Ciencias Marinas

Plastic debris (PD) ingestion was examined in 106 Franciscana dolphins (Pontoporia blainvillei) incidentally captured in artisanal fisheries of the northern coast of Argentina. Twenty-eight percent of the dolphins presented PD in their stomach, but no ulcerations or obstructions were recorded in the digestive tracts. PD ingestion was more frequent in estuarine (34.6%) than in marine (19.2%) environments, but the type of debris was similar. Packaging debris (cellophane, bags, and bands) was found in 64.3% of the dolphins, with a lesser proportion (35.7%) ingesting fishery gear fragments (monofilament lines, ropes, and nets) or of unknown sources (25.0%). PD ingestion correlated with ontogenetic changes in feeding regimes, reaching maximum values in recently weaned dolphins. Because a simultaneous increase in gillnet entanglement and the bioaccumulation of heavy metals take place at this stage, the first months after trophic independence should be considered as a key phase for the conservation of Franciscana dolphin stocks in northern Argentina.

A partir del análisis de 73 cráneos de Arctocephalus australis se determinó el patrón y orden de cierre de 12 suturas craneanas utilizando cuatro estadios de cierre sutural (1: sutura abierta, 2: sutura menos del 50 % cerrada, 3: sutura más del 50 % cerrada y 4: sutura cerrada). Las suturas presentaron patrones de cierre diferentes según la región del cráneo considerada. Las suturas del neurocráneo (Región Neural) son las primeras en mostrar un cierre parcial caracterizado por un único patrón de cierre, proporcional al incremento en el largo del cráneo, y alcanzan el cierre completo en una etapa temprana del desarrollo. Las suturas de la Región Rostral (rostro y paladar) comienzan su maduración en forma tardía, con una gran variación en las diferentes etapas de desarrollo del cráneo, y presentan tres patrones principales de cierre. El avance de cierre de las suturas de A. australis, responde a un patrón postero-anterior y dorso-basal. Pese al conocido dimorfismo sexual en los pinnípedos, no se observaron diferencias en el patrón y orden de cierre de las suturas estudiadas en machos y hembras. Algunas de las suturas estudiadas pueden ser consideradas como claras indicadoras del estadio de desarrollo de la especie, como el caso de las suturas basioccipital-basisfenoides y la basisfenoides-presfenoides, cuyos cierres completos definen claramente la madurez física del cráneo.

The present study provides information about the diet composition of franciscana dolphin, Pontoporia blainvillei, from southern Buenos Aires coast, Argentina. From 2003 to 2011 we collected 66 franciscana dolphins that were incidentally entangled in artisanal fishing nets. We analyzed the stomach contents and estimated the prey size in order to evaluate the diet composition and the overlapping with fisheries. We identified 11 prey species in the stomach contents; only two of them were important in the diet, the striped weakfish, Cynoscion guatucupa, and the squid, Loligo sanpaulensis. Almost all the prey found in the diet of franciscana dolphins are of commercial interest. The overlapping of target species and prey that are subject to overfishing could enhance the vulnerability of franciscana by reducing food availability.

Please cite this article in press as: Giardino, G.V., et al., Travel for sex: Long-range breeding dispersal and winter haulout fidelity in southern sea lion males. Mammal. Biol. (2014), http://dx.a b s t r a c t Southern sea lions (Otaria flavescens; SSLs) have a polygynous mating system and a prolonged socialsexual 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 700 km) 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.