Abstract: We analyzed the temporal and spatial distribution of jack mackerel (Trachurus japonicus) in the offshore northern South China Sea, based on the eight-cruise data of the offshore fishery resource survey in the northern South China Sea from 2014 to 2017 and remote sensing image data, including sea surface temperature, sea salt surface mass concentration, and chlorophyll concentration. We established habitat suitability index (HSI) model for each season with utilization of maximum model, minimum model, arithmetic mean model and geometric mean model separately. The catch per unit effort (CPUE) was used as suitability index (SI). The accuracy of each model was tested. The results showed that each SI model fitted accurately and had a normal distribution. Geometric mean model was better for habitat modeling, with an average accuracy of 92%. The area of high biomass mainly distributed in area with HSI more than 0.6, and the other area of high HSI would be potential fishing grounds. Results from principal component analysis showed that sea surface temperature was the most significant factor affecting the distribution of offshore jack mackerel. Our results indicated that HSI models can be used to analyze abundance and spatial distribution of offshore jack mackerel resources in the northern South China Sea.

Key words: nutrient limitation, grassland degradation, C:N:P stoichiometry, alpine meadow, soil extracellular enzyme.