Production of Akoya pearls from the Southwest coast of India

Abstract

The Indian pearl oyster Pinctada fucata (Gould) is typically capable of producing pearls of 3-5 mm diameter. The feasibility of production of pearls similar to Akoya pearls of 6-8 mm diameter was studied from the southwest coast of India. Along with this, mortality and retention rates of implanted oysters, rate of nacre production, thickness of nacre deposited, quality and type of pearls produced and effect of hydrographic variations on the mortality of implanted oysters were also studied. A total of 706 oysters were implanted, 311 with 5 mm, 395 with 6 mm nuclei and stocked in 30 cages for a period of 317 days. The mortality rates were highest, 0.173 ± 0.22 for the 6 mm nucleus implanted oysters followed by 5 mm nucleus implanted oysters at 0.107 ± 0.025 during the first 30 days after implantation. These rates were significantly different (P b 0.05) from the mortality rate of the control oysters (0.042 ± 0.04). The retention rates based on the surviving oysters, ranged from 33 to 61% (average 45.9 for 5 mm) and 31 to 60% (average 48.9% for 6 mm). The nacre deposition rates on the nuclei were found to be 4.0 ± 1.0 μm day − 1 and 3.0 ± 1.0 μm day − 1 for 6 and 5 mm nuclei respectively. Of the total 131 pearls obtained, 27.6% were A-grade, 31.3% B-grade, 19.8% C-grade, 7.6% baroques and 13.7% rejects or trash. The total suspended solids (TSS) in the water were found to be positively correlated (P b 0.05) with the monthly mortality rate of the implanted oysters. The study showed that it was possible to obtain relatively thick nacre within a short period of 10 months, the deposition rate being about 9 times higher than that observed in Japanese waters and 2.2 to 2.3 times more than that along the Indian southeast coast.

Heritable Characteristics in the Pearl OysterPinctada martensii: Comparisons of Growth and Shell Morphology of Chinese and Indian Populations, and Reciprocal Crosses

“…Both species are deficient in terms of appropriateness for nucleus implantation. The thin, fragile shell of the Indian cultured population complicates implantation and discourages attempts to produce pearls larger than 5 mm (Kripa et al 2007), whereas the long culture period and small size of the Chinese population increases the costs of commercial production. Interestingly, through crossbreeding, the desirable characteristics-such as large size and fast growth of the Indian population, and large relative thickness of the Chinese population-were inherited by the reciprocal crosses, and undesirable traits were reduced.…”

“…In this experiment, Indian and Chinese populations differ in morphology and growth rate, and are complementary in SH and ST. The Indian cultured population is large and fast growing; however, its shells are rather thin and fragile, and easy to crack during implantation, thus it is impossible to produce pearls larger than 5 mm (Kripa et al 2007). In comparison, as observed by local farmers, the local Chinese population has thick, tough shells, but it is small and has a low growth rate, and hence is unfit for the implantation of large nuclei.…”

“…If the nuclei are larger, oysters should be larger, too (Gu et al 2009). In addition to SH, ST is another criterion, because oysters with thin shells are unfit for implantation of large nuclei (Kripa et al 2007). In this experiment, Indian and Chinese populations differ in morphology and growth rate, and are complementary in SH and ST.…”

“…It is commercially cultured in Japan, China, India, and Vietnam (Southgate & Lucas 2008) for the production of round pearls, popularly known as ''Akoya pearls.'' These pearls are 5-10 mm in diameter and are most widely used in necklaces, especially the 14-16-inch choker and the 17-19-inch princess (Kripa et al 2007). In China, P. martensii oysters were introduced from Japan to China in the 1960s and have been cultured for more than 40 y in 3 southern coastal provinces: Guangdong, Guangxi, and Hainan.…”

Seasonal Fouling Stress on the Farmed Pearl Oyster, Pinctada fucata, from Southeastern Arabian Sea

“…During the last decade, attempts were made to farm the pearl oysters along the southwest coast of India in the Arabian Sea. Studies have shown that Port Kollam along the southwest coast of India is a potential site for pearl farming based on the fast growth rate (Mohamed et al 2006) and nacre deposition rates (Kripa et al 2007). During the pearl farming experiments at Kollam Bay, biofouling was found to be a problem and preliminary observations indicated that foulers settling on the oysters were different from those along the southeast coast and also that fouling is not uniform due to considerable temporal variation in the fouling biomass and species dominance.…”