SIX YEARS FROM FIRST RECORD TO POPULATION ESTABLISHMENT: THE CASE OF THE BLUE CRAB, CALLINECTES SAPIDUS RATHBUN, 1896 (BRACHYURA, PORTUNIDAE) IN THE NERETVA RIVER DELTA (SOUTH-EASTERN ADRIATIC SEA, CROATIA)

The data presented in this paper are based on the observation of 52 individuals of Callinectes sapidus Rathbun, 1896, collected in August and September 2010 by local fishermen using gillnets and traps in the area of the delta of the river Neretva (Croatian coast, south-eastern Adriatic Sea). Carapace width (CW) and carapace length (CL) frequency distributions indicate 3 age cohorts (modes) (CL: 7.2 cm, 8.4 cm, 9.0 cm; CW: 12.2 cm, 14.9 cm, 16.7 cm). The carapace width (CW)to- weight (W) relationship was calculated (for both sexes) as W = 0.816CW(2.281) (r(2) = 0.785). The current substantial records, the occurrence of ovigerous females and juveniles (observations by fishermen through visual census), as well as the fact that the species was regularly caught in the estuarine area, together constitute evidence of an established population of this species in the region investigated. In future, continuous monitoring of the C. sapidus population, the dispersal of the species in areas adjacent to the one now investigated, as well as all along the eastern Adriatic coast, will be necessary.