The Effects Of Caudal Fin Amputation On Swimming Performance And Metabolic Interaction Between Digestion And Locomotion In Juveniles Of Three Cyprinid Fish Species With Different Metabolic Modes

Under natural conditions, fish species often need to perform digestion andlocomotion simultaneously. Metabolic competitive modes between digestion andlocomotion are classified into three categories, termed the additive, digestion-andlocomotion-priority modes. In nature, the caudal fin is frequently observed to sustaindamage as a result of social rank, predation or disease. To test whether the metabolicmode changed differently for fish with different metabolic mode after caudal finamputation as a consequence of intensified energy competition, we investigated theswimming performance of fasting and fed fish with and without the caudal fin injuveniles of three cyprinid fish species: qingbo （Spinibarbus sinensis,locomotion-priority mode）, common carp （Cyprinus carpio, additive mode） andgoldfish （Carassius auratus, digestion-priority mode）.The results are as follows:1. In control groups, the critical swimming speed （Ucrit） of fasting qingbo was higherthan common carp and goldfish. Furthermore, the fasting qingbo showed asignificantly higher active metabolic rate （MO₂active）, maximum tail beatfrequency （TBFmax） and a lower maximum tail beat amplitude （TBAmax）compared with those of common carp and goldfish.2. The Ucritof fasting qingbo, common carp and goldfish decreased significantly by49%,32%and35%after caudal fin amputation. The TBAmax（all three fishes）,TBFmax（only common carp and goldfish） and （or） MO₂active（only common carp）increased significantly after caudal fin amputation.3. In the control fish, digestion let to a significantly lower Ucritin goldfish but not inqingbo and common carp, and the MO₂activeof digesting common carp was higher than that of fasting fish, suggesting locomotion-priority, additive anddigestion-priority metabolic modes in qingbo, common carp and goldfish,respectively.4. After fin amputation, digestion showed no effect on Ucritin any of the three fishes,and only the digesting common carp showed a higher MO₂activethan their fastingcounterparts. This result suggested that the metabolic mode of the goldfishchanged from the digestion-to the locomotion-priority mode, whereas themetabolic mode of the other two fishes remained the same after fin amputation.In conclusion:1. The strong swimmer showed a higher MO₂active, TBFmaxand a lower TBAmax. Itsuggested that the strong swimmer primary rely on TBFmaxto improve swimmingspeed which was supported by a higher MO₂active. Because a higher TBAmaxwouldlead to a higher drag.2. The metabolic mode of the common carp showed no change after fin amputationlikely due to the high flexibility of the cardio-respiratory capacity of this fish, asindicated by the increased MO₂active. Although the metabolic mode remained thesame, the feeding metabolism in the fin-amputated qingbo was down-regulated at alower swimming speed than that of the control group due to the intensifiedcompetition between digestion and locomotion. The underlying mechanism for themetabolic mode change in the goldfish is not clear and needs further investigation.3. We speculated that in caudal-fin-intact goldfish, the decreased swimming efficiency,rather than irreducible digestive loading, caused a decreased Ucrit in digesting fish（i.e. false digestion-priority mode）, and the metabolic mode should not be judgedsimply by the relative magnitude of the metabolic rates of fasting and digestingfish.