Study On Trophic Structure And Ecomorphology Of Stream Fish Community In Nanling

There is a unique stream ecosystem in Nanling region of Guangdong Province.This paper studies the fish community living in it,focusing on the relationship between the fish community and the environment,the analysis of fish morphology,the analysis of fish feeding ecology and the analysis of ecological morphology,for providing theoretical data and scientific basis for the protection of species diversity.The main results are showed as follows:1.A total of 1537 fish specimens were collected,which were identified as belonging to 3 orders,8 families,28 genera and 37 species.Among them,Cyprinid fishes were the dominant species in Nanling area,accounting for 54% of the total,with 16 genera and 20 species in 6 subfamilies.The correlation analysis of environmental factors showed that there was a significant correlation between dissolved oxygen and flow velocity,and there was no significant difference between fish abundance and environmental factors in streams in the six regions.The redundant analysis of fish environmental requirements and environmental factors showed that fish in Nanling area live benthic,omnivorous,multi-terminal or lower mouth,like rock bottom,like torrent,and the dominant species like high water temperature,high oxygen content,fast flow rate.2.Based on standardized morphological data,morphological analysis,comparison and clustering of 23 species of fish community in Nanling Stream were carried out.The results showed that there was a power function correlation between body length and body weight of the five dominant fish species.The more community in small and medium-sized fish,the Silurus cochinchinensis Cuvier and the Hemiculter leucisculus for big fish.The morphological differences of fish are mainly affected by the receptor width,fin length,mouth area,caudal stalk,gill pedicle length and head length behind the eyes.Most closely related fish are grouped into groups based on morphological characteristics.3.The feeding habits of 17 fish species in the fish community in Nanling Stream were analyzed,and the food composition was compared and analyzed with the weight index,which could represent the food composition well.The results showed that 17 species of fish could be divided into herbivorous fish,omnivorous fish and carnivorous fish.The mean values of dietary diversity of fish were 9.5,3.02 and 2.28,respectively,with niche widths ranging from 0.05 to 0.38,and fractional trophic levels ranging from2.12-3.10.According to the dietary overlap index,there is a significant dietary overlap between the Acrossocheilus parallens and the Parazocco spilurus spilurus,the Puntius semifasciolatus;the Varicorhinus lini Wu and the Parazocco spilurus spilurus,the Puntius semifasciolatus,and the Acrossocheilus beijiangensis.There is a significant dietary overlap between the Ctenogobius giurinus and the Ctenogobius cervicosquamus.According to the weight index,the fish community was divided into two trophic common groups and the food web structure was constructed.4.The ecomorphologic analysis of 17 species of fish in the community was carried out,and the fish community was divided into 3-guild nutrient common group according to the nutrient value,and 5-guild nutrient common group according to the non-metric multidimensional order of food weight index.Generalized linear model(GLM),linear discriminant analysis(LDA)and redundancy analysis(RDA)were used to analyze the relationship between nutrient values and morphological characteristics and the two classifications(3-guild and 5-guild).The results showed that 5-guild(94.22%)was better than 3-guild(92.15%)in explaining the proportion of nutrient value changes.Morphometric prediction accuracy of these two classifications was consistent,and they played an important role in food selection of fish(73.82%).The fish community in Nanling Stream has rich species diversity,and the environmental factors are interrelated.The morphology of fish in the community is diverse,and most of the closely related fish show morphological similarity.The analysis of feeding habits and the construction of food web revealed the nutrient structure of fish community in Nanling Stream.In terms of feeding structure or selectivity,5-guild is more suitable to reflect food structure,and morphological characteristics can well reflect the two feeding classification schemes(3-guild and 5-guild).Some morphological characteristics of fish are related to feeding selection of fish.The research provides theoretical and scientific basis for rational utilization of fishery resources and species protection.