Exposure to whale watching vessels affects dive ascents and resting behavior in sperm whales

Oliveira, Cláudia; Pérez‐Jorge, Sergi; Prieto, Rui; Cascão, Irma; Wensveen, Paul J.; Silva, Mónica

doi:10.3389/fmars.2022.914397

Cited by 4 publications

(8 citation statements)

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“…As mentioned above, the two species have strikingly different diets, although this indicates that their preferred prey items should have similar isotopic values. Both species are present year-round and exploit similar areas in the Azores, but T. truncatus forages mostly within the epipelagic layer, whereas P. macrocephalus feeds in waters deeper than 700 m depth (Oliveira et al, 2022). The two species could feed on prey undergoing diel vertical migration, therefore having access to the same prey at different depths and times of the day, explaining the similarity in stable isotope values.…”

Section: Intra-guild Niche Overlap and Trophic Redundancymentioning

confidence: 95%

Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores

Lebon,

Colaço,

Prieto

et al. 2024

Front. Mar. Sci.

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IntroductionThe oceanic waters around the Azores host a high diversity of cetaceans, with 28 species of toothed and baleen whales present year-round or seasonally. This high cetacean biodiversity likely plays an important role in the structure, functioning and productivity of the ecosystem, and may increase trophic redundancy, thus contributing to food web resilience to disturbances.MethodsHere we used stable isotope (δ13C and δ15N) analysis to characterize trophic niches, assess niche overlap, describe the trophic structure and discuss potential redundancy in the cetacean community. Using 407 samples from 12 species, we estimated Standard Ellipse Areas and overlaps between species and used a hierarchical clustering analysis to identify trophic guilds.Results and discussionδ13C and δ15N values ranged from -20.53 to -15.46‰ and from 7.78 to 14.41‰ respectively, suggesting the use of diverse habitats and resources among cetacean species. Clustering analysis revealed that species were grouped into four trophic guilds, segregated mainly by trophic position (TP): a low-TP guild with three zooplanktivore baleen whales, a mid-TP guild with micronektivores, a high-TP guild with micronekton and nekton consumers, and a cluster with only Pseudorca crassidens. There was significant isotopic niche overlap between one pair of species within each guild, indicating some potential for trophic redundancy in the community. Yet, these pairs also showed some form of spatial or temporal partitioning, suggesting that mechanisms promoting species coexistence could play a key role in structuring the cetacean community in the region and in its ecological role.

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Section: Intra-guild Niche Overlap and Trophic Redundancymentioning

confidence: 95%

Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores

Lebon,

Colaço,

Prieto

et al. 2024

Front. Mar. Sci.

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“…Data were collected from 12 sperm whales instrumented with Dtags (version 3; [32,33]) off the Azores archipelago between 2017 and 2019 (Additional file 1: Table A1). Dtags recorded 2-channel audio data (sampling frequencies of 192 kHz for 2017, and 120 kHz for 2018-2019) and collected pressure, 3-axis accelerometer, and 3-axis magnetometer data at 20 Hz in 2017, and 25 Hz in 2018-2019.…”

Section: Data Collectionmentioning

confidence: 99%

“…The objective of this study was to develop a predictive model of PCAs for sperm whales from low-resolution time-depth data. To achieve this, high-resolution movement and acoustic data from 12 sperm whales instrumented with digital acoustic recording tags (Dtags; [32,33]) was used to extract time-depth values at a sampling frequency of 1 s and detect buzzes, considered to represent PCAs. Using this dataset, a comprehensive modelling approach (Fig.…”

