Genetic population diversity of European eel Anguilla anguilla elvers in two Egyptian water bodies, Rosetta (Rachid) estuary and Burullus Lake

The European eel Anguilla anguilla is a species of great economic importance for Egypt. Its long trans-Atlantic migrations for semelparous spawning then larval homing provides a possible way for worldwide mixing of populations. Its natural habitats in Egypt, as in other Mediterranean countries, are under heavy load of pollution due to anthropogenic activities. Hence, a major priority should be given to assess the genetic diversity within/among eels' populations as a step towards revealing populations' status, identification of possible conservation units, and, subsequently, implementation of proper conservation and management strategies for them. For this, A. anguilla elvers were collected from Rosetta estuary and Burullus coastal lagoon in the North of Egypt. Sequencing of the barcode region of the cytochrome c oxidase subunit 1 gene (COI) was carried out for all collected elvers. The sequences were analyzed using various genetic, phylogenetic, and population analyses to assess their variability. A total of 33 haplotypes were identified, 14 of which were unique to Burullus Lake, and 11 to Rosetta estuary. Very low fixation (F-st = 0-0.04) was found for A. anguilla populations in Egypt and worldwide, except for the Turkish and Czech ones (F-st = 0.47-0.62 and 0.18-0.41, respectively). Both Egyptian populations showed signs of recent populations' expansion, besides low, non-significant raggedness values. The results suggested Burullus Lake and Rosetta estuary as separate conservation units for A. anguilla in Egypt. These units require special attention for proper protection and management of the existing eel diversity and permitting sustainability in the activities dealing with eel's fishing and aquaculture.