Periodic, spatially structured matrix model for the study of anchovy (Engraulis encrasicolus) population dynamics in N Aegean Sea (E. Mediterranean)

The development of a periodic, spatially structured population matrix model for the study of North Aegean Sea anchovy population structure and dynamics is presented on the basis of its life-cycle, and the ecosystem environmental features. System heterogeneity and species life-cycle leaded to model development on seasonal scale and sub-regional basis, incorporating survival, fecundity and migration rates. Several methodological aspects concerning the periodic dynamics on a seasonal basis combined with the existence of spatial heterogeneity and age—season specific migration patterns are examined and discussed. Special attention is devoted to a possible inflow of recruits originated from Black Sea Waters, introducing a “source-sink” effect in the model and resulting in reducible projection matrices. The model also accounts for a possible outflow from the study area, structurally implemented by another virtual “sink” sub-area incorporation. A first attempt was made to calibrate the model using parameters provided by older studies and original data provided by the ANREC project focused on the anchovy—environment interactions and carried out in the area. Then the model was used to check the efficiency of various fishing limitations in space and/or time and the results confirmed the importance of the fishing activity over the spawning grounds.