The combined effects of water temperature and salinity on the settlement rate and density (spats/cm 2 ) of Crassostrea gigas pediveliger larvae were studied under the hatchery conditions. Four water temperatures (20.0, 23.0, 26.0 and 29.0℃) were tested at three salinities (20.0, 30.0 and 40.0). The optimum water temperature by salinity conditions were 29.0℃ and 20.0, 30.0 which significantly (P < 0.05) the highest mean (±S.D) larval settlement rate of 43.1 ± 0.1%, 42.1 ± 0.1%, respectively. But the combination of water temperatures and salinities for settlement density was not effected, but each factor as water temperature (29.0℃), salinity (40.0) was shown significantly high and low settlement density, respectively (P < 0.05). The statistics result of settlement density frequency was appeared: mode (1.2-2.3 spats/cm
We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), γ-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of 42.7 ± 2.7%, followed by GABA (35.4 ± 2.0%), 5-HT (29.1 ± 2.2%), L-DOPA (19.2 ± 2.1%), epinephrine (15.2 ± 0.9%), and norepinephrine (11.0 ± 1.2%). The chemicals γ-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of 1.97 ± 1.42 and 2.37 ± 1.86 ind/cm 2 , reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery.
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