Research On The Status Of Fish Resources In The Lower Reaches Of Minjiang River

The Minjiang River is an important ecological function area in the upper Yangtze River.The lower reaches of Minjiang River plays an important role in the link of the upper reaches of the Minjiang River,Jinsha River and the Yangtze River.The comprehensive development of the port and waterway had been launched in the Minjiang River since 2015.After the completion of the engineering,the habitat of the lower reaches of the Minjiang River will be changed obviously.However,there is a lack of investigation of the background information before the construction of the engineering,and the status of fish resources is unknown.After the construction of the engineering,the trend of the change of resources can not be effectively analyzed,and the resource protection measures to be carried out are lack of data supportting.The study basted on survey of fishery resources from 2014 to 2016 and investigation on the fish with spawning drifting eggs of early life history stage between 2016 to 2017.This study investigated the current situation of fishery resources and the early stage fish resources in the lower reaches of the Minjiang River,and evaluated the fish resources and the trend of the change of resources.Further analyzed the composition and distribution characteristics of fish in the Minjiang River.The findings of this study are:1.A total of 71 fish species and subspecies representing 3 orders,11 families,and51 genera,were collected in the lower reaches of the Minjiang River,in which there were 53 species of Cypriniformes,accounting for 74.6%,Siluriformes 13,accounting for 18.3%.The amount of Perciformes was least,5 species,accounting for 7%.Among71 species,Cyprinidae accounted for the most,with 39 species.Followed by Cobitidae,11;Siluridae,Sisoridae,Ictaluridae and Gobiidae were least,only 1.16 species,and were endemic to the upper Yangtze River were Paracobitis potanini,Leptobotia microphthalma,Leptobotia elongata,Leptobotia rubrilaris,Sinibrama taeniatus,Hemiculterella sauvagei,Hemiculter tchangi,Coreius guichenoti,Rhinogobio cylindricus,Rhinogobio ventralis,Platysmacheilus nudiventris,Gobiobotia boulengeri,Procypris rabaudi,Jinshaia abbreviata,Jinshaia sinensis,Leiobagrus marginatoides.An alien species was Ictalus portatus.2.The similarity index analysis of fish composition from different river regions showed that the index from Yibin and Leshan reaches was the lowest(70.00%),while the index from Yibin and Pinshan reaches was the highest(92.19%).The species,Cyprinus carpio,Pelteobaggrus nitidus and Pelteobagrus vachelli were main economic fishes in the lower reaches of the Minjiang River,representing 16.10%,13.96%and 12.32%respectively.By analyzing the spawning type of 71 fish species sampled,the results suggested that fish species producing sticky eggs accounted for68.28%of the total weight of the catches,while species producing drifting eggs only accounted for 27.07%.Meanwhile,differences occurred in the diversity index among survey times and reaches.The diversity index from May to July was higher than that from October to December,and there were significant differences in Pielou index between Le Shan and Qian Wei reaches.To sum up,there were high fish species richness and biomass in the mainstream of lower Minjiang River.However,with the development of several hydraulic power plants in the lower Minjiang River as well as cascade impacts in the future,the prospects for fishery resource are still far from optimistic and protection measures should be urgently strengthened.3.The surveys of fish resources of early life stages were carried out in the lower reaches of the Minjiang River during May 7-July 30,from 2016 to 2017.The results showed that there were 18 species of fish spawning drifting eggs,among which 8species were endemic species in the lower reaches of the Minjiang River.They were Leptobotiamicrophthalrna,Leptobotiaelongate,Leptobotiarubrilaris,Xenophysogobio boulengeri,Xenophysogobio nudicorpa,Sinibrama taeniatus,Jinshaia sinensis and Jinshaia abbreviata.The fishes with largest spawning were Leptobotia microphthalrna and Leptobotia elongate,with the egg quantity was652.75×10~6 Ind.and 368.01×10~6 Ind.,respectively.The result of Canonical correspondence analusis showed that the increase of the flow stimulated the spawning of Hypophthalmichthys molitrix and Ctenopharyngodon idellus,decreased the transparency and increased the density.High transparency stimulated the spawning of Rhinogobio typus.As the velocity increased,the drift density of Jinshaia sinensis's and Jinshaia abbreviata's eggs was higher.4.The surveys of fish eggs and larvae were carried out at Yibin section in the lower reaches of Minjiang River from May 7th,2016 to July 30th,2017.According to the results,there were at least 18 species of fish spawning in the lower reaches of Minjiang River.In which there were 7 species of fish with large scale reproduction,they were Leptobotia microphthalrna,Leptobotia elongate,Botia superciliaris,Xenophysogobio boulengeri,Gobiobotia filifer,Pseudolaubuca engraulis and Jinshaia sinensis.Calculating the amount of spawning,according to the development periods of eggs and the flow speed,reckoned spawning grounds.The results showed that the early stage resources of Leptobotia microphthalrna was 651.58×10~6ind in 2016,only1.17×10~6ind in 2017.By balanced spawning ground of two years,we found that the Leptobotia microphthalrna spawning grounds mainly distributed in Xijie,Gaochang,Juexi.The early stage resources of Leptobotia elongate was 368.01×10~6ind in 2016,no spawning was found in 2017,and found Leptobotia elongate spawning grounds mainly distributed in Gaochang,Juexi,Xinmin and Xiaogu.The early stage resources of Botia superciliaris was 33.16×10~6ind in 2016,only 2.45×10~6ind in 2017.By balanced spawning ground of two years,we found that the Botia superciliaris spawning grounds mainly located in the sections from Gaochang to Xinmin.The early stage resources of Xenophysogobio boulengeri was 10.85×10~6ind in 2016,only 5.86×10~6ind in 2017.By balanced spawning ground of two years,we found that the Xenophysogobio boulengeri spawning grounds mainly located in the sections from Gaochang to Juexi.The early stage resources of Gobiobotia filifer was 6.86×10~6ind in 2016,only 3.67×10~6ind in2017,balanced spawning ground of two years,we found that the Gobiobotia filifer spawning grounds mainly located in the sections from Xijie to Juexi.The early stage resources of Pseudolaubuca engraulis was 9.68×10~6ind in 2016,2.66×10~6ind in 2017,and we found Pseudolaubuca engraulis spawning grounds mainly distributed in Xijie,Pinshan and Nixi.The early stage resources of Jinshaia sinensis was 6.33×10~6ind in2016,only 7.88×10~6ind in 2017.By balanced spawning ground of two years,we found that the Jinshaia sinensis spawning grounds mainly located in the sections from Xijie to Juexi.