scholarly journals Occurrence and distribution of cetaceans in São Tomé and Príncipe tropical archipelago and their relation to environmental variables

2009 ◽  
Vol 89 (5) ◽  
pp. 1071-1076 ◽  
Author(s):  
C. Picanço ◽  
I. Carvalho ◽  
C. Brito
Keyword(s):  
Bottlenose Dolphins ◽  
Humpback Whales ◽  
Tropical Region ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Sao Tome And Principe ◽  
Wide Range ◽  
Rest Areas ◽  
Pilot Whales ◽  
Stenella Attenuata

São Tomé and Príncipe is an archipelago located in the Gulf of Guinea. This archipelago seems to be an important area for cetaceans, probably due to large concentrations of prey, as well as the existence of several small bays and shallow water that constitute preferred rest areas. In comparison to other areas of the world, little is known about cetacean communities in this archipelago. Boat-based surveys to record sightings of cetaceans were conducted between 2002 and 2005, which represents the first approach to study the occurrence of whales and dolphins in this tropical region. Sightings of humpback whales (Megaptera novaeangliae), bottlenose dolphins (Tursiops truncatus), pantropical spotted dolphins (Stenella attenuata), killer whales (Orcinus orca), sperm whales (Physeter macrocephalus) and pilot whales (Globicephala melas) were recorded. Cetaceans were found throughout a range of sea surface temperature between 24 and 29°C and a wide range of depths. Significant differences were found regarding the occurrence of some species. Humpback whales showed a preference for shallower waters between 20 and 100 m. Bottlenose dolphins occurred most commonly along the continental shelf (20 to 100 m) and pantropical spotted dolphins occurred in deep slope waters (>1000 m).

Cetacean diversity of Mauritius

2020 ◽  
Vol 21 (1) ◽  
pp. 45-58
Author(s):  
Imogen Webster ◽  
Vic Cockcroft ◽  
Adele Cadinouche ◽  
Annette Huggins
Keyword(s):  
Diversity Index ◽  
Bottlenose Dolphins ◽  
Common Species ◽  
Shannon Index ◽  
Humpback Whales ◽  
Encounter Rate ◽  
Physeter Macrocephalus ◽  
Limited Information ◽  
Sperm Whales ◽  
Ziphius Cavirostris

There is limited information concerning the cetaceans inhabiting the coastal waters of Mauritius.  This document details the sightings of cetaceans encountered during April 2008 – September 2014. Boat-based surveys were conducted throughout the year, primarily focusing on spinner and bottlenose dolphin populations that are important for the local dolphin-watching industry.  More than 1246 hours over 749 days of surveys were spent searching for cetaceans.  All cetaceans encountered were recorded. During 2013 and 2014, dedicated diversity surveys were conducted and 2443.6km of search effort was covered around the islands. The encounter rate was 0.025 cetacean sightings/km. Over the total study period 13 species were recorded from 1459 sightings. Species included: Megaptera novaeangliae, Stenella longirostris, Tursiops aduncus, Tursiops truncatus, Globicephala macrorhynchus, Stenella attenuata, Physeter macrocephalus, Mesoplodon densirostris, Feresa attenuata, Peponocephala electra, Grampus griseus and Ziphius cavirostris. In addition, there were strandings of Kogia sima and Ziphius cavirostris. The most common species encountered were spinner dolphins, Indo-Pacific bottlenose dolphins, humpback whales and sperm whales. As expected only humpback whales showed any seasonality in monthly encounter rates (Kruskal-Wallis H = 42.39, Hc = 54.25, p < 0.001). The overall Shannon diversity index was 0.58 (95% CI 0.57–0.60) though this ranged between 0.77 in 2009 to 0.25 in 2014. The Shannon index value for the diversity study was 0.83 (95% CI 0.74–0.91). This study demonstrates the richness of the waters around Mauritius and the importance of the area for beaked whales, migrating humpback whales and the presence of resident sperm whales.

scholarly journals Severity Scoring of Behavioral Responses of Sperm Whales (Physeter macrocephalus) to Novel Continuous versus Conventional Pulsed Active Sonar

2021 ◽  
Vol 9 (4) ◽  
pp. 444
Author(s):  
Charlotte Curé ◽  
Saana Isojunno ◽  
Marije L. Siemensma ◽  
Paul J. Wensveen ◽  
Célia Buisson ◽  
...  
Keyword(s):  
Behavioral Responses ◽  
Physeter Macrocephalus ◽  
Vital Rates ◽  
Sperm Whales ◽  
Experimental Conditions ◽  
Active Sonar ◽  
Lower Amplitude ◽  
Pilot Whales ◽  
New Generation ◽  
Free Ranging

