The behavioural deficit of hatchery reared (HR) fish used for stock enhancement is the main cause of theirlow survival in the wild. In this study the effects of predator and shelter conditioning on survival and dispersalof HR white seabream (Diplodus sargus) released at sea were investigated. The hypotheses were that conditionedwhite seabream would avoid predators more efficiently and would be more capable to shelter,showing higher survival and smaller dispersal than naïve fish.Six thousand HR white seabream (6.32±0.93 cm total length) were allocated in twelve plastic tanks anddivided in four experimental groups: three groups were conditioned with a predator, a refuge or both,while one group was left unconditioned and used as a control. The conditioning phase lasted 30 daysand was conducted using live conger eels as predators and pyramids of perforated bricks as refuges. Flightinitiation distance (FID) and time to shelter (TS) were used as response variables to test the effects of conditioningin the arena, using a dummy conger eel. The effect of conditioning on post-release survival anddispersal was assessed through the monitoring of 1465 tagged seabream belonging to the four experimentalgroups, released at sea. Underwater visual census was used as monitoring technique. The sighting rate (SR)(sighted fish/ released fish×100) and the distance (D) of each sighted fish from the release site were usedas proxies for post-release survival and dispersion, respectively. In the arena, conditioned seabream showedsignificantly higher FID and lower TS than naïve fish. At sea, the estimated post-release survival of conditionedseabreams (SR=9.4%) was almost twice as much as that of naïve individuals (SR=5.5%). The dispersalof HR seabream acclimated to refuges from the release site (D=2.4±3.1 km) resulted lower thanin naïve fish (D=3.7±4 km). This study indicates that predator and shelter conditioning of HR whiteseabream is an effective practise to increase their post-release survival at sea, and our findings providesupport for effective stock enhancement initiatives.
|Numero di pagine||7|
|Stato di pubblicazione||Published - 2012|
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