Spatial and temporal distribution of Sciaenid species in Dachen Island

The Sciaenid species play essential roles in rocky reef area due to their large quantity of biomass. They are also important target fishes for the marine ranching programs in coastal area. We explored the temporal and spatial patterns of the Sciaenid species in the waters around Dachen Island based on data from 4 seasonal bottom trawl surveys in summer (Sep. 2020), autumn (Nov. 2020), winter (Jan. 2021) and spring (Apr. 2021) . This study examined 17 640 Sciaenid species individuals collected from 21 sites. Biological characteristics of Sciaenid species, including body length, body weight and the developmental stages were statistically analyzed using indices such as resource density, relative importance index and GIS spatial analysis. Regression analysis was explored to reveal the relationship between the abundance and environmental factors. The results showed that a total of 11 Sciaenid species were collected over four seasons, with significant seasonal variation in the dominant species and spatial distribution differences between different developmental stages of the same species. The population density of Sciaenid species were the highest in summer and the lowest in Autumn. Pennahia macrocephalus and Larimichthys polyactis dominanted in summer, the highest abundance of young fishes of the P. macrocephalus and the L. polyactis were found in the open ocean. Collichthys lucidus dominanted in autumn and winter, the highest abundance of adult fishes were found in autumn in the reef island area while the highest abundance of juveniles and young fishes were found in winter in the open ocean. L. crocea were found to be dominant species in spring, the highest abundance of juvenile and young fish were found in the near estuary area. Regression analysis indicated that temperature and salinity were important environmental factors influencing the distribution of croakers. Adaptation to temperature and salinity varies between developmental stages of the same fish species. Our results elucidated that (1) there were significant regional differences and seasonal dynamics in the local scale of the Sciaenid species in the Dachen Island area. (2) The island sea plays an important role in Sciaenid species early resource conservation. (3) We speculated that the L. crocea have formed a recruit population in the Dachen Island area. The study suggest that, for the protection of the early resources of Sciaenid species, the scope of the Dachenyang spawning ground reserve should be expanded to the near-estuarine area on the basis of the original reserve.