Publications by authors named "Alexandre N Zerbini"

Article Synopsis
  • Isolation by distance and geographic boundaries have shaped the population genetic structure of harbour porpoises along the Pacific coast, with a focus on Alaska where recent research used both tissue and environmental DNA (eDNA) samples to fill gaps in previous studies.* -
  • The study found limited genetic differentiation among harbour porpoise populations based on nuclear SNP data, but mtDNA analysis revealed significant structuring, especially between the Gulf of Alaska and the eastern Bering Sea, suggesting restricted gene flow and potential natal site fidelity.* -
  • The targeted eDNA sampling in Southeast Alaska significantly enhanced the genetic dataset, indicating a population boundary within the recognized Southeast Alaska Stock, which is vital for informing conservation efforts and mitigating fisheries conflicts.*
View Article and Find Full Text PDF

South American river dolphins face significant threats from intense human activities, resulting in habitat loss, fragmentation of their natural connectivity, overfishing, pollution, and incidental and intentional catches for use as bait for fisheries. From 1998 to 2022, 12 surveys were conducted in a river system in the Mamore River (Ibare-Tijamuchi-Mamore) basin, one of the primary distribution areas of the Bolivian river dolphin (BRD - Inia geoffrensis boliviensis). Generalized linear models (GLMs) were used to assess population trends.

View Article and Find Full Text PDF

Marine protected areas (MPAs) are a commonly used management tool to safeguard marine life from anthropogenic impacts, yet their efficacy often remains untested. Evaluating how highly dynamic marine species use static MPAs is challenging but becoming more feasible with the advancement of telemetry data. Here, we focus on southern right whales (Eubalaena australis, SRWs) in the waters off Aotearoa/New Zealand, which declined from 30,000 whales to fewer than 40 mature females due to whaling.

View Article and Find Full Text PDF

Improving our understanding of the effects of satellite tags on large whales is a critical step in ongoing tag development to minimise potential health effects whilst addressing important research questions that enhance conservation management policy. In 2014, satellite tags were deployed on 9 female southern right whales Eubalaena australis accompanied by a calf off Australia. Photo-identification resights (n = 48) of 4 photo-identified individuals were recorded 1 to 2894 d (1-8 yr) post-tagging.

View Article and Find Full Text PDF
Article Synopsis
  • Assessing environmental changes in the Southern Ocean is challenging due to its remote location and lack of data, but monitoring marine predators like the southern right whale (SRW) can help track human impacts on these ecosystems.
  • Research on 1,002 skin samples revealed that SRWs have increasingly been foraging in mid-latitude areas of the South Atlantic and Southwest Indian Ocean in recent decades, likely due to changes in prey distribution.
  • The study found that SRWs have maintained stable foraging patterns in mid-latitude regions over the past four centuries, attributed to the physical stability of ocean fronts that support productivity, unlike the more affected polar regions.
View Article and Find Full Text PDF

The Humboldt Current Ecosystem (HCE) is one of the most productive marine ecosystems, sustaining one of the largest fishing industries in the world. Although several species of cetaceans are known to inhabit these productive waters, quantitative assessments of their abundance and distribution patterns are scarce and patchy. Here, we present the first abundance and distribution estimates for fin whale (Balaenoptera physalus), southeast Pacific blue whales (Balaenoptera musculus), sperm whale (Physeter macrocephalus), dusky dolphin (Lagenorhynchus obscurus), and common dolphin (Delphinus spp.

View Article and Find Full Text PDF

Humpback whales (Megaptera novaeangliae) perform seasonal migrations from high latitude feeding grounds to low latitude breeding and calving grounds. Feeding grounds at polar regions are currently experiencing major ecosystem modifications, therefore, quantitatively assessing species responses to habitat characteristics is crucial for understanding how whales might respond to such modifications. We analyzed satellite telemetry data from 22 individual humpback whales in the Southwest Atlantic Ocean (SWA).

View Article and Find Full Text PDF

The population of humpback whales (Megaptera novaeangliae) wintering off eastern South America was exploited by commercial whaling almost to the point of extinction in the mid-twentieth century. Since cessation of whaling in the 1970s it is recovering, but the timing and level of recovery is uncertain. We implemented a Bayesian population dynamics model describing the population's trajectory from 1901 and projecting it to 2040 to revise a previous population status assessment that used Sampling-Importance-Resampling in a Bayesian framework.

View Article and Find Full Text PDF

Defining priority areas and risk evaluation is of utmost relevance for endangered species` conservation. For the blue whale (Balaenoptera musculus), we aim to assess environmental habitat selection drivers, priority areas for conservation and overlap with vessel traffic off northern Chilean Patagonia (NCP). For this, we implemented a single-step continuous-time correlated-random-walk model which accommodates observational error and movement parameters variation in relation to oceanographic variables.

View Article and Find Full Text PDF

Populations of freshwater dolphins are declining in response to increased human pressure, including habitat degradation, overfishing, bycatch, poaching and obstruction of free-flowing river corridors by dams. At least three river dolphin species occur in South America: the Amazonian river dolphin, or boto (Inia geoffrensis), the Bolivian river dolphin (Inia boliviensis) and the tucuxi (Sotalia fluviatilis). A fourth species, the Araguaian boto (Inia araguaiaensis), been proposed for the Tocantins-Araguaia, a large river basin in northern Brazil.

