Releasing of hatchery-reared
juveniles of the white seabream Diplodus sargus (L., 1758) in the
Gulf of Castellammare artificial reef area (NW Sicily)
G. D'Anna, V.M. Giacalone , F. Badalamenti, C.
Pipitone-2004
Aquaculture, 233(1-4): 251-268
Abstract:
A pilot experiment of marine ranching using
hatchery-reared juveniles of white seabream, Diplodus sargus, was
made in the Gulf of Castellammare (NW Sicily). The research aimed at
evaluating (i) if artificial reefs are suitable for the settlement of reared
young seabreams, (ii) what are the main causes of mortality and (iii) the
growth rate of released fishes in the open sea. A total of 6930 tagged
cultured juvenile white seabreams (305 days old) were released in an
artificial reefs (AR) area. Underwater visual census, sightings and
recaptures were used as a source of data for estimating abundance and size
of released fishes. The survey lasted 15 months and was carried out in
artificial (AR, breakwaters and harbours) and natural (river mouths, rocky
bottoms and Posidonia oceanica meadows) coastal habitats of the Gulf.
A few days after the release, more than 90% of the tagged seabreams left AR
and moved mainly towards harbours and breakwaters, which resulted to be
particularly suitable for their settlement and growth. The recapture was
8.2% of the released stock. During the first days after releasing, the main
ascertained sources of mortality were professional fishing (6.7%) and
predation by conger eel, Conger conger (1.1%). A behavioural deficit
of the reared seabreams in the use of refugia and food was observed in the
initial period following the release. The results obtained provide some
management suggestion for the feasibility of marine ranching initiatives
involving hatchery-reared fishes.