Age and Growth of the South American Sea Lion, Otaria flavescens (Shaw, 1800), in Southern Brazil

Rosas, Fernando C. W.; Haimovici, Manuel; Pinedo, Maria Cristina

doi:10.2307/1381913

Cited by 48 publications

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“…The sexual dimorphism observed in skull of A. australis corroborates the differences observed in other studies (VazFerreira, 1982;Ximénez et al, 1984;Páez, 1989;Dremer and Ferigolo, 1996;Sanfelice, 2004). Similar patterns of sexual dimorphism occur in many other polygynous species such as Otaria flavescens (Rosas et al, 1993;Sanfelice, 2004), Arctocephalus forsteri and Arctocephalus pusillus doriferus (Brunner, 1998;2000). All the characters used in male and female skulls in this study were dimorphic, but in physically immature skulls greatest width of internal nasal opening was nondimorphic.…”

Section: Discussionmentioning

confidence: 65%

Growth and skull development in the South American fur seal, Arctocephalus australis (Zimmermann, 1783) (Carnivora: Otariidae), from Rio Grande do Sul coast, Brazil.

Molina-Schiller¹,

Pinedo²

2004

Lat. Am. J. Aquat. Mamm.

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-Skulls of 157 Arctocephalus australis (94 males and 63 females) from animals stranded dead on the Rio Grande do Sul coast from Torres to Barra do Arroio Chuí between July 1977 and September 1997 were examined. These were analyzed to explore aspects of the cranial development. The growth layers groups (GLGs) in the dentine and cementum from upper canine teeth were counted. The oldest male and female were 14 and 18 years of age, respectively. Parameters of the von Bertalanffy equation suggest that males and females attain physical maturity at about the eight and six years of age, respectively. Hotelling T 2 test and discriminant functions using metric characters showed sexual dimorphism in physically mature and immatures skulls. The developmental classes were also examined using non-metric characters, but no sexual dimorphism was observed using these variables. The principal component analysis (PCA) showed a clear separation between physically mature skulls of males and females. The first factor explained 80.2 % of the total variation and the second factor explained 4.6% of the observed variability.Resumen -Fueron examinados 157 cráneos de Arctocephalus australis (94 machos y 63 hembras) provenientes de animales muertos en la costa de Río Grande do Sul, desde Torres hasta la Barra do Arroio Chuí entre Julio 1977 a Septiembre 1997. Estos cráneos fueron analizados para explorar el desarrollo craniano. En dientes caninos superiores fueron contados los grupos de capas de crecimiento (GLGs) en la dentina y cemento. El macho y hembra de mayor edad fue de 14 años y 18 años, respectivamente. Parámetros de la ecuación de von Bertalanffy sugieren que los machos y hembras alcanzarían la madurez física aproximadamente a los ocho y seis años de edad, respectivamente. Análisis de test Hotelling T 2 y funciones discriminantes utilizando los caracteres métricos mostraron dimorfismo sexual en cráneos físicamente maduros y físicamente inmaduros. Las clases de desarrollo también fueron examinadas usando caracteres no-métricos, pero el dimorfismo sexual no fue observado usando estas variables. El análisis de componentes principales (PCA) mostró una clara separación entre cráneos de machos y hembras físicamente maduros. El primer factor explico 80.2% de la variación total y el segundo factor explico 4.6% de la variabilidad observada.

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Section: Discussionmentioning

confidence: 65%

Growth and skull development in the South American fur seal, Arctocephalus australis (Zimmermann, 1783) (Carnivora: Otariidae), from Rio Grande do Sul coast, Brazil.

Molina-Schiller¹,

Pinedo²

2004

Lat. Am. J. Aquat. Mamm.

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“…Morphometric information and histological analyses were performed on all animals for which samples were taken and included in the NMMTB. Teeth were also removed to determine age by counting growth layer groups 31 . One specimen has not been aged (B260 in Table 1) but it has been estimated at 4 to 8 years based on the size and development of the sagittal crest.…”

Section: Samplesmentioning

confidence: 99%

Determination of HBCD, PBDEs and MeO-BDEs in California sea lions (Zalophus californianus) stranded between 1993 and 2003

