Otaria Research Articles

South American sea lions (Otaria flavescens) and killer whales (Orcinus orca) attending chub mackerel (Scomber japonicus) commercial trawl fisheries over the Patagonian Shelf: a first report

Killer whale-seal interactions have been reported for almost all pinniped species globally. However the literature on offshore interactions between killer whales and sea lions is rare for the South Atlantic, particularly in Argentine waters. Here we report for the first time the harassment of a South American sea lion (Otaria flavescens) by killer whales (Ornicus orca) while attending commercial fishing vessels in offshore national waters and describe a novel sea lion antipredator behaviour. These observations were made during an ongoing survey to assess seabird-fisheries interactions in the commercial trawl fishery off Argentina.

Finding of a skull of Pseudorca crassidens in Caleta de Los Loros, Rio Negro Province, Argentina

The false killer whale, Pseudorca crassidens, exhibits one of the widest and most continuous distributions among cetaceans. However, basic information about its biology is poorly known due to the low frequency of sightings and its offshore habits. Moreover, most of the knowledge on this species has been obtained from stranded animals. On 3 March 2012, in the proximity of a colony of South American sea lions (Otaria flavescens) located at Caleta de los Loros, Río Negro Province, Argentina (40o59’S, 64o14’W), a cetacean skull was found in the intertidal zone. The specimen was later identified as P. crassidens. The present note reports a new record of false killer whale in the continental shelf waters of Argentina and provides new data on the distribution and skull morphometrics of the species.

Exploring body size of modern South American fur seal (Arctocephalus australis) for osteometric studies in zooarchaeological remains from northern Patagonia, Argentina

In order to assess the role of pinnipeds in prehistoric subsistence of hunter–gatherers from northern Patagonia, traditional osteometric studies based on modern collections of Arctocephalus australis (Aa) and Otaria flavescens (Of) with known age and sex are being employed with the aim of identifying species, sex and age-classes found in zooarchaeological assemblages. A preliminary research based on a very small sample of Aa from the Uruguayan coast suggested the absence of changes in the skull size of this species during the last five decades. Of skull size reduction through time was observed as a consequence of a density-dependence process in northern and central Patagonia. In this study we discuss the use of modern analogues for the study of zooarchaeological remains of Aa. With this objective in mind, osteometrical data from modern skulls of 30 adult male Aa collected along northern and central Patagonia were analysed to assess potential diachronic changes in body size of this species. The results showed that there is no evidence of change in the body size during the last three decades (1990–2013) in the Aa population from northern and central Patagonia. This result supports the relevance of investigations if there are differences in the body size of living individuals that will be employed as analogues, for evaluating the potential of these measurements before using them in the analysis of zooarchaeological remains. The use of modern animals of Aa in osteometric analysis of fur seal assemblages recovered in archaeological sites at northern Patagonia is reasonable.

Annual, seasonal and daily variation in the abundance of the South American sea lion Otaria flavescens in two breeding colonies in northern Chile

Los estudios de variaciones de abundancia de las poblaciones a distintas escalas temporales permiten comprender como dichas poblaciones fluctuan en el tiempo y cuales son los factores que influyen sobre dichas variaciones. Se analizaron los patrones de abundancia del lobo marino comun (SASL, Otaria flavescens) a escalas diaria, mensual y anual en 2 loberas reproductivas del norte de Chile. Adicionalmente, se evaluo el efecto de El Nino sobre los patrones anuales de la especie. La abundancia de lobos marinos en Punta Negra (PN) disminuyo desde 1994 a 2011, mientras que en Punta Patache (PP) aumento, aunque el numero de crias fue proporcionalmente bajo. Los resultados demuestran un efecto importante de El Nino sobre la abundancia de lobos marinos, especialmente para hembras + juveniles en PN. La abundancia mensual de hembras y juveniles fue mayor en invierno, mientras que para machos adultos y subadultos no se encontro ningun patron. Finalmente, durante el dia la abundancia incrementa hasta llegar a un maximo hacia fines de la tarde, especialmente en el caso de hembras y juveniles. No se encontraron diferencias en los patrones de abundancia entre las epocas reproductiva y no reproductiva para ninguna de las clases de sexo/edad. Este estudio muestra que la abundancia en PP y PN muestra periodicidades anuales, mensuales y diarias, y que dichas periodicidades estan condicionadas tanto por factores intrinsecos (e.g., epoca reproductiva) como extrinsecos (e.g., hora del dia, El Nino). A escala anual, los resultados indican que aun a una escala local, las tendencias de abundancia en 2 colonias pueden ser diferentes.

