Marine Tucuxi Dolphin Research Articles

Marine tucuxi dolphin ( Sotalia guianensis) and its interaction with passive gill-net fisheries along the northern coast of the Rio de Janeiro State, Brazil

jailson fulgencio de moura, thais guimara~es correa sholl, e’derson da silva rodrigues, sandra hacon and salvatore siciliano Grupo de Estudos de Mamiferos Marinhos da Regiao dos Lagos, Projeto de Monitoramento de Mamiferos Marinhos na Bacia de Campos, CENPES/PETROBRAS & ENSP/FIOCRUZ, Escola Nacional de Saude Publica, FIOCRUZ, Departamento de Endemias, Rua Leopoldo Bulhoes, 1480-68 andar, Manguinhos, Rio de Janeiro, RJ 21041-210 Brazil, PPG em Saude Publica e Meio Ambiente, Escola Nacional de Saude Publica, ENSP/FIOCRUZ

Human-induced injuries to marine tucuxis ( Sotalia guianensis) (Cetacea: Delphinidae) in Brazil

Guanabara Bay constitutes the most degraded habitat along the marine tucuxi dolphin (Sotalia guianensis) distribution. Considering that these mammals are found year-round in this area, where the dolphin population is estimated to be approximately 70 individuals, interactions between cetaceans and human activities are of concern. From 1995 to 2005, photo-identification techniques have been employed to study marine tucuxis in Guanabara Bay and data on the individual injuries has been collected. Seven out of 78 photo-identified and catalogued individuals presented noticeable injuries on their bodies, including cut-like wounds, skin ulceration and mutilation. Parts of fishing gear attached to the bodies of some dolphins were also observed. The concern elicited by the injuries reported here is amplified if we consider that this cetacean population is highly exposed to contaminants of known immunosuppressive action, such as organochlorine, organotin and perfluoroalkyl compounds.

Organochlorine pesticides in marine tucuxi dolphin milk incidentally captured with its calf in Barra de São João, east coast of Rio de Janeiro State, Brazil

j.f. de moura, s. siciliano, p.n. sarcinelli and s. hacon Mestrado Saude Publica e Meio Ambiente, Escola Nacional de Saude Publica ENSP/FIOCRUZ, Projeto de Monitoramento de Mamiferos Marinhos na Bacia de Campos, CENPES/PETROBRAS & ENSP/FIOCRUZ, Grupo de Estudos de Mamiferos Marinhos da Regiao dos Lagos-GEMM-Lagos, Centro de Estudos da Saude do Trabalhador e Ecologia Humana, ENSP/FIOCRUZ, Departamento de Endemias Samuel Pessoa, ENSP/FIOCRUZ

Sexual coercion and aggression towards a newborn calf of marine tucuxi dolphins (Sotalia guianensis)

2002). Since 1994, our group has been conducting field studies inthis area with the objective of creating a visual database to assist in the study of theecology and behavior of marine tucuxi dolphins. Fieldwork was conducted using a7-m-long boat, which traveled on a non-systematic route until one or more groupsof dolphins were sighted. The geographical position of the target was marked andpictures were taken using a Canon EOS digital camera (Canon EOS 20D digitalcamera, Tokyo, Japan) fitted with a Canon EF 75–300-mm zoom lens. Due to thepoor underwater visibility, approximately 1.5 m, we could not conduct detailedunderwater observations.1

Marine tucuxi dolphin (Sotalia guianensis) injuries as a possible indicator of fisheries interaction in southeastern Brazil

Laboratorio de Ecologia e Bioacustica de Cetaceos, Departamento de Ciencias Ambientais, Instituto de Florestas, Universidade Federal Rural do Rio de Janeiro (BR 465, km 7, Campus Universitario, 23890-000 Seropedica, RJ, Brasil) maribioufscar@yahoo.com.br, mariana_especie@hotmail.com, smsimao@ufrrj.br Interactions between marine mammals and fisheries have been reported worldwide and may have potential effects on the stability of populations (READ et al

