Multivariate statistical analysiss of 18 morphometric characters were

Identification of franciscana dolphin stocks trough external morphology
Barbato1,2,3, B. H. A.; Secchi2, E. R.; Kinas3, P. G.; Di Beneditto4, A. P. M.; Ramos5, R. M. A.; Bertozzi6,
C.;Marigo6, J.
(1) Pós-Graduação em Oceanografia Biológica, FURG, C.P. 474, Cep: 96200-970, Rio Grande, RS,
Brazil.
(2) Laboratório de Tartarugas e Mamíferos Marinhos, FURG, C.P. 474, Cep: 96200-970, Rio Grande,
RS, Brazil.
(3) Laboratório de Estatística, FURG, C.P. 474, Cep: 96200-970, Rio Grande, RS, Brazil.
(4) Laboratório de Ciências Ambientais, UENF, Av Alberto Lamego, 2000, Cep: 28013-602, Campos
dos Goyatacazes, RJ, Brazil.
(5) Everest Tecnologia em Serviços Ltda, Av Nossa Senhora dos Navegantes, 675/1201, Cep: 29056-900,
Vitória, ES, Brazil.
(6) Ong Projeto Biopesca, R Paraguai, 241, Cep: 11702-070, Praia Grande, SP,Brazil.
[email protected]
The franciscana, Pontoporia blainvillei, is endemic to the coastal waters of the western South Atlantic,
from Itaúnas, Brazil to Golfo San Matias, Argentina. Incidental catches in coastal gillnets is the major
threath to the species survival, however, occurs at different levels along the species range. For
conservation, it is important to determine units for management. Franciscana’s range is currently split in
four Franciscana Management Areas (FMAs): FMA I - Espírito Santo and Rio de Janeiro States, Brazil;
FMA II - from São Paulo to Santa Catarina States, Brazil; FMA III - Rio Grande do Sul State, Brazil and
Uruguay and; FMA IV - Argentina. A principal component analysis (PCA) was carried out to determine
if franciscanas from FMA I to FMA III can be diferentiated by external morphology. Eighteen external
morphometric characters of 55 mature specimens incidentally caught in gillnet fisheries were used.
Immature animals were excluded to avoid effects of ontogenetic variation. Males and females were
analysed together as no pronounced sexual dimorphism occurs. The first four principal components (PCs)
explain 80.2% of overall variation. PC1 is frequently associated to variation in body length and is not
used in the analysis. PC2 to PC4 show correlations of different signs and magnitude with the variables,
representing shape variation. When the specimens were plotted in a graph of PC2 and PC3, the samples
from different FMAs show an evident separation. The specimens from FMA III place on the first and the
fourth quadrants and assume negative scores for PC2.The specimens from FMA I, assume positive scores
for the same component and place on the second and the third quadrants. The specimens from FMA II
assume a intermediate position, with its scores closer to the axis origin. Although preliminary, these
results are consistent with the proposed Franciscana Management Areas.