Robust demographic estimates are critical for effective conservation but often lacking for threatened species, demanding long-term, range-wide monitoring to generate data and assess risk. Here, we quantify key demographic parameters and evaluate extinction risk at a metapopulation scale to inform conservation planning for Lahille's bottlenose dolphin, an endangered dolphin endemic to the coastal waters of the Southwest Atlantic Ocean. Using Robust Design mark-recapture models on data from a coordinated photo-identification program (2018-2023) across five Management Units (MUs) in the southern Brazil-Uruguay subpopulation, we estimated abundance and survival. Best estimates indicate a total subpopulation abundance of 341 individuals (95% CI: 333-348), with annual survival varying among MUs from 0.934 (95% CI: 0.856-0.971) to 0.968 (95% CI: 0.926-0.986). Metapopulation-based Population Viability Analysis (PVA) projects a 2% decline in subpopulation size over three generations (63 years) under current conditions, with similar to 4% extinction risk for two MUs. Under a worst-case scenario with increased bycatch and habitat degradation, a 94% decline in the subpopulation is projected. Findings highlight the vulnerability of Lahille's bottlenose dolphins and the urgent need for habitat protection and bycatch mitigation. We recommend maintaining and expanding coordinated, long-term monitoring to support adaptive management.

Abstract Marine mammals can exhibit high plasticity in foraging strategies, but how such plasticity is driven by environmental conditions is poorly understood. The American manatee (Trichechus manatus), a large, endangered herbivore, inhabits marine, estuarine, and freshwater environments. To better understand their resource use, we analyzed dietary differences across three large Brazilian regions—the Northern Coast (NC), Dry‐Northeastern Coast (Dry‐NEC), and Humid‐Northeastern Coast (Humid‐NEC). The δ13C and δ15N values of manatee tissues increased from the NC to the Northeastern Coast. Stable isotope mixing models revealed that manatees from the Dry‐NEC feed almost exclusively on seagrasses, while those from the NC rely predominantly on saltmarsh vegetation. In the Humid‐NEC, manatees had a notable contribution from macroalgae, and exhibited the greatest dietary and habitat use diversity among the regions. These spatial patterns advance our understanding of large‐scale habitat use, guiding the establishment of marine protected areas to safeguard manatees and their habitats.

Pinnipeds exhibit diverse reproductive strategies influenced by ecological and environmental factors. Most species breed in well-established colonies that offer sheltered habitats, stable substrates, and reliable prey availability. However, rare reproductive events beyond range can provide insights into population dynamics, including shifts in distribution, and emerging threats, such as habitat disturbance and disease transmission. Here, we document the first records of pinniped births and abortions in the Brazilian coast between 1979 and 2024. These events were documented as part of systematic marine mammal stranding programs conducted year-round in the states of Rio Grande do Sul and Santa Catarina. Four births were recorded, two southern elephant seals (Mirounga leonina) and two South American fur seals (SAFS) (Arctocephalus australis). In addition, 11 abortion events were recorded-two confirmed (one subantarctic fur seal, A. tropicalis, and one South American sea lion (SASL), Otaria flavescens) and nine inferred cases involving SASLs and SAFSs, and unidentified fur seals. We speculate that live births in Brazil resulted from young females' inexperience, including limited prior reproductive activity and poorly developed site fidelity, as well as possible disorientation. However, given their rarity and the unsuitability of the sites where they occurred, such events are unlikely to indicate broader shifts in distribution. Abortions may have occurred as an attempt to reallocate resources for survival and/or as a direct response to stress, reflecting underlying life-history trade-offs influenced by individual condition and external pressures. While the number of reproductive events recorded is low and insufficient to draw population-level conclusions, these rare cases offer unique insights. Continued monitoring and interdisciplinary investigation are essential to understand their causes and broader conservation implications.

The South American sea lion, Otaria flavescens, is endemic to the Atlantic and Pacific coasts of South America, utilizing the southern Brazilian coast for resting and foraging. Due to the elevated biological productivity of the region, the fishing industry is one of the most important economic activities for the local human population. Gillnets and trawlers are the most prevalent fleets operating along the coastal region. The overlap between the foraging grounds of sea lions and fisheries leads to diverse interactions, with depredation being one of the most common, particularly in the case of gillnets. To evaluate and better comprehend this dynamic, a stomach content analysis was performed on sea lions washed ashore along the southern coast of Rio Grande do Sul in southern Brazil. The analysis focused on fragments of fishing gear that had been ingested. A total of 51 individuals were sampled through beach monitoring surveys, revealing that 16 (31.4 %) of them had ingested fragments of fishing nets. The predominant types identified were monofilament nets with mesh sizes of 90 mm, 100 mm, and 220 mm, corresponding to gillnet fisheries. GLMs showed that total length is a significant explanatory variable for both the presence and the weight of ingested fragments, likely reflecting a possible accumulation process over the animals’ lifetime. These results highlight the prevalence of interactions between southern Brazilian fisheries and sea lions, raising concern for this already impacted population.