View Article and Find Full Text PDF

Humpback whales (Megaptera novaeangliae) are known for their nearshore distribution during the breeding season, but their pelagic habitat use patterns remain mostly unexplored. From 2016 to 2018, 18 humpback whales were equipped with depth-recording satellite tags (SPLASH10) to shed light on environmental and social drivers of seamount association around New Caledonia in the western South Pacific. Movement paths were spatially structured around shallow seamounts (<200 m).

View Article and Find Full Text PDF
Article Synopsis
  • The recovery of western South Atlantic humpback whales, decimated by exploitation, is assessed using a Bayesian model that incorporates various data and assumptions.
  • Their population rebounded from about 450 in the 1950s to an estimated 93% of pre-exploitation levels, highlighting the impact of protective measures.
  • This recovery poses ecological concerns, particularly related to their feeding on Antarctic krill, necessitating ongoing monitoring to assess responses to human activities and climate change.
View Article and Find Full Text PDF

Background: The most traditional scheme for migration among baleen whales comprises yearly migrations between productive waters at high latitude summer feeding grounds and warmer waters at lower latitudes where whales calve and mate, but rarely feed. Evidence indicates, however, that large departures from this scheme exist among populations and individuals. Furthermore, for some populations there is virtually no information on migratory pathways and destinations.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

Cuvier's beaked whales () have stranded in association with mid-frequency active sonar (MFAS) use, and though the causative mechanism linking these events remains unclear, it is believed to be behaviourally mediated. To determine whether MFAS use was associated with behavioural changes in this species, satellite tags were used to record the diving and movements of 16 Cuvier's beaked whales for up to 88 days in a region of frequent MFAS training off the coast of Southern California. Tag data were combined with summarized records of concurrent bouts of high-power, surface-ship and mid-power, helicopter-deployed MFAS use, along with other potential covariates, in generalized additive mixed-effects models.

View Article and Find Full Text PDF

Whale tracking tags often penetrate semi-rigid blubber, with intramuscular sharp tips and toggling barbs under the subdermal sheath to reduce premature shedding. Tag sites can show persistent regional swellings or depressions. Fibroelastic blubber grips a tag, so if muscle shears relative to blubber during locomotion, the tag tip could cavitate the muscle within overall shearing distance.

View Article and Find Full Text PDF

Mediterranean fin whales comprise a genetically distinct population, listed as Vulnerable (VU) in the IUCN Red List. Collisions with vessels are believed to represent the main cause of human-induced mortality. The identification of critical habitats (including migration routes) incorporating satellite telemetry data is therefore crucial to develop focussed conservation efforts.

View Article and Find Full Text PDF
Article Synopsis
  • * Female humpback whales showed a preference for deeper waters up to 14 km from shore for breeding, while males' speed decreased in shallow waters, indicating social factors may influence their behavior more than environmental variables.
  • * The study highlights that coastal areas under human pressure are essential habitats for humpback whales, revealing their reliance on specific environmental conditions like ocean currents and chlorophyll levels to enhance their movements.
View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings.

View Article and Find Full Text PDF
Article Synopsis
  • Accurately estimating historical whale populations is crucial for understanding their recovery, but it's difficult due to incomplete records from pre-modern whaling.
  • Right whales, especially the New Zealand southern right whale, were heavily hunted in the 19th century due to their predictable behavior and habitat.
  • Using a Bayesian model, researchers estimate that the pre-exploitation population was between 28,800 and 47,100, which dropped to just 30-40 mature females by the 1920s, illustrating the long-term impacts of whaling and the importance of setting conservation targets for restoring their populations.
View Article and Find Full Text PDF
Article Synopsis
  • The humpback whale population in New Caledonia displays a unique migratory pattern involving various directions, long distances, and frequent stops at underwater features called seamounts.
  • 34 tracked whales migrated south from breeding grounds, traveling between 270 and 8540 km with an average speed of about 3.53 km/h.
  • The research indicates that seamounts are vital habitats for these whales, serving roles such as breeding areas, resting spots, navigational aids, and potential feeding grounds, highlighting the need for conservation efforts in these less recognized habitats.*
View Article and Find Full Text PDF

Acoustic parameters of killer whale (Orcinus orca) whistles were described for the western South Atlantic Ocean and highlight the occurrence of high frequency whistles. Killer whale signals were recorded on December of 2012, when a pod of four individuals was observed harassing a group of sperm whales. The high frequency whistles were highly stereotyped and were modulated mostly at ultrasonic frequencies.

View Article and Find Full Text PDF

Humpback whale seasonal migrations, spanning greater than 6500 km of open ocean, demonstrate remarkable navigational precision despite following spatially and temporally distinct migration routes. Satellite-monitored radio tag-derived humpback whale migration tracks in both the South Atlantic and South Pacific include constant course segments of greater than 200 km, each spanning several days of continuous movement. The whales studied here maintain these directed movements, often with better than 1° precision, despite the effects of variable sea-surface currents.

View Article and Find Full Text PDF

Often abundance of rare species cannot be estimated with conventional design-based methods, so we illustrate with a population of blue whales (Balaenoptera musculus) a spatial model-based method to estimate abundance. We analyzed data from line-transect surveys of blue whales off the coast of Chile, where the population was hunted to low levels. Field protocols allowed deviation from planned track lines to collect identification photographs and tissue samples for genetic analyses, which resulted in an ad hoc sampling design with increased effort in areas of higher densities.

View Article and Find Full Text PDF