Pontoporia Blainvillei Research Articles

Charismatic Species as Indicators of Plastic Pollution in the Río de la Plata Estuarine Area, SW Atlantic

Marine plastic pollution is projected to increase globally in the next few decades. This holds true for South America where the number of species that interacts with plastics is increasing. In this study, we explore for the first time the potential of certain charismatic species of marine turtles, mammals and seabirds as indicators of plastic pollution in the Río de la Plata (RdP), one of the largest and most important estuarine areas of the Southwest Atlantic. Through a revision of published studies integrated with unpublished data, we summarize studies on the interaction of charismatic marine species with plastics in the region and evaluate their role as indicators of plastic pollution in the RdP based on aspects of their local ecology and key attributes (i.e., biological/ecological, methodological, and conservation attributes) of indicator species. We found that at least 45 charismatic marine species interact –whether by ingestion or entanglement– with plastics in the region. Eight of these species were selected as potential indicators given their occurrence, probability of sampling and interaction with plastics in the RdP, namely:Chelonia mydas,Caretta caretta,Dermochelys coriacea,Pontoporia blainvillei,Arctocephalus australis,Otaria flavescens,Larus dominicanus, andSpheniscus magellanicus. The species shared some key attributes of indicator species, e.g., they are relatively well studied, but differed in critical aspects such as their home range and mobility. We discuss whether the species’ attributes are strengths or weaknesses according to the available knowledge on their ecology in the RdP, and propose a multispecies indicator of plastic pollution given that those strengths and weaknesses can be compensated among species. Monitoring plastic pollution through a combination of species would enable a better understanding of plastic pollution in this relevant area.

Temporal trends of trace elements bioaccumulation by a vulnerable cetacean (Pontoporia blainvillei) before and after one of the largest mining disasters worldwide

One of the largest environmental disasters worldwide occurred on November 5th, 2015, when the Fundão dam collapsed in Mariana (Minas Gerais State, Southeast Brazil). The tailing mud flooded the Doce River basin and reached the sea in the coast of Espírito Santo State (ES), Southeast Brazil. This coastal region is the habitat of the most isolated population of franciscana dolphins (Pontoporia blainvillei), with the lowest populational census and lowest genetic diversity in Franciscana Management Area Ia (FMA Ia) - 18° 25′S and 21° 17′S. This study aimed to assess the bioaccumulation of trace-elements (As, Cd, Cu, Fe, Hg, Mn, and Zn) in muscle, liver and kidney of franciscana dolphins collected near the Doce River's mouth before (n = 32) and after (n = 19) the tailing mud reached the sea. The Generalized Additive Model (GAM) showed increasing temporal trends of Hg and Zn in muscle and liver after the dam failure, probably related to higher concentrations and bioavailability in the water column and sediments from the Doce River. Declining trends were found for As and Cu muscular and hepatic concentrations and Fe concentrations in kidney due to their lower bioavailability after the disaster, caused by association with tailings mud trapped in the riverbanks and suspended particulate material. Additionally, higher As and Hg concentrations found in the first period of sampling may be due to historical contamination by mining activities. The full extent of the impacts caused by the Fundão dam failure is still unknown. However, due to their rapid increase and remobilization process, toxic effects can be induced in the biota by these elements. Elements' bioaccumulation in this study contributes to the knowledge of franciscana dolphins from FMA Ia. Considering the conservation concern regarding this franciscana population and its scarce knowledge, the impact of this disaster can be alarming for species conservation.

Long-term assessment of trace elements in franciscana dolphins from the Río de la Plata estuary and adjacent Atlantic waters

The estuary of Río de la Plata, in the eastern coast of South America, is a highly anthropized area that brings a high load of contaminants to the surrounding waters, which may have detrimental effects on the local marine fauna. The franciscana dolphin (Pontoporia blainvillei) is a small cetacean species endemic of the southwestern Atlantic Ocean listed as Vulnerable in the IUCN red list. In this study, we assessed the concentrations of 13 trace elements in bone samples from 100 franciscana dolphins that were found stranded dead or incidentally bycaught in the Río de la Plata and adjacent coast between 1953 and 2015. Elements were, in decreasing order of mean concentrations: Zn > Sr > Fe > Al > Mn > Cu > Pb > Cr > Ni > As > Hg > Cd > Se. The concentrations of Al, Cr and Fe were slightly higher in females than in males. The concentrations of As, Ni, and Pb significantly decreased with body length. Throughout the study period, the concentrations of Al, Cr, Cu, Fe, Mn and Ni significantly increased, while the concentrations of As, Pb and Sr significantly decreased. The increasing trends may be due to increased inputs from river discharges, the leather industry and petroleum refineries, while the decrease in Pb may be due to the ban in the use of this element as an additive in gasoline and as component of car batteries. This investigation supports the validity of analysing trace element in bone, a tissue available in scientific collections and museums, to retrospectively examine variation over long temporal scales and thus assess long-term trends in pollution.