Stapleton

Dodder

Kucklick

et al. 2006

Marine Pollution Bulletin

146

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Blubber samples from male California sea lions (Zalphophus californianus)stranded between 1993 and 2003 were analyzed for 27 polybrominated diphenyl ether (PBDE) congeners, three isomers of hexabromocyclododecane (HBCD) and 14 methoxylated polybrominated diphenyl ether (MeO-BDE) congeners. Total PBDEs ranged from 450 ng/g to 4740 ng/g wet mass and total HBCD ranged from <0.3 ng/g to 12 ng/g wet mass. The concentration of HBCD increased from 0.7 ng/g to12.0 ng/g wet mass in sea lion blubber between 1993 and 2003. However, no significant temporal trend was observed for any of the other brominated compounds over this ten year period.Only one of the 14 MeO-BDE congeners was detected in the blubber samples, 6-methoxy-2,2',4,4'-tetrabromodiphenyl ether (6-MeO-BDE 47), and concentrations ranged from <0.2 ng/g to 12 ng/g wet mass. A bromo-, chloro-heterocyclic compound, 1,1'-dimethyl-tetrabromo-dichloro-2,2'-bipyrrole (DBP-Br 4 Cl 2 ), previously reported in marine species along the Pacific coast, was also identified in the sea lion blubber. DBP-1 Br 4 Cl 2 ranged from 44 ng/g wet mass to 660 ng/g wet mass and was present at concentrations rivaling the dominant PBDE congener, BDE 47 (2,2',4,4'-tetrabromodiphenyl ether). Concentrations of DBP-Br 4 Cl 2 were positively correlated with 6-MeO-BDE 47 (r= 0.7; p<0.05). Both of these compounds have been identified in marine algae and sponges, and studies suggest they are both produced from natural sources. This study demonstrates that brominated compounds from both anthropogenic and biogenic sources can accumulate to similar levels in marine mammals. In addition, HBCD concentrations appear to be increasing in California sea lion populations, whereas PBDE concentrations, between 1993 and 2003, were highly variable.

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“…The latest years (1998)(1999)(2000)(2001)(2002) were marked by a recovery of the South American sea lion population as well as the collapse of the hake fishery. Skull size is highly correlated with body size in South American sea lions (Rosas et al 1993) and remains almost invariable after 7 or 8 years of age for males and 5 or 7 years of age for females (Rosas et al 1993, Drago et al 2009b, Grandi et al 2010. Hence only skulls from adult individuals of known age were used to avoid any age-related bias.…”

Section: Samplingmentioning

confidence: 99%

“…Data analyses. Males and females were analyzed separately because of the marked sexual dimorphism of South American sea lions (Rosas et al 1993, Sanfelice & De Freitas 2008, Drago et al 2009b). The stability of the CBL/SL ratio through time within each sex was tested by linear regression analysis, whereas the influence of birth year on each craniometrical variable was tested using the non-parametric Spearman's ρ correlation coefficient.…”

Section: Samplingmentioning

confidence: 99%

“…Assessing changes in the body size of South American sea lions throughout the 20th century is one possible way of understanding the correlations between somatic growth and the effects of limiting factors such as population density and prey availability, since mammal adult body size is positively correlated with food availability before puberty (Scheffer 1955) and body size is highly correlated with skeletal measurements in otariids (Scheffer 1950, Scheffer & Wilke 1953, Rosas et al 1993, Miller et al 2000. Furthermore, skeletal measurements are easily standardized and thereby measurement errors are minimized.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of skull size in South American sea lions reveals density-dependent growth during population recovery

Drago¹,

Cardona²,

Crespo³

et al. 2010

Mar. Ecol. Prog. Ser.

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Craniometrical data of male and female skulls collected from 1974 to 2007 were used to test the hypothesis that the somatic growth of South American sea lions Otaria flavescens in northern Patagonia has been affected by a reduction in the per capita food availability, due to a combination of the population recovery after cessation of sealing and the development of industrial fishing targeting Argentine hake Merluccius hubbsi. Most of the 19 craniometric variables considered decreased through time in both sexes, and the same trend was found for a variable extracted by means of principal component analysis that was related to skull volume. Most of the reductions in skull size and volume have happened since 1990, when the sea lion population peaked and the hake population collapsed. This evidence, combined with a review of supplementary data derived from stable isotope analysis, supports the hypotheses that the somatic growth of South American sea lions is densitydependent and that industrial fishing has reduced the carrying capacity of the ecosystem for South American sea lions.

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Age and Growth of the South American Sea Lion, Otaria flavescens (Shaw, 1800), in Southern Brazil

Cited by 48 publications

References 0 publications

Growth and skull development in the South American fur seal, Arctocephalus australis (Zimmermann, 1783) (Carnivora: Otariidae), from Rio Grande do Sul coast, Brazil.

Growth and skull development in the South American fur seal, Arctocephalus australis (Zimmermann, 1783) (Carnivora: Otariidae), from Rio Grande do Sul coast, Brazil.

Determination of HBCD, PBDEs and MeO-BDEs in California sea lions (Zalophus californianus) stranded between 1993 and 2003

Reduction of skull size in South American sea lions reveals density-dependent growth during population recovery

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