Contributions to the knowledge of the biology of the Arabian abalone haliotis mariae wood, 1828

Abstract EN

The Arabian abalone occurs ٨؛ the Arabian Sea's rocky coastal zone ٨؛ association with onspicuous macroalgal ''' in which it represents the dominant herbivorous component.

Despite such ecological importance and although the commercial exploitation of abalone presents a considerable contribution to Omani fisheries, almost nothing is known about the biology of this species.

This report presents results of research carried out in the field and with laboratory cultures, and draws general conclusions related also to the fisheries management of these possibly overexploited abalone populations.

Cohort observations in the field and measured increments of cultured specimens showed a growth rate ' higher than in other abalone species, i.e.

greater than 3 mm hcll-increment per month.

The very early sexual maturity demonstrated by captivity spawnings of approximately one year old animals is also quite unusual.

The ejected eggs formed mucous monolayers attached to the substratum whereas other abalone species produce pelagic eggs.

Juvenile cohorts in nature and the periodic spawning of cultured animals indicate the major spawning in spring and postmonsoon one in autumn.

The models previously applied in fisheries management of abalone in Oman assumed only one spawning per year - the first being at age 2+ - and a slower growth-rate.

These models should be reconsidered using the new data, which may partially explain why abalone are less overexploited than one would expect looking at heavy harvesting.

In view of a projected commercial abalone cultivation our laboratory rearing experiments showed that both natural and/or artificial food may be used, provided this contains -apart fiom standard ingredients - the seaweed-borne components (probably phycobillins) required for a normal parasite - resistant shell formation.

With regard to artificial reproduction, our preliminary trials showed that spawning, fertilization, and initial larval rearing present no problems.

The steps from the pediveliger to larval settlement, however, seem to be fatally exposed to c؛l؛ate attacks.

Further research is needed in order to eliminate this critical problem.