Colistin-resistant Enterobacter kobei carrying mcr-9.1 and blaCTX-M-15 infecting a critically endangered franciscana dolphin (Pontoporia blainvillei), Brazil.

The emergence of mobile mcr genes mediating resistance to colistin is a critical public health issue that has hindered the treatment of serious infections caused by multidrug‐resistant pathogens in humans and other animals. We report the emergence of the mcr‐9.1 gene in a polymyxin‐resistant extended‐spectrum β‐lactamase (ESBL)‐producing Enterobacter kobei infecting a free‐living franciscana dolphin (Pontoporia blainvillei), threatened with extinction in South America. Genomic analysis confirmed the presence of genes conferring resistance to clinically relevant β‐lactam [bla CTX‐M‐15, bla ACT‐9, bla OXA‐1 and bla TEM‐1B], aminoglycoside [aac(3)‐IIa, aadA1, aph(3'')‐Ib and aph(6)‐Id], trimethoprim [dfrA14], tetracycline [tetA], quinolone [aac(6')‐Ib‐cr and qnrB1], fosfomycin [fosA], sulphonamide [sul2] and phenicol [catA1 and catB3] antibiotics. The identification of mcr‐9.1 in a CTX‐M‐15‐producing pathogen infecting a critically endangered animal is of serious concern, which should be interpreted as a sign of further spread of critical priority pathogens and their resistance genes in threatened ecosystems.

Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

AbstractThe franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squidDoryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

Genetic identification of Anisakis spp. (Nematoda: Anisakidae) from cetaceans of the Southwestern Atlantic Ocean: ecological and zoogeographical implications.

Adult Anisakis Dujardin, 1845 were found in two specimens of killer whale Orcinus orca and one specimen of franciscana Pontoporia blainvillei stranded from off the coast of Buenos Aires Province, Argentina. Genetic identification of the nematodes (N = 144) was performed by sequence analysis of the mitochondrial (mtDNA cox2) and the nuclear (nas 10 nDNA) gene loci. Anisakis pegreffii and Anisakis berlandi were detected in the two individuals of O. orca, while Anisakis typica and A. pegreffii were identified in P. blainvillei. Morphological and morphometric analysis also carried out on adult specimens of A. pegreffii and A. berlandi has allowed to underlining the usefulness of genetic/molecular markers in their recognition. This represents the first record of A. pegreffii in O. orca and P. blainvillei and of A. berlandi in O. orca. This is also the first sympatric and syntopic occurrence, as adults, of A. pegreffii and A. berlandi from the Austral Region of the Atlantic Ocean waters. These results provide insights into the knowledge of the host ranges and geographical distribution of these parasites in the basin waters of the region. Pontoporia blainvillei showed low abundance values of infection with Anisakis spp., which is the general pattern for coastal dolphins in the area, whereas O. orca harboured higher abundance of Anisakis spp. than those previously recorded among cetacean species in the Argentine Sea. Differences in the Anisakis spp. distribution and their parasitic loads, observed among the three host specimens, are discussed in relation to the oceanographic parameters, as well as to the host ecology. The usefulness of genetic/molecular markers in the recognition of adults of the sibling species A. pegreffii and A. berlandi with considerable overlapping in morphometric and morphological characters was underlined. The distribution of Anisakis species from Southwestern Atlantic waters is discussed in relation to their value as indicators for studies on the zoogeography of their hosts at a regional-scale level.

