Dinâmica populacional de Podocnemis erythrocephala, no rio Ayuanã, Amazonas, Brasil.
Podocnemis erythrocephala is a species of turtle that inhabits black water rivers and lakes in the Rio Negro Basin and ventures into clear water habitats as well in the Tapajós and Trombetas rivers, in Brazil, as well as the extreme eastern tip of Colômbia and most of the states within the Venez...
| Autor principal: | Bernhard, Rafael |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Assuntos: | |
| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12279 http://lattes.cnpq.br/2651936340353488 |
| Resumo: |
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Podocnemis erythrocephala is a species of turtle that inhabits black water rivers and
lakes in the Rio Negro Basin and ventures into clear water habitats as well in the
Tapajós and Trombetas rivers, in Brazil, as
well as the extreme eastern tip of
Colômbia and most of the states within the Venezuelan part of the Amazon Basin. As
with all species in the family Podocnemididae their populations have suffered from
the collection eggs and adults for human consumption. Even though this species is
an important item in the food of the local population of river people where ever P.
erythrocephala occurs, there are no studies documenting the natural size of these
turtle populations nor monitoring programs. The existing information concerning the
decline of natural populations of Podocnemididae are scarce, and not well studied,
therefore the monitoring studies are needed for all of the species in this family
utilizing methods that can measure the size of adult populations, size structure within
populations, and sex ratios.
The objective of this study was to characterize aspects of the population dynamics of
P. erythrocephala in the Ayuanã River, middle Rio Negro, Amazonas State. The size
at reproductive maturity in a population of turtles is important to determine such that
the adult sex ratio of the population can be calculated. For this reason it was
necessary to study growth and sexual maturity using the gonads, external dimorphic
features, gravid females, growth rates of individuals between captures, and the
model of von Bertalanffy with Fabens adjustment. The size at sexual maturity in
males and females was 161 and 218 mm in straight line maximum carapace length,
respectively. Juveniles growth faster than adults and have a negative linear
relationship between the growth rate and the carapace length in males and females.Sexual maturity in both males and females was estimated to be nine years, however
in the case of males this needs to be examined more extensively.
In order to characterize the population structure, sex ratio, and proportion of juveniles
in the population, as well as relative abundance of P. erythrocephala in the Ayuanã
River, I marked 4.111 individual turtles from 2003 to 2008 in a section of 148.5 km of
the Ayuanã River, a small lake in an island in the channel of Rio Negro and the
Jurubaxi River. These population parameters differ between the capture methods
used. Trammel nets proved to be more efficient than free diving for turtles. The
capture index between turtles caught in trammel nets with mesh size of 18 and 21
were greater than for trammel nets with the mesh size of 11 cm. The corrected sex
ratio for the population in the Ayuanã River was (0,41♂:1♀). The proportion of
juveniles was corrected to be 40% for the population studied. The frequency of
recaptures suggests that only a small part of this population was captured during this
study. The study concerning movement patterns (defined as the linear distance
between the points of capture) of P. erythrocephala indicates that this species
disperses along the entire Ayuanã River, without having a small fixed area of use.
The linear distance moved by females was greater than that observed for males. The
longest linear distances moved were greater than 27.000 m, including the
movements between Ayuanã River and a lake in the middle of the Rio Negro or to
the next river entering the Rio Negro, Jurubaxi River. |