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Munoz L.,University of Valparaiso | Pavez G.,University of Valparaiso | Quinones R.A.,University of Concepcion | Oliva D.,University of Valparaiso | And 3 more authors.
Revista de Biologia Marina y Oceanografia | Year: 2013

Diet studies of the South American sea lion (SASL) in Chile suggest that this species is an opportunistic and generalist predator whose diet varies depending on the distribution of prey species and spatial and temporal variations in the abundance of these dams. However, these studies have been sporadic, geographically limited and based on stomach content analysis, which does not allow an integral analysis of the composition of the diet of this species and its potential spatial and temporal variability. In this study we analyzed the diet of the SASL in 3 geographic zones of the coast of Chile using analysis of stable isotopes δ13C and δ15N on hair and skin tissues. In the northern zone, the main prey species consumed by SASL were Isacia conceptionis (19.5%) for skin and Cilus gilberti (23.3%) for hair; in the central zone were Thyrsites atun (40.1%) for skin and Strangomera bentincki (31.1%) for hair, whereas in the southern zone the main species were pelagic fish (such as T. atun and Trachurus murphyi, 20.8%) for skin and farm-raised salmonids (20.7%) for hair analysis. These differences indicate variation in the composition of its diet. Variations between the analyzed tissues and also with previous studies suggest that this species is capable of adapting to intra- and inter-annual variations in the presence/absence of its prey. Source

Sepulveda M.,University of Valparaiso | Sepulveda M.,Research Center Eutropia | Santos M.,University of Valparaiso | Santos M.,Research Center Eutropia | And 5 more authors.
Revista de Biologia Marina y Oceanografia | Year: 2015

Studies on population abundance variations at different temporal scales contribute to the understanding on how these populations change over time and what are the factors influencing those variations. We analyzed daily, monthly and annual haul-out abundance patterns of South American sea lions (SASL, Otaria flavescens) in 2 breeding colonies of the north of Chile. Additionally we analyzed the effect of El Niño events on the sea lions’ annual patterns. The abundance of sea lions in Punta Negra (PN) decreased from 1994 to 2011, whereas in Punta Patache (PP) increased, although the number of pups was proportionately low. Our results indicated a strong effect of El Niño over the abundance of sea lions, especially for females + juveniles in PN. The haul-out monthly abundance of females and juveniles increased during austral winter months, whereas adult and subadult males did not show a clear pattern. Finally, the haul-out abundance tended to increase throughout the day reaching a maximum by late afternoon, especially for females and juveniles. No difference in daily patterns between breeding and non-breeding seasons for any of the sex/age classes was found. This study shows that the number of animals in the PP and PN breeding colonies presented annual, monthly and daily periodicities, and that these periodicities are conditioned by both intrinsic (e.g., breeding period) and extrinsic (e.g., time of day, El Niño) factors. On an annual basis, our results indicate that even at a local scale, SASL population trends at 2 colonies may be different. © 2015, Universidad de Valparaiso. All rights reserved. Source

Perez-Alvarez M.J.,University of Chile | Perez-Alvarez M.J.,Research Center Eutropia | Perez-Alvarez M.J.,University of Valparaiso | Carrasco P.,University of Concepcion | And 3 more authors.
Revista de Biologia Marina y Oceanografia | Year: 2013

In a polygynous mating system males and females have different reproductive strategies; so it is expectable that both sexes have evolved different reproductive behavioral responses to maximize their reproductive success. We analyze the behavior of different sex/age classes of Otaria flavescens during breeding (BS) and non-breeding seasons (NBS) at a Nature Sanctuary breeding colony, central Chilean coast. From May 2008 to December 2009 data of males, females, juveniles and pups were recorded. Males performed more aggression, locomotion and recognizing behaviors during the BS, while they mostly rested during the NBS. Females and juveniles performed more recognizing behavior in the NBS, while the other behavior categories did not show differences between the NBS and the BS. As reproductive behavioral strategies, male aggression and maternal care may increase the overall population viability. This study contributed to a better understanding of the reproductive behavior patterns of this species based on what is to our knowledge the most continuous monitoring of a South American sea lion breeding colony. Since the study has been undertaken in a Nature Sanctuary, the results may be used as a baseline to compare with behavioral data from colonies perturbed by human activities. Source

Sepulveda M.,University of Valparaiso | Sepulveda M.,Research Center Eutropia | Oliva D.,University of Valparaiso | Urra A.,University of Valparaiso | And 11 more authors.
Revista Chilena de Historia Natural | Year: 2011

The onshore distribution and abundance of the South American sea lion Otaria flavescens along the central Chilean coast was estimated during the period January-February 2007. Additionally, changes in population abundance during the period 1970-2007 were examined. Population surveys were based on photographs taken from boats or aircraft. A total of 16301 sea lions (CI = 16209-16375) were counted in 33 colonies (6 breeding and 27 non-breeding sites). After correction to account for the proportion of individuals at sea and for pups not seen at the time of the survey, the mean estimated abundance was 18179 (95 % CI = 17777-18851) sea lions. Population trend analysis showed that from 1970 to 1985, South American sea lions showed a positive increase of approximately 2.1 % yr -1. Nevertheless, between 1985 and 1997 and between 1997 and 2007, the estimated number of sea lions showed a stable or slightly negative trend of 0.4 ± 0.1 % yr -1 and 0.5 ± 0.1 % yr -1, respectively. We suggest that the overexploitation and decline of the principal fisheries in Central Chile could adversely impact the abundance and distribution of the South American sea lion in the study area. © Sociedad de Biología de Chile. Source

Sepulveda M.,University of Valparaiso | Sepulveda M.,Research Center Eutropia | Olea D.,University of Valparaiso | Carrasco P.,University of Concepcion | And 4 more authors.
Aquatic Biology | Year: 2014

In otariids, the condition and growth of offspring are linked to prey availability because females show a strong dependence on local food availability. Thus, it is expected that body condition of sea lion pups will vary spatially and/or temporally as a response to variations in the abundance of prey species on which females feed. The objective of this study was to analyze the geographic and temporal variation in the body condition of South American sea lion Otaria flavescens pups in Chile, and to relate it to spatio-temporal variations in prey availability. We captured 340 live pups in 2 distant colonies, Punta Patache/Punta Negra and Cobquecura, along the Chilean coast during consecutive breeding seasons. A morphometric index of pup body condition was estimated by comparing pups in all years using least-squares linear regression of the log10 transformed measurements of standard length vs. body mass. We analyzed the relationship between this index and estimates of fish biomass (as a proxy of prey availability) at each locality. We found that body condition was significantly different between years and between colonies, suggesting that animals of the central-south area were in better condition than those in the north. A positive relationship between body condition and fish biomass was found, suggesting that differences in body condition may be explained by spatial and temporal differences in prey availability. © The authors 2014. Source

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