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The marine ecosystem provides numerous goods and services, dampens the impacts of floods and storms, and provides climate control, through the regulation of carbon fluxes, nutrient cycling, and the bioremediation of human waste and tourism. However, the ocean is vulnerable to anthropogenic threats and has been severely altered by humans.Seabirds and marine mammals are long lived, highly mobile, easily identifiable, and occupy the upper levels of trophic webs. These ecological features make them suitable as sentinels of the marine ecosystem.Sighting data collected during eight oceanographic surveys were analysed to describe and compare the biodiversity of the communities of top predators within the marine protected areas (MPAs) of Namuncurá/Burdwood Bank I and II and the surrounding areas in two contrasting seasons (summer and winter). Data were grouped into six zones based on depth and geographic position.Twenty‐five species of seabirds and 13 species of marine mammals were recorded in 113 days of surveys between 2014 and 2018. Top predator community composition varied seasonally in the different zones.A suite of indicator species was identified according to their specificity and fidelity to a particular zone. Most of the species identified as potentially useful indicators differed between summer and winter, highlighting the importance of conducting systematic surveys in both periods.The MPAs Namuncurá/Burdwood Bank I and II are key areas for top predator communities in the region, mainly in summer when the number and abundance of species increase. However, the waters around Isla de los Estados and the channel between Isla de los Estados and Burdwood Bank were also identified as a relevant habitat for many species. This knowledge should be included to create a regional network of areas under special management considerations that connect the established MPAs with other key pelagic and coastal areas (as found in this study) for the conservation of subantarctic marine megafauna. [ABSTRACT FROM AUTHOR]

Common dolphins, Delphinus delphis, in the southwestern Atlantic Ocean are subject to incidental mortality in fishing gear. However, no information on trends in abundance or estimates of bycatch mortality are available to evaluate the impact of this threat on the population. This study presents estimates of life history parameters using postmortem data obtained over a 17‐year period in Argentina. Ages were determined for 93 specimens, and reproductive organ samples were examined (n = 89). Immature animals ranged from 0 to 6 years in females and from 0 to 9 years in males. Mature animals ranged from 7 to 21 years in females and from 6 to 23 years in males. The asymptotic body length (L∞) described by a Gompertz model fit to age‐length data was 196 cm, 95% CI [192.45, 199.76] for females and 210.75 cm, 95% CI [206.64, 215.30] for males and was attained at 14 years in females and 15 years in males. Comparison to other populations showed that L∞ were shorter than estimates from New Zealand, similar to L∞ from eastern North Atlantic, and longer than estimates from North Pacific common dolphins. Lmax reported here were shorter than New Zealand ones but similar to those previously reported from other populations. [ABSTRACT FROM AUTHOR]

The article discusses the study on the sounds produced by wild Burmeister's porpoises. Burmeister's porpoise is reportedly a species of Phocoenidae which can be found from North Peru to South Brazil. The study was reportedly conducted in the Beagle Channel, Tierra del Fuego, Argentina on January 2 to 3, 2017. Also explored are the characteristics of Burmeister's porpoises and the similarities between the sounds produced by Phocoenidae species.

Commerson’s dolphins (Cephalorhynchus c. commersonii) and Peale’s dolphins (Lagenorhynchus australis) are two of the most common species of cetaceans in the coastal waters of southwest South Atlantic Ocean. Both species are listed as Data Deficient by the IUCN, mainly due to the lack of information about population sizes and trends. The goal of this study was to build spatially explicit models for the abundance of both species in relation to environmental variables using data collected during eight scientific cruises along the Patagonian shelf. Spatial models were constructed using generalized additive models. In total, 88 schools (212 individuals) of Commerson’s dolphin and 134 schools (465 individuals) of Peale’s dolphin were recorded in 8,535 km surveyed. Commerson’s dolphin was found less than 60 km from shore; whereas Peale’s dolphins occurred over a wider range of distances from the coast, the number of animals sighted usually being larger near or far from the coast. Fitted models indicate overall abundances of approximately 22,000 Commerson’s dolphins and 20,000 Peale’s dolphins in the total area studied. This work provides the first large-scale abundance estimate for Peale’s dolphin in the Atlantic Ocean and an update of population size for Commerson’s dolphin. Additionally, our results contribute to baseline data on suitable habitat conditions for both species in southern Patagonia, which is essential for the implementation of adequate conservation measures. [ABSTRACT FROM AUTHOR]

We explored the potential of using energy-dispersive X-ray analysis (EDX), a non-destructive technique, to assess elemental contents in dolphin bones. Specimens were deposited in museum collections, and prepared by different methodologies. Fifty eight Commerson’s dolphins (Cephalorhynchus c. commersonii) chevron bones and 24 Franciscana dolphins (Pontoporia blainvillei) were analysed. The EDX allowed us to detect the following elements: Ca, P, Na, Mg, Fe, K, Zn, S, Cl and Al; and quantify their proportion (weight percent of element). Principal components analysis differentiates two groups according to the cleaning procedures applied, supporting that cleaning methods could influence the chemical integrity of bone. No significant age-dependent increase was found for elements analysed in species, and no significant differences were found between sex and physical maturity stages. Alternative assessment was made through atomic absorption spectrophotometry, providing quantitative information on the principal elements in bones (Ca, P, Mg, Na, Fe and Zn) and allowing comparisons with other studies. A standard protocol for bone cleaning and conditioning is needed to exclude any effect on the mineral integrity of calcified tissue. This would enable future comparative studies on the bone mineral matrix over time housed in natural history museums or other scientific collections. [ABSTRACT FROM PUBLISHER]

