World Status, Exploitation and Trade - WIDECAST

SEYCHELLESaround Lhe Mozambiqup Channel (Hornell, 1927), and local informants suggestthat turtles may move from Aldabra to Assumption (this is a local movementinvolving only some 30 km) (Frazier, 1984). One turtle tagged at Aldabrahas been recaptured in Tanzanian waters (Mortimer, pers. comn.).POPULATION: KretmochelY3 imbricataNesting sites Nesting is very widespread in the Seychelles, having beenreported on more than 20 islands, from each main group; any suitable beachin the Seychelles is likely to have some E. imbricata nesting (Frazier,1984). Nesting appears to be insignificant on Assumption, Astove, St Pierreand Providence, all in the southern islands (Frazier, 1984, Table 3;Mortimer, 1984, Table 7). Most E. imbricata nest in the Granitic group ofislands, fewest in the southern group (Aldabra Providence). Hornell (1927)reported the same pattern of nesting density in the 1920s. Contrary toFrazier (1984), Cousin seems unlikely to have the largest knownconcentration of nesting E. imbricata in the western Indian Ocean; accordingto Mortimer (1984), numbers are far higher on St Joseph Atoll, Platte andCoetivy. See next section for named sites.Nesting numbers Two turtle fieldworkers have spent extended periods inthe Seychelles: Frazier (1984) in 1972-1973 and Mortimer (1984) in1981-1983; both workers have recently published results of their work. Forcomparative purposes, nesting estimates by both authors are given in Table176 (Mortimer's data are based on more field time and may thus be generallymore representative). On this evidence, the Seychelles E. imbricatapopulation is the largest in the western Indian Ocean.Trends in nesting numbers Little direct information is available, buttrade data and verbal reports strongly suggest a general downward trend innesting numbers during the present century. Mortimer (1984, Fig. 11) hasgraphed the annual export weight of raw tortoiseshell (converted intoapproximate turtle-equivalents), and the price earned per kg, between the1890s and the 1980s. Grouped into five-year means, these data show thatshell exports had declined overall from 1894 to 1960, but rose steeply inthe period between 1961 and the early 1980s. According to Mortimer (1984,p. 12) the apparent decline in the numbers of E. imbricata harvestedannually up to 1960 "is probably attributable to an over-all drop in thesize of the Hawksbill population as a result of over-harvesting". Thesudden increase in numbers harvested from 1961 is attributed by Mortimer toan increase in the price of shell and improved hunting techniques (use ofmasks, snorkels, and outboard motors). Mortimer (1984, p. 13) also citesfield observations made by R. Salm; on average he encountered one Hawksbillin every 1.5 dives around Mah6, Praslin and La Digue in 1976, but only twoin 15 dives in 1983. In addition, virtually every fisherman and turtlehunter interviewed by Mortimer reported a significant decrease in the numberof E. imbricata encountered around the Granitic Seychelles and the Amlrantes.Nesting season Most nesting on Cousin occurs between October and January(during the north-east monsoon), with a peak in November-December, but withsome nesting recorded in most months (Frazier, 1984). In the Seychellesgenerally, most nesting is in September-November (Hornell, 1927).Foraging sites The species is likely to occur widely in the Seychelles,particularly wherever rich coral reefs exist; Bale Ternay (Mah^) and the4S9