Influencias climáticas en la dieta del delfín costero del litoral brasileño

The Guiana dolphin (Sotalia guianensis) is a small-bodied dolphin distributed along the Atlantic coast from Honduras to southern Brazil. It preys on fish, squid and shrimps. Several seminal studies have described its diet, yet relationships between the species’ feeding plasticity and climate gradients remain unknown. We compiled a large database of Guiana dolphin stomach remains from southeast coastal Brazil. We described the species’ diet using a number of descriptors, multivariate analysis of variance to test possible differentiation in diet composition, and the Morisita index to estimate the extent of trophic niche overlap between groups. We also analysed feeding plasticity using a regression tree analysis followed by an ordination analysis. We present new records of prey for the species in Brazil. Our results suggest that the Guiana dolphin has opportunistic feeding habits, which may exhibit the species’ feeding plasticity. Such feeding plasticity is associated with the capability to prey throughout a wide array of climate conditions. From a conservation ecology perspective, we conclude that estuaries—even ones that are over-depleted and succumbing to human impacts—are paramount environments for the Guiana dolphin, serving as important sources of prey for the species and other sympatric marine mammals.Sotalia guianensis es un delfín de pequeño porte cuya área de ditribución abarca el litoral atlántico desde Honduras hasta el sur de Brasil. Al día de la fecha, pese a que la dieta de este delfín ya ha sido descrita en anteriores trabajos, las posibles relaciones entre la ingesta de determinadas presas y los cambios en las variables ambientales aún se ignoran. En nuestro trabajo, describimos la dieta de estos delfines a través del análisis de contenidos estomacales y recopilamos una extensa base de datos a efectos de desvendar posibles patrones en la ecologia trófica de la especie a lo largo de la costa atlántica sudoriental brasileña. Usamos un conjunto de descriptores para caracterizar la dieta de estos delfines, probamos posibles diferencias por medio de un análisis de variancia multivariada y cuantificamos el grado de solapamiento trófico entre grupos utilizando el índice de Morisita. Además, analizamos la plasticidad trófica de la especie por medio de un árbol de regresión seguido de una ordenación. Presentamos nuevos registros de presas para la especie en Brasil. Los principales resultados que obtuvimos confirman los hábitos oportunistas que caracterizan a estos delfines y evidencian que sus presas más frecuentes y abundantes son a su vez abundantes en estuarios, como peces pertenecientes a la familia Sciaenidae. Dichos hábitos oportunistas podrían estar relacionados con la característica plasticidad trófica de la especie. Corroboramos que la plasticidad trófica del delfín costero se debe a su capacidad de predar en un amplio rango de condiciones climáticas, aunque sus presas más comunes se encuentran en estuarios. Desde el punto de vista de la Ecología de la Conservación, concluímos que los estuarios son ambientes de relevante importancia para estos delfines y otros mamíferos marinos simpátricos, por ser éstos una importante fuente de recursos alimenticios, aunque están en ambientes que soportan un fuerte impacto antrópico

Japan’s whaling is unscientific

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Dieta da toninha (Pontoporia blainvillei) na costa norte do Espírito Santo, Brasil

The franciscana dolphin (Pontoporia blainvillei) is the most threatened dolphin species in the Brazilian coast. The study area is the northernmost distribution range of the species and the stock inhabiting the northern State of Espírito Santo is isolated from other populations. Likewise, there is no information on feeding habits of franciscana dolphins in the study area. Hence, the aim of this study was to describe the diet of franciscana dolphins from the Northern Espírito Santo State coast. Stomach contents of 18 individuals stranded in the study area between January 2012 and March 2015 were analyzed. We ranked each specific prey item found in stomach contents using the frequency of occurrence, the total count of prey items, and the relative abundance of prey. It was found novel records of prey species for the franciscana dolphin and we explored possible feeding strategy patterns. The fish Isopisthus parvipinnis was the most common prey consumed by the dolphins. Our report agrees with previous studies showing demersal fish species, mainly sciaenids, as the most common preys consumed by the franciscana dolphin followed by pelagic fish species.A toninha (Pontoporia blainvillei) é considerada a espécie de golfinho mais ameaçada da costa do Brasil. As populações de toninha que ocorrem no litoral norte do estado do Espírito Santo constituem populações isoladas, separadas por um hiato geográfico das demais populações. Da mesma forma, não há informações sobre hábitos alimentares de golfinhos franciscanos na área de estudo. O objetivo desta pesquisa é descrever a dieta da toninha na costa norte do Espírito Santo. Foram analisados 18 conteúdos estomacais de carcaças encalhadas no período de janeiro/2012 a março/2015. Foram contabilizados os itens da dieta identificados e calculadas a frequência de ocorrência e a abundância relativa das presas. São apresentados novos registros de presas para a espécie. A presa mais comum encontrada na dieta da toninha foi Isopisthus parvipinnins. Assim como em outras localidades, a família Sciaenidae foi o grupo mais importante na dieta de Pontoporia blainvillei no Espírito Santo, seguida por presas pelágicas da ordem Clupeiformes