Diet-to-female and female-to-pup isotopic discrimination in South American sea lions.

The use of accurate, species-specific diet-tissue discrimination factors is a critical requirement when applying stable isotope mixing models to predict consumer diet composition. Thus, diet-to-female and female-to-pup isotopic discrimination factors in several tissues for both captive and wild South American sea lions were estimated to provide appropriate values for quantifying feeding preferences at different timescales in the wild populations of this species. Stable carbon and nitrogen isotope ratios in the blood components of two female-pup pairs and females' prey muscle from captive individuals were determined by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS) to calculate the respective isotopic discrimination factors. The same analysis was carried out in both blood components, and skin and hair tissues for eight female-pup pairs from wild individuals. Mean diet-to-female Δ(13) C and Δ(15) N values were higher than the female-to-pup ones. Pup tissues were more (15) N-enriched than their mothers but (13) C-depleted in serum and plasma tissues. In most of the tissue comparisons, we found differences in both Δ(15) N and Δ(13) C values, supporting tissue-specific discrimination. We found no differences between captive and wild female-to-pup discrimination factors either in Δ(13) C or Δ(15) N values of blood components. Only the stable isotope ratios in pup blood are good proxies of the individual lactating females. Thus, we suggest that blood components are more appropriate to quantify the feeding habits of wild individuals of this species. Furthermore, because female-to-pup discrimination factors for blood components did not differ between captive and wild individuals, we suggest that results for captive experiments can be extrapolated to wild South American sea lion populations.

Ecology and Conservation of Sea Turtles in Chile

Abstract Chilean marine habitats have supported sea turtle species since prehistorical times. Although information exists regarding their contemporary distribution and ecological role in the region, it is diffuse. This study aims to bring such data together and provide an up-to-date review of the ecology and conservation status of sea turtles in Chile. Detailed available data largely reflect interactions between Dermochelys coriacea and Caretta caretta with oceanic fisheries. Newspaper and local studies have reported the regular presence of Chelonia mydas and Lepidochelys olivacea in certain locations in northern Chile during the past decade. The latter species were particularly abundant in the area around a thermal discharge from a water-cooled power plant (Mejillones Bay, 23°S) in the Antofagasta Region, and accounts included several reports of negative interactions between these species and sea lions (Otaria flavescens). Sea turtles found in Chilean waters are probably juveniles or subadults. No estima...

Shifting niches of marine predators due to human exploitation: the diet of the South American sea lion (Otaria flavescens) since the late Holocene as a case study

Abstract—Stable isotope ratios of carbon and nitrogen in archaeological and modern bone samples have been used to reconstruct the dietary changes of the South American sea lionOtaria flavescensfrom the late Holocene to the present in the southwestern Atlantic. We sampled bones from archaeological sites in northern-central and southern Patagonia, Argentina, and bones housed in modern scientific collections. Additionally, we analyzed the stable isotope ratios in ancient and modern shells of intertidal molluscs to explore changes in the isotope baseline and allow comparison between bone samples from different periods after correction for baseline shifts. Results confirmed the trophic plasticity of the South American sea lion, demonstrated the much larger impact of modern exploitation of marine resources as compared with that of hunter-gatherers, and underscored the dissimilarity between the past and modern niches of exploited species. These conclusions are supported by the rather stable diet of South American sea lions during several millennia of aboriginal exploitation, in both northern-central and southern Patagonia, and the dramatic increase in trophic level observed during the twentieth century. The recent increase in trophic level might be related to the smaller population size resulting from modern sealing and the resulting reduced intraspecific competition. These results demonstrate how much can be learned about the ecology of modern species thanks to retrospective studies beyond the current, anthropogenically modified setting where ecosystem structure is totally different from that in the pristine environments where current species evolved.

Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the Río de la Plata plume

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 525:261-272 (2015) - DOI: https://doi.org/10.3354/meps11236 Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the Río de la Plata plume M. Drago1,*, V. Franco-Trecu2, L. Zenteno3, D. Szteren4, E. A. Crespo5, F. G. Riet Sapriza2,8, L. de Oliveira6, R. Machado6,7, P. Inchausti1, L. Cardona3 1Department of Ecology & Evolution, Centro Universitario Regional Este (CURE), University of the Republic, C/ Tacuarembó s/n, 20000 Maldonado, Uruguay 2Proyecto Pinnípedos, Sección Etología, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay 3IRBIO and Department of Animal Biology, Faculty of Biology, University of Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain 4Dpto de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay 5Laboratory of Marine Mammals, Centro Nacional Patagonico (CENPAT-CONICET), and National University of Patagonia, Blvd. Brown 3600, 9120 Puerto Madryn, Chubut, Argentina 6Study Group of Aquatic Mammals of Rio Grande do Sul (GEMARS), Av. Tramandaí 976, RS 95625-000, Imbé, Brazil 7Laboratório de Sistemática e Ecologia de Aves e Mamíferos Marinhos (LabSMar), Departamento de Zoologia/IB, Universidade Federal do Rio Grande do Sul (UFRGS), Av. Bento Gonçalves 9500, RS 91509-900, Porto Alegres, Brazil 8Present address: Lab. de Ecología Molecular de Vertebrados Acuáticos (LEMVA), Departamento Ciencias Biológicas, Facultad de Ciencias, Universidad de los Andes, Carrera 1E No 18A - 10, Bogotá, Colombia *Corresponding author: m.drago@ub.edu ABSTRACT: Stable carbon and nitrogen isotopes in skin and bone of South American sea lions from Brazil and Uruguay were analysed to test the hypothesis that trophic overlap between the sexes is lower during the pre-breeding season than throughout the rest of the year. The isotopic values of skin and bone were used to infer the trophic relationships between the sexes during the pre-breeding period and year round, respectively. Prey species were also analysed to establish a baseline necessary for interpreting the stable isotope ratios of skin and bone. Standard ellipse areas, estimated using Bayesian inference in the SIBER routine of the SIAR package in R, suggested that males and females used a wide diversity of foraging strategies throughout the year and that no differences existed between the sexes. However, the diversity of foraging strategies was largely reduced during the pre-breeding period, with all the individuals of each sex adopting similar strategies, but with the two sexes differing considerably in stable isotope values and the ellipse areas of males and females not overlapping at all. Nevertheless, the results revealed a general increase in the consumption of pelagic prey by both sexes during the pre-breeding period. The progressive crowding of individuals in the areas surrounding the breeding rookeries during the pre-breeding period could lead to an increase in the local population density, which could explain the above reported changes. KEY WORDS: Otaria flavescens · Sexual foraging segregation · Skin · Bone · Stable isotope Bayesian ellipses Full text in pdf format PreviousNextCite this article as: Drago M, Franco-Trecu V, Zenteno L, Szteren D and others (2015) Sexual foraging segregation in South American sea lions increases during the pre-breeding period in the Río de la Plata plume. Mar Ecol Prog Ser 525:261-272. https://doi.org/10.3354/meps11236 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 525. Online publication date: April 09, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Biochemical and hematological profile of Otaria flavescens in the reproductive colony of Cobquecura, central-south Chile

