of Yangtze River. S. dolichonema Herzenstein was even recorded as one of the endangered fishes (EN) in the China Species Red List and was one of the most important fishes needed to be protected in Sichuan Province. They took short distance migration in breeding season. S. wangchiachii Fang was recognized as one kind of "NT" species by World Conservation Union. In recent years, many cascade hydroelectric power stations were built in the upper reaches of Jinshajiang River, which resulted in the fragmentation of the habitat and impeded the distribution and migration of fishes. Particularly the number of endemic fishes would decrease sharply and even became extinct. For the purpose of reducing the bad effect of hydropower station on fishes, fishpass facilities should be built to help fishes get through the station. Researches on the swimming performance of fishes were key points in the designing of fishpass facilities. Nowadays, little were known about the swimming performance of S. dolichonema Herzenstein and S. wangchiachii Fang. To investigate their swimming performance, experiments were done on the wild fishes of S. dolichonema Herzenstein and S. wangchiachii Fang collected in the upper reaches of Jinshajiang River. Burst swimming speed and critical swimming speed were measured, and swimming energetics and swimming behavior at different swimming speed were calculated as well. Results were shown as follows:1. Burst swimming speeds and the relationships between burst swimming speeds and body length. Burst swimming speeds were105.00~146.25cm/s and102.50~142.00cm/s, relative burst swimming speeds were4.84~7.41BL/s and4.03~6.51BL/s for S. dolichonema Herzenstein (21.6±2.5cm) and S. wangchiachii Fang (23.4±2.1cm), respectively, calculated by the increasing velocity method. Absolute burst swimming speeds showed no relationships with body length, however, both the relative burst swimming speeds decreased significantly with the body length increasing for S. dolichonema Herzenstein and S. wangchiachii Fang, the functions were Ur-burst=11.96~ 0.28BL (R2=0.58, p=0.006) and Ur-burst=10.97-0.25BL (R2=0.51, p=0.008), respectively. In the process of fishway design, burst swimming speed usually used to determine the head difference between two pools. To ensure that all the target fishes pass the fishway successfully, the flow velocity in the fishway must not exceed the maximum swimming speed of all the fishes.2. Critical swimming speeds and swimming energetics of S. dolichonema Herzenstein and S. wangchiachii Fang. Critical swimming speeds were69.73~91.33cm/s and63.92~86.67cm/s, relative critical swimming speeds were3.04~4.93BL/s and2.54~3.70BL/s for S. dolichonema Herzenstein (19.78±2.23cm) and S. wangchiachii Fang (23.83±2.47cm), respectively. Absolute critical swimming speed did not vary with body length ranging. But both the relative critical swimming speeds decreased significantly with the body length increasing for S. dolichonema Herzenstein and S. wangchiachii Fang, the functions were Ur-crit=7.96-0.20BL (R2=0.64, p<0.001) and Ur-crit=5.81-0.11BL (R2=0.42, p<0.05), respectively.Power functions could best fit the relationships between oxygen consumption rates and swimming speed for both S. dolichonema Herzenstein and S. wangchiachii Fang, functions were MO2=129.67+15.63U234(R2=0.983,p<0.001) and MO2=100.00+42.61U181(R2=0.995, p<0.001), respectively. The relationships between cost of transports and swimming speeds could also be described by power functions, functions were COT=0.14U-1+0.04U0.80(R2=0.844,P<0.001) and COT=0.12U-1+0.04U1.02(R2=0.898,p<0.001), respectively.3. Kinematics at different swimming speeds of S. dolichonema Herzenstein and S. wangchiachii Fang. High-speed video camera (frames/s) was used to record the swimming behavior of fishes at different swimming speed. Recordings were analyzed using the software of KMPlayer in slow motion to determine the tail beat frequencies, tail beat amplitudes and stride lengths. Tail beat frequencies increased significantly with swimming speeds increasing for both S. dolichonema Herzenstein and S. wangchiachii Fang, the positive relationships could be described by the functions:TBF=68.93+52.46U (R2=0.979, p<0.001) and TBF=66.60+61.98U (R2=0.990, p<0.001), respectively. Tail beat amplitudes did not change much at different swimming speed. Tail beat amplitudes were0.25±0.03BL (0.18~0.32BL) and0.21±0.02BL (0.17~0.26BL) for S. dolichonema Herzenstein and S. wangchiachii Fang, respectively. Stride lengths also increased with swimming speed increasing, Ls=0.51+0.09U (R2=0.978. p <0.001) and Ls=0.47+0.08U (R2=0.994, p<0.001) can best describe their relationships for S. dolichonema Herzenstein and S. wangchiachii Fang, respectively.