Search

The small population paradigm assumes that populations with low numbers of individuals intrinsically have a high probability of extinction. The small population of Lahille's bottlenose dolphins Tursiops truncatusgephyreus that specializes in foraging with artisanal fishers in Laguna, southern Brazil, faces human pressures including bycatch in fishing gear. The viability of this population was modelled over 30 and 100 years under different levels of bycatch, including the current scenario of two bycatches every year, two scenarios with higher incidence of bycatches and three management scenarios. The sensitivity of predicted growth rates to fixed‐proportion and observed‐variation changes in life history parameters was explored.The current scenario predicted a declining population (r = −0.014; λ = 0.986) with a high probability of extinction in the long term (PE = 0.71). A small increase in bycatches would result in a marked increase in the probability of extinction. Management scenarios seem promising, but only the zero‐bycatch management scenario would make the difference between a declining and an increasing population.As expected for slow‐growing species, population growth rate was most sensitive to proportional changes in adult female and juvenile survival. However, considering observed variation in vital rates, population dynamics were most influenced by variation in reproductive rates.To determine the highest priority for management action, another simulation was made of how additional threat scenarios of recognized human activities (i.e. bycatch influencing adult survival and increased underwater noise or pollution influencing calf survival) would affect population dynamics. Population growth rate was very sensitive to changes in adult bycatch (especially females), as expected, and only subtly sensitive to a reduction in calf survival.The current level of bycatch is unsustainable. Bycatch needs to be eliminated to maximize the probability of long‐term persistence of this dolphin population. However, this population's persistence could be threatened by natural variation in reproductive rates. [ABSTRACT FROM AUTHOR]

Assessing fish stocks harvested by small-scale fisheries is challenging. The lack of official fisheries data constrains the proper management of such fisheries. Thus, alternative sources of information are crucial to enrich data-poor fisheries. Here, we evaluated different sources of data for the mullet (Mugil liza) fishery, one of the most important but overexploited fisheries in Brazil. We gathered three alternative sources of catch data by artisanal fisheries: 14 years of self-reported catches by artisanal fishers across 24 municipalities; 16 years of catches by traditional beach seines mined from news outlets; and 13 years from a single community monitoring their beach seine catches. We tested whether alternative data sources follow the same trends of landing reports from systematic, official monitoring of the industrial fleet. We fitted Bayesian time-series models to test if environmental changes and stock abundance can predict these data. We found that only self-reported catches matched the official reporting trends, thereby improving our understanding of changes in the mullet stock. These findings reveal that self-reported catches by fishers provide reliable additional data useful for management. Self-reporting data are cost-effective, deals with the complexity of small-scale fisheries, and welcomes fishers as key stakeholders in management practices. [ABSTRACT FROM AUTHOR]

Coastal and offshore ecotypes of common bottlenose dolphins have been recognized in the western South Atlantic, and it is possible that trophic niche divergence associated with social interactions is leading them to genetic and phenotypic differentiation. The significant morphological differentiation observed between these ecotypes suggests they represent two different subspecies. However, there is still a need to investigate whether there is congruence between morphological and genetic data to rule out the possibility of ecophenotypic variation accompanied by gene flow. Mitochondrial DNA (mtDNA) control region sequence data and 10 microsatellite loci collected from stranded and biopsied dolphins sampled in coastal and offshore waters of Brazil as well as 106 skulls for morphological analyses were used to determine whether the morphological differentiation was supported by genetic differentiation. There was congruence among the data sets, reinforcing the presence of two distinct ecotypes. The divergence may be relatively recent, however, given the moderate values of mtDNA nucleotide divergence (dA = 0.008), presence of one shared mtDNA haplotype and possibly low levels of gene flow (around 1% of migrants per generation). Results suggest the ecotypes may be in the process of speciation and reinforce they are best described as two different subspecies until the degree of nuclear genetic divergence is thoroughly evaluated: Tursiops truncatus gephyreus (coastal ecotype) and T. t. truncatus (offshore ecotype). The endemic distribution of T. t. gephyreus in the western South Atlantic and number of anthropogenic threats in the area reinforces the importance of protecting this ecotype and its habitat. [ABSTRACT FROM AUTHOR]

Sympatric 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. [ABSTRACT FROM AUTHOR]