A pesar de la importancia ecologica del lobo marino comun Otaria flavescens, existe escasa informacion referente a su quimica sanguinea y hematologia, los cuales pueden ser utilizados para evaluar el estado de salud de las poblaciones. El presente trabajo, reporta por primera vez la determinacion de 14 parametros quimicos sanguineos de O. flavescens y su formula leucocitaria obtenida desde 15 individuos pertenecientes a una colonia reproductiva localizada en Cobquecura, zona centro-sur de Chile, durante 2 muestreos realizados, 2009 y 2011. Los resultados indican que existe una alta regularidad bioquimica para los parametros estudiados. No obstante, se presentan diferencias significativas en la concentracion plasmatica de calcio entre ambos sexos y entre las concentraciones promedio de proteinas totales, globulinas, colesterol y actividad de colinesterasa de los 2 muestreos estudiados. Comparado con otros perfiles bioquimicos reportados para mamiferos marinos, en esta especie se determino una alta concentracion de globulinas y capacidad inhibitoria de antiproteasa (cercana al 100%), una moderada a baja actividad de colinesterasa y una concentracion de glucosa en el rango de lo ya reportado. Finalmente, la formula leucocitaria muestra una eosinofilia moderada a alta para el primer muestreo analizado (8,3-17,6%), lo que sugiere la posible presencia de alguna parasitosis en la poblacion estudiada. La presente informacion puede ser util para la determinacion del estado de salud de poblaciones de O. flavescens, y por lo tanto, podria contribuir a la conservacion de la especie en el Pacifico Sur Oriental.

Operational interactions between South American sea lions and gillnet fishing in southern Brazil

Abstract This study describes operational interactions between coastal gillnet fishing and South American sea lions (Otaria flavescens) off the southern Brazilian coast. In total, 263 onboard surveys were carried out during three periods between 1992 and 2012 in fishing boats from two harbours on the northern coast of Rio Grande do Sul State: Passo de Torres (29°19'S; 49°43'W) and Imbé (29°58'S; 50°07'W). Interactions of South American sea lions were observed in 116 (24.0%) out of 484 fishing operations. These interactions were more frequent in fishing boats from Passo de Torres (frequency of occurrence FO = 42.8%) than those from Imbé (FO = 14.8%; P < 0.001) and during autumn and winter months. Interactions between South American sea lions and fishing activities with fixed bottom gillnets in Imbé were most frequent during period III of the study (2011/2012) (FO = 52.0%; P = 0.032). These results demonstrated that interactions are not as high as reported/complained about by the local fishermen who tend to exaggerate the impact of these interactions. It is suggested that reduced fish stock and increased fishing effort during recent decades is raising the frequency of encounters with South American sea lions during fishing activities off the southern Brazilian coast. Therefore, the implementation of fishery management measures that reduce fishing effort and that integrate environmental education programmes are essential to reduce conflicts between fishing activities and the sea lions in the region. Copyright © 2015 John Wiley & Sons, Ltd.

Dietary consistency of male South American sea lions (Otaria flavescens) in southern Brazil during three decades inferred from stable isotope analysis

Marine predators may undergo remarkable dietary changes through time as a result of both anthropogenic and natural changes in the environment, but this variability is often difficult to tackle and seldom incorporated into ecosystem models. This paper uses the stable isotope ratios of carbon and nitrogen in skeletal material of South American sea lions from Brazilian scientific collections to investigate whether these animals modified their diet from 1986 to 2009, as reported for other marine predators in the region. Stable isotope ratios indicated that demersal potential prey were always enriched in 13C as compared with pelagic prey. Accordingly, the absence of any statistically significant correlation between stranding year and the δ13C values of adult males indicated no major increase in the consumption of pelagic prey from 1986 to 2009. Likewise, the results of the mixing model SIAR revealed a mixed diet including pelagic and demersal prey, with a central role for demersal fishes throughout the whole period. Furthermore, SIAR suggested no major changes in the proportion of pelagic and demersal prey in the diet of adult male South American sea lions during the past three decades. Demersal fishes were also relevant prey for juvenile South American sea lions during the whole period, but they always consumed a larger proportion of pelagic prey than the adults did. These results suggest no major changes in the diet of male South American sea lions during the past three decades in southern Brazil, contrary to what has been reported for other to predators in the regions and for the species in northern Patagonia.

