Spatial and temporal distribution of narwal shrimp Plesionika narval (Decapoda, Pandalidae) in the Aegean Sea (eastern Mediterranean Sea)

In the Aegean Sea the trap fishery for narwal shrimp, Plesionika narval, contributes to social and cultural cohesion of local fishery communities. Spatial and temporal distribution patterns of narwal shrimp was studied during an annual cycle, including catch per unit effort (CPUE), sex ratio and proportion of ovigerous females in the population. Shrimps were sampled at five localities within the depth range of 10 to 170 m. Catch per unit effort increased during the summer period at all depths, when seawater temperature increase. Differences in CPUE were observed between depths, with highest catches at depths below 70 m. The proportion of females decreased significantly with depth, a pattern especially evident during the summer period (May to August), indicating a migration of females to shallower waters. Significant higher abundance of ovigerous females was observed during the period May to October, concurrently with a vertical migration of females to warmer waters. To further support this pattern, the proportion of ovigerous individuals among females increased with decreased depth at all seasons. We suggest that the findings of our study have significant implications to current and future management of narwal shrimp in the Mediterranean Sea.