Biodiversity And Biological Characteristics Of Dominant Fish Species Of Typical Reef Fishes In South China Sea

Coral reef ecosystems are rich in species and highly productive,and are known as the‘rainforests’of the oceans.Coral reef fish is an important component of coral reef ecosystem and a key biological group to maintain the health of coral reef ecosystem.With the continuous impact of global climate change and anthropogenic activities,coral reef fishes are facing a rapidly decline all over the world,which has attracted extensive concern of the international community.Coral reef is a unique ecosystem in the south China sea.With a high degree of biodiversity and productivity,coral reef ecosystem is a‘hotspot’area for biodiversity protection in China.Understanding the biological characteristics of the diversity and dominant species of reef-dwelling fishes is the basis for the conservation and management of coral reef fishery resources.Based on survey data since 1999 and historical data from the 1970s,systematically summarized the species composition of Zhubi reef and Qianlianyu island,and by using taxonomic diversity index and G-F index the diversity measure index analysis of the coral reef fish species composition and biodiversity.In order to further understand the structural characteristics of reef-dwelling fish communities on Zhubi reef in spring and summer,a preliminary study on species composition,seasonal variation of dominant populations,dietary characteristics and diversity of Zhubi reef fish communities was conducted based on the fishery resources survey conducted on Zhubi reef in spring and summer of 2018.On this basis,a preliminary study was conducted on the body length and body mass,sex ratio and sexual maturity,feeding intensity,fatfulness,age and growth of Epinephelus merra,the dominant species of reef-dwelling fish,according to the samples taken from Nansha and central Xisha waters in 2018-2019.The main conclusions are drawn as follows:（1）Taxonomy and diversity of fish species in Zhubi Reef.There are 152species of 43 families,93 genera and 11 species of reef fish in the Zhubi Reef.Among them,the Perciformes fish accounted for an absolute advantage（76%）;TheΔ⁺of the Zhubi Reef fish is 58.75,andΛ⁺is 102.60.Compared with the composition of fish communities in different ecosystems at home and abroad,it is found that theΔ⁺of the fish in the Zhubi Reef is higher than that of Zhaoshu Island,Milne Bay and San Jose Island,lower than the East China Sea Shelf,the South China Shelf of the Nansha Islands,the Beibu Gulf and the Daya Bay.Λ⁺is lower than other islands.It is indicated that the genetic relationship between the species of the Zhuubi Reef fish community is closer than that of the East China Sea shelf,the southwest shelf of the Nansha Islands,the Beibu Gulf and Daya Bay,but farther than Zhaoshu Island,Milne Bay and San Jose Island.In Zhubi reef,the main features of fish diversity is the higher species diversity and lower taxonomic diversity.（2）Diversity of fish species in qilianyu island.The 175 fish species were collected from Qilianyu islands belonging to 8 orders,33 families and 70 genus.Perciformes were the most abundant species,which accounting for 81%of the total number of fish species.The average classification difference index（Δ⁺）is about 54.19,and the classification difference variation index（Λ⁺）is about 112.35,Compared with the fish community composition in different regions at home and abroad,it is found that theΔ⁺of the Qilianyu fish is lower than the East China Sea shelf.Daya Bay and Zhubi Reef,whileΛ⁺are lower than the East China Sea Shelf and Daya Bay,higher than the Zhubi Reef;The average grade-of-diversity index（F-index）was 6.23,which is a diversity index.The（G-index）average was 3.09,and the normalized G-F index average was 0.40.The above results indicate,the classification of species in the fish community of Qilianyu is higher,and the genetic relationship is closer than that of the East China Sea Shelf,Daya Bay and Zhubi Reef.From the perspective of G-index,F-index and G-F index,the species diversity of the reef-bearing fishes in Qilianyu is relatively high,and the distribution of families and genera is reasonable and has important protection value.（3）Structural characteristics of reef-dwelling fish communities in spring and summer on Zhubi reef.The 45 species of coral reef fish caught in the spring and summer of the Zhubi Reef,belonging to 5 orders,14 families and 25 genera,of which the scorpion shape dominated,accounting for 80%of the total catch species.The dominant species has obvious seasonal changes.Fish with a relative importance index（IRI）greater than 500 is considered a dominant species,The dominant species in spring are mainly Pentapodus caninus,Epinephelus merra and Scolopsis margaritifer,The dominant species in summer are mainly Epinephelus merra,Gnathodentex aureolineatus,Lutjanus kasmira,Pentapodus caninus,Cheilinus chlorourus,Parupeneus trifasciatus,Cephalopholis leopardus,and Scolopsis affinis.there were obvious seasonal changes in dominant species.In spring and summer,the characteristics of fish feeding functional groups changed obviously,and omnivorous fish was dominant,indicating that the fish community structure had responded to the change of water quality.Moreover,the diversity level of fish community was higher in spring and summer,and the diversity index in summer was higher than that in spring.（4）The biological characteristics of Epinephelus merra in the South China Sea.The dominant species for reef-dwelling fishes in the Nansha and Central and Western Sands—Epinephelus merra body length and weight,sex ratio and sexual maturity,feeding intensity,fullness,age and growth preliminary study of the scientific characteristics was carried out.The results showed that the body length of honeycomb grouper in Nansha and Zhongxisha waters ranged from 62 to 195 mm,and that of the dominant grouper group ranged from 80 to 140 mm,with an average body length of113.86 mm.The body mass ranged from 6.15 to 132.98 g,with an average body mass of 35.07g.The body length distribution of both male and female groupers in the two regions was significantly different.Gonad maturity is given priority to withⅡperiod,each month the female gonad maturity ratio are higher than the male,the first sexual maturity length 187.96 mm.The main feeding grade was 1.The mean fatness of the two regions was 2.24 and 2.02 respectively,and there was no significant difference in the mean fatness.The relationship between body length and body mass was 2.7835and 2.5925,respectively.Among the 59 otolith samples,the age ranged from 1 to 6years.The dominant age group was 1～2 years,accounting for 64.29%.The growth parameters of the von Bertalanffy growth equation are L∞=162.4mm,k=3.0,and t₀=-0.253.