Definition of no‐fishing zones and fishing effort limits to reduce franciscana bycatch to sustainable levels in southern Brazil

AbstractFranciscana dolphin Pontoporia blainvillei bycatch has been high for near six decades in western South Atlantic, with large regional variation. In 2012, the Brazilian Government‐regulated gillnet fisheries in south and southeast Brazil by reducing fishing effort and establishing no‐fishing zones. However, there is evidence that the magnitude of franciscana bycatch remains high and unsustainable. The aims of this study were to identify hotspot areas of franciscana bycatch associated with two main gillnet fisheries and to propose no‐fishing zones combined with limited total allowable fishing effort (i.e. total net length per season) in order to meet management objectives in southern Brazil. A hierarchical Bayesian model using integrated nested Laplace approximation (INLA) was employed based on 1427 reported settings from 1999 to 2003 and 2006 to 2009. Hotspot zones were detected and are proposed as no‐fishing zone during the white croaker Micropogonias furnieri and striped weakfish Cynoscion guatucupa gillnet fishing seasons. Their extents represent 6% (1466.8 km2) and 19% (4493.7 km2) of the fishing ground (23 204.1 km2) during croaker and weakfish fishing seasons respectively. The total allowable fishing effort estimated outside the no‐fishing zones were estimated at 541 km (95% credible interval (CrI) [339; 940]) during croaker and 688 km (CrI [312; 2,166]) during weakfish fishing seasons, one order of magnitude lower than the current total fishing effort. The drastic reduction of total fishing effort estimated in this study is largely due to weak protection measures since the gillnet fisheries became the major conservation concern for franciscana by the end of 1970s in southern Brazil. Although the implementation of the proposed exclusion zones and limiting fishing effort will strongly impact the status quo, they were based on the best scientific evidence and on a clearly defined management goal to reduce the risk of the franciscana population’s collapse in southern Brazil.

Microsatellite markers for the endangered franciscana dolphin (Pontoporia blainvillei).

The franciscana (Pontoporia blainvillei) is the most threatened small cetacean in the South Atlantic. In this study we report the development of 13 microsatellite markers for franciscanas through next-generation sequencing, and the characterization of those loci in 38 samples from the species' northernmost population (Espírito Santo, Brazil). Besides providing diversity indices for the new, specific loci, we also report on the transferability of heterologous loci which had not been screened in franciscanas before, and review all loci used in previous studies. Expected heterozygosity in the new loci ranged between 0.107 and 0.595, and all but one were in Hardy Weinberg Equilibrium. These are the first microsatellite loci isolated from franciscanas, and they are an important addition to heterologous markers that were available previously.

Trophic ecology and foraging areas of cetaceans sampled in the coastal waters of south-eastern Brazil assessed through skin δ13C and δ15N

AbstractWe 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 relationships and use of area of two sympatric small cetaceans in the Southwestern Atlantic Ocean determined by carbon and nitrogen stable isotopes.

As cetaceans are sentinels of the marine environment, studying their life history is of utmost importance in understanding their habits and their interaction with the environment. To achieve this goal, it is important to study their ecological niches through the investigation of their habitat use patterns and trophic relationships. This study aimed to evaluate if there are differences in the habitat use patterns and the trophic ecology of franciscana (Pontoporia blainvillei) and Guiana dolphins (Sotalia guianensis) accidentally caught off the south coast of São Paulo State, and Guiana dolphins biopsied in the Cananeia estuary, southeastern Brazil, based on the carbon and the nitrogen stable isotopes analysis. Isotopic ratios were estimated from skin samples. The isotopic niche size and overlap were calculated using the SIBER package (R software). The gathered results showed evidence of spatial segregation between Guiana dolphins and franciscanas. The Guiana dolphins sampled inside and outside the estuary showed evidence of trophic and spatial segregation. No difference in isotopic values between sexes was found for both species. Such differences between franciscanas and Guiana dolphins were expected as both species have distinct life histories as a result of different evolutionary pathways.

Low Genetic Diversity of the Endangered Franciscana (Pontoporia blainvillei) in Its Northernmost, Isolated Population (FMAIa, Espírito Santo, Brazil)