The sei whale ( I Balaenoptera borealis i ) spends the winters of both hemispheres in warm subtropical waters and migrates seasonally to temperate and polar areas to feed during the summer (Horwood, 1987). Marking of sei whales (Balaenoptera borealis) in the Southern Hemisphere (the Soviet Marking Programme). A preliminary assessment of endangered sei whales (Balaenoptera borealis) in two candidate Key Biodiversity Areas in West Falkland (Falklands Conservation report, Version 1.2). [Extracted from the article]

Background: Human-animal interactions with mutual benefits in the wild are rare. Such positive interactions seem to require an intricate knowledge from the human side on the animals' behavior and their habitat. In southern Brazil, dolphins and human net-casting fishers have specialized in a cooperative foraging, in which fishers report being able to identify and name dolphins. Here, we evaluate the consensus in their ability to recognize the individual dolphins they interact with. By investigating the reliability of this recognition process, we assess the pros and cons of relying on the fishers' traditional knowledge to further understand the behavior and ecology of dolphins at the individual level. We also assess the potential role of traditional knowledge for the maintenance of this unusual interaction. Methods: We interviewed 38 fishers using a semi-structured questionnaire. During each interview, we evaluate their recognition ability of dolphins by showing high-quality photos of dorsal fins of different dolphins, asking questions about the dolphins' behavior and traits, and about how fishers recognize each dolphin. We also evaluated information about the fishers. Different indices were used to measure the fishers' ability to recognize dolphins via photos, and their consensus on individual identification. These indices were modeled as functions of traits of both dolphins and fishers to investigate which ones influence the recognition process. Results: We found that fishers can primarily recognize dolphins by natural marks in the dorsal fin but there was little consensus in recognition. Fishers also tend to repeat the name of the most "popular" dolphins for different photos, indicating low reliability in individual recognition. We also found that fishers who learned from relatives (vertical learning) how to interact with dolphins tend to be more accurate and have higher consensus in dolphin recognition than those fishers who learned from friends (horizontal learning) or individually. Conclusion: Artisanal fishers have a deep understanding of the dolphins and the system they are inserted in. However, the lack of consensus in identifying individual dolphins herein reported indicates that using their traditional knowledge to further understand dolphin behavior and ecology at the individual level requires caution. Our study also suggests that the transmission of this tradition from parents to sons can be crucial to preserve such a unique human-animal positive interaction in its original form. [ABSTRACT FROM AUTHOR]

A subset of the bottlenose dolphin Tursiops truncatus gephyreus population in Laguna, southern Brazil, specialize in foraging cooperatively with fishermen. In this study, we describe reproductive parameters for these dolphins and investigate whether this specialized tactic generates reproductive advantages for females that frequently engage in this unusual behavior. We analyzed photo-identification data collected during 233 boat-based surveys during 2007–2009 and 2013–2017. From 27,808 high-quality photographs, we identified and tracked the fate of 24 reproductive females and 45 of their calves. Calving was found to be seasonal, with most births occurring in late spring/summer. The average crude birth rate was 0.09, and estimated fecundity was 0.17. The mean inter-birth interval was 2.09 (for all calves) or 2.43 years (for surviving calves only). Survival to 1 and 2 years estimated by the Kaplan–Meier method was 0.78 (95% CI 0.65–0.92) and 0.65 (95% CI 0.51–0.83), respectively—which represents a survival rate in the second year of 0.83. We investigated the potential influence of birth timing, resource availability, and maternal foraging tactic, home range size and frequency of interaction with fishermen on calf survival. Timing of birth was a significant predictor of calf survival. Giving birth close to the local mullet season would provide lactating females with increased seasonal prey resources, leading to increased calf survival. Due to our sample size (n = 9 cooperative and 15 non-cooperative females), we could not conclude whether or not the cooperative foraging tactic influences calf survival and female reproductive success. We emphasize the importance of long-term monitoring of populations to understand regional life history characteristics and provide accurate information for viability analyses. [ABSTRACT FROM AUTHOR]

