Irma Cascão

Irma Cascão
Institute of Marine Sciences - Okeanos, University of the Azores

PhD Marine Science

About

78
Publications
15,177
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552
Citations
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July 2005 - present
Institute of Marine Research - IMAR, University of the Azores
Position
  • Researcher

Publications

Publications (78)
Article
Full-text available
Background Prioritizing groupings of organisms or ‘units’ below the species level is a critical issue for conservation purposes. Several techniques encompassing different time-frames, from genetics to ecological markers, have been considered to evaluate existing biological diversity at a sufficient temporal resolution to define conservation units....
Article
Full-text available
Animals use varied acoustic signals that play critical roles in their lives. Understanding the function of these signals may inform about key life history processes relevant for conservation. In the case of fin whales (Balaenoptera physalus), that produce different call types associated with different behaviours, several hypotheses have emerged reg...
Conference Paper
Full-text available
Dolphins living in the oceanic waters off the Azores consistently use seamounts to forage at night. These dolphins rely entirely on broadband echolocation clicks and burst-pulsed signals to sense their environment, detect and capture prey. Underwater noise from vessels can interfere with the ability of these dolphins to forage successfully. We meas...
Conference Paper
Full-text available
Shipping noise overlaps with baleen whales’ vocalizing frequencies and in high levels, may disrupt their behaviour and affect their communication ranges via masking. In this study, we measured underwater noise levels and quantified time with shipping noise at a single location southeast of the Faial-Pico Islands channel, in the Azores Archipelago,...
Article
Full-text available
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Article
Full-text available
The identification of important areas during the annual life cycle of migratory animals, such as baleen whales, is vital for their conservation. In boreal springtime, fin and blue whales feed in the Azores on their way to northern latitudes while sei whales migrate through the archipelago with only occasional feeding. Little is known about their au...
Article
Full-text available
Population structure studies play an increasingly integral role in conservation and management of marine mammal species. Genetic markers are commonly used; however, ecological markers (i.e. chemical compounds) are a fairly recent and useful tool to investigate ecological management units. The objective of this study is to investigate the population...
Article
Full-text available
Several seamounts have been identified as hotspots of marine life in the Azores, acting as feeding stations for top predators, including cetaceans. Passive acoustic monitoring is an efficient tool to study temporal variations in the occurrence and behaviour of vocalizing cetacean species. We deployed bottom-moored Ecological Acoustic Recorders (EAR...
Article
The importance of seamounts as foraging hotspots for cetaceans depends on interactions between ocean flow and topographical features that concentrate prey. However, the oceanographic processes driving these aggregations are still unclear. Here, we analyzed two months of passive acoustic recordings from two remote seamounts in the Northeast Atlantic...
Article
Full-text available
We examined the diel vertical migration (DVM) behavior and vertical spatial structure of sound-scattering layers (SLs) at two seamounts (Condor and Gigante) in the Azores and in surrounding open-waters. Active acoustic data were recorded day and night during nine cruises conducted in spring, summer and autumn between 2009 and 2011. SLs were permane...
Presentation
Biophysical coupling at seamounts may lead to the formation of pelagic foraging hotspots, which can attract predators like cetaceans. Spatial and temporal dynamics of prey has a strong effect on the foraging success and performance of predators. Dolphins change their distribution and foraging strategy in response to changes in micronekton prey abun...
Article
Full-text available
Assessment of underwater noise is of particular interest given the increase in noise-generating human activities and the potential negative effects on marine mammals which depend on sound for many vital processes. The Azores archipelago is an important migratory and feeding habitat for blue (Balaenoptera musculus), fin (Balaenoptera physalus) and s...
Article
Full-text available
Knowledge of the dynamics of micronekton at seamounts is critical to understanding the ecological role of these ecosystems. Active acoustic techniques are an effective tool to monitor the distribution and movements of pelagic organisms. We carried out several day- and nighttime active acoustic surveys over a 3-year period (2009–2011) to characteriz...
Article
Full-text available
Genetic studies have shown that there are small but significant differences between the short-beaked common dolphin populations in the Atlantic Ocean and those in the Mediterranean Sea. The short-beaked common dolphin is a highly vocal species with a wide sound production repertoire including whistles. Whistles are continuous, narrowband, frequency...
Article
Full-text available
To improve our understanding of the complex genetic and ecological structure of bottlenose dolphin ( Tursiops truncatus ) populations, we examined the acoustic features of communication signals from two geographically contiguous areas: the Central–Eastern North Atlantic and the Mediterranean Sea. Variations in the whistles were evaluated for four l...
Presentation
