Four fin whale sub-species are currently considered valid: Balaenoptera physalus physalus in the North Atlantic, B. p. velifera in the North Pacific, B. p. quoyi and B. p. patachonica in the Southern Hemisphere. The last, not genetically validated, was described as a pygmy-type sub-species, found in low to mid latitudes of the Southern Hemisphere. Genetic analyses across hemispheres show strong phylogeographic structure, yet low geographic coverage in middle latitudes of the Southern Hemisphere impeded an assessment within the area, as well as evaluating the validity of B. p. patachonica. New mtDNA sequences from the Southeastern Pacific allowed an improved coverage of the species’ distribution. Our phylogenetic analyses showed three main lineages and contrasting phylogeographic patterns between Northern and Southern Hemispheres. Absence of recurrent female mediated gene flow between hemispheres was found; however, rare dispersal events revealing old migrations were noted. The absence of genetic structure suggests the existence of one single taxa within the Southern Hemisphere. Thus, until further evidence supporting this subspecies can be produced, such as genetic, ecological, behavioral, or morphological data, we propose that all fin whales from the Southern Hemisphere, including those from middle latitudes of the Southeastern Pacific belong to B. p. quoyi subspecies. This information is important for the current assessment of fin whales, contributing to the evaluation of the taxonomic classification and the conservation of the species.

Fin whales (Balaenoptera physalus) have been documented along the coast of Chile since the early 20th century; however, information on their ecology and movement patterns remains poorly known. In the spring of 2015, six implantable satellite tags were deployed on fin whales around the marine reserves of Isla Chañaral and Islas Choros‐Damas (approximately 29°S) to evaluate their movements and habitat use off the coast of Chile. A switching state–space model was used to estimate the predicted track of the whales as well as behavioural modes classified as ‘transiting’ and ‘area‐restricted search’ (ARS). Whales were tracked for periods ranging between 4 and 162 days (mean = 68 ± 52 days), covering an average distance of 3225.7 ± 2871.6 km. Five of the six whales remained at middle latitudes for prolonged periods of time, moving in a north–south pattern near the coast, and spending most of their time in ARS behaviour (72.5% of the locations). Only one individual showed a clear southbound migratory behaviour, and remained in transit behaviour for most of the period it was followed. These results suggest that some of the fin whales that are observed in Chile do follow a migration to high latitudes, whereas others remained at middle latitudes, probably using critical habitats as feeding grounds during the summer. This information not only contributes new information on the behaviour and foraging patterns of this species, but is also of particular interest to promote the growing whale‐watching activity, and also to better inform conservation and management efforts for this species in Chile.

We analyzed spatial, temporal, and age/sex variation in the diet of the South American sea lions (SASL, Otaria byronia) in southern Chile via δ13C and δ15N isotope analysis, with emphasis on exotic farmed and feral salmonids as a source of prey for this generalist predator. Isotope mixing models show that the primary prey consumed by SASL were demersal and benthopelagic fishes. Individuals sampled in summer and in the outer coast had higher δ15N values than those from winter or from the inner coast due to consumption of high trophic level demersal fish. We also found evidence of an ontogenetic shift in isotopic niche width as measured by δ13C and δ15N standard ellipse areas, with juveniles showing a restricted isotopic niche width (1.0‰2) in comparison to subadult (2.2‰2) and adult males (1.9‰2). The proportion of salmonids in the diet of the SASL was negligible and lower than reported in previous studies, which may be related to a recent drop in the production of salmon aquaculture in the region. Our study suggests that the SASL are able to adapt to shifts in spatiotemporal variations in the abundance of potential prey, including feral and farmed salmonids.