The Biodiversity of Pelagic Fish Caught by Purse Seines in Tripoli, northern Lebanese Coast.

This study highlights for the first time the biodiversity of fish assemblages in purse seine fisheries in the Tripoli region, north of Lebanon. A total of 925 specimens from 17 species of 11 families were identified and studied from the monthly samples collected between April and November 2017. The catch was dominated by 3 families (Clupeidae, Engraulidae and Dussumieriidae) in varying abundances. Seasonal variation of abundance was detected with Sardina pilchardus (32%) in Spring, Engraulis encrasicolus (56%) in Summer and Sardinella maderensis (58%) in Fall. Weight length relationships (W=aLb ) were estimated for the most abundant species, and they show a positive allometry for Engraulis encrasicolus (b=3.276), as well as, Herklotsichthys punctatus (b=3.477), and a negative allometry for Sardinella aurita (b=2.886). Seasonal diversity was evaluated and the highest diversity was observed during the spring season following Shannon Index (H’=1.44), Pielou evenness (J’=0.74) and Simpson Index (1-D=0.74). The Shannon Index differed from one season to another reaching the highest value in Spring. Despite the progress in studying diversity and abundance, variation in pelagic fish catches is evident in Lebanese sea water, where a management plan for purse seine fisheries should be applied under the framework of ecosystem approach to fisheries.