Daniela Ferro de Godoy

Beaked whales, deep-diving cetaceans from the family Ziphiidae, exhibit cryptic behaviors, and data on these species in Brazilian waters are limited to strandings and isolated sightings. This study characterizes the occurrence and acoustic behavior of beaked whales in the Foz do Amazonas Basin using combined visual and passive acoustic monitoring along the Brazilian Equatorial Margin. Audio files were analyzed to identify clicks with frequency-modulated pulses, a diagnostic characteristic of beaked whales. The PAMpal package in R was used to calculate acoustic parameters, including peak frequency, 3- and 10-dB bandwidths, and inter-pulse intervals. Three sightings, eight acoustic detections, and one combined visual-acoustic detection were recorded. Based on diagnostic features, sighting D01 likely corresponds to Mesoplodon europaeus, D05 may represent Mesoplodon, and D06 could belong to either Ziphius or Mesoplodon. Unsupervised clustering based on peak frequency and inter-pulse intervals revealed three distinct acoustic clusters, suggesting that at least three different beaked whale species were detected. Further acoustic classification studies are needed to determine the specific species associated with each cluster. These findings contribute to a broader understanding of the distribution and acoustic ecology of deep-diving beaked whales in the Foz do Amazonas Basin, a region where information on marine megafauna remains scarce.

Anthropogenic activities have altered the structure and function of coastal and estuarine ecosystems, affecting the animals that occur in these areas. Predictive models are useful to evaluate the impact of anthropogenic characteristics over species distribution. In this study, we used generalized linear models to assess the influence Valo Grande canal, which allows fresh water to enter the Estuarine Lagunar Complex of Cananéia, has on the occurrence of Guiana dolphins. A population of this species resides in the study area, which comprises many coastal and marine protected areas. Abiotic data and information on species occurrence were gathered between January 2012 and November 2014, during three fieldworks per season, covering four sectors within the estuary. The predictions resulting from generalized linear models indicated that the discharge of fresh water, which decreases salinity in the estuary, has a negative influence on the populations of dolphins in all sectors but, mainly, on sector IV, the closest to Valo Grande Canal. Thus, it is clear that Guiana dolphins presented a heterogeneous distribution within the studied estuary, and the areas of higher concentration of individuals deserve greater attention during the elaboration of conservation strategies.

This study used models to assess how the type of prey caught by artisanal fishermen influenced the occurrence of Guiana dolphins (Sotalia guianensis) in the region of the estuarine lagunar comple.x of Cananéia (São Paulo, Brazil). The data were collected from January 2012 to November 2014, during three fieldwork expeditions per season (spring, summer, autumn, winter). Mullets (Mugil liza) were the fish with the highest association to dolphins, followed by Oligoplites spp. and Lobotes spp.; Mugil curema and shrimp, on the other hand, negatively influenced their distribution. The presence of fish‐weir fisheries in the estuary also had a positive influence on the occurrence of dolphins, since this fishing gear is used as a barrier, minimizing the potential for their prey to escape.