The winged pearl oyster, Pteria penguin, is cultured primarily to produce half‐pearls (mabé). The mabé quality is influenced by culture techniques, but there is limited information in this field. P. penguin with mean (±SE) dorso‐ventral height of 250 ± 6.5 mm were used to investigate the influence of culture period and nucleus position on mabé quality. Oysters were relaxed using 1‐propylene phenoxetol, and five nuclei were glued at different positions to the inner surfaces of the oyster shells; three on the more concave left valve and two on the right valve. Nucleated oysters were then cultured for 10 months under commercial pearl farming conditions at Savusavu in Fiji. Nacre deposited at the base and top of the nuclei was measured monthly, from the 6th to the 10th months of culture and the different qualities of mabé produced at different positions were scrutinized. Nacre thicknesses at the base and top of the resulting mabé were significantly different at different months (P < 0.05) and the rate of nacre deposition was highest during the warmer months. The different positions of nuclei on the valve greatly affected the quality of mabé formed. After a 10‐month culture period, around 1 mm of nacre covered the nuclei although the best quality mabé were obtained after 9 months.
This study documents the complete larval development of the Monkey River Prawn Macrobrachium lar using a new greenwater rearing technique. Approximately 6,000 larvae were reared for 110 days at an initial stocking density of 1 ind./6 L. Salinity at hatch was 10 ± 2 ppt and progressively increased to 30 ± 2 ppt until decapodids had metamorphosed. Temperature was maintained at 28 ± 0.5°C, pH at 7.8 ± 0.2, DO2 > 6.5 mg/L and NH4+ and NH3 ≤ 1.5 and ≤0.1 ppm respectively throughout the culture period. Larval development was extended and occurred through 13 zoeal stages, with the first decapodid measuring 6.2 ± 0.63 mm in total length observed after 77 days. 5 decapodids in total were produced, and overall survival to this stage was 0.08%. Overall, the pattern of larval growth shares similarities with those of other Macrobrachium spp. that have a prolonged/normal type of development, and it is likely that larvae underwent mark time moulting which contributed to the lengthened development duration. While this study represents a significant breakthrough in efforts to domesticate M. lar, improvement of larval survival rates and decreased time till metamorphosis are required before it can become fully viable for commercial scale aquaculture.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-568) contains supplementary material, which is available to authorized users.
The scalloped hammerhead shark, Sphyrna lewini, is endangered throughout its global distribution. Management and protection of this species is challenging in many locations because of limited scientific data and the vulnerable life-history traits of the species. Our study investigated anecdotal evidence that the Rewa River estuary in Fiji serves as an important nursery area for this shark. Research findings indicated that the average length of both males (60.6 ± 6.78 cm, n = 31) and females (60.4 ± 6.85 cm, n = 51) was well within published size limits of juvenile S. lewini studied in other locations (range = 38.0–89.5 cm). On the basis of published reference points for umbilical scar status we postulate that the first captured juveniles were born in January of the study year. Stomach content analysis found the following prey items: Decapoda (represented by prawns and shrimps), Stomatopoda, anguilliformes and osteichthyes. Decapods were the most numerous prey item by both count (59.17% of total prey items) and weight (60.25% of total weight). Our study provides strong support that the Rewa River estuary is an important aggregation area for S. lewini in Fiji.
A newly-discovered Lapita settlement at Bourewa on southwest Viti Levu Island, Fiji, was established originally on an offshore island perhaps as much as 1220 BCE by people whose main concern was optimal access to the broad fringing reef. Satellite settlements were established at nearby Rove and Waikereira later in Lapita times. The three oldest radiocarbon dates obtainedfrom the base of the tightly-packed shell midden layer excavated at Bourewa and charcoal in the beach sand below are calibrated/corrected to 1220-970 BCE, 1210-940 BCE, and 1130-910 BCE.The BourewaLapita site appears to be the oldest-known in Fiji.
At the Lapita‐era (1100‐550 B.C.) settlements (Bourewa and Qoqo) along the Rove Peninsula in Fiji, valves of the reef‐surface‐dwelling giant clam Hippopus hippopus (long extirpated in Fiji) occur in shell midden. Valve size/weight increase with depth, suggesting that human predation contributed to its local disappearance. The timing of this event is constrained by (a) the confinement of H. hippopus remains to the lower part of the midden, (b) their likely association with only the stilt‐platform occupation phase at both Bourewa and Qoqo (approximately 1100‐900 B.C.), and (c) radiocarbon ages. All these suggest that H. hippopus disappeared from reefs here about 750 B.C. Yet human predation is not considered to be a significant cause of extirpation of H. hippopus in the entire Fiji group. More plausible is that (climate‐driven) sea‐level fall (55 cm) during Lapita times in Fiji (approximately 1100‐550 B.C.) forced changes to coral‐reef ecology that saw this sensitive species extirpated throughout the Fiji archipelago. It is also considered possible that the Lapita colonizers introduced bivalve predators or diseases to Fiji that spread independently of humans throughout these islands.
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