World Status, Exploitation and Trade - WIDECAST

REUNION AND ILESEPARSESNesting numbers Hughes (1970) calculated the minimum number of nestingfemales on Europa as A274, based on fieldwork between 5 November and20 December 1970 (estimated as nightly emergence total, multiplied byre-nesting interval by percent nesting success). Around 50 females emergednightly on Station Beach during this period, with a nightly island total ofaround 710 (Hughes, 1974, Table 11). Around 43% of emergences resulted insuccessful nesting (Hughes, 1970). Hughes (1974, Table 15) later estimatedan annual nesting population of 4000-9000 females. Servan (1976) veryrarely recorded more than 10 females nightly on Station Beach betweenFebruary 1973 and February 1974, and estimated the annual female populationas 1300. Servan (1976) suggested that the difference between his estimateand that of Hughes (1970) was due to annual fluctuation in nesting numbers;it seems likely that some may be due to different methods of data collectionand analysis. Vergonzanne et al (1976) recorded a mean of 20 femalesnightly between 10 August and 2 October 1973, involving around 1000 turtles,and more than 3000 emergences in January 1974; they estimate the totalfemale population between February 1973 and February 1974 was around 2000.It is not clear how many nest beaches were covered. Bonnet (1986) reportsbetween 200-550 emergences nightly during January, the period of mostconcentrated nesting.Le Gall et al (1985 and 1986) have recently provided nesting and hatchlingdata for 1981-1985, based on consistent field and analytical methods.Salient figures from this work are given in Table 171.Table 171. Nesting and productivity data for Europa (data from Le Gallet al. , 1985 and 1986; including their re-analysis of data from Servan,1976). The 1970 figure is from Hughes (1970), the 1973-74 (S) figure isfrom Servan (1976). Note that the 1985 work by Le Gall et al gives figuresof 698 and 8149 for Station Beach and Total nests in 1981-82, the data citedare from Le Gall et al (1986). The peak quarter comprisesNovember-January, during which 50-70% of annual nesting occurs. Femalenumbers are derived by dividing the total number of nests observed by themean number of nests in a marked sample of females. The annual total isextrapolated from the peak quarter figure. Monitoring has been concentratedon Station Beach. The island totals are extrapolated from Station Beachdata; the factor employed in this calculation is clearly critical to thesize of the final estimate of female numbers.Year