Daniel Danilewicz

Habitat use patterns of franciscana dolphins (Pontoporia blainvillei) off southern Brazil in relation to water depth

The patterns of habitat use by the franciscana dolphins (Pontoporia blainvillei) along its distribution are poorly known. This study investigates the patterns of habitat use with respect to depth for 181 individuals of different age, size, gender and reproductive condition off Rio Grande do Sul, southern Brazil. The results reveal that franciscanas are very homogeneously distributed according to depth. Individuals from all lengths utilize nearly the entire range of depths of the surveyed area. Larger or older animals do not use deeper waters than younger animals, indicating that body size and age are not limiting factors for franciscanas that occupy deeper or offshore waters. Gestation seems to not cause a change in the distribution of females. Although the sex-ratio of the overall data did not vary from 1:1 in different depth intervals, a small-scale comparison between the northern and southern coast demonstrated the existence of some kind of sexual segregation. Franciscana by-catch in Rio Grande do Sul is not sustainable and it is agreed that management procedures are needed. Nevertheless, the available data on species distribution do not allow the designing of a protected area in order to minimize the by-catches of a particular sex/reproductive class.

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.

Age and growth of franciscana dolphins, Pontoporia blainvillei (Cetacea: Pontoporiidae) incidentally caught off southern Brazil and northern Argentina

Age and length data of 291 franciscana dolphins (Pontoporia blainvillei) incidentally captured on the coast of Rio Grande do Sul State (RS), southern Brazil, were used to fit growth curves using Gompertz and Von Bertalanffy growth models. A small sample of franciscanas (N ¼ 35) from Buenos Aires Province (BA), Argentina, were used to see if there are apparent growth differences between the populations. Male and female franciscana samples from both areas were primarily (78–85%) ,4 years of age. The Von Bertalanffy growth model with a data set that excluded animals ,1 year of age provided the best fit to data. Based on this model, dolphins from the RS population reached asymptotic length at 136.0 cm and 158.4 cm, for males and females, respectively. No remarkable differences were observed in the growth trajectories of males and females between the RS and BA populations.

Occurrence of the Atlantic spotted dolphin, Stenella frontalis , in southern Abrolhos Bank, Brazil

daniel danilewicz, paulo h. ott, eduardo secchi, artur andriolo and alexandre zerbini Laboratorio de Ecologia e Conservacao de Mamiferos Marinhos (ECOMMAR), Universidade Estadual de Santa Cruz, Departamento de Ciencias Biologicas, Rodovia Ilheus/Itabuna, km 16, Ilheus, BA, 45662-900, Brazil, Instituto Aqualie, Rua Edgard Werneck 428/32, Rio de Janeiro, RJ, 22763-010, Brazil, Grupo de Estudos de Mamiferos Aquaticos do Rio Grande do Sul (GEMARS), Avenida Tramandai, 976, Imbe, 95625-000, Rio Grande do Sul, Brazil, Departamento de Zoologia, Instituto de Ciencias Biologicas, Universidade Federal de Juiz de Fora, Minas Gerais, Brazil, Universidade Estadual do Rio Grande do Sul (UERGS), Laboratorio da Biologia e Conservacao de Aves e Mamiferos Aquaticos, Avenida Mostardeiro, 3635, Cidreira, 95595-000, Rio Grande do Sul, Brazil, Laboratorio de Mamiferos Marinhos, Instituto de Oceanografia, Universidade Federal do Rio Grande (FURG), Rio Grande, RS, Brazil, National Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA Fisheries, 7600 Sand Point Way NE, Seattle, Washington 98115, USA, Cascadia Research Collective, 218 2 4th Avenue, Olympia, WA, 98501, USA

Body Fat Condition in Franciscanas (Pontoporia blainvillei) in Rio Grande do Sul, Southern Brazil

Abstract In cetaceans almost all the energy reserves in lipid form are allocated to blubber and are related to basal metabolism and thermal insulation. Our study analyzed the blubber of 57 specimens of franciscana (Pontoporia blainvillei) from the state of Rio Grande do Sul, Brazil. Body fat condition was estimated through blubber weight, girth, and thickness of blubber. Blubber weight increased along with growth, from 2.27 kg in calves to 8.86 kg in mature franciscanas. Blubber weight decreased from 33.91% of total weight in calves to 24.32% in mature franciscanas. A significant difference was found when age classes were compared to each other (P < 0.001) for both males and females, indicating that blubber varied according to growth, independent of sex. Girth showed a good correlation with blubber weight at all 6 locations where it was measured, and thickness of blubber presented a low correlation at all 19 locations where it was measured. Calves face the physiologic problems of low surface to volume ratio, whereas adults expend energy in feeding, reproduction, and taking care of calves.

