Assessing the Impact of Temperature and Chlorophyll Variations on theFluctuations of Sardine Abundance in Al-Hoceima (South Alboran Sea)

Landings of small pelagic fish in Moroccan Mediterranean Sea show large fluctuations and trends, a fact that has a considerable socio-economic impact. These changes are often related to the impact of the environmental conditions on recruitment processes. We investigate fluctuations of the sardine’s abundance at one of the most important fishing areas of the Moroccan Mediterranean Sea (i.e., Al-Hoceima region) and try to assess the impact of environmental changes on the availability of pelagic fish in this area. In these regards, we analyzed Seasonal and Trends Loess’ (STL) decomposition of time series between 2008 and 2015 of catch-per-unit-effort (CPUE) data along with environmental parameters (i.e., sea surface temperature and chlorophyll-a) from remote sensing and we applied nonlinear models (GAM). Results show an inverse relationship between fluctuations of sardine CPUE and sea surface temperature. Nonlinear relationships confirm that the temperature is the most important parameter affecting abundance, whereas chlorophyll-a, is generally, weakly correlated to the CPUE data at monthly and seasonal level variations, except for annual trends. The analysis also shows positive trend of chlorophyll-a, from 2003 and a negative one starting from 2011, revealing an inter-annual variability that support fish landings fluctuations. Modeling based on the relationships between the CPUE and temperature/chlorophyll-a, allowed better prediction of the sardine abundance in the Al-Hoceima fishing area (South Alboran Sea).