The franciscana,Pontoporia blainvillei, is the most endangered small cetacean in the Southwestern Atlantic Ocean, occurring from Itaúnas, Espírito Santo, Brazil to Chubut province, Argentina. This area is divided into four Franciscana Management Areas (FMA). The northern portion of this species distribution is not continuous and a previous genetic study using mitochondrial DNA (mtDNA) separated it into FMAIa (Espírito Santo state) and FMAIb (North of Rio de Janeiro state). In order to increase the information about this population we expanded the sample number and evaluated mitochondrial and nuclear DNA diversity. Samples of 68 franciscanas found stranded on beaches from 2005 to 2020 were analyzed. Analyses included 350 bp of the mtDNA control region (D-loop) and 12 microsatellite loci. We identified three control region haplotypes in FMAIa, two of them not previously observed in this population, one being a new haplotype. Haplotype and nucleotide diversities were 0.0408 and 0.00012 respectively, the lowest reported for all FMAs analyzed until now. The Neutrality tests were not significant and Mismatch Distribution analysis did not reject the hypothesis of population expansion. One of the microsatellite loci was monomorphic, and for the other loci, two to nine alleles were identified, with expected heterozygosities ranging from 0.306 to 0.801. No substructure was revealed and effective population size (Ne) was estimated in 117.9 individuals. Even with an increased sample size, the high mitochondrial genetic homogeneity suggested for the population in a previous study was confirmed. Among six loci previously analyzed in other franciscana populations, five showed the lowest observed heterozygosities for the Espírito Santo population. The novel microsatellite data also showed low genetic diversity and could not reject the hypothesis of a single, panmitic population along the coast of Espírito Santo. This species has been intensively impacted in the last years by incidental capture during fishing activities and habitat degradation, caused by pollution, coastal development and environmental disasters in FMAIa. Considering that this population is small, isolated, and with low levels of genetic diversity, we reinforce the necessity of different conservation actions, focusing mainly on the reduction of bycatch of this species in the region.

Head adaptation for sound production and feeding strategy in dolphins (Odontoceti: Delphinida).

Head morphology in toothed whales evolved under selective pressures on feeding strategy and sound production. The postnatal development of the skull (n=207) and mandible (n=219) of six Delphinida species which differ in feeding strategy but exhibit similar sound emission patterns, including two narrow-band high-frequency species, were investigated through 3D morphometrics. Morphological changes throughout ontogeny were demonstrated based on the main source of variation (i.e., prediction lines) and the common allometric component. Multivariate trajectory analysis with pairwise comparisons between all species was performed to evaluate specific differences on the postnatal development of skulls and mandibles. Changes in the rostrum formation contributed to the variation (skull: 49%; mandible: 90%) of the entire data set and might not only reflect the feeding strategy adopted by each lineage but also represents an adaptation for sound production and reception. As an important structure for directionality of sound emissions, this may increase directionality in raptorial feeders. Phylogenetic generalized least squares analyses indicated that shape of the anterior portion of the skull is strongly dependent on phylogeny and might not only reflect feeding mode, but also morphological adaptations for sound production, particularly in raptorial species. Thus, postnatal development seems to represent a crucial stage for biosonar maturation in some raptorial species such as Pontoporia blainvillei and Sousa plumbea. The ontogeny of their main tool for navigation and hunting might reflect their natural history peculiarities and thus potentially define their main vulnerabilities to anthropogenic changes in the environment.

Age and growth of franciscana, Pontoporia blainvillei, and Guiana, Sotalia guianensis, dolphins from southeastern Brazil

TABLE S1 Summary of total length (TL) and predicted lengths-at-age (L[t]) derived from the Gompertz growth model fitted to the data of male and female franciscanas dolphins (Pontoporia blainvillei), from southeastern Brazil. The ages at attainment of the asymptotic length estimated from the model are highlighted in bold. TABLE S2 Summary of total length (TL) and predicted lengths-at-age (L[t]) derived from the original form of von Bertalanffy growth model fitted to the pooled data of Guiana dolphins (Sotalia guianensis), from southeastern Brazil. The age at attainment of the asymptotic length estimated from the model is highlighted in bold. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Assessing the growth rate of endangered Franciscana dolphin in Argentina, South America

Cetacean populations are vulnerable to decline due to anthropogenic threats and life history traits. The Franciscana dolphin (Pontoporia blainvillei) has been considered the most affected small dolphin in the Southwestern Atlantic Ocean. In this study a method is presented for estimating the growth rate of the Franciscana dolphin affected by incidental mortality (bycatch) in coastal marine areas of Argentina, South America. We used a general approach based on vital parameters information such as reproductive rates and survival probabilities for an age-structured population. The Franciscana’s growth rate was estimated using Leslie’s approach through an algorithm implemented in a 14 × 14 matrix model. Then, the population was characterized analysing the discrete-time evolution of the age–population vector. We found that the potential growth rate <1 indicates that Franciscanas in Argentina are susceptible to decline under current levels of incidental mortality.

