Incidental catches of franciscana in coastal gillnet fisheries in the Franciscana Management Area III: period 1999-2000

Abstract –Bycatch of franciscanas in fishing operations along the western South Atlantic Ocean has been observed for approximately 60 years. Reports on bycatch in shark gillnet fisheries off Uruguay date back to the early 1940s. A decade later, gillnet fisheries for bottom-dwelling fish became the major conservation concern for franciscanas in both Brazil and Argentina. A small portion (c. 10%), of the coastal gillnet fleet which operate from the port of Rio Grande (southern Rio Grande do Sul, Brazil) was monitored in 1999-2000. The total annual bycatch was estimated to be 946 franciscanas (non-parametric CI = 467 – 1525) for the year 1999 and 71

Reproductive biology of male franciscanas (Pontoporia blainvillei) (Mammalia: Cetacea) from Rio Grande do Sul, southern Brazil

The reproductive biology of male franciscanas (Pontoporia blainvillei), based on 121 individuals collected in Rio Grande do Sul State, southern Brazil, was studied. Estimates on age, length, and weight at attainment of sexual maturity are presented. Data on the reproductive seasonality and on the relationship between some testicular characteristics and age, size, and maturity status are provided. Sexual maturity was assessed by histological examination of the testes. Seasonality was determined by changes in relative and total testis weight, and in seminiferous tubule diameters. Testis weight, testicular index of maturity, and seminiferous tubule diameters were reliable indicators of sexual maturity, whereas testis length, age, length, and weight of the dolphin were not. Sexual maturity was estimated to be attained at 3.6 years (CI 95% =2.7–4.5) with the DeMaster method and 3.0 years with the logistic equation. Length and weight at attainment of sexual maturity were 128.2 cm (CI 95%=125.3–131.1 cm) and 26.4 kg (CI 95% =24.7–28.1 kg), respectively. It could not be verified that there was any seasonal change in the testis weight and in the seminiferous tubule diameters in mature males. It is suggested that at least some mature males may remain reproductively active throughout the year. The extremely low relative testis weight indicates that sperm competition does not occur in the species. On the other hand, the absence of secondary sexual characteristics, the reversed sexual size dimorphism, and the small number of scars from intrassexual combats in males reinforce the hypothesis that male combats for female reproductive access may be rare for franciscana. It is hypothesized that P. blainvillei form temporary pairs (one male copulating with only one female) during the reproductive period

Spatiotemporal use predicts social partitioning of bottlenose dolphins with strong home range overlap

© 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Ranging behaviour and temporal patterns of individuals are known to be fundamental sources of variation in social networks. Spatiotemporal dynamics can both provide and inhibit opportunities for individuals to associate, and should therefore be considered in social analysis. This study investigated the social structure of a Lahille's bottlenose dolphin (Tursiops truncatus gephyreus) population, which shows different spatiotemporal patterns of use and gregariousness between individuals. For this, we constructed an initial social network using association indices corrected for gregariousness and then uncovered affiliations from this social network using generalized affiliation indices. The association‐based social network strongly supported that this dolphin population consists of four social units highly correlated to spatiotemporal use patterns. Excluding the effects of gregariousness and spatiotemporal patterns, the affiliation‐based social network suggested an additional two social units. Although the affiliation‐based social units shared a large part of their core areas, space and/or time use by individuals of the different units were generally distinct. Four of the units were strongly associated with both estuarine and shallow coastal areas, while the other two units were restricted to shallow coastal waters to the south (SC) and north of the estuary (NC), respectively. Interactions between individuals of different social units also occurred, but dolphins from the NC were relatively more isolated and mainly connected to SC dolphins. From a conservation management perspective, it is recommended that information about the dolphin social units should be incorporated in modeling intrapopulation dynamics and viability, as well as for investigating patterns of gene flow among them

PRESENCE OF THE LEOPARD SEAL, HYDRURGA LEPTONYX (DE BLAINVILLE, 1820), ON THE COAST OF CHILE: AN EXAMPLE OF THE ANTARCTICA - SOUTH AMERICA CONNECTION IN THE MARINE ENVIRONMENT

