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/cm2, reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery.
