This study represents the first survey of the parasitic fauna of cetaceans off the northeastern coast of Brazil. Parasites were collected from 82 animals rescued from the states of Ceará to Bahia, including the archipelago of Fernando de Noronha. A total of 14 species of cetaceans were evaluated: Sotalia guianensis, Stenella sp., Stenella clymene, Stenella longirostris, Stenella coeruleoalba, Stenella frontalis, Megaptera novaeangliae, Peponocephala electra, Steno bredanensis, Kogia breviceps, Kogia sima, Globicephala macrorhynchus, Tursiops truncatus, Physeter macrocephalus and Lagenodelphis hosei. The parasites were fixed and preserved in 70% ethanol or alcohol-formalin-acetic acid solution (AFA), clarified in phenol and mounted on slides for morphological identification. In total, 11 species and 8 genera of endo- and ectoparasites were identified: Halocercus brasiliensis, Halocercus kleinenbergi, Stenurus globicephalae, Halocercus sp., Anisakis sp., Crassicauda sp. (Nematoda), Phyllobothrium delphini, Monorygma grimaldii, Scolex pleuronectis, Strobicephalus triangularis, Tetrabothrius forsteri, Tetrabothrius sp., Trigonocotyle sp., Diphyllobothrium sp. (Cestoda), Campula sp. (Trematoda), Bolbosoma sp. (Acanthocephala), Cyamus boopis, Syncyamus pseudorcae and Xenobalanus globicipitis (Crustacea). The identification of some species represented novel records for the country and increased the occurrence of some parasites to new hosts. The use of standardized methodologies for collecting and evaluating a larger number of animals is essential for a better understanding of host-parasite relationships in cetaceans and their use as biological indicators in the region.

Alive Antillean manatee stranding is one of the main challenges for the conservation of the species in Brazil. In the present study, data on Antillean manatee stranding recorded by the CMA/ICMBio's Wild Animals Rehabilitation Center from 1987 to 2015 were analyzed. The CMA and the REMANE's (Northeastern Aquatic Mammal Stranding Network's) institutions have rescued on average five Antillean manatees per year. Approximately 56% of the animals were alive when rescued, and 43.7% were found dead. The states of Ceará and Rio Grande do Norte have the highest records of stranding, rescue, and assistance of alive calves. Stranding of alive specimens is more frequent during the austral summer, especially in January, February, and March. In the North region, the main threat to the Antillean manatee population seems to be interaction with fishing activities. Studies on the causes of dependent calf stranding in northeast Brazil are urgently needed to promote the development of public policies for the conservation of the species. Brazil's manatee rehabilitation centers must undergo improvements to better assist stranded calves, which need special care to survive.

The present study investigated both circadian and seasonal fluctuations in the daytime activities of the spinner dolphin, Stenella longirostris, from the Fernando de Noronha Archipelago in Brazil. The number of dolphins, and aerial, and reproductive activities were documented. The observations were carried out from January 1997 to December 2001. Temporal series and rhythmic characteristics (mesor, rhythmic percentage, and acrophase) were obtained by COSINOR analysis and later compared. The dolphins entered the bay in the morning, displayed aerial and reproductive activities during daytime, and left the bay in late afternoon to the open ocean. This study indicated that the rainy season affected the three behaviors investigated decreasing the rhythms parameter and advancing the beginning of these activities. The number of individuals was higher during the dry season and the animals stayed longer inside the bay. During the dry season, there was a bimodal expression of aerial activity, expressing a longer use of the temporal niche than in the rainy season. The phases with high frequencies of aerial activity seemed associated with those showing high reproductive activity, both with peak frequencies at about 0800. The results represent an important contribution to the advancement of chronobiological studies, and to the biology of cetaceans, considering that the existence of circadian and seasonal rhythms was proven in the behavior of spinner dolphins in an area of the SW Atlantic. Moreover, it allows restricting periods of the day for the activities of tourism as a form of minimizing the impacts of the boats on the dolphins.

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The present study demonstrates the influence of the time of the day and tide on the frequency of individuals and on the social and foraging behaviour of an equatorial population of Sotalia guianensis. A population of S. guianensis from enseada do Curral (6813 0 00 00 S 3583 0 36 00 W), north-eastern Brazil, was investigated from October 1999 to September 2003. Social and foraging activities oscillated significantly, being less intense at high tide in comparison to other analysed tides. Socialization was more intense between 1000 and 1300 hours and foraging was more intense in between tides, than at high tide. No diurnal or tidal fluctuation was found on the frequency of individuals, which remained constant throughout the day. These results demonstrate the influence of circadian factors on an equatorial population which is highly impacted by human activities and highlights a need for protective measures.