Sightings of 114 leopard seals, Hydrurga leptonyx, have been recorded along the Chilean coasts from 1944 to 2010. Mostly immature seals occurred in northern and central Chile (18°30´S-39°59´S), especially in winter, while immature and adult individuals of both sexes and in good condition were commonly sighted year-round in glacial areas of southern Chile, especially Tierra del Fuego (south of 53°43´S), suggesting that this Antarctic species can be consider as a regular member of the marine fauna of Chile, with occasionally hauling out on the northern coastline not as vagrants, but as seasonal transients. Keeping in mind data limitation, we discuss some ways of northern dispersion and the subsequent residence of some animals in the Southern region of South America. These include, respectively: the close proximity of the Fueguian channels with the Antarctic Peninsula facilitated by the northward extension of the Antarctic pack ice during winter and/or through the influence of the Malvinas current; and the suitable habitat of the Fuegian channels, with similar characteristics to the Antarctic environment and locally abundant food resources.PRESENCIA  DE  LA  FOCA  LEOPARDO,  HYDRURGA  LEPTONYX  (DE  BLAINVILLE,  1820)  EN  LA COSTA DE CHILE: UN EJEMLO DE CONEXIÓN DE AMBIENTE MARINO ENTRE ANTÁRTICA Y AMÉRICA DEL SUR.  Entre 1927 y 2010, 115 focas leopardos, Hydrurga leptonyx, han sido egistradas a  lo  largo  de  la  costa  chilena.  En  la  región  centro-norte  (18°20´S-39°59´S),  especialmente  en  invierno,  la mayoría de los registros corresponden a individuos inmaduros; mientras que ejemplares maduros e inmaduros de ambos sexos y en buenas condiciones físicas son avistados durante todo el año, en áreas de glaciares del sur de Chile, especialmente en Tierra del Fuego (sur de los 53°43´S), sugiriendo que esta especie antártica puede ser considerado como un miembro regular de la fauna marina de Chile, con presencia ocasional en las costas norteñas, como vagabundo estacional. Teniendo en cuenta la limitación de los datos, discutimos algunas vías de dispersión hacia el norte y la presencia durante todo el año de los animales en la región austral de América del Sur. Estas incluyen, respectivamente: la cercana proximidad de los canales fueguinos con la Península Antártica, facilitado por la extensión hacia el norte del hielo marino antártico durante el invierno y/o a través de la influencia de la corriente de las Malvinas; y el hábitat apropiado de los canales fueguinos, con características similares al ambiente Antártico y abundante recursos alimenticios locales. Palabras claves: Foca leopardo; Chile; América del Sur; Océano austral.PRESENÇA DA FOCA-LEOPARDO, HYDRURGA LEPTONYX (DE BLAINVILLE, 1820), NA COSTA DO CHILE: UM EXEMPLO DA CONEXÃO ENTRE ANTÁRTICA E AMÉRICA DO SUL NO AMBIENTE MARINHO.  Entre 1927 e 2010, 115 focas-leopardo, Hydrurga leptonyx, foram avistadas ao longo da costa Chilena. Na região centro-norte (18°20´S-39°59´S), especialmente no inverno, a maioria dos registros esteve representada por indivíduos imaturos. Indivíduos imaturos e adultos de ambos os sexos ocorreram ao longo do ano, em boas condições físicas, em áreas glaciais da região sul do Chile, especialmente na Terra do Fogo (ao sul de 53°43´S). Nesta revisão, há evidências robustas para sugerir que a espécie é uma visitante regular da fauna Antártica em território austral chileno, ocorrendo eventualmente como vadios sazonais na costa norte do país. Apesar das limitações inerentes aos dados, discutem-se sobre a dispersão da espécie em direção ao norte e subsequente presença de indivíduos na porção austral da América do Sul. Estas incluem respectivamente: a proximidade entre os canais Foguinos e a Península Antártica, favorecida pela expansão da capa de gelo em direção ao norte durante o inverno e/ou pela influência da corrente das Malvinas; o habitat adequado nos canais Foguinos, com características similares àquelas do ambiente Antártico, somado à presença de recursos alimentares localmente abundantes. Palavras-chave: Foca-leopardo; Chile; América do Sul; Oceano Austral

Changes in phytoplankton communities along the Northern Antarctic Peninsula: Causes, impacts and research priorities

The Northern Antarctic Peninsula (NAP), located in West Antarctica, is amongst the most impacted regions by recent warming events. Its vulnerability to climate change has already led to an accumulation of severe changes along its ecosystems. This work reviews the current findings on impacts observed in phytoplankton communities occurring in the NAP, with a focus on its causes, consequences, and the potential research priorities toward an integrated comprehension of the physical–biological coupling and climate perspective. Evident changes in phytoplankton biomass, community composition and size structure, as well as potential bottom-up impacts to the ecosystem are discussed. Surface wind, sea ice and meltwater dynamics, as key drivers of the upper layer structure, are identified as the leading factors shaping phytoplankton. Short- and long-term scenarios are suggested for phytoplankton communities in the NAP, both indicating a future increase of the importance of small flagellates at the expense of diatoms, with potential devastating impacts for the ecosystem. Five main research gaps in the current understanding of the phytoplankton response to climate change in the region are identified: (i) anthropogenic signal has yet to be disentangled from natural climate variability; (ii) the influence of small-scale ocean circulation processes on phytoplankton is poorly understood; (iii) the potential consequences to regional food webs must be clarified; (iv) the magnitude and risk of potential changes in phytoplankton composition is relatively unknown; and (v) a better understanding of phytoplankton physiological responses to changes in the environmental conditions is required. Future research directions, along with specific suggestions on how to follow them, are equally suggested. Overall, while the current knowledge has shed light on the response of phytoplankton to climate change, in order to truly comprehend and predict changes in phytoplankton communities, there must be a robust collaboration effort integrating both Antarctic research programs and the whole scientific community under a common research framework