High Accumulation of Perfluorooctane Sulfonate (PFOS) in Marine Tucuxi Dolphins (Sotalia guianensis) from the Brazilian Coast

Perfluorooctane sulfonate (PFOS) and other perfluoroalkyl compounds (PFCs) were measured in liver samples from 29 marine tucuxi dolphins from Rio de Janeiro state (RJ), Brazil. PFC measurement combined liquid chromatography and mass spectrometry, using a CapLC system connected to a Quadrupole-LIT mass spectrometer. PFOS was the only PFC detected and it was so in all samples. PFOS concentrations (ng x g(-1) dw) of dolphins (n=23) from the highly contaminated Guanabara Bay (in RJ) varied between 43 and 2431 as well as between 76 and 427 from areas of RJ other than the quoted bay (n=6). Concentrations of three fetuses and one neonate varied between 664 and 1590. Fetus/mother ratios were calculated in two situations (2.75 and 2.62). It seems that mother-to-calf transference plays important role for relationships between PFOS and age. When a one-year-old male calf presenting 2431 ng x g(-1) dw was excluded from the test, significant correlations were observed between PFOS concentrations and both age and total length. Despite the placental transference, PFOS concentrations were not significantly lower in females than in males. PFOS levels in marine tucuxi dolphins from Guanabara Bay are among the highest detected to date in cetaceans, and this may represent a threat to the small population concerned.

Social Organization of Marine Tucuxi Dolphins, Sotalia guianensis, in the Cananéia Estuary of Southeastern Brazil

Social organization is an important component of the population biology of a species that influences gene flow, the spatial pattern and scale of movements, and the effects of predation or exploitation by humans. An important element of social structure in mammals is group fidelity, which can be quantified through association indices. To describe the social organization of marine tucuxi dolphins (Sotalia guianensis) found in the Cananeia estuary, southeastern Brazil, association indices were applied to photo-identification data to characterize the temporal stability of relationships among members of this population. Eighty-seven days of fieldwork were conducted from May 2000 to July 2003, resulting in direct observations of 374 distinct groups. A total of 138 dolphins were identified on 1-38 distinct field days. Lone dolphins were rarely seen, whereas groups were composed of up to 60 individuals (mean 6 1 SD ¼ 12.4 6 11.4 individuals per group). A total of 29,327 photographs were analyzed, of which 6,312 (21.5%) were considered useful for identifying individuals. Half-weight and simple ratio indices were used to investigate associations among S. guianensis as revealed by the entire data set, data from the core study site, and data from groups composed of � 10 individuals. Monte Carlo methods indicated that only 3 (9.3%) of 32 association matrices differed significantly from expectations based on random association. Thus, our study suggests that stable associations are not characteristic of S. guianensis in the Cananeia estuary.

Prey-transfer in the marine tucuxi dolphin, Sotalia fluviatilis, on the Brazilian coast

The first record of prey-transfer behaviour between adult and calf animals in Sotalia fluviatilis is recorded. Five clear episodes of prey-transfer from adult animals to calves were observed, occurring in north-eastern Brazil at Pipa's Beach. These results suggest that food-sharing is a naturally occurring behaviour in the marine tucuxi dolphin, and that it may act as both a food supply and as an opportunity to obtain information about the food that is eaten by other group members.

Descrição do comportamento de superfície do boto cinza, Sotalia guianensis, na Praia de Pipa - RN

O estudo do comportamento animal é uma área de pesquisa consolidada, que cresceu e se diversificou em vários países e que deu origem a disciplinas e abordagens de investigação, como a Etologia, a Ecologia Comportamental, a Neuroecologia, a Psicologia e a Psicologia evolucionista. No estudo do comportamento animal, o etograma é a base para estudos comportamentais de espécies pouco conhecidas, como também para comparar comportamentos de populações distintas de uma mesma espécie. Tradicionalmente, um etograma descreve de forma detalhada eventos comportamentais realizados por indivíduos de uma espécie. O presente estudo apresenta um etograma dos eventos comportamentais realizados na superfície por uma espécie de golfinho costeiro, boto cinza, na praia de Pipa - RN.

