World Status, Exploitation and Trade - WIDECAST

ASCENSION AND ST HELENAASCENSIONPOPULATION:Chelonia mydasNesting sites There are 32 cove beaches distributed along the west andnorth-west coasts of Ascension Island, ranging in length from 10 to 915 m.Much earlier information (Carr, 1975; Mortimer and Carr, 1984) issynthesised by Mortimer and Carr (1987).Nesting numbers Relatively comprehensive population data are available,gathered by Mortimer during the 1976-77 and 1977-78 nesting seasons. Nestnumbers were estimated by counting tracks during the nesting season, andcorrecting for the mean 1.7 trial emergences before nesting actuallyoccurred, and with a further correction for imperfect tagging efficiency.Numbers of nesting turtles were calculated assuming either 3 or 4 clutchesper female per season (respectively providing the upper and lower limits ofeach annual estimate). Information given by Mortimer and Carr (1987) issummarised in Table 13.Table 13. Estimates of numbers of tracks, nests and nesting females atAscension, during the 1976-77 and 1977-78 seasons (data from Mortimer andCarr, 1987).Tracks Nests Nesting Females1976-77 18 192 7910-10 764 1980-35901977-78 12 093 5257-7154 1317-2386A total of 5375 and 5599 tracks were counted in the 1980-81 and 1981-82seasons respectively (R. Whitla in litt. , 10 October 1986). Although thesecounts are much lower than Mortimer's, it is not clear how comparable thesurvey procedures were, and some small beaches were omitted.The Ascension colony, with an average of around 1650-3000 females a season(Mortimer and Carr, 1987), is one of the three large populations extant inthe Atlantic; it is much smaller than the Tortuguero (Costa Rica) population(which has between 5000 and 50 000 females a season), and perhaps a littlelarger than the Suriname population (which has around 1500-2000 a season).Trends in nesting numbers Little information is available; numbers areprobably stable (J. Mortimer in litt. . 12 December 1981; R. Whitla in litt. .29 August 1986). The 1981-1982 track counts (see above) are much lower thanthose for 1977-1978; this difference may to some extent be due to a declinein nesting numbers, to between-year fluctuations in nesting numbers, or(perhaps most likely) to different survey procedures. Parsons (1962)reported evidence from 1926 that turtle nesting populations appeared to havedeclined as a result of the continuing exploitation over the past twocenturies.Nesting season The season is quite clearly-defined, and extends fromDecember to May, coinciding with the wettest time of year and the period ofheaviest wave action (the Ascension sand is coarse and dry and this timingmay increase reproductive success). Nesting peaks in March-April (Mortimerand Carr, 1987)70