The Growth And Its Response To Climate Change Of Ptychobarbus Kaznakovi An Schizopygopsis Thermalis In The Upper And Middle Reaches Of The Nu River

Climate change has profoundly influenced the world.Compared with the terrestrial ecosystem,the aquatic ecosystem is suffering more from climate change.Aquatic ecosystem of Qinghai-Tibet Plateau,which is known as“the third pole”,is extremely sensitive to climate change.Fishes are important organisms of aquatic ecosystems whose growth response to climate change is an essential access to studying the environmental stress that the aquatic ecosystem suffered under the impact of climate change.Ptychobarbus kaznakovi and Schizopygopsis thermalis are two Schizothoracinae fish species of different specialization levels which live in the upper and middle reaches of the Nu-Salween River.Response of the growth of these two fishes to climate change provides access to objective recognition of the dynamic of aquatic ecosystem of Qinghai-Tibet Plateau in the climate scenario.In this paper,research was conducted with a comprehensive understanding of climate change impact on fish growth in the world.P.kaznakovi and S.thermalis were the main objects.Field sampling and experiment analysis were used to discuss growth traits and response patterns to climate change of these two fishes.The main results and conclusions of this paper were listed below.(1)Less than 1%of global fishes(309 fish species)were considered in the research of climate change impacts on fish growth.Distribution pattern,body size,trophic level and feeding habit varied with these fish species.Fishes of small body size and low trophic level were less studied;Chondrichthyan fishes of high research and economic value and Actinopterygii fishes except Perciformes,Cypriniformes,Salmoniformes,and Clupeiformes were less studied;fishes of high-latitude areas,including Qinghai-Tibetan,were less studied;fishes from lakes and high seas were less studied.Temperature was the top considered variable in relevant studies and showed a negative impact on fish growth.Some studies also contained various environmental factors induced by climate change such as biological invasion,flow alteration and water quality degradation.Researchers of climate change impacts on fish growth preferred to conduct their study via field surveys rather than controlled experiments.(2)The growth pattern of P.kaznakovi was isometric.Their ages ranged from 3 to19.Individuals of 4 years old had the greatest number which accounted for 25.34%of all samples.The length-weight relationship function equation of P.kaznakovi was(2=0.00002^2.9001.The von Bertalanffy growth equation fitted the growth of P.kaznakovi best which can be described as=627.93813(1-0)^{-0.06944(+2.22654)}).The growth pattern of S.thermalis was isometric too.Their ages ranged from 2 to 12.Individuals of 4 years old had the greatest number which accounted for 48.25%of all samples.The length-weight relationship function equation of S.thermalis was(2=0.00001^3.0499.The von Bertalanffy growth equation fitted the growth of S.thermalis best which can be described as=415.1586(1-0)^{-0.05861(+0.66909)}).(3)The results of the linear mixed effects model found that the growth variation of the two fish species mainly comes from the intrinsic and extrinsic fixed effects.Intrinsic growth indicated that growth rate of P.kaznakovi and S.thermalis decreased in logarithm with the increase of age.The different sexes of these two species had different growth patterns.Females grew faster than males over all ages.Otolith growth biochronologies P.kaznakovi and S.thermalis covered 19 years and 12 years respectively,which indicated significant annual variation in growth.As for extrinsic factors,average annual temperature,total annual precipitation,Arctic Oscillation(AO),North Atlantic Oscillation(NAO),Southern Oscillation index(SOI),El Nino-Southern Oscillation(ENSO)and Sea Surface Temperature(SST)explained the growth of P.kaznakovi and S.thermalis considerably in the model.The growth of P.kaznakovi was significantly and negatively correlated with total annual precipitation.The growth of S.thermalis was significantly and positively correlated with annual temperature.These two fishes showed a similar response pattern to two local environmental factors,air temperature and precipitation.However,their response patterns to those global factors,AO,NAO,SOI,ENSO and SST,are different.In conclusion,this study revealed climate change impact on the growth of P.kaznakovi and S.thermalis in the upper and middle reaches of the Nu-Salween River.Similar response patterns of these two fishes to local climate factors were found,while response patterns of these two fishes to global climate factors were different.Growth responses of P.kaznakovi and S.thermalis to climate change in the upper and middle Nu-Salween River helped us to understand the stability of the river ecosystem in Qinghai-Tibet Plateau.The results provided references for the protection of the ecosystem and environment in the upper and middle Nu-Salween River.