| Based on the field investigation of Yalong Rive basin several typical fish including Schizothorax chongi and Coreius guichenoti were taken as research object. Laboratory study of their swimming capability (critical swimming speed, endurance swimming time, burst swimming speed, kinematics) and physiology response (standard metabolic rate, activity metabolic rate, aerobic metabolic scope) were conducted at different key habitat conditions (flow velocity, water temperature) in a flume-type respirometer equipped with a high speed video camera system to record swimming behaviour. Evaluation models of swimming capability and bioenergetic models were derived, based on swimming speed and oxygen consumption rate respectively. For comparison purpose, this experiment also studied the Hypophthalmichthys molitrix and Aristichthys nobilis that widely spread in the Yangtze Rive basin and Schizothorax macropogon which was one of the fish objects of Zangmu Hydropower Station fishway. By comparing the swimming capability and physiology metabolism of the five cyprinid fish, the change characteristics of swimming behavior at different habitat conditions, physiological mechanism of fatigue and adaptive strategies of energetic metabolism were analyzed. This investigation provides data on the swimming ability of cyprinid fish that will add to the basic science required for fishway design. The primary results were as follows:1. Swimming capability and energetic metabolism of Schizothorax chongiThe critical swimming speed (Ucrit), aerobic metabolic rate, tail beat frequency (TBF) and tail beat amplitude (TBA) of juvenile S. chongi were measured during steady swimming at varying flow rates for fish of similar mass. A power function accurately described the relationship between oxygen consumption rate (MO2) and swimming speed (U). The estimated standard metabolic rate (SMR) calculated from the power function was445.34mgO2kg-1h-1, similar to the experimental result of431.5mgO2kg-1h-1. The relationship between cost of transport (COT) and U was, characteristically, inverse bell-shaped, with COTmin=44.6J kg-1m-1at Uopt=5.5 body lengths per second (bl/s). There was a significant positive linear correlation between TBF and U. The slope of the correlation (0.33) was lower than for many other species, implying that S. chongi swim efficiently. The TBA, ranging from0.15to0.2bl, was found to be independent of U. Kinematic analyses indicates that S. chongi primarily depends on the caudal fin to generate forward thrust and employs three velocity-dependent swimming gaits. The Ucrit reached6.5bl/s (b19.5-13.2cm) at25℃which means the S. chongi was a fish with high swimming ability.2. Swimming capability and energetic metabolism of Coreius guichenotiThe critical swimming speed (Ucrit), standard metabolic rate (SMR) and maximum metabolic rate (MO2,max) of juvenile C. guichenoti were determined during steady swimming at four water temperatures (10℃,15℃,20℃and25℃). The swimming endurance at five swimming speeds was determined at natural water temperature. The swimming behavior was recorded with a high speed video camera system during the Ucrit protocol. The Ucrit of juvenile C. guichenoti increased with the temperature from10℃to25℃and the relation was approximately linearity (P<0.001). The maximum Ucrit at25℃,7.37bl/s (～1.28m/s), was calculated according to the regression equation. A power function accurately described the relationship between oxygen consumption rate (MO2) and swimming speed (U) at the four temperatures (P<0.05). The SMR, MO2,max, and aerobic metabolic scope increased with increasing temperature. The relationship between cost of transport (COT) and U were characteristically inverse bell-shaped, with minimum COT at Uopt=4.5-5.0bl/s. The swimming endurance decreased with the increase of flow velocity at18.0±1.5℃(P<0.01) and showed obvious individual difference. There was a significant positive linear correlation between tail beat frequency (TBF) and U (P<0.001) and the increase is more significant as the temperature is higher.3. Swimming capability and energetic metabolism of Schizothorax macropogonThe critical swimming speed (Ucrit) and activity metabolism rate (MO2) of the subadult S. macropogon lived in Yaluzangbujiang River were measured and compared at four water temperature (5,10,15and18℃) to reflect seasonal water temperatures. In addition, the burst swimming speed (Uburst) and swimming endurance were determined at natural water temperature. The Ucrit increased with the temperature from5℃to18℃and the relation was approximately linearity (P<0.001). The Ucrit