Ecological aspects of marine tucuxi dolphins (<i>Sotalia guianensis</i>) based on group size and composition in the Cananéia Estuary, southeastern Brazil

Observations on group size and composition of marine tucuxi dolphins, Sotalia guianensis, found in the Cananéia estuary (25°03'S, 47°55'W), southeastern Brazil, were conducted from May 2000 to July 2003. Correlations among four environmental variables (water temperature, salinity, transparency and depth) and group size were investigated, as well as on the way foraging and feeding behavioral patterns related to group formation in S. guianensis. The surveyed area comprised approximately 132km² and field efforts were conducted in 87 days. A total of 378 groups were recorded. Group size (mean ± SD: 12.4 ± 11.4 individuals) varied from lone individuals, rarely seen, to aggregations of up to 60 individuals. No significant differences were found regarding group size among seasons. Groups with calves (89.7% of all observed groups) were more frequent than groups without calves. Feeding associations with marine birds were common in winter when waters were clearer. A positive correlation was only reported when investigating group size and water depth (Spearman's rank test, r=0.4716, p=0.0000). Marine tucuxis usually form large aggregations (20 to 60 individuals) when engaged in feeding activities in deeper waters. Groups were larger (mean ± SD: 18.3 ±15.0 individuals, n=90) in the main estuary entrance, where water is deeper, and smaller in inland shallower waters (mean ± SD:7.8 ± 6.9 individuals, n=47). Because of these common observed aggregations, this area of the estuary has been used as a dolphin watching site since the late 1990s without specific regulations. Guidelines are urgently needed to conduct dolphin watching tours as calves are seen year-round and uncontrolled tourism may disrupt important social interactions.

Twelve microsatellite loci for marine and riverine tucuxi dolphins (Sotalia guianensis and Sotalia fluviatilis)

AbstractTwelve dinucleotide polymorphic microsatellite loci were isolated from the marine tucuxi dolphin (Sotalia guianensis). Levels of genetic diversity were assessed using 34 individuals from the coasts of Rio de Janeiro and Pará, Brazil. Numbers of alleles varied between two and 14, and observed and expected heterozygosities ranged from 0.040 to 0.704, and from 0.093 to 0.818, respectively. Moreover, eight of these loci were variable in the riverine tucuxi Sotalia fluviatilis. This is the first description of microsatellite primers from a dolphin that does not belong to the Delphininae. These loci are currently being used in the analysis of population structure of both tucuxi species.

Stomach contents of the marine tucuxi dolphin (Sotalia guianensis) from Rio de Janeiro, south-eastern Brazil

Along the central coast of Rio de Janeiro State (22°25′S–23°00′S), south-eastern Brazil, the marine tucuxi dolphin (Sotalia guianensis) feeds on neritic prey that are distributed through the water column and are abundant all year round. The most frequently found species were the teleost fish Trichiurus lepturus, Cynoscion guatucupa, Isopisthus parvipinnis and Porichthys porossisimus. Fish species were more important than cephalopod species in the diet of the marine tucuxi. Back calculations of prey sizes indicated that they feed mainly on young specimens. The present study provided additional information on the feeding habits of the marine tucuxi dolphin.