Section: Introductionmentioning

confidence: 99%

Predictive model of sperm whale prey capture attempts from time-depth data

et al. 2023

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Background High-resolution sound and movement recording tags offer unprecedented insights into the fine-scale foraging behaviour of cetaceans, especially echolocating odontocetes, enabling the estimation of a series of foraging metrics. However, these tags are expensive, making them inaccessible to most researchers. Time-Depth Recorders (TDRs), which have been widely used to study diving and foraging behaviour of marine mammals, offer a more affordable alternative. Unfortunately, data collected by TDRs are bi-dimensional (time and depth only), so quantifying foraging effort from those data is challenging. Methods A predictive model of the foraging effort of sperm whales (Physeter macrocephalus) was developed to identify prey capture attempts (PCAs) from time-depth data. Data from high-resolution acoustic and movement recording tags deployed on 12 sperm whales were downsampled to 1 Hz to match the typical TDR sampling resolution and used to predict the number of buzzes (i.e., rapid series of echolocation clicks indicative of PCAs). Generalized linear mixed models were built for dive segments of different durations (30, 60, 180 and 300 s) using multiple dive metrics as potential predictors of PCAs. Results Average depth, variance of depth and variance of vertical velocity were the best predictors of the number of buzzes. Sensitivity analysis showed that models with segments of 180 s had the best overall predictive performance, with a good area under the curve value (0.78 ± 0.05), high sensitivity (0.93 ± 0.06) and high specificity (0.64 ± 0.14). Models using 180 s segments had a small difference between observed and predicted number of buzzes per dive, with a median of 4 buzzes, representing a difference in predicted buzzes of 30%. Conclusions These results demonstrate that it is possible to obtain a fine-scale, accurate index of sperm whale PCAs from time-depth data alone. This work helps leveraging the potential of time-depth data for studying the foraging ecology of sperm whales and the possibility of applying this approach to a wide range of echolocating cetaceans. The development of accurate foraging indices from low-cost, easily accessible TDR data would contribute to democratize this type of research, promote long-term studies of various species in several locations, and enable analyses of historical datasets to investigate changes in cetacean foraging activity.

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“…Companies are instructed to record the predominant behavioural state at the time of arrival (foraging, resting, socialising and travelling). However, the behaviour at the boat's arrival can still be influenced by it or can result from the previous presence of other boats in the area (see, for the Azores, Visser et al (2010) , Cecchetti et al (2017) , Oliveira et al (2022) ). Additionally, sightings are often of short duration (a few minutes), so main behaviour is not always possible to assess in this short time.…”

Section: Additional Informationmentioning

confidence: 99%

MONICET: The Azores whale watching contribution to cetacean monitoring

García¹,

Fernández²,

Azevedo³

2023

BDJ

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The Azores islands have been historically linked to cetaceans, becoming an example of a successful transition from whaling to whale watching. Twenty-eight cetacean species have been sighted in these waters, making the archipelago one of the most recognised whale and dolphin watching destinations worldwide. The business is well-established in the region, operates in four of the nine islands year-round or seasonally and provides an excellent opportunity to collect long term information on cetacean distribution and abundance in an affordable way. Continuous monitoring is indeed essential to establish baseline knowledge and to evaluate cetacean response to potential natural or anthropogenic impacts. Opportunistic data greatly complement traditional dedicated surveys, providing additional support for appropriate management plans. The MONICET platform has been running continuously since 2009 as a collaborative instrument to collect, store, organise and disseminate cetacean data voluntarily collected by whale watching companies in the Azores. In the period covered by this dataset (2009-2020), 11 whale watching companies have voluntarily provided data from the four islands of the archipelago where whale watching takes place. The dataset contains more than 37,000 sightings of 25 species (22 cetaceans and three turtles). This manuscript presents the first long-term whale watching cetacean occurrence dataset openly available for the Azores. We explain the methodology used for data collection and address the potential biases and limitations inherent to the opportunistic nature of the dataset to maximise its usability by external users.

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Exposure to whale watching vessels affects dive ascents and resting behavior in sperm whales

Cited by 4 publications

References 74 publications

Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores

Isotopic niches reveal the trophic structure of the cetacean community in the oceanic waters around the Azores

Predictive model of sperm whale prey capture attempts from time-depth data

MONICET: The Azores whale watching contribution to cetacean monitoring

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