gems, pearl, Ceylon, Sri Lanka, Gulf of Manaar

Examines the irregularity of Ceylon’s pearl fisheries and assesses whether biological management could make them annually productive. Drawing on more than fifteen years’ experience and reviewing investigations by Herdman, Hornell, and Southwell, Pearson challenges explanations centred on predatory fishes, encroaching sand, and overfishing. He acknowledges that rays and shifting sand can destroy oyster beds but finds insufficient evidence that they explain the fisheries’ prolonged interruptions. Proposed remedies, including intensive trawling, protective wire netting, laying attachment material, and transplanting young oysters, are considered economically impracticable. He also rejects accusations of overfishing, arguing that traditional diving leaves substantial breeding stocks and that unharvested oysters may die before a fishery can be organized. Pearson instead attributes the fundamental uncertainty to the geography of the Gulf of Mannar banks and the dispersal of free-swimming oyster larvae. Suitable rocky grounds occupy a narrow shelf bordered by extensive sand, deep offshore water, and unsuitable coastal shallows; currents and monsoon conditions can therefore carry larvae away from places where they could settle successfully. The resulting variability in spatfall explains why abundant breeding stocks do not ensure future harvests. He concludes that available scientific methods cannot control these conditions and that intermittent fisheries are likely to persist.