Acoustic signals are expressions of phenotypic diversity and their variation could provide important information on differentiation patterns within species. Due to a number of selective pressures acting on signals, the contribution of genetic drift is often complex to outline. This study aims at evaluating if an examination of the acoustic structur...
Article
Full-text available
Cetaceans living in offshore waters are under increasing pressure from anthropogenic activities. Yet, due to the lack of survey effort, relatively little is known about the demography or ecology of these populations. Spatial and temporal distribution of cetaceans in mid-Atlantic waters were investigated using a long term dataset collected from boat...
Article
Full-text available
Short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) are the two most abundant cetacean species in the oceanic waters of Madeira and the Azores. They are of similar size, occur in similar habitats and are regularly observed in mixed-species groups to forage together. Genetic analyses suggested that, wi...
Article
Full-text available
Geographic variation in the acoustic features of whistles emitted by the striped dolphin (Stenella coeruleoalba) from the Atlantic Ocean (Azores and Canary Islands) and the Mediterranean was investigated. Ten parameters (signal duration, beginning, end, minimum and maximum frequency, the number of inflection points, of steps, of minima and maxima i...
Presentation
Full-text available
Several seamounts have been identified as hotspots of marine life in the Azores, possibly acting as feeding stations for top predators, including cetaceans. The pelagic predator-prey interaction is a crucial ecological factor affecting animal distribution and abundance. To understand this relationship, this study explores cetacean movements in rela...
Poster
Full-text available
Micro- and macro-geographic variations of the whistles of striped dolphins (Stenella coeruleoalba)
Article
Full-text available
A right whale (Eubalaena glacialis) from the western North Atlantic population, sighted in the Azores, was subsequently found to have moved back to the northwest Atlantic. The whale was sighted in the Azores on 5 January 2009 travelling in a west-south westerly direction at a constant speed. A photographic match was found to an adult female in the...
Technical Report
Full-text available
Active acoustic techniques are a powerful tool to assess pelagic prey densities and their diel movements. The present study used acoustic techniques to obtain information on the abundance of Sound-scattering layers (SSLs) on Condor seamount. Several active acoustic surveys, with a Simrad EK500 echosounder, were carried out per year during day and n...
Technical Report
Full-text available
This study focused on the midwater fauna around the Condor Seamount, sampled with an open 10’ IKMT. The catch includes 630 specimens of 42 species (12 families) weighing 330.3 g. Myctophidae dominate the captures and was the most specious family. Gonostomatids, stomiids and sternoptychids were also important. Lobianchia dofleini, Diaphus rafinesque...
Technical Report
Full-text available
Cetaceans are known to seek and associate with regions of high biological activity, such as oceanic fronts and areas of abrupt topography. Seamounts are important discontinuity structures in the open ocean that may generate local currents which in turn may serve to cluster high densities of prey. The “aggregator effect” has often been invoked to ex...
Presentation
Full-text available
North Atlantic fin whales are thought to migrate between low latitude winter mating/ calving grounds and high latitude summer feeding areas. Although there is some information on fin whale distribution and behavior at the feeding grounds, location of the breeding areas remains unknown and migratory patterns are poorly understood. Fin whales cross t...
Presentation
Acoustic features of short-beaked common dolphin’s whistles were investigated in two adjacent macro geographic areas: Atlantic Ocean and Mediterranean Sea. From each whistle 12 parameters were measured: duration, beginning, end, minimum and maximum frequency, frequency range, beginning and ending slope, inflection points, steps, number of minima in...
Article
Full-text available
The first mid-Atlantic diet of Mesoplodon beaked whales is presented, from ten Sowerby's Mesoplodon bidens stranded in the Azores region between 2002 and 2009. This doubles the worldwide number of stomachs sampled, and reveals new feeding habits for this species. The mean number of prey items per stomach was 857 89 (range: 12-238), with fish accoun...
Presentation
Full-text available
Satellite telemetry as a tool to help defining the International Whaling Commission whale management areas
Presentation
Acoustic estimation of Sound-scattering layer at the Condor seamount
Presentation
Diversity and relative abundance of cetaceans
Article
Full-text available
The first mid-Atlantic diet of Mesoplodon beaked whales is presented, from ten Sowerby's Mesoplodon bidens stranded in the Azores region between 2002 and 2009. This doubles the worldwide number of stomachs sampled, and reveals new feeding habits for this species. The mean number of prey items per stomach was 85±89 (range: 12–238), with fish account...
Technical Report
Full-text available
This study focused on the midwater fauna around the Condor Seamount, sampled with an open 10’ IKMT. The catch includes 630 specimens of 42 species (12 families) weighing 330.3 g. Myctophidae dominate the captures and was the most specious family. Gonostomatids, stomiids and sternoptychids were also important. Lobianchia dofleini, Diaphus rafinesque...
Article
Full-text available
Several cetacean species exhibit fine-scale population structure despite their high dispersal capacities and the apparent continuity of the marine environment. In dolphins, most studies have focused on coastal areas and continental margins, and they revealed differentiated populations within relatively small geographic areas, sometimes in conjuncti...
