The effect of stocking density, temperature and light on the early larval survival of the abalone Haliotis asinina Linné

Newly hatched trocophore larvae of the abalone haliotis asinina linne were stocked at densities of 1000, 3000 and 5000 larvae/1 at low (20-25oC) and high (ambien, 28-30oC) water temperature levels in light (transparent) and dark (black cloth-coered) lass container. Larvae were reared in UV light-irradiated sea water until pre-settement stage. Aeration was not provided during the 20-h incubation periond. A 3x2x2 factorial design with three replicates per treatment was folloed. A three-way analysis of variance (ANOVA) showed a significant interaction among the factors tested. Analysis at each density level showed that at stocking density of 1000 larvae/1, no significant difference between temperatures and between light or dark condition was observed. However, at densities of 3000 and5000, significantly higher survival was obtained at low, than high temperature (P<0.05), but no difference between the light and darck conditions. Analysis at each temperature showed that, at high temperature,better survival was obtained at stocking density of 1000, than higher densities (P<0.001), and at light than at darck condition (P<0.05). However, at low temperature, no significant difference between light abd darck conditions was detected. ANOVA at light or darck condition showed that at any of these conditons, larvae survival was always higher at 1000 stocking density that t other density (P 0.05). Survival was not significntly different between stockng density of 3000 and 5000 larvae/1 at any of those light conditions. Theredore, during incubation of newly hatched trocophore larvae of H. Asinina to pre-settlement stage, the optimum stocking density at high temperature (28-30oC) was 1000/1, in a light-penetrable rearing container. When reared at higherstocking densities of 3000 or 5000, a higher survival was obtained when temperature was lower to 20-25oC in either rearing conditions tested

Response of the tropical abalone, Haliotis asinina, larvae on combinations of attachment cues

The effects of different diatom species and types of substrates in combination with 0.45 μM GABA on the metamorphosis of Haliotis asinina larvae were tested. Diatom slurry elicited the best metamorphic response followed by Amphora sp., Amphora + Nitzschia and Nitzschia cf. frustulum in that order. With regards to substrate types, roughened plexiglass seemed to be the most preferred while fibrocement the least preferred surface. Overall, diatom slurry grown on plexiglass surface promoted the greatest number of metamorphosed H. asinina postlarvae. For economic considerations and practical reasons, chemical inducers like gamma-aminobutyric acid (GABA), should be used singly or separately from other settlement-inducing cues, such as the “substrate-diatom” complex.We thank R. Sañares for the statistical advice, N. Bayona, B. Boja, and F. Sumalinog for the technical assistance and the anonymous reviewers for their constructive comments on the manuscript. The financial support of SEAFDEC/AQD under Study Code Nr-01-M98T is gratefully acknowledged

Induction of larval settlement and metamorphosis in the donkey-ear abalone, Haliotis asinina Linnaeus, by chemical cues

The effects of the chemical inducers, gamma-aminobutyric acid (GABA) and potassium chloride (KCl), on the larval settlement and metamorphosis of the donkey-ear abalone, Haliotis asinina, was investigated. H. asinina larvae (5–6 h post-hatch) were exposed to a range of GABA (0.125–2.00 μM) and KCl (1.00–12.00 mM) concentrations for 72 h. Results of the dose response experiments showed that settlement and metamorphosis vary according to the dose levels of the inducer compounds. Under controlled laboratory conditions, 0.45–0.50 μM and 6.0 mM seemed to be the optima for GABA and KCl, respectively, as these concentrations elicited the greatest number of postlarvae that metamorphosed, settled or survived. However, GABA generally promoted better attachment and metamorphic response as well as survival than KCl in H. asinina postlarvae.The authors thank N. Bayona for the technical assistance, Dr M. Catacutan for the helpful comments on the earlier draft and the two anonymous referees for critically reviewing the final version of the manuscript. This research work was financially supported by SEAFDEC/AQD under Study Code Nr-01-M98T