LARVAL SETTLEMENT AND JUVENILE SURVIVAL IN THE RED ABALONE (HALIOTIS-RUFESCENS) - AN EXAMINATION OF INDUCTIVE CUES AND SUBSTRATE SELECTION

Settlement and metamorphosis of red abalone, Haliotis rufescens, larvae were examined in the presence of three inductive settlement cues (conspecific mucus, a sympatric diatom assemblage, and gamma-aminobutyric acid). All experiments were conducted without the use of antibiotics. Larval settlement success differed significantly with substrate type. Mucus from juvenile H. rufescens yielded the highest levels of successful larval settlement. Larval settlement success varied and was highest between August and mid-September when examined from late spring (May) to early winter (December). Larval metamorphosis and juvenile survival to appearance of the first respiratory pore also varied with substrate type. After 11 weeks, approximately 53, 84, and 100% of the larvae had suffered mortality on substrates of conspecific mucus and diatoms, diatoms, and gamma-aminobutyric acid and diatoms, respectively. In all treatments, an initial high rate of juvenile mortality and reduced rates of juvenile development suggested abalone were nutrient-limited. High larval settlement rates and survival of juvenile H. rufescens on substrates of conspecific mucus indicate that this inductive cue may be of significance in situ as well as offering a convenient methodology for the rearing of red abalone in mass-culture systems.