Postharvesting population dynamics of the South American sea lion (Otaria byronia) in the southwestern Atlantic

AbstractMany pinniped populations precipitously declined during the 19th and 20th centuries due to overharvesting. In Uruguay, the South American sea lion (SASL) was harvested until 1986. Birth rates in two nearby breeding colonies have had opposite trends for at least 20 yr. We assessed different mechanisms that could explain opposite trends in birth rates in the two SASL colonies. We compared feeding habits (δ15N and δ13C) of breeding females, birth mass, individual growth rate and early survival of pups and the social structure between colonies. Breeding females from the two colonies did not differ in their feeding habits. However, male and female pups grew faster but had a lower survival in the second month in the smallest colony. We found differences in the social structures, with a higher proportion of males in the smallest colony. The latter is important because peripheral SASL males may abduct and kill pups, which may explain the lower survival of pups in smaller colonies. We believe that the cumulative effects of population extractions have lowered the local SASL population size and disrupted its social structure to the point where Allee‐like effects could become important and hamper the recovery of the Uruguayan SASL population.

Travel for sex: Long-range breeding dispersal and winter haulout fidelity in southern sea lion males

Southern sea lions (Otaria flavescens; SSLs) have a polygynous mating system and a prolonged social-sexual maturation period for males. Male haulouts are common in this species, with some very distant from central breeding rookeries, although the functions of these aggregations are not clearly understood. To estimate the potential connectivity between northern Argentina male colonies and breeding rookeries in Patagonia and Uruguay, we monitored the summer breeding activities and winter presence of 559 individually identified SSL males from haulouts in Mar del Plata and Quequén harbors. Our results confirm that male groups are formed by sexually active sea lions that show a strong annual connection with distant (up to 700km) breeding colonies. Circa 70% of the marked males made long-distance round-trips (72±26.7 days; n=325) from northern Argentina to Patagonia and Uruguay, indicating a high degree of winter site fidelity. Mating activity was confirmed for 53% of the sea lions re-sighted in breeding colonies, with approximately 80% of them having central positions on the beach and holding harems of up to nine females. The chronology of this cycle is finely tuned with the onset of the breeding season, which may result in comparative advantages such as anticipating female arrival or a prolonged participation in mating activities. Our results suggest a model of male haulouts spatially segregated from the central breeding areas, but with a summer recurrent flow of animals that contributes a significant proportion of the male population of northern Patagonia and Uruguay.

Latitudinal variation in local productivity influences body condition of South American sea lion pups