A small population of coastal bottlenose dolphins (Tursiops truncatus gephyreus) inhabits the inland waters of Laguna, southern Brazil. A subset of this population interacts with artisanal fishermen. This specialized foraging tactic structures dolphin society into 'cooperatives' (participants of the interaction) and 'non‐cooperatives' (non‐participants).Between 2012 and 2015, a bridge was constructed in Laguna over an important core area for dolphins. Photo‐identification and georeferenced data collected on boat surveys, conducted both before and during bridge construction, were used to evaluate changes in both 'cooperative' and 'non‐cooperative' dolphin distribution.Changes in dolphin distribution were analysed with kernel densities and hurdle models. A grid of 120 cells of area 1 km2 was used to model dolphin distribution, and the minimum distance from the grid cell centre to the bridge and to the area of gillnet use were defined as explanatory variables of human activities. Habitat descriptors (depth and distance) from the lagoon margin were also considered in the model procedure.Dolphin distribution patterns shifted between periods. A core area used by 'non‐cooperative' dolphins near the bridge construction works disappeared. The effects of habitat descriptor and anthropogenic activity on dolphin distribution also differed between periods. Before bridge construction, the abundance of 'non‐cooperative' dolphin was higher close to the bridge area (p < 0.05). During bridge construction, the presence of 'cooperative' and 'non‐cooperative' dolphins decreased significantly with the distance from gillnet fishing activity (p < 0.01 and p < 0.001 respectively).This study highlights the importance of accounting for individual variations in response when assessing the effects of a habitat disturbance, or when implementing conservation plans. [ABSTRACT FROM AUTHOR]

Recent years have seen an increasing interest in individual behavioral variation. However, the implications of such variation for population dynamics are often unknown. We studied the dynamics of a bottlenose dolphin (Tursiops truncatus gephyreus) population from southern Brazil, where some individuals forage cooperatively with artisanal fishermen. We fitted mark‐recapture models to 10 yr of photo‐identification data to investigate the influence of this foraging specialization on dolphins' population parameters, controlling for sex and ranging behavior. We estimated adult survival to be high (0.949 ± 0.015 SE), weakly influenced by home range size, sex or the frequency of interaction with fishermen. The slightly higher survival probability for individuals with smaller home ranges could stem from the benefits of reduced spatial requirements implied by the specialized foraging. Foraging also influenced the probability of resighting individuals, and there was no temporary or permanent emigration. Abundance fluctuated slightly over the years from 54 (95% CI = 49–59) to 60 (95% CI = 52–69) individuals, with no evident population trend. Despite such apparent population stability, we confirm this population remains small and geographically isolated which may threaten its viability and the viability of its unusual, localized foraging specialization. Our study also illustrates how accounting for individual variation can portray animal population dynamics more realistically. [ABSTRACT FROM AUTHOR]

Several studies have explored dolphins feeding ecology in coastal ecosystems; However, research gauging the predatory effects of delphinid on ecosystems, which can be applied to management and conservation efforts, is still lacking. The northwestern section of the bay of Santa Catarina Island, locally known as North Bay, in Southern Brazil, inhabits the southernmost population of the Guiana dolphin (Sotalia guianensis). This small and resident population is structured in a single and highly cohesive group, using a small home range restricted to the western section of the bay. Like many other coastal dolphins, this dolphin population negatively interacts with fisheries, with frequent bycatch events or by sharing feeding resources. To explore the ecological role of dolphins in the North Bay ecosystem, we constructed an Ecopath food web model to estimate ecosystem and compartmental attributes. Mixed trophic impact and keystoneness index were used to assess the predatory effects of the species in the ecosystem. As a complementary approach to Ecopath, we used ecological network analysis (ENA) to determine the ecological role of the compartments using control analysis and the throughflow centrality. According to our model, North Bay is a mature detritus-based ecosystem. Dolphins showed the highest keystoneness index score among all functional groups, while control analysis showed they are also the most controlled component in the ecosystem. The dolphins rely mainly on the Whitemouth croaker (Micropogonias furnieri), a hub species showing the greatest centrality of flows. We concluded that the Guiana dolphin inhabiting the North Bay is a crucial compartment in the ecosystem. It shows the greatest ecosystem impact per biomass unit among all functional groups, while it is the most vulnerable compartment. • The ecological role of Sotalia guianensis was highlighted using food-web models. • Dolphins showed the highest keystoneness index in North Bay (South of Brazil). • Control analysis showed dolphins are the most controlled component in the ecosystem. • Micropogonias furnieri is a hub species in the food web and should be managed. • Sotalia guianensis is a critical and highly vulnerable species in the North Bay. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins are widespread off South America with patchy distributions throughout coastal, nearshore and offshore waters. Only limited information on the connectivity between individuals from these different habitats exists, despite the importance of understanding the overall population structure. A group of bottlenose dolphins in an insular habitat off Brazil may help provide evidence of the structure of a larger pelagic population in Brazilian waters. It is unknown whether the dolphins that use this habitat seasonally are part of an open population, a closed population of transient animals, or even individuals from offshore or nearshore groups. To explore the nature of these seasonal visitors we combined two strategies. First, by assessing the population parameters, we described a small group of individuals (maximum of 38 individuals in 2004 and five individuals in 2010) characterized by wide-ranging behavior, low survival probabilities (64%) and an apparent population decline. Secondly, by exploring their social organization at a fine scale, we observed that within a stable group, the dyadic associations are fluid and mostly of short duration, similar to well-known coastal bottlenose dolphin societies. The evidence of a non-structured social network seems to be coupled with apparent seasonal use of this insular protected area for calf rearing and/or reproductive strategies. Overall, our findings suggest that this group may not be an aggregation of individuals from different populations in a specific area, but a relatively stable group formed by the same animals. While continuing research efforts are necessary along the South America coast, the abandonment of the study area by this group may hamper the understanding of population structure and connectivity among pelagic and coastal populations of bottlenose dolphins, as well as the ecological and behavioral mechanisms driving their seasonal occurrence in oceanic habitats. [ABSTRACT FROM AUTHOR]

