The Current Situation And Protection Measures Of Fish Resources In Luoma Lake

Six monitoring points(S1,S2,S3,S4,S5,and S6)were set up in the Luoma Lake,Jiangsu Province,to monitor fish resources in four frequency periods from December 2016 to April 2018.The fish community composition,fish community diversity and spatial differences,body length and weight of major economic fishes and dominant species,food habits of the Coilia nasus,and fish productivity were analyzed based on the investigative data.And some countermeasures and suggestions for the protection of fishery resources in the Luoma Lake were proposed in the present study.A total of 64 fish species that representing 8 orders and 16 families,were collected in the lower reaches of the Luoma Lake.Compared with historical documents,the number of fish species has decreased.Migratory fish have not been found except for settled fish:Coilia nasus.Two new records were collected:Tridentiger trigonocephalus and Microphysogobio microstomus.The number of species of migratory fish is significantly reduced except that rely on artificial enhancement or propagationthe(e.g.types of Hypophthalmichthys molitrix,Aristichthys nobilis,etc.).Fish such as Elopichthys bambusa and Luciobrama macrocephalus not found by investigation.There is a certain degree of spatial difference in the dominant species composition of fish.Fish such as Carassius auratus and Coilia nasus are dominant species at each monitoring point.In addition,two alien fish species,Ictalus portatus and Carassius auratus auratus,were captured at these monitoring points.The Loma Lake has suffered from invasion of alien fish species.The CPUE values of the catches at the six monitoring points were counted.From the seasonal point of view,the CPUE values of spring and summer frequency points were higher.From the spatial point of view,the CPUE values of the S4 and S5 points in different seasons are significantly higher than that of other points.The diversity indices of fishery resources were calculated.The results showed that fish diversity of the Luoma Lake had certain differences:Shannon-wiener biodiversity index of western regions(S3,S4,S5)were higher than eastern regions(S1,S2,S6).Shannon-wiener biodiversity index of the point S2 was significantly lower than that of other points.From the spatial extent of the Luoma Lake,the highest diversity index was detected in the point S3,the piont S5 and the point S4 followed relatively low diversity index,then there are lower diversity index in the pionts S1,S2and S6.The results of cluster analysis of the fish community composition at each point showed that the highest similarity between points S2-S3 and S1-S4.And the fish community composition between S6 and the other five monitoring points are significant different.The results also showed that fish such as Carassius auratus and Pseudorasbora parva are more evenly distributed at various points,and Squalidus argentatus,Saurogobio dabryi,Hemibarbus maculatus and so on have obvious spatial distribution unevenness.Most of fish are found in the monitoring points S1,S2,S3,and S4,and the fish populations are similar.The dominant groups of fish species in the Luoma Lake are concentrated in the young and small body-size individuals.Most of the small fish have small size difference and excellent population structure.Overall,currently the Luoma Lake is experiencing the problem of fish miniaturization and younger-age maturity.Coilia nasus is a dominant species in the fish community of the Luoma Lake and investigation on its diet composition contributes to understanding interspecific relationship and ecosystem structure of this lake.The dietary composition of Coilia nasus covered 29 small categories.Mainly feeding on zooplankton,a small amount of fish and shrimps.Its food composition has a certain spatial difference.The results showed that plankton and exogenous food in the Luoma Lake could support the productivity of silver carp and bighead carp for 135.99 kg/hm~2each year,benthic organisms(such as crustaceans,snails,aquatic insects,etc.)could support the productivity of omnivorous fish for 54.6 kg/hm~2.The reasonable stocking rate for silver carp is 76.5kg/hm~2,for bighead carp is 92.5 kg/hm~2,and for omnivorous fish is54.6 kg/hm~2in the Luoma Lake.In order to make better use of fishary and aquatic biological resources and protect aquatic ecological environment of the Luoma Lake,we need to establish a sustainable development and legal concepts,improve the ecological environment as well as to further improve the fishery management system,to achieve the goal of sustainable development of fisheries in the Luoma Lake.