Southern right whales (Eubalaena australis) off Torres, Brazil: group characteristics, movements, and insights into the role of the Brazilian-Uruguayan wintering ground

Abstract The southern right whale (SRW), Eubalaena australis, was heavily depleted by the whaling in the Southern Hemisphere. In the southwestern Atlantic, studies on SRWs have been concentrated in two main breeding grounds: Península Valdés, Argentina (~42°′S) and Santa Catarina (SC) State, Brazil (~28°′S). To better understand the ecology of SRWs in the region located between these breeding grounds, shore-based surveys were carried out off Torres (29°19′S, 49°43′W), Rio Grande do Sul (RS). Whales were observed in the area between July and October with peaks in August and September. Group sizes were relatively small (x̅=1.6; range=1–3). Distribution in relation to distance from the coast varied from 0.5 to 8.9 km (median=1.9 km). Unlike in other areas, mother-calf pairs were not observed to occur in shallower waters more often than unaccompanied whales. Mother-calf pairs presented northbound movements to SC more frequently than unaccompanied whales. A comparison of the present data with those from Uruguay and SC revealed that SRWs of different gender/reproductive status may use distinctively the eastern coast of South America. Within these regions, the proportion of mother-calf pairs increases progressively as latitude decreases (from 8% in Uruguay to 58.5% in SC), while the proportion of unaccompanied SRWs presents an opposite trend. This study indicates that RS is an important area for reproduction of SRWs because the three phases (birth, nursing, and mating) proposed for a breeding ground occur there.

Refining estimates of availability bias to improve assessments of the conservation status of an endangered dolphin

Estimation of visibility bias is critical to accurately compute abundance of wild populations. The franciscana, Pontoporia blainvillei, is considered the most threatened small cetacean in the southwestern Atlantic Ocean. Aerial surveys are considered the most effective method to estimate abundance of this species, but many existing estimates have been considered unreliable because they lack proper estimation of correction factors for visibility bias. In this study, helicopter surveys were conducted to determine surfacing-diving intervals of franciscanas and to estimate availability for aerial platforms. Fifteen hours were flown and 101 groups of 1 to 7 franciscanas were monitored, resulting in a sample of 248 surface-dive cycles. The mean surfacing interval and diving interval times were 16.10 seconds (SE = 9.74) and 39.77 seconds (SE = 29.06), respectively. Availability was estimated at 0.39 (SE = 0.01), a value 16–46% greater than estimates computed from diving parameters obtained from boats or from land. Generalized mixed-effects models were used to investigate the influence of biological and environmental predictors on the proportion of time franciscana groups are visually available to be seen from an aerial platform. These models revealed that group size was the main factor influencing the proportion at surface. The use of negatively biased estimates of availability results in overestimation of abundance, leads to overly optimistic assessments of extinction probabilities and to potentially ineffective management actions. This study demonstrates that estimates of availability must be computed from suitable platforms to ensure proper conservation decisions are implemented to protect threatened species such as the franciscana.

Changes in the feeding ecology of South American sea lions on the southern Brazilian coast over the last two decades of excessive fishing exploration

In the last decades, an increasing fishing effort and a decreasing trend in fish catches have been observed in southern Brazil. Considering that marine mammals and fisheries usually compete for the same resources, it is reasonable to presume that the feeding ecology of these predators is affected by the current scenario. To evaluate this hypothesis, long-term variation in the diet of the South American sea lion (Otaria flavescens) relative to fisheries exploitation was analyzed for two periods (1993–2003 versus 2004–2014). The degree of overlap between the relative biomass of the sea lions’ diet and the target species of six types of local fishery was analyzed. An increase in prey overlap between sea lions and fisheries was observed in the more recent sampling period, along with an increase in prey diversity, richness, and niche breadth of the sea lions’ diet. These results suggest that the overfishing scenario could partly explain the modified feeding ecology of the sea lions. In this context, we recommend a review and better regulation of the current fishing effort in the region, which we believe will be an important step to maintain the fish stocks and minimize the impact of fishing on marine top predators.

Preliminary calculation of individual echolocation signal emission rate of Franciscana dolphins (Pontoporia blainvillei)

Calculation of echolocation signals emission rate is necessary to estimate how many individuals are vocalizing, especially if passive acoustic density estimation methods are to be implemented. We calculated the individual emission rate of echolocation signals of franciscana dolphin. Fieldwork was between 22 and 31 January of 2014 at Babitonga Bay, Brazil. Acoustic data and group size were registered when animals were within visual range at maximum distance of 50 meters. We used a Cetacean Research™ hydrophone. The sound was digitized by Analogic/Digital IOtech, stored as wav-files and analyzed with Raven software. A band limited energy detector was set to automatically extract echolocation signals. The emission rate was calculated dividing the clicks registered for each file by the file duration and by the number of individuals in the group. We analyzed 240 min of sound of 36 groups. A total of 29,164 clicks were detected. The median individual click rate was 0.290 clicks/s (10th = 0.036 and 90th = 1.166 ...

Aves, Passeriformes, Cotingidae, Phytotoma rutila (Vieillot, 1818): new record in Brazil

The White-tipped Plantcutter Phytotoma rutila has only one documented record for Brazil, that occurred in 1974 in the extreme west of Rio Grande do Sul. We report herein a second record - one individual photographed in April 2009 at a dunefield in the municipality of Capao da Canoa, northern coast of Rio Grande do Sul, about 700 km from the previous one. This new record corroborates the status of vagrant for this species in Brazil.