Controlled exposure experiments (CEEs) have demonstrated that naval pulsed active sonar (PAS) can induce costly behavioral responses in cetaceans similar to antipredator responses. New generation continuous active sonars (CAS) emit lower amplitude levels but more continuous signals. We conducted CEEs with PAS, CAS and no-sonar control on free-ranging sperm whales in Norway. Two panels blind to experimental conditions concurrently inspected acoustic-and-movement-tag data and visual observations of tagged whales and used an established severity scale (0–9) to assign scores to putative responses. Only half of the exposures elicited a response, indicating overall low responsiveness in sperm whales. Responding whales (10 of 12) showed more, and more severe responses to sonar compared to no-sonar. Moreover, the probability of response increased when whales were previously exposed to presence of predatory and/or competing killer or long-finned pilot whales. Various behavioral change types occurred over a broad range of severities (1–6) during CAS and PAS. When combining all behavioral types, the proportion of responses to CAS was significantly higher than no-sonar but not different from PAS. Responses potentially impacting vital rates i.e., with severity ≥4, were initiated at received cumulative sound exposure levels (dB re 1 μPa2 s) of 137–177 during CAS and 143–181 during PAS.

scholarly journals Estimated Abundances of Cetacean Species in the Northeast Atlantic from Norwegian Shipboard Surveys Conducted in 2014–2018

2020 ◽  
Vol 11 ◽  
Author(s):  
Deanna Leonard ◽  
Nils Øien
Keyword(s):  
Barents Sea ◽  
Humpback Whales ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Target Species ◽  
Independent Observer ◽  
Southern Boundary ◽  
Norwegian Sea ◽  
Northeast Atlantic ◽  
Fin Whales

A ship-based mosaic survey of Northeast Atlantic cetaceans was conducted over a 5-year period between 2014–2018. The area surveyed extends from the North Sea in the south (southern boundary at 53oN), to the ice edge of the Barents Sea and the Greenland Sea. Survey vessels were equipped with 2 independent observer platforms that detected whales in passing mode and applied tracking procedures for the target species, common minke whales (Balaenoptera acutorostrata acutorostrata). Here we present abundance estimates for all non-target species for which there were sufficient sightings. We estimate the abundance of fin whales (Balaenoptera physalus) to be 11,387 (CV=0.17, 95% CI: 8,072–16,063), of humpback whales (Megaptera novaeangliae) to be 10,708 (CV=0.38, 95% CI: 4,906–23,370), of sperm whales (Physeter macrocephalus) to be 5,704 (CV=0.26, 95% CI: 3,374–9,643), of killer whales (Orcinus orca) to be 15,056 (CV=0.29, 95% CI: 8,423–26,914), of harbour porpoises (Phocoena phocoena) to be 255,929 (CV=0.20, 95% CI: 172,742–379,175), dolphins of genus Lagenorhynchus to be 192,767 (CV=0.25, 95% CI: 114,033–325,863), and finally of northern bottlenose whales (Hyperoodon ampullatus) to be 7,800 (CV=0.28, 95% CI: 4,373–13,913). Additionally, our survey effort in the Norwegian Sea in 2015 contributed to the 6th North Atlantic Sightings Survey (NASS) and the survey was extended into the waters north and east of Iceland around Jan Mayen island. This NASS extension, along with our Norwegian Sea survey in 2015, was used to estimate the abundance of fin whales, humpback whales, and sperm whales. All estimates presented used mark-recapture distance sampling techniques and were thus corrected for perception bias. Our estimates do not account for additional variance due to distributional shifts between years or biases due to availability or responsive movement.

scholarly journals Correcting Positional Errors in Shore-Based Theodolite Measurements of Animals at Sea

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Ophélie Sagnol ◽  
Femke Reitsma ◽  
Christoph Richter ◽  
Laurence H. Field
Keyword(s):  
New Zealand ◽  
Habitat Use ◽  
Marine Mammal ◽  
Positional Information ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Vertical Angle ◽  
Position Accuracy ◽  
Wide Range ◽  
The Difference

Determining the position of animals at sea can be particularly difficult and yet, accurate range and position of animals at sea are essential to answer a wide range of biological questions. Shore-based theodolite techniques have been used in a number of studies to examine marine mammal movement patterns and habitat use, offering reliable position measurements. In this study we explored the accuracy of theodolite measurements by comparing positional information of the same objects using two independent techniques: a shore-based theodolite station and an onboard GPS over a range of 25 km from the shore-based station. The technique was developed to study the habitat use of sperm whales (Physeter macrocephalus) off Kaikoura, New Zealand. We observed that the position accuracy fell rapidly with an increase in range from the shore-based station. Results showed that the horizontal angle was accurately determined, but this was not the case for the vertical angle. We calibrated the position of objects at sea with a regression-based correction to fit the difference in distance between simultaneously recorded theodolite fixes and GPS positions. This approach revealed the necessity to calibrate theodolite measurements with objects at sea of known position.