Bigeye tuna (Thunnus obesus) is among the most prized tuna species sustaining fisheries worldwide. However, information on the feeding habits for the species is mostly restricted to the size range harvested by commercial fisheries. In this study, we report the diet composition of juvenile bigeye tuna schooling near the surface at night in the oceanic area of the southwestern Atlantic Ocean. We combined short-term dietary information derived from stomach content analysis (n = 14) with time-integrated diet information from carbon (delta C-13) and nitrogen (delta N-15) stable isotope analysis (n = 8) to characterize diet composition and estimate trophic position (TPbulk) of the individuals. The prey-specific index of relative importance (%PSIRI) indicated that Teleostei (79.1%) was the most important taxon, followed by Cephalopoda (7.6%) and Crustacea (3.9%). Myctophidae was the most frequent Teleostei in the diet (frequency of occurrence: 85.7%). The delta C-13 values on juvenile tuna muscle tissue ranged from -18.6 parts per thousand to -17.4 parts per thousand (mean +/- SD: -18.1 +/- 0.5 parts per thousand) and delta N-15 values ranged from 7.2 parts per thousand to 8.4 parts per thousand (mean +/- SD: 7.8 +/- 0.3 parts per thousand). TPbulk (4.15 +/- 0.47) results corroborated a diet based on lanternfishes and the predation upon relatively small-sized oceanic squids. Our results address a knowledge gap by highlighting important trophic links for bigeye tuna before they reach a size suitable for exploitation.

The ingestion of debris by marine fauna is a growing threat to biodiversity. This study aimed to evaluate and characterize litter ingestion by odontocetes from the Western South Atlantic. Between 2018 and 2022, 154 stomachs from six species were collected from stranded individuals and incidental captures. Stomach contents were analyzed with the naked eye and items of anthropic origin found were counted and physically/chemically characterized. Generalized Linear Models were used to evaluate the influence of biological factors on the presence/absence of litter in stomachs, and for Pontoporia blainvillei only, the influence of these factors on the number of ingested items was also tested; additionally, a temporal analysis of ingestion was done for this species (1994-2022). A total of 156 items, mainly macro-sized plastics made of polypropylene, were found in 52 stomachs of four species: Tursiops spp. (FO% = 3.3%), Steno bredanensis (10.0%), Delphinus delphis (28.6%) and P. blainvillei (47.5%). The presence/absence of litter was explained only by species (chi(2) = 28.29 and p < 0.001). For P. blainvillei, a threatened species in the region, the number of items was positively influenced by individual size (chi(2) = 6.01 and p = 0.01) and sex (chi(2) = 7.93 and p = 0.005). There was an increase in plastic ingestion by this species over the years (chi(2) = 121.6 and p < 0.001) and it was estimated that 75% of P. blainvillei stomachs will contain plastic by 2040. The ingestion of litter by odontocetes from the Western South Atlantic was confirmed and the potential risks posed by this type of pollution were evidenced, especially since these species also face other anthropic pressures. These results further demonstrate the increasing threat of litter in the ocean and highlight the importance of circularity of plastics and proper waste management.