Switching Gillnets to Longlines: An Alternative to Mitigate the Bycatch of Franciscana Dolphins (Pontoporia blainvillei) in Argentina

The franciscana dolphin (Pontoporia blainvillei) is considered the most threatened cetacean in the South Western Atlantic due to bycatch in gillnet fisheries of Argentina, Uruguay, and Brazil. As gillnet fisheries operate in the same areas inhabited by dolphins, methods and strategies to reduce bycatch require particular attention. This study investigated the potential of switching gillnets to bottom longlines to reduce franciscana bycatch rates while maintaining economic returns in a small-scale artisanal fishery in Argentina. Trials were conducted in Bahía Samborombón and Cabo San Antonio between October 2004 and January 2007, in cooperation with artisanal fishermen who simultaneously fished using bottom longlines and gillnets. Target and non-target catch composition, fishing yield, catch size distribution and quality of catch, as well as bycatch of dolphins, sea turtles and interaction with sea lions were compared between the two fishing methods. An economic analysis of the fishery was performed to evaluate the potential to assess the profitability of switching fishing gears. Hauls of both gear types deployed simultaneously in the same locations showed similar fish catch composition and catch size with both gears but reduced catch of juvenile fishes in longlines. Bycatch of franciscana in bottom longlines was limited to only one dolphin in three consecutive years of trials, and no direct interaction between turtles and hooks were recorded. interaction with sea lions and sea turtles was reduced. The economic analysis showed financially acceptable perspectives under a five-year scenario. Reducing gillnet effort by switching to bottom longlines appears a practical approach to creating a sustainable fishery that could result in significant mitigation of current bycatch of franciscana dolphins in Argentina. However, implementation requires acceptance and compliance by the artisanal gillnet fishery.

Niche overlap and diet composition of three sympatric coastal dolphin species in the southwest Atlantic Ocean

AbstractSympatric species are expected to differ in ecological requirements to minimize niche overlap and avoid competition. Here we assess the trophic interactions among three coexisting dolphin species from southern Brazil: the franciscana dolphin (Pontoporia blainvillei), the Guiana dolphin (Sotalia guianensis), and the Lahille's bottlenose dolphin (Tursiops truncatus gephyreus). We evaluated temporal variation in carbon (δ13C) and nitrogen (δ15N) isotope values of bone collagen to examine potential dietary shifts resulting from increased fishing activity over the past three decades. We estimated the degree of niche overlap among these species and the contribution of potential prey sources to their diet. δ15N values were consistent among species and across years, while δ13C values increased for Guiana dolphins and decreased for bottlenose dolphins, suggesting changes in diet and/or foraging habitats through time. The similar δ13C and δ15N values and the high niche overlap between Guiana and bottlenose dolphins indicate that these species are primarily feeding on demersal prey. The franciscana diet is primarily composed of pelagic prey, resulting in a lower niche overlap in comparison with the other dolphin species. Our study provides further information about the foraging ecology of this unique dolphin community in southern Brazil with implications for its management and conservation.

A new small, mesorostrine inioid (Cetacea, Odontoceti, Delphinida) from four upper Miocene localities in the Pisco Basin, Peru

AbstractThe moderately rich past diversity of the superfamily Inioidea (Cetacea, Odontoceti) in both the Atlantic and Pacific oceans contrasts with the present survival of a single genus (Inia, Amazon river dolphin, family Iniidae) in freshwater deposits of South America and of a single species (Pontoporia blainvillei, franciscana, family Pontoporiidae) along the eastern coast of that continent. However, part of the late Miocene – Pliocene inioid fossil record consists of relatively fragmentarily known species, for which systematic affinities remain poorly understood. Based on a sample of six cranial specimens from lower upper Miocene (Tortonian, 9.5–8.6 Ma) marine deposits of the Pisco Formation exposed at four localities of the East Pisco Basin (southern coast of Peru), we describe a new genus and species of inioid, Samaydelphis chacaltanae. This mesorostrine, small‐sized species is characterized by an upper tooth count of c. 30 teeth per row, a moderately elevated vertex of the cranium displaying a long anteromedial projection of the frontals and interparietal, and the plesiomorphic retention of a premaxilla–nasal contact. Recovered as a member of the family Pontoporiidae in our phylogenetic analysis, S. chacaltanae falls as sister group to Meherrinia isoni, from the upper Miocene of North Carolina (USA), which has previously been tentatively referred to the Iniidae or regarded as a stem Inioidea. Originating from the P1 allomember of the Pisco Formation, the mesorostrine S. chacaltanae was contemporaneous and sympatric with two other inioids, the brevirostrine pontoporiid Brachydelphis mazeasi and the longirostrine iniid Brujadelphis ankylorostris.

