Research On The Fish Eco-physiological (Thermal Tolerance, Metabolism And Swimming) Response Based On Temperature Changes

Environmental biology that is an important branch of environmental science hasbeen paying attention to the environmental effect of temperature on creatures. Fish aretypical poikilotherm, so the effects of temperature on the behavior of fish (e.g. survival,development, growth) are evident. As an important ecological factor, temperature canchange with the temporal and spatial patchiness and human disturbance. In this study,we reviewed the scientific literatures about the temperature variation pattern for fish inthe rivers and carried out some eco-physiological research for the fish species aroundthis theme of the temperature changes. Furthermore, we have discussed the thermalmotive force that is highly correlated with the organismal evolution. A series of fiveexperiments were conducted mainly in qingbo (Spinibarbus sinensis), one of thecommercial fish species in the middle and upper reaches of the Yangtze River of China.In experiment I, the effects of exhaustive exercise training and fasting on thermaltolerance were examined at different temperatures in qingbo. In experiment II, theeffects of temperature and exhaustive exercise training on critical swimming andmetabolic performance were examined in qingbo. In experiment III, the effects oftemperature on repeat constant accelerating swimming performance and on anaerobicmetabolic capacity were examined in qingbo. In experiment IV, the effects of fastingperiods on critical swimming performance were examined at different temperatures inqingbo. In experiment V, the effects of temperature on metabolic interaction betweendigestion and locomotion were examined in three cyprinid fish species [gold fish(Carassius auratus), common carp (Cyprinus carpio) and qingbo]. The objectives ofthis study include:(1) realize some characteristics of plasticity (thermal tolerance,metabolism and swimming) in fish;(2) investigate the effects of temperature onphysiological functions in fish;(3) reveal eco-physiological adaptation strategies andenrich related theories about physiological ecology of fish;(4) provide practicalinformation for the environmental protection, fishery enhancement and release, and forthe building of fishway etc.The main contents and research results are summarized as follows:(1) Temperature had significant effects on the thermal tolerance in qingbo. Thecritical thermal both minimum (CTmin) and maximum (CTmax) significantly increasedwith temperature rose. Exhaustive exercise training of2weeks resulted in significant decrease in CTminand increase in CTmaxin qingbo. Fasting of2weeks had no effect onCTminand CTmaxat low temperatures (10and20oC). However, fasting of2weeksresulted in a significant decrease in either CTminor CTmaxat high temperature (30oC).These results indicated that exhaustive exercise training could improve the thermaltolerance performance; short-term fasting had no significant effect on the thermaltolerance performance at low temperature, a significant negative effect on hightemperature tolerance performance, and positive effect on low temperature toleranceperformance.(2) Temperature had a significant effect on critical swimming performance inqingbo. The optimal swimming temperature for the critical swimming speed (Ucrit) was27.2°C. Exhaustive exercise training produced a significant increase in swimmingperformance at a low temperature (15°C), but it had no effect on swimmingperformance at a higher temperature (25°C). The different effects of exercise trainingon swimming performance at different temperatures may be related to changes inaerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen,imbalances in ion fluxes and the intensity of the stimulus to remodel tissues withchanges in temperature.(3) Temperature significantly affected the constant acceleration swimmingperformance (UCAT) and anaerobic metabolic capacity (EPOC, i.e. excess post-exerciseoxygen consumption) in qingbo. The optimal swimming temperatures for UCATandEPOC were25.1and25.6oC, respectively. Temperature had different effects on repeatconstant acceleration swimming performance and on anaerobic metabolic capacities(that included an hour interval of rest). The recovery of the constant accelerationswimming performance was poorer at high temperatures than at low temperatures.These results may be related to larger anaerobic metabolism, a lower pH value in blood,larger ionic fluid and/or higher levels of hormones at high temperatures.(4) Both fasting treatment and temperature acclimation had profound effects oncritical swimming performance in qingbo. The critical swimming speed (Ucrit) decreasedless in the early stage of the fasting but more in the later stage at the low temperature(15oC) compared to the high temperature (25oC). The different responses in criticalswimming performance to fasting stages at different temperatures might be related tothermal acclimation period, resting metabolism, energy stores, respiratory capacity,enzymatic activity in muscle tissue and energy substrate utilization. The divergentresponse of the swimming performance to fasting in qingbo at different temperature might be an adaptive strategy to seasonal temperature and food resource variation intheir habitat.(5) Under the low temperature (15oC) condition, all fish species showed anadditive metabolic mode and there was no competition between digestion andswimming. When the temperature increased from15to25oC, the metabolic scope (MS)for digestion increased182,49and17%and locomotive MS increased129,58and138%in goldfish, common carp and qingbo, respectively. The total MS for bothdigestion and locomotion increased about106,58and78%in goldfish, common carpand qingbo, respectively. The metabolic mode of goldfish changed to digestion-prioritymode, as illustrated by the large increase in digestive MS, and the metabolic mode ofqingbo changed to locomotion-priority mode, as illustrated the large increase inlocomotive MS, when the temperature increased from15to25oC. The metabolic modeof common carp showed no change, as illustrated by the parallel increase in digestiveand locomotive MS and cardio-respiratory capacity.(6) It was suggested that the paleoclimate changes (high temperature environment)were propitious to biological evolution from aquatic to terrestrial animals.