Abstract
Amazon river turtles are increasingly threatened by habitat loss and alteration due to the Brazilian energy policy based on construction of hydroelectric dams, meanwhile, populational studies remain scarce. We described the population structure, and established body allometric relationships of Podocnemis unifilis in the Terra do Meio Ecological Station in the Iriri River, tributary of the Xingu River upstream the Belo Monte dam under construction Turtles were captured by hand net and diving in 2012 and 2013 dry seasons, and 2013 rainy season. A total of 728 males, 296 females and four juveniles were captured. Adult sex ratio was male-biased by 9.15 ♂:1 ♀. Females were significantly larger than males. Mean straight carapace length was 268.9 ± 46.7 mm (165 - 403) for females; and 232.7 ± 24.8 mm (167 - 303) for males. The sexes were morphologically distinct in function of a proportionally larger plastron, and higher carapace, on females. Allometric relationships between straight carapace length and other morphometric traits were strong for males (R2 range = 0.87 - 0.96 and females (R2 range =0.79 - 0.98. Exploitation of P. unifilis in biomass extirpated from the Middle Xingu River may be estimated from body parts found post-consumption by the presented regressions.
Highlights
River turtles have been consumed by indigenous people as a food source since pre-colonial times in the Amazon region (Bates 1863, Johns 1987)
The present paper describes the population structure and establishes the length-weight relationship and other allometric relationships of interest for a Podocnemis unifilis population living in a 3.3 million ha protected area, located about 450 km upstream from the future reservoir of the Belo Monte dam
The data presented may be used as a reference of a P. unifilis natural population in a typical clear water river in the Amazon basin, an ecosystem increasingly threatened by habitat alteration
Summary
The study was carried out inside the Terra do Meio Ecological Station (TMES), one of the most restrictive Protected Areas under the Brazilian environmental legislation (National System of Protected Areas – SNUC - law 9,985). TMES comprises 3,373,133.89 ha, covered mostly by pristine tropical forest and drained by Iriri River and its smaller tributaries. During the high water season the marginal forest is flooded and provides food source for the aquatic fauna, whilst in the low water season deep pools and extensive shallows remain in the river bed, and islands, sand banks and rocky rapids emerge. These ecosystems are currently threatened by gold mining activities and the construction of the Belo Monte dam (Ferreira et al 2013)
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