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 23:39-47 (2014) - DOI: https://doi.org/10.3354/ab00604 Latitudinal variation in local productivity influences body condition of South American sea lion pups Maritza Sepúlveda1,2,*, Danai Olea1, Pablo Carrasco3,4, Macarena Santos-Carvallo1,2, Jorge Castillo5, Renato A. Quiñones3,4 1Centro de Investigación y Gestión de los Recursos Naturales (CIGREN), Instituto de Biología, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, Valparaíso 2360102, Chile 2Centro de Investigación Eutropia, Ahumada 131 Oficina 912, Santiago 8320238, Chile 3Programa de Investigación Marina de Excelencia (PIMEX), Facultad de Ciencias Naturales y Oceanográficas, Casilla 160-C, Universidad de Concepción, Concepción 4070205, Chile 4Interdisciplinary Center for Aquaculture Research (INCAR-FONDAP), Universidad de Concepción, O’Higgins 1695, Concepción 4070007, Chile 5Instituto de Fomento Pesquero, Casilla 8v, Valparaíso, Almte. Manuel Blanco Encalada 839, Valparaíso 2361827, Chile *Corresponding author: maritza.sepulveda@uv.cl ABSTRACT: 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. KEY WORDS: Body condition index · Body mass · Environmental effects · Morphometrics · Otaria flavescens · Southern sea lion Full text in pdf format PreviousNextCite this article as: Sepúlveda M, Olea D, Carrasco P, Santos-Carvallo M, Castillo J, Quiñones RA (2014) Latitudinal variation in local productivity influences body condition of South American sea lion pups. Aquat Biol 23:39-47. https://doi.org/10.3354/ab00604 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 23, No. 1. Online publication date: December 02, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

A comparative analysis on cranial ontogeny of South American fur seals (Otariidae:Arctocephalus)

We analysed the cranial ontogeny of male Arctocephalus australis (Zimmermann, 1783) (N = 116), Arctocephalus gazella (Peters, 1875) (N = 69), and Arctocephalus tropicalis (Gray, 1872) (N = 51) to study skull growth and its allometric patterns in the genus. We used 15 metric variables with bivariate and multivariate approaches to detect interspecific similarities and differences between growth trends, which we discussed in the context of phylogeny and life history. We found common trajectories in 20% of variables, detecting that the differences between adults were associated with size. We detected higher growth rates in A. gazella than in A. australis and A. tropicalis, which were associated with shape differences. Amongst the three species, A. tropicalis was morphologically intermediate, showing additional common trends with A. gazella and A. australis, and an intermediate position in the multivariate morphospace. Allometric patterns were also compared with growth trends described for Otaria byronia (Peron, 1816) and Mirounga leonina (Linnaeus, 1758). We detected positive allometry in Arctocephalus for the mastoid width (MW) but negative allometry in O. byronia and M. leonina. This could indicate that males of Arctocephalus exhibited a delayed development of MW. Finally, the presence of common growth trends for the skull length and the postorbital constriction could indicate a conservative pattern within otariids. © 2014 The Linnean Society of London

Morphology of the lingual surface of South American fur seal (Arctocephalus australis) and sea lion (Otaria flavescens).

In this study, we aimed to describe the morphological characteristics of the lingual papillae in two species of Otariidae family by stereomicroscopy and scanning electron microscopy. We used tongues of two South American Otariidae species. The tongues were elongated and terminated in bifid apex and there was no median sulcus on the dorsal lingual surface. The most numerous type of lingual papilla was filiform in the South American fur seal (SASL) and entire dorsal lingual surface was covered by these filiform papillae but the dorsal surface of the tongue of the South American sea lion was covered by numerous polygonal projections, which were different in size. Fungiform papillae were detected in only SASL and they randomly distributed on the lingual apex and body, and some fungiform papillae were collected into twosome or threesome groups on the posterior part of the lingual body. Circumvallate papilla was found in the center of the lingual radix of South American sea lion. Thread-like conical papillae were common for both species and they located on the lingual radix. We determined that lingual surface morphology was completely different in each species, although they were members of the same family, Otariidae.

