Miguel Iñíguez Bessega

A total of 49 records of beaked whales stranded along approximately 900 km of coast of Santa Cruz Province, Argentina, were documented between 1895 and March 2023. These include 29 previously published and unpublished records (including one specimen re-identified through DNA analysis) and 20 new records. All of these involve at least seven species in five genera. All strandings correspond to single individuals. The most frequent species found stranded were Cuvier’s beaked whales (Ziphius cavirostris) with 14 records, followed by strap-toothed whales (Mesoplodon layardii; n = 13). Species identities were based on skull morphology, tooth morphology and position in the jaw, and morphometric measurements. Additionally, mitochondrial control region DNA was sequenced to confirm species identification for 10 individuals, although confirmation was only possible in seven individuals. This study provides the first record of Arnoux’s beaked whale and Hector’s beaked whale from Santa Cruz Province and emphasizes the importance of the Southwest Atlantic Ocean for multiple beaked whale species. The potential impacts on these whale species of changing sea surface temperatures and ocean warming are unknown.

Detailed here are records of 34 franciscanas (Pontoporia blainvillei) that stranded, including nine rescued alive and returned to sea, from the Río Negro Estuary, Patagonia, Argentina, between 2003 and 2023. The years with the highest stranding records were 2014 and 2020 (n = 6/ each). Autumn and winter/spring were the seasons with the lowest and highest number of strandings, respectively. These strandings comprised 15 females, six males, and 13 unknowns. Total body length of females ranged from 64 to 155 cm and for males ranged from 70 to 138 cm. Five of the strandings involved calves and occurred within the birthing periods previously reported for the species at the Río Negro Estuary. A complete necropsy was performed on three animals. One showed multifocal pneumonic lesions from which Klebsiella pneumoniae was isolated and identified microbiologically. In a second specimen, Pseudomonas sp. and coagulase-negative Staphylococcus sp. were identified, and in a third individual tuberculosis caused by a member of the Mycobacterium tuberculosis complex was identified. Despite these results, it was not possible to be certain that they were the causes of death of these three individuals. Three franciscanas had beak deformities. A total of 79 otoliths representing 41 specimens of white croaker (Micropogonias furnieri) were found in one stomach content analyzed. Eleven franciscanas showed signs of having been bycaught (four with net marks, four entangled in gillnets or reported by the fishermen who bycaught them (n=3)). This is the first report of franciscana entanglements in sport fishing gear at the Río Negro Estuary. This paper provides information highlighted as important by the International Whaling Commission Conservation Management Plan for franciscana, and contributes to knowledge of the species in the Franciscana Management Area IVe. Keywords: bycatch, calves, disease, fishing rods, gillnets, odontocetes

Cetaceans rely on sounds for their survival. Marine environmental degradation due to increased noise levels, including noise from seismic surveys, is an issue of great concern. In many Latin American (LA) countries, these activities proceed without robust environmental impact assessments (EIAs) and effective mitigation plans to minimize impacts on marine life. Only Brazil and Peru have enacted statutory guidelines to mitigate such impacts within their national waters. Colombian environmental authorities impose adoption of JNCC Seismic Guidelines. Some countries and oil companies voluntarily adopt mitigation measures set in the legislation of other countries. EIAs are mandatory to obtain licenses for seismic surveys in 11 countries of the region; however, only Argentina, Brazil and Colombia have specific guidelines to conduct such EIAs but they still suffer some flaws. Application of EIAs, baseline surveillance and real-time monitoring and mitigation of seismic surveys by most LA countries is very poor. There is an urgency to increase awareness among LA countries and urge regulators to enact and enforce proper legislation for marine seismic survey activities. This paper supports the idea of an international legislation to regulate seismic surveys and make some recommendations that should be addressed by the international guidelines.

Killer whales Orcinus orca are found in all oceans of the world, but most of our knowledge on the species comes from studies conducted at higher latitudes. Studies on killer whales in the Caribbean have been scarce. We compiled 176 records of killer whales from the Caribbean, including 95 previously unreported records and 81 records recovered from the literature, consisting of 27 capture or kill records, 4 stranding records and 145 sighting records. Our results indicate that killer whales are widespread in the Caribbean Sea and can be found year‐round in the region. Mean group size was 3.7 animals. A diversity of prey items was recorded, including sea turtles and marine mammals and possibly fish. We cannot exclude ecotype or morphotype‐specific dietary specialization in the Caribbean population. A preliminary morphological analysis of 10 characters in 52 individuals from 21 different groups suggests that Caribbean killer whales do not represent any of the four Antarctic and subantarctic types, type 1 from the northwest Atlantic, or ‘resident’ and ‘transient’ killer whales from the northwest Pacific. Some Caribbean killer whales share a combination of characters typical of type 2 in the North Atlantic, whereas others share those typical of ‘offshore’ killer whales in the northwest Pacific. The significance of this is unclear. Comparison of Caribbean killer whales to previously described morphotypes and ecotypes is hampered by the lack of detailed, quantitative data on variation within other types, as well as by the lack of comparisons of genetic diversity. Our study adds to the growing knowledge of the diversity of killer whales worldwide but underscores that additional research is warranted in the tropics.

This paper reports on the occurrence of the sei whale (Balaenoptera borealis) in the south-western Atlantic. Only in recent years have sei whale sightings been reported regularly within the surveyed area. In a total of 20 sightings, 65% were reported from August to September. Group size was small, averaging 1.94 (SD = 1.21) individuals per group. During this study, feeding behaviour and interactions with seabirds were observed and are here described. Comparison of our results with historical data from the whaling industry showed that whales were observed where expected based on past catches. Further studies are necessary in order to assess the status of sei whales in the south-western Atlantic. However, our data might indicate a slow recovery in the region. This information will be useful for the conservation of the species in this area and in the southern hemisphere.