Whistles of small groups of Sotalia fluviatilis during foraging behavior in southeastern Brazil

Whistle emissions were recorded from small groups of marine tucuxi dolphins (Sotalia fluviatilis) in two beaches located in an important biological reserve in the Cananéia estuary (25 degrees 03'S, 47 degrees 58'W), southeastern Brazil. A total of 17 h of acoustic data was collected when dolphins were engaged in a specific feeding foraging activity. The amount of 3235 whistles was recorded and 40% (n=1294) were analyzed. Seven acoustic whistle parameters were determined: duration (ms), number of inflection points, start and end frequency (kHz), minimum and maximum frequency (kHz), and frequency range (kHz). Whistles with up to four inflection points were found. Whistles with no inflection points and rising frequency corresponded to 85% (n=1104) of all analyzed whistles. Whistle duration varied from 38 to 627 ms (mean=229.6+/-109.9 ms), with the start frequency varying between 1 and 16 kHz (mean=8.16+/-3.0 kHz) and the end frequency between 2 and 18 kHz (mean=14.35+/-3.0 kHz). The importance of this study requires an accurate measurement of the whistles' emissions in an unusual foraging feeding behavior situation on two beaches where several tucuxis, mostly mother-calf pairs, are frequently present. These two beaches are located in a federal and state environment Environmental Protected Area threatened by the progressive increase of tourism.

Biology of the marine tucuxi dolphin (Sotalia fluviatilis) in south-eastern Brazil

Age, growth and reproductive parameters related to the marine tucuxi are presented, as well as feeding habits and parasitism. The specimens' age ranged from zero (newborn) to 21 years for males and 0·5 to 30 years for females. In relation to the body dimension, length distributions were bell-shaped for both sexes with male marine tucuxi ranging from 86·0 to 200·0 cm in length and females from 117·5 to 198·0 cm. The body length of new-born and calves varied between 86·0 to 117·5 cm and the postnatal growth curve an asymptotic reached length of 191·0 cm. According to the relationship between age, body length and reproductive characteristics, male and female specimens were considered sexually mature when [ges ]6 years and body length [ges ]180·0 cm and [ges ]6 years and body length [ges ]160·0 cm, respectively. Males and females up to six years old represented around 80% of the captures, indicating a bias towards juveniles and individuals that have yet to reach sexual maturity. The youngest specimen with solid contents in the stomach was 119·0 cm in length and seven months old. The marine tucuxi feeds on neritic prey, preferentially on the teleost fishes Trichiurus lepturus and Porichthys porossisimus, and on the cephalopods Loligo sanpaulensis and L. plei. Back calculation of prey lengths indicated that fish ranged from 1·2 to 106·9 cm and cephalopods from 3·4 to 22·2 cm. The barnacle Xenobalanus globicipitis was recorded attaching to the caudal fin and the helminths Braunina cordiformis, Anisakis typica, Halocercus brasiliensis and Nasitrema sp. were found in the internal organs.

Home ranges and movement patterns of the marine tucuxi dolphin, <i>Sotalia fluviatilis</i>, in Baía Norte, southern Brazil

Marine tucuxi dolphins (Sotalia fluviatilis) studied in Baía Norte, southern Brazil, exhibited very small overall home ranges with daylight movements in consistent water depths of around 3m. Mean overall home range areas calculated through two methodologies were similar, measuring 13.38km² ± 1.92 using the Minimum Convex Polygon method and 15.22km² ± 0.66 through the kernel estimator. Mean core areas calculated by kernel were extremely small [mean = 1.49km² at 50% UD (utilization distribution) and 0.87km² at 25% UD levels]. The geographical distributions of home ranges and core areas overlapped extensively at both 50% UD and 25% UD. Daylight movements ranged from 0.16 to 28.97 km/day (mean = 5.65 ± 0.56km/day, SD = 5.36) with mean minimum rate of movement of 2.6 ± 0.2km/h (SD = 2.02). Daylight movement patterns varied seasonally with higher values of distance moved and rate of movement in winter and winter and autumn, respectively. The marine tucuxi home ranges and daylight movement patterns presented here are smaller than much of what is known for other coastal small cetaceans. The percentage of overall home range within the limits of a protected area designated for the tucuxis could be considered moderate to high depending on the estimator used (54.06% or 5.9km² by MCP and 74.71% or 11.35km² using the kernel). Nevertheless, core areas are completely within the protected area. Conservation implications of these findings include the need to: (i) create a buffer zone to the south of the existing protected area which will encompass the overall home range of the tucuxis; (ii) establish constant, adequate enforcement of fishery and boat traffic regulations in the core areas; and (iii) regulate boat traffic and aquaculture farming in important areas which are not yet subject to specific regulations.