A subgroup of a population of Tursiops truncatus in southern Brazil is known for a cooperative behavior with artisanal fishermen whereby the dolphins shoal fish towards net-casting fishermen. Combining photo-identification data collected between September 2007 and 2009 with mark-recapture and Pollock's robust design models, we assessed abundance within seasons and survival and temporary emigration rates of dolphins between seasons. We also reanalyzed a previous data set collected during 1989-1991, and Cormack-Jolly-Seber models were applied to estimate survival rates for each of the study periods. The abundance of marked 'cooperative' dolphins varied between seasons from 18 (CI: 17-24) to 21 (CI: 20-24). The total abundance varied from 59 in the winter of 2008 (CI: 49-72) to 50 in the autumn of 2009 (CI: 40-62). The annual adult survival was estimated to be 0.917 (CI: 0.876-0.961), close to that estimated from data collected in the 1990s (0.941; CI: 0.888-0.998). The emigration probability was low (0.031; CI: 0.011-0.084) and different capture probabilities between the 'cooperative' and 'noncooperative' dolphins indicated a degree of behavioral segregation. The precision of our estimates is likely to provide sufficient power to detect population change, but we recommend a precautionary management approach to protect this vulnerable dolphin community and its unique cooperative feeding tradition. [ABSTRACT FROM AUTHOR]

The article discusses a study about the presence of lobomycosis-like disease (LLD) in wild bottlenose dolphins Tursiops truncatus of Laguna in southern Brazil. Researchers identified 47 adult dolphins and 10 calves, seven of which showed some form of epidermal lesion while 5 had evidence of LLD. The growth of the lesion at a slow but constant rate on the adult was observed during the first few months of observation, while also noted are the rapid increase of the growth rate and the appearance of the first lesions on the calf in the 14th month. Findings suggested that there is a need to monitor both the health of cetaceans and the quality of their habitat.

The poxviruses identified in cetaceans are associated with characteristic tattoo or ring skin lesions. However, little is known regarding the prevalence and progression of these lesions and the molecular characterization of cetacean poxviruses in the Southern Hemisphere. This manuscript describes the progression of poxvirus-like skin lesions in 5 free-ranging Guiana dolphins Sotalia guianensis. Additionally, 151 skin samples from 113 free-ranging cetaceans from Brazil, including 4 animals with tattoo skin lesions, were selected for poxvirus testing. Poxviral DNA polymerase gene PCR amplification was used to detect the virus in β-actin-positive samples (145/151). DNA topoisomerase I gene PCR was then used in Cetaceanpoxvirus (CePV)-positive cases (n = 2), which were further evaluated by histopathology and electron microscopy. Based on photo-identification, adult Guiana dolphins presented regressing or healed poxvirus-like lesions (2/2), while juveniles presented persistent (2/3) or healed and progressive lesions (1/3). CePV DNA was amplified in a common bottlenose dolphin Tursiops truncatus and in a Guiana dolphin. Intracytoplasmic inclusion bodies and viral particles consistent with poxvirus were identified by histology and electron microscopy, respectively. CePV-specific amino acid motifs were identified through phylogenetic analysis. Our findings corroborate previous studies that suggest the placement of poxviruses from cetaceans within the novel CePV genus. This is the first molecular identification of poxvirus in South American odontocetes.