Size-weight relationships and condition factor of the invasive Atlantic blue crab Callinectes sapidus Rathbun, 1896 (Decapoda: Brachyura: Portunidae) from northern Tunisia: a preliminary investigation

We determined the condition factor and relative growth patterns of the newly established invasive Atlantic blue crab Callinectes sapidus in the Ghar El Melh Lagoon, northern Tunisia, central Mediterranean Sea using two biometric relationships: carapace width-weight and carapace length-weight. Crabs were sampled (luring winter and summer 2020. Growth coefficient (slope b) for width-weight relationship ranged from 2.037 to 3.008 according to sex and seasons, indicating an isometry to negative allometry growth patterns. Length-weight relationship, however, demonstrated isometry growth patterns, with the exception of the summer sample, which displayed a positive allometry. The allometry seems to be not affected by seasons, but sex demonstrated a strong effect for the width-weight relationship, as indicated by ANCOVA. The Fulton's condition factor, however, showed significant variation between seasons, but not between sexes.