Professor Júlio Ernesto Baumgarten: (1965 – 2022)

This is an obituary for Professor Júlio Ernesto Baumgarten

Carcass non-recovery rate of franciscana dolphin (Pontoporia blainvillei), calibrated with a drift mark-recapture study at FMA Ia, Brazil

The franciscana dolphin (Pontoporia blainvillei) is one of the smallest dolphins globally and the most threatened in the Southwest Atlantic Ocean. Beach monitoring helps to investigate cetacean strandings within their distributions and assess impacts that cause mortality. Using drifters in mark-recapture studies helps to estimate recovery rates when carcasses are unavailable. The study aims to estimate the non-recovery rate of franciscana carcasses from FMA Ia by comparing the spatial distribution between carcasses and drifters along the coast; correlating the influence of cold fronts with the recovery rate of drifters; estimating the non-recovery rate of carcasses according to the drifters’ results and the meteorological profile in the pre-stranding period; characterizing the death diagnostic with temporal distribution of franciscanas by considering the stranding index and the carcass non-recovery rates. We repeated the release of 54 drifters in two campaigns close to the coast within the range of franciscana dolphins, where beaches are monitored daily, in the north region of Espírito Santo state, Brazil. The carcass stranding hotspots (21%) and drifters (18%) were 10 km apart. Cold fronts significantly increase the number of strandings. Considering the incidence of cold fronts in the pre-stranding period and linear regression from drifters, the median carcass recovery rate is 0.26, 95% IC [0.22 - 0.29], which means that for each stranding, the carcass non-recovery rate varies from 0.78 to 0.71. The range between 265 to 350 estimates the total of carcasses from 77 strandings observed from 2003 to 2021. The record year of strandings was 2014 (n = 14). About 52% of records occurred in summer, and January is the month with the highest occurrence of strandings. Of the conclusive diagnoses (n = 43), around 77% (n = 33) were attributed to incidental capture in gillnets. Estimating the number of carcasses based on stranding records is essential for population viability analyses and conservation purposes, especially considering small and isolated populations as in the present study. To prevent local extinction, a solution to avoid incidental capture, especially along summers, must be addressed quickly

Novel herpesviruses in riverine and marine cetaceans from South America

Herpesvirus (HV) infections in cetaceans are frequently associated with skin and mucosal lesions. Although HV infections have been reported worldwide, their occurrence in southern Atlantic marine mammals is still poorly understood. We tested skin, oral and genital mucosal beta-actin PCR-positive samples from 109 free-ranging Brazilian cetaceans using a universal herpesvirus DNA polymerase PCR. Herpesvirus-positive skin samples from a Guiana dolphin (Sotalia guianensis), a dwarf sperm whale (Kogia sima), a Bolivian river dolphin (Inia boliviensis), and a lingual sample from an Atlantic spotted dolphin (Stenella frontalis) were histologically evaluated. Additional tissue samples from these animals were also PCR-positive for HV, including a novel sequence obtained from the dwarf sperm whale's stomach and mesenteric lymph node. Four novel HV species were detected in the Guiana dolphin (one), the dwarf sperm whale (two) and the Bolivian river dolphin (one). The cutaneous lesions (marked, focally extensive, chronic proliferative dermatitis) of the Guiana dolphin and the Bolivian river dolphin were similar to previous HV reports in cetaceans, despite the absence of intranuclear inclusion bodies. This is the largest HV survey in South American cetaceans and the first detection of HV infection in riverine dolphins worldwide. © 2018 Elsevier B.V