Relationship between spatiotemporal distribution of chub mackerel and marine environment variables in the waters near Mauritania

Abstract:

From data collected at 112 sites in waters near Mauritania from September 20th to December 31st, 2017, the relationship model based on Quantile Regression method was established using 78% randomly selected sites between catch per unit effort(CPUE) of chub mackerel (Scomber japonicus) and environmental factors such as chlorophyll-a concentration, sea surface temperature and sea surface salinity, and the predicted CPUE model was validated by the remaining 22% site data, then General Additive Model (GAM) was used to evaluate the impact of environmental factors to CPUE. The integrated habitat index (IHI) of chub mackerel in the waters near Mauritania was calculated. The predicted CPUE values of the modeled and validated sites were tested by Wilcoxon test. The predicted CPUE values were tested by Spearman correlation and double tail tests. The relationship between IHI and CPUE was analyzed. The results showed that:the most significant environmental factor affecting CPUE of chub mackerel was sea surface temperature, followed by the interaction between temperature and salinity and sea surface salinity, while chlorophyll-a concentration had no significant effect on CPUE; there were no significant differences between the predicted CPUE and the nominal CPUE of the modeled sites or the verified sites; the IHI model had good predictive ability on CPUE of chub mackerel; the higher IHI were defined in the areas of 17°25'W-17°45'W and 20° 15'N-20 °45'N. It was suggested that the Chinese fishing vessels should concentrate their fishing efforts in this area on the second half of the year in order to increase their catch.