The Fish Resources And Angling Fishery Status In The Middle Reaches Of Jialing River

A decade-long ban on fishing in the Yangtze River Basin began in 2020,with fishermen going ashore and moving to new businesses without allowing any productive fishing activities,in an effort to restore the river's fish stocks.Before that,it is very important to investigate fish resources and collect the background data about fish.Jialing River is an important tributary of the upper reaches of Yangtze River,and the middle reaches of Jialing River have abundant fish resource.However,the latest systematic investigation of fish resources in the middle reaches of Jialing River was years ago.At present,15 cascade water conservancy projects have been completed in the main stream of Jialing River.The construction of cascade hydropower stations has greatly changed the river channel and basin conditions of Jialing River,which will affect the growth and reproduction of fish.In addition,angling activities have little impact on the river native fish resources,but if the anglers'behavior is not standard or even illegal,it will damage the fish resources.In this study,the status of fish resources and fishing fishery in the middle reaches of Jialing River were explored,which will provide some scientific basis for the protection and restoration of fish resources in the middle reaches of Jialing River.In order to explore the fish resources and angling fishery status in the middle reaches of Jialing River,a survey was carried out on the middle reaches of Jialing River from 2017 to2019 by selecting typical sampling points.The main results and conclusions are as follows:(1)A total of 22 560 fish specimens(weights:?1914 kg)were collected,and 94species were identified,belonging to 58 genera,18 families and 7 orders.44 species were Chinese endemic fish,and 16 species were endemic fish of the upper reaches of the Yangtze River.According to the Red List of Vertebrates,there are eight vulnerable species,including Xenocypris fangi,Procypris rabaudi,Leptobotia microphthalma et al.One species(Ancherythroculter wangi)was near threatened,while the other species were not at risk or data were scarce.According to Index of Relative Importance division,the dominant species in the middle reaches of Jialing River are Saurogobio dabryi,Cyprinus carpio,Carassius auratus,Xenocypris davidi and Pseudobagrus nitidus.The Shannon-Wiener diversity index H'was 2.845,the Margalef richness index D was 9.278,the Pielou evenness index J'was0.626,and the Simpson ecological dominance index C was 0.117.Compared with the survey results ten years ago,the diversity of fish community in the middle reaches of Jialing River increased,while the dominant species'dominant position weakened.According to fish community structure analysis,10 sections can be divided into 3 groups at 50%similarity level.The group?is Caojie Reservoir,the group?is Tingzikou Reservoir,and the group?including Shaxi Reservoir,Jinyintai Reservoir,Xinzheng Reservoir et al.ANOSIM group similarity test results showed that Global R=0.878,P=0.002<0.05,indicating that there were significant differences among these groups.The average intra-group similarity of the group?was 57.93%.Carassius auratus,Xenocypris davidi,Saurogobio dabryi,Pseudobagrus fulvidraco,Hemibagrus macropterus,Cyprinus carpio is the main species contributes to the similarity in the group?.The average dissimilarity between group?and group?,group?and group?,group?and group?were 57.74%,56.02%and 53.19%,respectively.Xenocypris fangi,Saurogobio dabryi,Pseudobagrus nitidus and Xenocypris davidi were the divergent species which contributed more to the heterogeneity among these groups.The statistical analysis of fish ecological types showed that the main reproductive types of fish in the middle reaches of Jialing River were the viscous ovivores,the feeding types were mainly carnivorous and omnivorous,and the bottom living fish accounted for a large proportion of the fish habitat water layer types.Nine introduced species were found,among which,Gambusia affinis and Pseudorasbora parva have formed stable populations,Neosalanx taihuensis and the mirror carp may have formed certain populations.Other species only collect a few individuals,and they should be a breeding escape.(2)A total of 138 boats,17 959 fish,weighing about 1 594 kg,were collected from the survey of the main economic fish in the middle reaches of Jialing River,which consisted of76 species,13 families,47 genera and 5 orders.The main commercial fish species were determined based on the catches in the waters.The biological parameters and growth characteristics of 7 main commercial fishes(Cyprinus carpio,Carassius auratus,Xenocypris davidi,Culter alburnus,Chanodichthys mongolicus,Pseudobagrus fulvidraco,and Saurogobio dabryi)were analyzed with FiSAT?software.The annual catches of each species were calculated by the Catch Per Unit Effort(CPUE),and the fishery resources were preliminarily estimated using FiSAT?software and to calculate the total resources of fish in the middle reaches of Jialing River.The results showed that the growth index b of seven species ranges from 2.86 to 3.03,indicating these fish species all grow at a uniform rate.The growth coefficient K of all the seven species are greater than 0.2,suggesting that these fish species have a rapid growth.The growth performance index??ranges from 4.40 to 5.30.The E value of Saurogobio dabryi is less than the corresponding E_max,which indicates the underutilization of resources.However,the E values of other species are greater than the corresponding E_max,which indicates the excessive exploitation of resources.Among these fish species,the age of inflecting point of Pseudobagrus fulvidraco was the largest(4.26years old),and that of Saurogobio dabryi was the least(1.58 years old),but most of the others are younger than three years old.The annual resource weights of Cyprinus carpio,Carassius auratus,Xenocypris davidi,Culter alburnus,Chanodichthys mongolicus,Pseudobagrus fulvidraco,and Saurogobio dabryi were 3 883 t,9 246 t,2 469 t,1 259 t,862 t,376 t,and 1391 t,respectively.The total annual resource of fish in the middle reaches of Jialing River was 37 400 t.It is found that the community structure and population structure of the main commercial fishes in the middle reaches of Jialing River are both miniaturized due to overfishing.The main economic fish resources are over-exploited,and the length of the catch should be controlled above the inflection point.(3)Angling fishery survey results show that the angling activities in the middle reaches of Jialing River have the following characteristics:the anglers have a wide range of ages and diverse occupational composition,but the majority of them are retirees and middle aged and elderly people;Angling is most active in autumn,and overcast days are the anglers'favorite weather.The kinds of fishing tackle and bait are various and abundant.Fishing tackle is mainly based on hand pole,and the bait is mainly based on commercial bait.The anglers have a high investment in fishing tackle and bait,and the choice of angling is generally not far from the place of residence.Therefore,there is almost no consumption in transportation,accommodation,meals and other expenses.The fish captured by anglers are mainly Cyprinus carpio and Carassius auratus.There are also many kinds of fish such as Chanodichthys mongolicus,Xenocypris,Culter alburnus,Hemiculter,Pseudobagrus et al.Most anglers'maximum single catch is less than 5 kg and the average single catch is less than 0.5 kg.Catch disposal is mainly self-retention,only less than 10%of the anglers will sell the catch,and less than 2%of anglers choose to release.The average angler density is about 6.4 people/km,and the estimated number of anglers in the middle reaches of Jialing River is about 4 041 people,and the total annual fishing amount is about 279 tons.It is found that the anglers in the middle reaches of Jialing River fishing nearby to amuse themselves,and no illegal fishing was found.The fish captured by anglers are common economic fish,and the catch did not pose a great threat to the fish resources.