Cetaceans along the southeastern Brazilian coast: occurrence, distribution and niche inference at local scale

Abstract

It is deemed important to understand cetacean occurrence and distribution to comprehend their ecological roles. The geographical occurrence of species’ niche can be used to better describe their potential distribution. The niche can be defined using environmental variables. Those variables are considered static and not affected by biological activities. The present study goal was to assess the occurrence and distribution of cetaceans along the southeastern Brazilian coast, as well as to define the fundamental and realized niche of each species and to investigate niche overlap at local scale. The environmental requirements for each species were also investigated throughout statistical tests. Sighting data were obtained through oceanographic surveys conducted between 2012 and 2015. The environmental variables available on MARSPEC and the software NicheA were used for the ecological niche modeling. A total of twelve cetacean species were identified and the potential distribution areas of the six commonest ones were defined. Even though the species presented different environmental preferences, most of them had partial overlap among niches and potential distribution areas. The environmental heterogeneity of the study area might support the co-occurrence of different species with different environmental requirements.

Trophic ecology and foraging areas of cetaceans sampled in the coastal waters of south-eastern Brazil assessed through skinδ13C andδ15N

“…The isotopic values estimated for T. truncatus indicate the consumption of coastal/benthic prey and relatively higher trophic position than the other species analysed. This is in agreement with previous studies on the same species in south-eastern Brazil, that also suggested the use of inshore areas along the 16 and 45 m isobaths (Figueiredo et al, 2020;Paschoalini & Santos, 2020) and high trophic level (Bisi et al, 2013). Additionally, stomach content analyses of T. truncatus from south-eastern Brazil showed a great importance of demersal piscivorous fish, such as cutlass fish (Trichiurus lepturus), banned grunt (Conodon nobilis) and Atlantic midshipman (Porichthys The number of skin samples obtained from stranded (STR), incidentally caught (IC) or biopsied (BP) individuals and the total number of samples (N) for each species; Mean (± SD) of C/N ratios, measured and mathematically corrected carbon (δ 13 C and δ 13 C cor , respectively), and nitrogen stable isotopes (δ 15 N).…”

“…We considered T. truncatus, S. frontalis, S. guianensis and P. blainvillei as resident species, based on available information resulting from sightings, strandings and accidental catches along the south-eastern coast of Brazil (Santos et al, 2010(Santos et al, , 2017(Santos et al, , 2019, as well as recent results on local cetacean niche modelling (Figueiredo et al, 2020). The large Euclidean distance between T. truncatus and the remaining odontocetes is related to its significantly higher δ 15 N values in comparison to the remaining cetacean species.…”

“…Cetaceans are known to play several ecological roles in the ecosystems they inhabit, including the control of prey populations, and vertical and horizontal transport of nutrients (Roman et al, 2014). To date, eight baleen whale and 27 odontocete species have been recorded in south-eastern Brazilian waters (Santos et al, 2010;Miranda et al, 2019;Figueiredo et al, 2020). Except for the Bryde's whale (Balaenoptera edeni), for which movement knowledge is limited in south-eastern Brazil (Siciliano et al, 2004;Santos et al, 2019), the other species of baleen whales are seasonal visitors during their migration to their reproductive areas in tropical regions (e.g.…”

“…Odontocete species include resident species such as franciscana (Pontoporia blainvillei) and Guiana dolphins (Sotalia guianensis), which occur in the inner part of the continental shelf and estuaries along the region (Figueiredo et al, 2020). Other species, such as the Atlantic spotted dolphin (Stenella frontalis) and bottlenose dolphin (Tursiops truncatus) occur in coastal waters mainly in the 20-50 m isobaths (Santos et al, 2017;Figueiredo et al, 2020;Paschoalini & Santos, 2020). Some other species such as the common dolphin (Delphinus delphis) and orcas (Orcinus orca) are assumed to be occasional visitors (Santos et al, 2010(Santos et al, , 2019.…”

Echolocation characteristics of franciscana dolphins (Pontoporia blainvillei)

“…The results presented here share spectral and temporal details of the echolocation and burst pulse clicks of P. blainvillei from coastal waters in the southeastern Atlantic Ocean. When modeling the niche of local cetaceans, Figueiredo et al (2020) warned that onboard sightings were not the best tool when considering P. blainvillei , which was not sighted in an area of a large number of incidental captures (see Campos et al, 2020) where they are camouflaged by turbid waters. Thus, our descriptions of P. blainvillei acoustic parameters provide new tools for further investigations of this species occurrence in local waters using PAM.…”