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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]

This study represents the first attempt to study the population dynamics of Guiana dolphins ( Sotalia guianensis), by evaluating a set of demographic parameters. The population of the Caravelas River estuary, eastern Brazil, was systematically monitored through a long-term mark-recapture experiment (2002-2009). Abundance estimates revealed a small population (57-124 dolphins), comprised of resident dolphins and individuals that temporarily leave or pass through the study area. Temporary emigration from the estuary to adjacencies (γ″= 0.33 ± 0.07 SE) and return rate (1 −γ′= 0 .67) were moderate and constant, indicating that some dolphins use larger areas. Survival rate (ϕ= 0.88 ± 0.07 SE) and abundance were constant throughout the study period. Power analysis showed that the current monitoring effort has high probability of detecting abrupt population declines (1 −β= 0.9). Although the monitoring is not yet sensitive to subtle population trends, sufficient time to identify them is feasible (additional 3 yr). Despite such apparent stability, this population, as many others, inhabits waters exposed to multiple human-related threats. Open and closed population modeling applied to photo-identification data provide a robust baseline for estimating several demographic parameters and can be applied to other populations to allow further comparisons. Such synergistic efforts will allow a reliable definition of conservation status of this species. [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.

Cooperation is generally the most advantageous strategy for the group; however, on an individual level, cheating is frequently more attractive. In a fishery, one can choose to cooperate by fishing only the regulated amount or not to cooperate, by fishing to maximize profits. Top-down management can help to emulate a cooperative result in fisheries, but it is costly and not always a viable alternative for development states. Here, we investigate elements of a fishing system that can be strategically managed to encourage a cooperative behaviour. Using bioeconomic data, we modelled an evolutionary game between two populations of fishers that differ if they cooperate or do not cooperate with a fishing restriction. We penalized players including risk tolerance and control perception, two social parameters that might favour cooperation. We assessed the degrees to which risk tolerance and control perception affect the cooperative behaviours of fishers in a restricted fishing effort small-scale fishery (RSSF) in southern Brazil. We also assessed the likelihood of a scenario wherein a cooperative strategy can evolve and dominate the system. We identified dominance and coexistence outcomes for the RSSF. Sensitivity analyses suggested that both control perception and risk tolerance could facilitate a cooperative outcome for the fishery., Competing Interests: We declare we have no competing interests., (© 2020 The Authors.)

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.