were3.96±0.21bl/s,4.4±0.16bl/s,4.9±0.18bl/s and5.35±0.14bl/s respectively at four different temperatures. Power function models at four different temperatures well described the correlation between MO2and swimming speed with high correlation coefficient (P<0.05). The derived models showed that MO2increased with the increase of swimming speed and the increase was more significant as the temperature was higher. The speed exponents of the power fit at four different temperatures were2.4,2.6,2.8and3.1, which meant the efficiency of aerobic swimming decreased with the increase of temperature and temperature had a significant effect on swimming performance in subadult S. macropogon. The Uburst was in the range of0.90-1.50m/s (4.23-6.28bl/s) and the swimming endurance decreased quickly with the increase of flow velocity at natural water temperature (5-9℃). There was a significant positive linear correlation between TBF and swimming speed (P<0.001), but stride length (Ls, the distance the fish traveled per tail beat) was only weakly correlated with swimming speed and showed three different stages which has been shown to be an energy-saving swimming behaviour.4. Swimming capability and energetic metabolism of Hypophthalmichthys molitrix and Aristichthys nobilisThe critical swimming speed (Ucrit), swimming endurance and activity metabolism rate (MO2) of juvenile H. molitrix and A. nobilis were determined during steady swimming at three water temperatures (10℃,15℃and20℃). The swimming behavior was recorded with a high speed video camera system at varied swimming speed (U). The Ucrit of both fish linearly increased with the temperature from10℃to20℃(P<0.05) and the linear slope were close, but the Urit of juvenile H. molitrix was higher. For the two species, the power function models at three different temperatures both well described the correlation between MO2and U (P<0.05) but the speed exponents of the H. molitrix was lower than A. nobilis which meant the former had a higher swimming efficiency. The endurance swimming time was both decreased quickly with the increase of flow velocity and the decrease trend was more obvious when the temperature was increased, but the difference of endurance between two species was reduced with the decrease of temperature. The two species had similar swimming behaviour from the video record:there was a significant positive linear correlation between TBF and U (P<0.05) but TBA was found to be independent of U. Initially, TBA increased slightly with increased velocity up to5-6bl/s and then decreased with further increases in velocity.5. The comparison of swimming performance of five cyprinid fish and its applicationThe critical swimming speed (Ucrit) of five test fish linearly increased with the temperature during the survival temperature range. The C. guichenoti had the highest Ucrit among the five species. The experience formula Ucrit=aL0.5had good prediction of Ucrit according to the body length of fish, but the coefficient a changed in different species. The endurance swimming time of test fish was all decreased significantly with the increase of flow velocity. The endurance of fish changed markedly with species, determination method and experimental apparatus, so there was no general applicable experience formula to predict the endurance time. The burst speed of S. chongi and C. guichenoti was relatively high and approximately applied to the’10bl/s-rule’. For S. macropogon, H. molitrix and A. nobilis the burst speed was much slower which meant the burst capacity of fish depended very much on the fish species and the duration of the performed burst. The power function model well described the correlation between MO2and swimming speed with high correlation coefficient for the five species. The optimal swimming speed (Uopt) could be derived for the model. Higher Uopt and lower speed exponents of the power fit for S. chongi and C. guichenoti implied they were of higher swimming efficiency. Kinematic analyses indicated that stride length (the distance the fish traveled per tail beat) of S. chongi and C. guichenoti reached above2.0b1during the swimming test and much higher than the other three species. It could be inferred that S. chongi and C. guichenoti had a lager sectional area of white muscle. According to the research results we roughed out some ideas for the design of fishway for the passage of S. chongi and C. guichenoti. The future studies should focus on the physical model test and behaviour simulation of fish in the real fishway to optimize the design structure of fishway. |
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