Spatial and temporal distribution of small yellow croaker (Larimichthys polyactis) in Eastern Ma'an Archipelago

Fish tends to use different habitats in different life cycle stages. A comprehensive understanding of habitat selection strategy by fish plays key roles in polulation protection, utilization, target species selection as well as on stock enhancement in marine ranching programs. Based on the bottom trawl survey in summer (August, 2016), autumn(December, 2016), winter (March, 2017) and spring (May, 2017) in Eastern Ma’an Archipelago, we examined 3496 Larimichthys polyactis individuals collected from 19 sites. Biological characteristics of small yellow croaker, including age structure, sex ratio, sexual maturity and the food composition were statistically analyzed using indices such as resource density, relative importance index and GIS spatial analysis. Regression analysis was performed to reveal the relationship between the biological parameters and environmental factors. Our results showed that the population of small yellow croaker in the Eastern Ma’an Archipelago expressed a strong seasonal variation and spatial difference:the population density of small yellow croaker was the highest in summer. There was a higher population density in the areas adjacent to islands than that in the areas off islands. In terms of age structure, 1-year-old small yellow croaker dominanted allmost all seasons except for summer, when 0-year-old small yellow croaker accounted for 75. 7% of the toal. Contrary to spring and autumn, the preys richness for small yellow croaker in areas adjacent to islands was significantly higher than that in areas off islands in summer. Regression analysis indicated that the primary productivity in the areas off islands was the most significant factor(p<0. 05). Correlation analysis revealed that higher abundance of phytoplankton contributed to higher population density of small yellow croaker. However no such significant correlation was tested in the areas adjacent to islands. The research revealed that in Eastern Ma’an Archipelago, large scale of reefs and artificial habitats, provide suitable habitats for small yellow croaker as feeding, breeding and sheltering ground. Small yellow croaker in the areas adjacent to islands didn’t show obvious preference for specific environmental factors except for the food factor, but showed a certain preference for the habitats constituted by various environmental factors in the areas adjacent to rocky islands.