Strandings of cetaceans on the Espírito Santo coast, southeast Brazil, 1975-2015.

Espírito Santo state is located on the eastern margin of Brazil, in a transitional tropical-subtropical area (18°S–21°S) dominated by oligotrophic waters. With the exception of humpback whales (Megaptera novaeangliae), the cetacean community of Espírito Santo has been understudied. In addition to the chronic impacts from fisheries, marine pollution, urban development, and coastal habitat degradation, in November 2015 the cetacean communities of Espírito Santo were challenged by the greatest environmental disaster in Brazil’s history. The Mariana dam disaster caused 60 million cubic meters of mining waste to be washed into the Doce River, which ultimately flowed to the coastal waters of Espírito Santo, with a high concentration of heavy metals. This study reviews and updates information on cetacean strandings in the state of Espírito Santo (excluding humpback whales) prior to this disaster. From 1975 to September 2015, there were 461 recorded cetacean strandings, representing 20 species. An average 1.18 strandings per 100 km per month were recorded since a state-wide daily beach survey program was implemented in October 2010, contrasting with the 0.14 strandings per 100 km per month in previous years. Six species comprised the majority (94.7%) of stranding events: Guiana dolphin (Sotalia guianensis), Franciscana (Pontoporia blainvillei), rough-toothed dolphin (Steno bredanensis), bottlenose dolphin (Tursiops truncatus), sperm whale (Physeter macrocephalus), and melon-headed whale (Peponocephala electra). Oceanic cetaceans stranded most frequently on the southern portion of Espírito Santo, where the continental platform is narrower, whereas the strandings of coastal cetaceans such as Guiana dolphins and Franciscanas were concentrated near estuaries, especially the Doce River. This is particularly concerning in face of the Mariana dam disaster, which drastically altered the estuarine and coastal environment associated with the Doce River.

Oceanographic processes driving the feeding ecology of franciscana dolphin off Southern Brazilian coast

The franciscana (Pontoporia blainvillei) is a coastal dolphin endemic to the south-western Atlantic Ocean. Incidental captures in fishing gillnets are the greatest conservation concern for this species. The present study examines the biophysical interactions between the franciscana prey composition and the marine environment. The feeding regime of franciscana was investigated from stomach contents of incidentally caught animals along the southern Brazilian coast. The characteristics of the franciscana habitat may reveal potential factors affecting the distribution and abundance of marine species, thus the franciscana prey (species number and size) was treated as a function of the oceanographic variables (sea surface temperature and chlorophyll-a), and the spatial (latitude and water depth), and temporal (season) parameters, through Linear and Generalized Linear Models (LM and GLM). Season and latitude were important predictors of the franciscana diet, followed by water temperature and depth. Chla parameter only influenced one fish species and therefore was not useful as an explanatory variable for our study. The influence of the predictors and prey distribution of the franciscana diet are similar to that found in the habitat by research cruise data. Some structures analysed (e.g. squid beaks) may remain longer in the stomachs. Therefore, the findings not only suggest a fairly opportunistic behaviour but it is likely that franciscana may occupy, and possibly for long periods, small spatial ranges. This behaviour might be a strategy for minimizing energetic costs by restricting movements to short distance areas, which can be an important factor for conservation planning along the southern Brazilian coast.

Feeding habits of the franciscana dolphin (Pontoporia blainvillei) in south-eastern Brazil

AbstractThis study evaluated the feeding habits of the franciscana dolphin (Pontoporia blainvillei) in south-eastern Brazil. Stomach contents were collected from a total of 145 dead specimens found incidentally caught by fishing vessels or stranded between 2005 and 2015. Fish otoliths, cephalopod beaks and whole non-digested prey were used for prey species identification. A total of 9337 prey items were identified, including 26 species of teleost fishes and three species of cephalopods. The most important prey families were Sciaenidae among fish and Loliginidae among cephalopods. Franciscana dolphins tended to feed on small fish (mean = 5.25 cm) and cephalopods (mean = 8.57 cm). The index of relative importance (IRI) showed thatPellona harroweriandDoryteuthis pleiwere the most important prey for both males and females. The PERMANOVA test confirmed that there is no significant difference between the feeding habits of different sexes, but detected a significant difference among seasons. Overall, our results show that franciscana dolphins are predominantly ichthyophagous and non-selective in relation to the type of prey, feeding on pelagic, demersal and pelagic-demersal prey.