The Commerson's dolphin is the most common endemic odontocete of subantarctic waters of Tierra del Fuego, Argentina incidentally caught in fishing nets. The species is classified as “Data Deficient” by the IUCN. Metallothioneins (MTs) are considered as suitable biomarkers for health and environmental monitoring. The aims of the study were to assess MT concentrations in the liver and kidney of bycaught specimens. Moreover, correlations with Zn, Se, Cd, Ag and Hg, and the molar ratios of MT:metals were estimated to evaluate if there is an indication of their respective protective role against metal toxicity in tissues. Hepatic and renal MT concentrations were similar, ranging from 11.6 to 29.1 nmol·g − 1 WW, and Kidney/Liver ratios ranging from 0.73 to 1.93 corresponded to normal ranges. Results suggest that MTs are related to physiological ranges for the species. This information constitutes the first MT report on Commerson's dolphins and possibly considered as baseline for species' conservation. [ABSTRACT FROM AUTHOR]

The article focuses on a study aimed at determining sexual dimorphism across ontogeny in the Commerson's dolphins found in South America. The authors studied more than 300 pelvic bones from male and female Commerson's dolphins. Sex of the dolphins was found by directly observing the genital patch or genital organs during necropsies.

Effects of climatic oscillations on populations in marine environments are produced mainly through the lower trophic levels. Marine mammals, as top predators, are affected indirectly by these fluctuations, showing variations in their survival, growth and reproduction. The main objective of this study was to determine whether we could detect the effect of climatic oscillations on Commerson's dolphins ( Cephalorhynchus c. commersonii) off Tierra del Fuego, Argentina, by examining the presence and proportion of anomalous dentinal growth layer groups ( GLGs). The relative deposition of anomalous GLGs was determined using calendar years from 1960 to 2005, and related to the Southern Annular Mode ( SAM) and El Niño Southern Oscillation ( ENSO) events, and to mean annual sea surface temperatures ( SST). Then, growth parameters between animals that did and did not show anomalous dentinal growth layer patterns in one or more of their GLGs were compared. The presence of anomalous GLGs was related to the SAM, increasing in frequency with negative values of the SAM. No relationship was found among anomalous GLGs, ENSO, and SST. There were no significant differences in growth parameters between animals with and without anomalous GLGs. Using recording structures such as teeth provided a unique way of reconstructing time series to evaluate the effects of these climatic patterns on a top predator species in an area where no similar studies have been conducted, primarily due to a lack of suitable long-term data sets. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to estimate the age of Commerson's dolphins, Cephalorhynchus c. commersonii, through the growth layer patterns of its teeth. It says that the study used teeth from 198 Commerson's dolphins from the R. Natalie P. Goodall (RNP) collection, formalin, and stereo microscope. Results show that the uniformity and consistency in the teeth growth layer group (GLG) structure can be used to create age determination guidelines for the animal.

The skin of bycaught Commerson’s dolphins was tested for mercury (Hg) and selenium (Se) biomonitoring in Subantarctic environments. The correlation of levels detected in the skin with those found in internal tissues – lung, liver, kidney and muscle – was assessed to evaluate how skin represents internal Hg and Se distribution for monitoring purposes. Mercury in skin had a concentration range of 0.68–3.11 μg g −1 dry weight (DW), while Se had a higher concentration range of 74.3–124.5 μg g −1 DW. There was no significant correlation between selenium levels in any of the analyzed tissues. Thus, the skin selenium concentration did not reflect the tissular Se levels and did not provide information for biomonitoring. The lack of correlation is explained by the biological role of Se, provided that each tissue regulates Se levels according to physiological needs. However, the skin Hg level had significant positive correlation with the levels in internal tissues (ANOVA p < 0.05), particularly with that of muscle ( R 2 = 0.79; ANOVA p = 0.0008). Thus, this correlation permits the estimation of Hg content in muscle based on the multiplication of skin biopsy levels by a factor of 1.85. Mercury bioindication using skin biopsies is a non-lethal approach that allows screening of a large number of specimens with little disturbance and makes possible an adequate sampling strategy that produces statistically valid results in populations and study areas. The correlation between Hg levels in the skin and internal tissues supports the use of the epidermis of Commerson’s dolphins for Hg biomonitoring in the waters of the Subantarctic, which is a poorly studied region regarding Hg levels, sources and processes. [ABSTRACT FROM AUTHOR]

Commerson's dolphins Cephalorhynchus c. commersonii are the small cetacean most frequently found stranded along the coast of Tierra del Fuego, Argentina, but little is known about their pathologies. We examined the postcranial axial skeleton of 425 Commerson's dolphins collected in the period 1974-2011 for the presence of pathologies. Miscellaneous lesions were detected in 107 (25.2%) of the specimens. Among them, idiopathic hyperostosis was the most frequent pathology (73.8%), followed by spondyloarthropathy (40.2%). Traumata (25.2%), spondylitis (10.3%) and osteoarthritis (11.2%) occurred less frequently. The type of lesion was statistically associated with the region of the vertebral column. Idiopathic hyperostosis occurred significantly more frequently in the lumbar vertebrae than in other parts of the vertebral column, while spondyloarthropathy was more frequent in the thoracic and caudal vertebrae. Both conditions were predominantly seen in mature dolphins. Osteoarthritis affected the transverse processes of the thoracic vertebrae of 6 males, 3 females and 3 individuals of undetermined sex, all mature. Healed and unhealed fractures were observed in the ribs of 27 specimens and in the transverse processes of 3 others. Spondylitis of various degrees of severity affected the cervical, thoracic, lumbar and caudal regions of 11 individuals. Together these data indicate that bone lesions and traumata commonly occur in Commerson's dolphins, likely causing pain and morbidity in severe cases.