Assessing bias in aerial surveys for cetaceans: Results from experiments conducted with the franciscana dolphin

Line transect aerial surveys are widely used for estimating abundance of biological populations, including threatened species. However, estimates obtained with data collected from aircraft are often underestimated because of visibility bias and bias in estimating group sizes from a fast-moving platform. An assessment of multiple sources of bias in aerial surveys were carried out in Brazilian coastal waters by experiments on multiple survey platforms (i.e., boat, airplane and helicopter). These studies focused on evaluating visibility bias (perception and availability bias) and potential differences in the estimation of group sizes from different types of platforms used in franciscana (Pontoporia blainvillei) abundance surveys. The ultimate goal was to develop correction factors to improve accuracy of estimates of density and population size for this threatened dolphin. Estimates of density and group sizes computed from boats were assumed to be unbiased and were compared to estimates of these quantities obtained from an airplane in the same area and period. In addition, helicopter surveys were conducted in two areas where water turbidity differed (clear vs. murky waters) to determine surfacing-diving intervals of franciscana groups and to estimate availability for aerial platforms. Abundance computed from the aerial survey data underestimated the true abundance by about 4-5 times, with ~70% of the total bias resulting from visibility bias (~80% from availability bias and ~20% from perception bias) and ~30% from bias in estimates of group size. The use of multiple survey platforms in contrasting habitats provided the opportunity to compute correction factors that can be used to refine range wide abundance estimates of the threatened franciscana given certain assumptions are met. Visibility bias and group size bias were substantial and clearly indicate the importance for accounting for such correction factors to produce unequivocal population assessment based on aerial survey data.Fil: Sucunza, Federico. Grupo de Estudio de Mamiferos Aquaticos de Rio Grande Do Sul.; Brasil. Universidade Federal de Juiz de Fora; Brasil. Instituto Aqualie; BrasilFil: Danilewicz, Daniel. Instituto Aqualie; Brasil. Grupo de Estudio de Mamiferos Aquaticos de Rio Grande Do Sul.; Brasil. Universidade Federal de Juiz de Fora; BrasilFil: Andriolo, Artur. Instituto Aqualie; Brasil. Universidade Federal de Juiz de Fora; BrasilFil: de Castro, Franciele R.. Instituto Aqualie; BrasilFil: Cremer, Marta. Universidade da Região de Joinville; BrasilFil: Denuncio, Pablo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Ferreira, Emanuel. Associação R3 Animal; BrasilFil: Flores, Paulo A. C.. Instituto Chico Mendes para a Conservação da Biodiversidade; BrasilFil: Ott, Paulo H.. Universidade Estadual do Rio Grande do Sul; Brasil. Grupo de Estudio de Mamiferos Aquaticos de Rio Grande Do Sul.; BrasilFil: Perez, Martin S.. Grupo de Estudio de Mamiferos Aquaticos de Rio Grande Do Sul.; BrasilFil: Pretto, Dan. Instituto Chico Mendes Para A Conservação Da Biodiversidade; BrasilFil: Sartori, Camila M.. Universidade da Região de Joinville; BrasilFil: Secchi, Eduardo Resende. Universidade Federal do Rio Grande; BrasilFil: Zerbini, Alexandre. Marine Ecology And Telemetry Research; Estados Unidos. Cascadia Research Collective; Estados Unidos. Instituto Aqualie; Brasil. Universidade Federal de Juiz de Fora; Brasil. The George Washington University; Estados Unido

Identifying seasonal distribution patterns of fin whales across the Scotia Sea and the Antarctic Peninsula region using a novel approach combining habitat suitability models and ensemble learning methods

Following their near extirpation by industrial whaling of the 20th century, the population status of Southern Hemisphere fin whales (SHFW) remains unknown. Systematic surveys estimating fin whale abundance in the Southern Ocean are not yet available. Records of fin whale sightings have been collected by a variety of organisations over the past few decades, incorporating both opportunistic data and dedicated survey data. Together, these isolated data sets represent a potentially valuable source of information on the seasonality, distribution and abundance of SHFW. We compiled records across 40 years from the Antarctic Peninsula and Scotia Sea from multiple sources and used a novel approach combining ensemble learning and a maximum entropy model to estimate abundance and distribution of SHFW in this region. Our results show a seasonal distribution pattern with pronounced centres of distribution from January-March along the West Antarctic Peninsula. Our new approach allowed us to estimate abundance of SHFW for discrete areas from a mixed data set of mainly opportunistic presence only data

