Seasonal and interannual changes of Indian oil sardine, Sardinella longiceps landings in the governorate of Muscat (the Sea of Oman)

Monthly data on Muscat's landings of the Indian oil sardine, Sardinella longiceps, along with 23 environmental parameters ( sea surface temperature, temperature of the mixed layer, wind speed, kinetic energy of mesoscale eddies, concentration of nitrates, dissolved oxygen, chlorophyll-a, abundance of phytoplankton, zooplankton, and several others) were analyzed for the period 1994-2011. Seasonal changes were associated with the time of the winter (Northeast) monsoon, with maximal landings in February. The multiple regression analysis of the statistically significant variables selected through the Principal Component Analysis has implied that 51% of seasonal variability in sardine landings might be approximated by the seasonal variations of the zonal component of wind speed and chlorophyll-a concentration in the coastal and open-sea regions. In terms of interannual changes, sardine landings exhibited a declining trend from 2001 to 2011 (the time covered by the most complete data set). Rising sea temperature, thermal stratification of the water column, and the trophic pressure imposed on sardine populations by large pelagic predators (talang queenfish, Scomberoides commersonnianus; kingfish, Scomberomorus commerson; longtail tuna, Thunnus tonggol; and some others) might be the factors mediating this trend.