Chlorinated pesticides and polychlorinated biphenyls in marine tucuxi dolphins ( Sotalia fluviatilis) from the Cananéia estuary, southeastern Brazil

The Cananéia estuary is an important biological area on the southeast coast of Brazil. In the past, it was impacted by both chlorinated pesticides and polychlorinated biphenyls (PCBs) due to its natural location. The marine tucuxi dolphin ( Sotalia fluviatilis) is a top predator in this ecosystem and can be found year round in Cananéia estuarine waters that represent an important nursing area for the species. This work investigated chlorinated compounds in the blubber of nine individuals from the Cananéia estuary. Residue levels of DDTs (0.541–125 μg g −1 lipid wt.) were the highest, followed by PCBs (0.2–9.22 μg g −1 lipid wt.), mirex (0.014–0.312 μg g −1 lipid wt.), chlordanes (0.001–0.047 μg g −1 lipid wt.), HCHs (<0.003–0.044 μg g −1 lipid wt.), and HCB (n.d.−0.024 μg g −1 lipid wt.). The mean p, p′-DDE/Σ DDT ratio was approximately 0.8 and is indicative of the former DDT application in the study area. PCB contamination is suggested to be associated with atmospheric transport and relative proximity to the Cubatão industrial complex—the most important along the Brazilian coast. Low levels of HCHs and HCB can be attributed to their high volatility in tropical environments. Concentrations of organochlorines in the blubber of marine tucuxis from the Cananéia estuary were lower than levels found in small cetacean species from developed countries, where the input of these compounds was considerably greater than in Brazil. At extremes, male dolphins can present DDT burden several orders of magnitude higher than females. Despite the high levels of total DDT found in males, the major detected compound was p, p′-DDE which is considered to be of low toxicity.

Age estimation of marine tucuxi dolphins (Sotalia fluviatilis) in south-eastern Brazil

This study reports the age estimation of marine tucuxi dolphins (Sotalia fluviatilis) found dead along the south-east coast of Brazil (24°40′S–25°30′S). The investigated specimens were collected from August 1995 to December 1998. Ages were estimated through the number of Growth Layer Groups (GLGs) from decalcified and stained thin sections of teeth. A total of 36 individuals was investigated. Estimated ages of marine tucuxis varied from zero to 29 years. The growth curve was attained from a modification of the von Bertalanffy equation applied to body length and age data. It was possible to estimate the total length of 97·8 cm in newborns, physical maturity was attained at seven years of age, and an asymptotic length of 179·8 cm.

Insights on site fidelity and calving intervals of the marine tucuxi dolphin (Sotalia fluviatilis) in south-eastern Brazil

Ecological aspects of the marine tucuxi dolphin, Sotalia fluviatilis (Cetacea: Delphinidae), remain poorly known. Important information can be gathered in long-term studies using photo-identification. Using this methodology, the authors present the first evidence of site fidelity for marine tucuxis in the Cananéia Estuary (25°03′S 48°01′ W), south-eastern Brazil. A total of 86 easily recognizable individuals was catalogued from June 1996 to August 2001, but most of them have been sighted from May 2000. From June 1997 to August 2001, three female tucuxis were sighted on nine (KN #19), 22 (KN #30) and 28 (KN #10) different days in a relatively small area (∼16 km2). Each of them was observed with a calf in 1997–1998 and again with a new offspring in 2000–2001. Thirteen other individuals were reported on eight to 19 different days in the same area between May 2000 and August 2001. Our observations lead to conclusions on the evidence of site fidelity and indicate that calving intervals may range between two and three years for this species in the surveyed area.