溶氧水平对鳊鱼、中华倒刺鲃幼鱼游泳能力的影响

THE EFFECTS OF DISSOLVED OXYGEN LEVEL ON THE SWIMMING PERFORMANCES OF JUVENILE PARABRAMIS PEKINENSIS AND SPINIBARBUS SINENSIS

在(25±1)℃条件下,以鳊鱼(Parabramis pekinensis)[体重(4.70±0.11)g,n=32]、中华倒刺鲃(Spinibarbussinensis)[体重(3.26±0.06)g,n=32]幼鱼为研究对象,采用鱼类游泳代谢测定仪在水体溶氧为8、4、2、1 mgO2/L条件下分别测定其临界游泳速度(Ucrit)和游泳代谢率(MO2),并计算出静止代谢率(MO2rest)、最大游泳代谢率(MO2max)、代谢范围(MS)及单位位移能耗(COT)等相关参数。结果显示,随着溶氧水平的下降,鳊鱼、中华倒刺鲃幼鱼的Ucrit均逐渐下降,除中华倒刺鲃幼鱼的值在4与8 mgO2/L下没有显著性差异外,其他各组均差异显著(P<0.05);在同一溶氧水平下的中华倒刺鲃Ucrit显著大于鳊鱼(P<0.05)。两种鱼的MO2max和MS均随DO的下降而显著下降,但MO2rest在溶氧水平低于1 mgO2/L才显著下降(P<0.05)。研究还发现鳊鱼、中华倒刺鲃幼鱼的MO2在同一游泳速度下随溶氧水平下降而降低,而在相同溶氧水平下随游泳速度的上升而显著升高(P<0.05);COT随游泳速度上升而显著降低(P<0.05),但在高游泳速度下相对稳定,在同一游泳速度下随着DO的下降有所减小。中华倒刺鲃的COT整体上小于鳊鱼,且在低游泳速度下差异更大。87.5%(1—8mgO2/L)溶氧水平的下降导致两种鱼类相似的Ucrit变化(53%vs.50%),但溶氧水平由8降到4 mgO2/L时,鳊鱼32%MO2max的下降导致Ucrit下降13%,但同样的溶氧水平下降虽然导致中华倒刺鲃的MO2max下降20%,但由于MO2rest和COT的下降,其Ucrit并没有显著的变化。实验结果表明:不同溶氧水平对不同鱼种游泳能力的影响存在差异,这种差异与其代谢对策密切相关。

To investigate the effect of dissolved oxygen（DO） level on swimming performance of juvenile Chinese bream（Parabramis pekinensis） [n=32,body mass： 4.70±0.11 g] and Qingbo（Spinibarbus sinensis） [n=32,body mass： 3.26±0.06 g],we measured the critical swimming speed（Ucrit） and swimming metabolic rate（MO2） and calculated the resting metabolic rate（MO2rest）,maximum metabolic rate（MO2max）,metabolic scope（MS）,and cost of transport（COT） during swimming at 25℃ and DO 8（100% saturation）,4,2,and 1 mgO2/L.Ucrit values of Chinese bream and Qingbo were 8.47 ± 0.19 vs 9.49 ± 0.14,7.40 ± 0.17 vs 9.40 ± 0.28,5.64 ± 0.16 vs 7.51 ± 0.21 and 4.02 ±0.23 vs 4.75 ± 0.13 BL/s at above different DO levels,respectively.Ucrit decreased significantly with DO in both fish species（P0.05） except that of Qingbo between 4 and 8 mgO2/L.Ucrit of Qingbo was significantly higher than those of Chinese bream under all DO levels（P0.05）.Both MO2max and MS decreased significantly with DO from 8 to 1（P0.05） while MO2rest showed a significantly decrease till DO was below 1 mgO2/L.In comparison,MO2 increased significantly with Ucrit（P0.05）.COT of both fish species decreased with Ucrit within lower swimming speed range but remained unchanged at high Ucrit range.COT of Qingbo was lower than that of Chinese bream（P0.05）.In addition,COT decreased with DO,suggesting that down-regulation of the physiological processes under hypoxic conditions.When DO decreased from 100% to 50%,Chinese bream showed a 13% decrease in Ucrit due to the decreased respiratory capacities（as suggested by a 32% decrease in MO2max） while Qingbo showed no significant decrease in Ucrit despite a 20% decrease in MO2max due to the decrease in maintaining metabolism and COT.However,when DO decreased to 12.5%,both Qingbo and Chinese bream showed similar decreases in Ucrit compared to those under 100% DO（53% vs 50%）.This observation suggested that the swimming performance varied differently with the DO decrease between Chinese bream and Qingbo and was closely related to the metabolic strategy of different fish species.