Marine Mammal ScienceEarly View e13163 NOTE Impacts and lessons learned from the first highly pathogenic avian influenza (H5N1) outbreak in South American pinnipeds along the southern Brazilian coast Renan C. de Lima, Corresponding Author Renan C. de Lima [email protected] orcid.org/0000-0002-9311-7085 Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Correspondence Renan C. de Lima, Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil. Email: [email protected] Contribution: Conceptualization, Data curation, Formal analysis, ​Investigation, Methodology, Writing - original draftSearch for more papers by this authorSérgio C. Estima, Sérgio C. Estima Núcleo de Educação e Monitoramento Ambiental, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorMaurício Tavares, Maurício Tavares orcid.org/0000-0003-3618-9928 Centro de Estudos Costeiros, Limnológicos e Marinhos, Universidade Federal do Rio Grande do Sul, Imbé, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorPaula L. Canabarro, Paula L. Canabarro orcid.org/0009-0001-5413-5301 Centro de Recuperação de Animais Marinhos, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorSilvina Botta, Silvina Botta orcid.org/0000-0001-6219-6932 Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorLiane A. Dias, Liane A. Dias Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, ​Investigation, Writing - review & editingSearch for more papers by this authorAndrine P. da Silva, Andrine P. da Silva Núcleo de Educação e Monitoramento Ambiental, Rio Grande, RS, Brazil Contribution: Data curation, ​Investigation, Writing - review & editingSearch for more papers by this authorDerek B. de Amorim, Derek B. de Amorim Centro de Estudos Costeiros, Limnológicos e Marinhos, Universidade Federal do Rio Grande do Sul, Imbé, RS, Brazil Contribution: Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorLarissa R. de Oliveira, Larissa R. de Oliveira orcid.org/0000-0002-5735-3697 Laboratório de Ecologia de Mamíferos, Universidade do Vale do Rio dos Sinos, São Leopoldo, RS, Brazil Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul, Torres, RS, Brazil Contribution: Conceptualization, Funding acquisition, ​Investigation, Supervision, Writing - review & editingSearch for more papers by this author Renan C. de Lima, Corresponding Author Renan C. de Lima [email protected] orcid.org/0000-0002-9311-7085 Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Correspondence Renan C. de Lima, Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil. Email: [email protected] Contribution: Conceptualization, Data curation, Formal analysis, ​Investigation, Methodology, Writing - original draftSearch for more papers by this authorSérgio C. Estima, Sérgio C. Estima Núcleo de Educação e Monitoramento Ambiental, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorMaurício Tavares, Maurício Tavares orcid.org/0000-0003-3618-9928 Centro de Estudos Costeiros, Limnológicos e Marinhos, Universidade Federal do Rio Grande do Sul, Imbé, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorPaula L. Canabarro, Paula L. Canabarro orcid.org/0009-0001-5413-5301 Centro de Recuperação de Animais Marinhos, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorSilvina Botta, Silvina Botta orcid.org/0000-0001-6219-6932 Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorLiane A. Dias, Liane A. Dias Laboratório de Ecologia e Conservação da Megafauna Marinha, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil Contribution: Conceptualization, Data curation, ​Investigation, Writing - review & editingSearch for more papers by this authorAndrine P. da Silva, Andrine P. da Silva Núcleo de Educação e Monitoramento Ambiental, Rio Grande, RS, Brazil Contribution: Data curation, ​Investigation, Writing - review & editingSearch for more papers by this authorDerek B. de Amorim, Derek B. de Amorim Centro de Estudos Costeiros, Limnológicos e Marinhos, Universidade Federal do Rio Grande do Sul, Imbé, RS, Brazil Contribution: Data curation, Funding acquisition, ​Investigation, Writing - review & editingSearch for more papers by this authorLarissa R. de Oliveira, Larissa R. de Oliveira orcid.org/0000-0002-5735-3697 Laboratório de Ecologia de Mamíferos, Universidade do Vale do Rio dos Sinos, São Leopoldo, RS, Brazil Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul, Torres, RS, Brazil Contribution: Conceptualization, Funding acquisition, ​Investigation, Supervision, Writing - review & editingSearch for more papers by this author First published: 30 July 2024 https://doi.org/10.1111/mms.13163Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. 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Stomach contents of South American (Arctocephalus australis) (n = 219) (SAFS) and sub-Antarctic (A. tropicalis) (n = 37) (SFS) fur seals were opportunistically sampled from 1980 to 2021 to examine their feeding habits and resource partitioning in southern Brazil while in their nonreproductive periods. SAFSs mainly consumed abundant coastal pelagic species, such as Anchoa marinii and Doryteuthis sanpaulensis, resulting in high sexual trophic niche overlap. The frequency of occurrence (%FO) of fish prey, especially the overexploited Micropogonias furnieri, decreased between 1980-1992 and 2007-2021, while squid increased. For SFSs, offshore squids such as Ommastrephes bartramii and Illex argentinus were the most important prey considering both sexes in the long-term. The interspecific trophic niche overlap was low, but it is likely underestimated since it increased with the inclusion of scat samples from SFSs. This sample-size effect was also observed in Shannon's diversity index, which was lower for underrepresented SFSs. Marine debris ingestion was detected in both species (SAFS %FO = 2.7; SFS %FO = 8.3), with only flexible plastic material found. This study brings novel information on feeding habits of fur seal species in the extreme south of Brazil, as well as unprecedented information about their ecology during the nonreproductive period.

This study presents the pattern of occurrence of sub-Antarctic fur seals (SAFS), Arctocephalus tropicalis , in the southern Brazilian coast and evaluate its association with climatic variability and anomalies in the concentration of chlorophytes and sea surface temperature in the reproductive colonies of Gough and Tristan da Cunha Islands. Date, sex, and age class of 254 stranded SAFS recorded between 1992 and 2013 were analyzed. Representative indexes of the patterns of climatic variability and environmental variables were obtained between four and five months before the records, the assumed interval of displacement for species between their closest breeding colonies and the southern Brazilian coast. The species was observed in southern Brazil between May and November each year, and most individuals were adult males. The records of SAFS on the southern Brazilian coast were associated with low concentration of chlorophytes interacting with negative sea surface temperature anomalies, and positive events of South Annular Mode, South Atlantic Ocean Dipole and Indian Ocean Dipole. Climatic variability is influencing the ecology SAFS, because it affects the environmental factors, that act as a driver of dispersion of the species. These variables had been interacting together in the region of the breeding colonies, and possibly during the fur seals’ journey towards the Brazilian coast. Considering the current scenario of global climate change, we expect that SAFS will continue to disperse to areas beyond their regular distribution, not only in the direction of the coasts of southern continents, but also further south, towards higher latitudes.