Identifying seasonal distribution patterns of fin whales across the Scotia Sea and the Antarctic Peninsula region using a novel approach combining habitat suitability models and ensemble learning methods

Following their near extirpation by industrial whaling of the 20th century, the population status of Southern Hemisphere fin whales (SHFW) remains unknown. Systematic surveys estimating fin whale abundance in the Southern Ocean are not yet available. Records of fin whale sightings have been collected by a variety of organisations over the past few decades, incorporating both opportunistic data and dedicated survey data. Together, these isolated data sets represent a potentially valuable source of information on the seasonality, distribution and abundance of SHFW. We compiled records across 40 years from the Antarctic Peninsula and Scotia Sea from multiple sources and used a novel approach combining ensemble learning and a maximum entropy model to estimate abundance and distribution of SHFW in this region. Our results show a seasonal distribution pattern with pronounced centres of distribution from January-March along the West Antarctic Peninsula. Our new approach allowed us to estimate abundance of SHFW for discrete areas from a mixed data set of mainly opportunistic presence only data.publishedVersio

Genetic divergence between two phenotypically distinct bottlenose dolphin ecotypes suggests separate evolutionary trajectories

Due to their worldwide distribution and occupancy of different types of environments, bottlenose dolphins display considerable morphological variation. Despite limited understanding about the taxonomic identity of such forms and connectivity among them at global scale, coastal (or inshore) and offshore (or oceanic) ecotypes have been widely recognized in several ocean regions. In the Southwest Atlantic Ocean (SWA), however, there are scarce records of bottlenose dolphins differing in external morphology according to habitat preferences that resemble the coastal‐offshore pattern observed elsewhere. The main aim of this study was to analyze the genetic variability, and test for population structure between coastal (n = 127) and offshore (n = 45) bottlenose dolphins sampled in the SWA to assess whether their external morphological distinction is consistent with genetic differentiation. We used a combination of mtDNA control region sequences and microsatellite genotypes to infer population structure and levels of genetic diversity. Our results from both molecular marker types were congruent and revealed strong levels of structuring (microsatellites FST = 0.385, p < .001; mtDNA FST = 0.183, p < .001; ΦST = 0.385, p < .001) and much lower genetic diversity in the coastal than the offshore ecotype, supporting patterns found in previous studies elsewhere. Despite the opportunity for gene flow in potential “contact zones”, we found minimal current and historical connectivity between ecotypes, suggesting they are following discrete evolutionary trajectories. Based on our molecular findings, which seem to be consistent with morphological differentiations recently described for bottlenose dolphins in our study area, we recommend recognizing the offshore bottlenose dolphin ecotype as an additional Evolutionarily Significant Unit (ESU) in the SWA. Implications of these results for the conservation of bottlenose dolphins in SWA are also discussed

Whale, whale, everywhere: increasing abundance of western South Atlantic humpback whales (Megaptera novaeangliae) in their wintering grounds

The western South Atlantic (WSA) humpback whale population inhabits the coast of Brazil during the breeding and calving season in winter and spring. This population was depleted to near extinction by whaling in the mid-twentieth century. Despite recent signs of recovery, increasing coastal and offshore development pose potential threats to these animals. Therefore, continuous monitoring is needed to assess population status and support conservation strategies. The aim of this work was to present ship-based line-transect estimates of abundance for humpback whales in their WSA breeding ground and to investigate potential changes in population size. Two cruises surveyed the coast of Brazil during August-September in 2008 and 2012. The area surveyed in 2008 corresponded to the currently recognized population breeding area; effort in 2012 was limited due to unfavorable weather conditions. WSA humpback whale population size in 2008 was estimated at 16,410 (CV = 0.228, 95% CI = 10,563–25,495) animals. In order to compare abundance between 2008 and 2012, estimates for the area between Salvador and Cabo Frio, which were consistently covered in the two years, were computed at 15,332 (CV = 0.243, 95% CI = 9,595–24,500) and 19,429 (CV = 0.101, 95% CI = 15,958–23,654) whales, respectively. The difference in the two estimates represents an increase of 26.7% in whale numbers in a 4-year period. The estimated abundance for 2008 is considered the most robust for the WSA humpback whale population because the ship survey conducted in that year minimized bias from various sources. Results presented here indicate that in 2008, the WSA humpback whale population was at least around 60% of its estimated pre-modern whaling abundance and that it may recover to its pre-exploitation size sooner than previously estimated.Publisher PDFPeer reviewe