Article
Full-text available
Biological samples of free-ranging dolphins are increasingly used to gain information on population structure and ecology. In small cetaceans, the gender of individuals usually cannot be determined at sea, and population sex ratio has to be inferred indirectly. We used molecular sexing to determine the gender of 340 biopsy samples of bottlenose dol...
Presentation
Full-text available
The sei whale (Balaenoptera borealis) can be found in all ocean basins, normally in pelagic waters. Like most large whales, sei whales undertake extensive, seasonal, latitudinal migrations, spending the summer feeding in sub-polar waters and returning to lower latitudes in the winter to calve. On a global scale, the sei whale has the broadest range...
Presentation
Movimentos dos cetáceos em relação à dinâmica da camada de dispersão acústica nos Açores
Presentation
TRACE - Associação de cetáceos com o habitat em ecossistemas oceânicos: um estudo integrado
Presentation
Movements, habitat use and dispersal of demersal fish in the Azores/Condor bank
Presentation
Na esteira da relação entre os cetáceos e o habitat: do pequeno morador ao grande migrador
Technical Report
This report presents the work performed during the survey “CONDOR_PAC_Ago09 - Oceanographic Component”, onboard R/V Arquipélago, between days 11th and 13th (the first), between 17th and 18th (the second) and on 20th of August 2009 (the third). This was the sixth survey with oceanography team participation in the framework of CONDOR project - Observ...
Technical Report
This report presents the work performed during the surveys “004.09_GIG_CON_CSM – Oceanographic Component” and “005.09_PAL– Oceanographic Component”, onboard R/V Arquipélago, between days 15th and 19th June and days 22nd and 23rd of June 2009, respectively. This was the fifth survey with the oceanography team participation in the framework of CONDOR...
Presentation
Full-text available
Seamounts are hotspots of marine life in the Azores, acting as feeding stations for diverse top predators, including cetaceans. Long-term monitoring of remote marine ecosystems is logistically difficult and expensive, involving high costs in terms of ship time and human resources, as well as being reliant on sea conditions. Passive acoustic methods...
Presentation
Tracking cetacean-habitat associations: from coastal dwellers to oceanic migrants
Technical Report
Full-text available
MARMAC II aimed to promote a pilot network of Marine Biodiversity Interpretation Centres in the Macaronesia. These Centres constitute one of the foundations of the Macaronesian strategy for a sustainable development of the marine protected areas within the Natura 2000 Network in the region. The project sought to plan and structure the most adequate...
Article
Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonl...
Poster
Full-text available
The short-beaked common dolphin, Delphinus delphis, and the Atlantic spotted dolphin, Stenella frontalis, are two of the most abundant cetacean species in the archipelagos of Azores and Madeira but seem to show same spatial-temporal segregation. In Azores D. delphis is present year-round, but its abundance is highest in spring with a decline during...
Technical Report
O objectivo deste projecto consiste em investigar a utilização diferencial do nicho espacial e trófico entre duas espécies de golfinhos, o golfinho-comum (Delphinus delphis) e o golfinho-pintado (Stenella frontalis, também chamado golfinho-malhado), nos Açores e Madeira. Estas duas espécies parecem demonstrar uma segregação espacial e temporal, e p...
Poster
Full-text available
The short-beak common dolphin (Delphinus delphis) and the Atlantic spotted dolphin (Stenella frontalis) are very common species around the Azores and Madeira. Preliminary data suggest that the maximum abundance of one species in a given archipelago corresponds with the minimum of the other. These two species seem to segregate spatially and temporal...
Poster
Full-text available
An important step to define conservation management strategies for natural populations is to analyze their genetic structure and dynamics based on biological samples of free-ranging individuals. In small cetaceans, biological material for genetic analyses can be obtained by skin swabbing or biopsy darting. Gender of individuals is usually not known...
Presentation
Population genetics of common and spotted dolphins in the Azores and Madeira
Poster
Full-text available
Searching for the existence of distinct ecotypes of dolphins in the Azores and Madeira using molecular markers
Presentation
Uso de marcadores moleculares para investigar a existência de ecótipos de golfinhos nos arquipélagos dos Açores e da Madeira
Poster
Full-text available
Dolphin acoustic communication strongly relies on whistles, particularly on their instantaneous frequencies, which are commonly referred to as contours. The time–frequency visualization of whistles using commercially available software allows their contours to be manually extracted, for instance by sampling some of their points or retrieving their...
Poster
Full-text available
Bioacoustics research on the classification of dolphin whistles relies on the extraction of whistle contours from time–frequency representations of dolphin vocalizations, which are usually based on the spectrogram. Although whistle classification studies can be based on a few, manually extracted contour parameters, using the full contours should be...
Poster
Full-text available
The Sado Estuary bottlenose dolphin, Tursiops truncatus, resident population is very small. The increasing dolphin-watching activity may pose this declining population at a higher risk. In order to understand the response of these dolphins in the presence of boats within 300 m, this study monitored respiration and behaviour of dolphins in the prese...