Uncovering deep mysteries: The underwater life of an amphibious louse

Despite the incredible success of insects in colonizing almost every habitat, they remain virtually absent in one major environment – the open sea. A variety of hypotheses have been raised to explain why just a few insect species are present in the ocean, but none of them appears to be fully explanatory. Lice belonging to the family Echinophthiriidae are ectoparasites on different species of pinnipeds and river otters, i.e. they have amphibious hosts, who regularly perform long excursions into the open sea reaching depths of hundreds of meters (thousands of feets). Consequently, lice must be able to support not only changes in their surrounding media, but also extreme variations in hydrostatic pressure as well as breathing in a low oxygen atmosphere. In order to shed some light on the way lice can survive during the diving excursions of their hosts, we have performed a series of experiments to test the survival capability of different instars of Antarctophthirus microchir (Phthiraptera: Anoplura) from South American sea lions Otaria flavescens, when submerged into seawater. These experiments were aimed at analyzing: (a) immersion tolerance along the louse life; (b) lice’s ability to obtain oxygen from seawater; (c) physiological responses and mechanisms involved in survival underwater. Our experiments showed that the forms present in non-diving pups – i.e. eggs and first-instar nymphs – were unable to tolerate immersion in water, while following instars and adults, all usually found in diving hosts, supported it very well. Furthermore, as long as the level of oxygen dissolved in water was higher, the lice survival capability underwater increased, and the recovery period after returning to air declined. These results are discussed in relation to host ecology, host exploitation and lice functional morphology.

The recovery process of a population is not always the same: The case of Otaria flavescens

Populations of the South American sea lion (Otaria flavescens) were decimated throughout its range along the Atlantic coast. Responses to this decline have been different in different parts of the species' distribution range. Some stocks are still decreasing, some remain stable, and some are recovering slowly. In the Southwestern Atlantic, sea lion populations are now increasing. However, 50 years after the cessation of hunting these populations have not recovered to the levels they had before exploitation, with the recovery process occurring at the same time as increasing development of human coastal activities. The aims of this study were to present recent information on abundance and trends in the southern Patagonian population of sea lions and to test the hypothesis of population expansion with a particular recolonization process. Results showed that there was an increase in the number of sea lions in all colonies and a change in the social composition of nine colonies, but no new breeding colonies were found. The population trajectory of O. flavescens from southern Patagonia was similar to that observed in the rest of the South Atlantic populations, but the recovery and recolonization processes are still in progress. Here we discuss possible explanations of which factors could have delayed the recovery within the Southwestern Atlantic stocks.

Captura incidental de um leão-marinho-sul-americano na pesca de arrasto de parelha no sul do Brasil

The population of the South American sea lion, Otaria flavescens (Shaw, 1800), in Uruguay is declining at an annual rate of 1.6 to 2.0%. Although the reasons are still unknown, interactions with fishing activities have been identified as a major cause. The individuals that arrive along the coast of Brazil come from the breeding colonies off Uruguay after their breeding period. We report here the first record of incidental catch of South American sea lions in Brazilian waters by a pair trawl. On July 17th, 2008 a young male of South American sea lion was incidentally caught during a commercial pair trawl fishing trip along the southern Brazilian coast (32o57’S, 52o31’W), in a depth ranging from 15 to 20 m. Despite being punctual, this record is an evidence of a potential major threat to South American sea lions in southern Brazil and Uruguay, since trawl industrial fishing is a very important economic activity in South Brazil. Keywords: Pinnipeds, Otaria flavescens , human impact, human-carnivore conflicts, fishery interactions.

Adhesive and invasive capacities of Edwardsiella tarda isolated from South American sea lion.

Edwarsiella tarda is a zoonotic bacterium that can be isolated from humans, animals and the environment. Although E. tarda is primarily considered a fish pathogen, it is the only species of its genus considered to be pathogenic for humans as well. A survey of zoonotic intestinal bacteria in fresh feces from South American sea lions (SASL) Otaria flavescens, reported E. tarda as the most frequently isolated species. In this study, we used HEp-2 cells to establish in vitro the adherence and invasive ability of 17 E. tarda strains isolated from SASL fecal material. All the strains were able to adhere and invade HEp-2 cells with adhesion and invasion percentages ranging from 56 to 100% and 21 to 74%, respectively. Despite the expression of these pathogenic factors, further investigation is needed to determine whether this bacterium could play a role as primary pathogen for this and other species of pinnipeds.