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

Abstract

We investigated the habitat use and feeding ecology of 10 cetacean species encountered along the south-eastern coast of Brazil (24–26°S) using carbon (δ13C) and nitrogen (δ15N) stable isotopes. Hierarchical cluster analysis distinguished two main groups based on their isotopic patterns. One group included migratory baleen whales (Megaptera novaeangliae and Eubalaena australis) with the lowest δ13C and δ15N values, reflecting baseline isotopic values of their Subantarctic feeding grounds and consumption of lower trophic level prey. Resident species and those occasionally occurring in Brazilian coastal waters highly differed from the migratory whales in their isotopic values. In this group, Tursiops truncatus had the highest δ13C and δ15N values, indicating coastal habits and relatively higher trophic position. Similar δ13C values were observed in Sotalia guianensis, Pontoporia blainvillei, Orcinus orca and Steno bredanensis. However, the former two species had lower δ15N values than the latter two, indicating different trophic positions. The relatively lower δ13C values observed in Stenella frontalis suggest greater influence of pelagic prey in their diet. Furthermore, the lower δ13C values observed in Delphinus delphis and Balaenoptera edeni were associated with upwelling events that occur along the region, affecting the isotopic values of their main prey. Juvenile M. novaeangliae had higher δ13C and δ15N than the adults, which may indicate feeding in areas with different isoscapes and consumption of pelagic schooling fish with relatively higher trophic levels than krill. This study provides preliminary information that are useful to understand the habitat use and coexistence of cetacean species occurring in south-eastern Brazil.

Trophic ecology and small‐scale differentiation of ecological groups of franciscana dolphin, Pontoporia blainvillei, in southeastern Brazil, revealed by carbon and nitrogen stable isotopes

“…Because the δ 13 C values are related to the primary source of carbon in the food web, from this result, one can primarily infer that franciscana dolphins from these two regions feed on different carbon sources, i.e., there may be a difference in the use of the area by the species from both subareas. Studies have previously investigated δ 13 C values in cetaceans in other regions of Brazil to ascertain the existence of distinct ecological groups (Bisi et al, 2013; Hardt et al, 2013; Paschoalini et al, 2021). Bisi et al (2013) differentiated four populations of Guiana dolphin on the coast of Rio de Janeiro from the distinct δ 13 C values between the regions.…”

First mercury and stable isotope assessment from an unusual mass stranding of rough-toothed dolphins (Steno bredanensis) (Artiodactyla: Delphinidae) in Azuero peninsula, Pacific coast of Panama

“…The high THg levels likely reflect the rough-toothed dolphins high-trophic prey preferences, which appear to be indicated by the isotopic values enriched in δ 15 N that have been reported in dolphins' skin here and in other areas worldwide (SMT3). Examples include the southern Rio de Janeiro State in Brazil (δ 15 N-mean = 14.5; SD = 0.1 ‰; n = 3; δ 15 Nmean-autumn = 18.1; SD = 0.5 ‰; N = 4; δ 15 Nmean = 18.6; SD = 0.2 ‰; n = 5; Paschoalini et al, 2021;Troina et al, 2020Troina et al, , 2021, La Guajira in the Colombian Caribbean (δ 15 N-mean = 12.8; SD = 0.1 ‰; n = 3; Barragán-Barrera, Farías-Curtidor, Chávez-Carreño et al, 2019), and Moorea Island in the Society Archipelago (δ 15 N-mean = ~ 14.7 ‰; N = 35; Kiszka et al, 2010). The rough-toothed dolphin diet consists of cephalopods and fish of various sizes, including large and carnivorous fish with high trophic levels like black skipjack (Euthynnus lineatus Kishinouye, 1920), mahimahi (Coryphaena hippurus Linnaeus, 1758), and ribbonfish (Trichiurus lepturus Linnaeus, 1758) (Ortega-Ortiz et al, 2014;Pitman & Stinchcomb, 2002;West et al, 2011).…”

The Validation of a Non-Invasive Skin Sampling Device for Detecting Cetacean Poxvirus

“…Cetaceans' skin is considered a multidimensional feature that can provide a wealth of information, forming the basis of research in a wide number of studies covering a broad range of scientific branches [1][2][3][4][5][6][7][8]. Hence, this tissue has been used for long-term health assessments, enabling us to gain a closer look at the health status of marine mammals and aquatic ecosystems [9][10][11][12].…”