Stable isotope analyses reveal seasonal and inter-individual variation in the foraging ecology of sperm whales

2020 ◽  
Vol 638 ◽  
pp. 207-219
Author(s):  
M Guerra ◽  
L Wing ◽  
S Dawson ◽  
W Rayment
Keyword(s):  
Stable Isotope ◽  
Individual Variation ◽  
Large Scale ◽  
Isotope Ratios ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Foraging Patterns ◽  
Seasonal Differences ◽  
Top Predators ◽  
Wide Range

Studying inter-individual variation in foraging by top predators is key for understanding the ecology of their populations, while knowledge of seasonal variability in foraging helps explain temporal changes in habitat use and ecological role. We investigated the inter-individual and seasonal differences in stable isotope ratios of sperm whales Physeter macrocephalus in the temperate foraging ground of the Kaikóura Canyon, New Zealand. Isotope ratios of carbon and nitrogen were measured in 107 samples of sloughed skin from 37 individual males with a wide range of residency patterns and body lengths, sampled over 4 summers and 3 winters. Variability in individual isotope ratios was analysed with generalised additive mixed models. The whales’ residency patterns, but not body size, accounted for most heterogeneity of δ13C and δ15N. Specifically, whales that visited Kaikóura occasionally had more diverse and lower isotope ratios than more frequent visitors (by ca. -1‰ δ13C and -2‰ δ15N), likely reflecting a range of foraging habitats further offshore and/or south of Kaikóura Canyon. We suggest that these patterns reflect differences in large-scale foraging patterns within the population. In addition, whales sampled in winter had significantly lower values of δ13C than whales sampled in summer (by ca. -0.5‰), indicating seasonal differences in the use of food resources. Our results provide new insights into foraging patterns of sperm whales, and highlight the value of accounting for individual differences in the ecology of top predators.

Killer whales (Orcinus orca) in Angolan and Gulf of Guinea waters, tropical West Africa

2010 ◽  
Vol 90 (8) ◽  
pp. 1601-1611 ◽  
Author(s):  
Caroline R Weir ◽  
Tim Collins ◽  
Inês Carvalho ◽  
Howard C. Rosenbaum
Keyword(s):  
Group Size ◽  
Orcinus Orca ◽  
Humpback Whales ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Killer Whales ◽  
External Appearance ◽  
Tropical Waters ◽  
Photo Identification ◽  
Mola Mola

Killer whales Orcinus orca are considered to be relatively uncommon in tropical waters. Few sightings have been reported from the west coast of Africa due to a paucity of survey coverage. We present data on 32 killer sightings from tropical waters off Angola (N = 18), Gabon (N = 7), São Tomé (N = 6) and Cameroon (N = 1), comprising a combination of dedicated survey sightings (N = 21) and reliable anecdotal records (n = 11). Killer whales were reported from coastal waters, the shelf edge and deep, oceanic areas. Sightings indicate a probable year-round occurrence of killer whales within the region. Mean group size was 5.6 animals. There was no difference in group size between sightings in waters >200 m deep and those on the continental shelf. No photo-identification matches were found between Angola, Gabon and São Tomé. Re-sightings of two individuals occurred annually in São Tomé during 2002–2004. Killer whales had external appearance consistent with the Type A nominate species form. Antagonistic encounters were recorded between killer whales and humpback whales Megaptera novaeangliae off Angola, Gabon and Cameroon, and with sperm whales Physeter macrocephalus off Angola. Predation on ocean sunfish Mola mola was recorded in São Tomé, and possible predation on sharks was recorded twice in Gabon.

scholarly journals Quantifying the energy stores of capital breeding humpback whales and income breeding sperm whales using historical whaling records

2017 ◽  
Vol 4 (3) ◽  
pp. 160290 ◽  
Author(s):  
Lyn G. Irvine ◽  
Michele Thums ◽  
Christine E. Hanson ◽  
Clive R. McMahon ◽  
Mark A. Hindell
Keyword(s):  
Sampling Site ◽  
Humpback Whales ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Body Lipid ◽  
Pregnant Females ◽  
Income Breeding ◽  
Energy Stores ◽  
Total Body ◽  
Lipid Stores

Cetacean energy stores are known to vary according to life history, reproductive status and time of year; however, the opportunity to quantify these relationships is rare. Using a unique set of historical whaling records from Western Australia (1952–1963), we investigated energy stores of large cetaceans with differing life histories, and quantified the relationship between total body lipid and length for humpback whales ( Megaptera novaeangliae) ( n  = 905) and sperm whales (Physeter macrocephalus) ( n  = 1961). We found that total body lipid increased with body length in both humpback and sperm whales, consistent with size-related energy stores. Male humpback whales stored 2.49 kl (15.6 barrels) (31.9–74.9%) more lipid than male sperm whales of equivalent length, to fuel their annual migration. Relative lipid stores of sperm whales (males) were constant throughout the year, while those of humpback whales varied with reproductive class and sampling date. Pregnant female humpback whales had higher relative energy stores than non-pregnant females and males (26.2% and 37.4%, respectively), to fuel the energy demands of gestation and lactation. Those that reached the sampling site later ( en route to their breeding grounds) carried higher lipid stores than those that arrived earlier, possibly reflecting individual variation in residency times in the Antarctic feeding grounds. Importantly, longer pregnant females had relatively larger energy stores than the shorter pregnant females, indicating that the smaller individuals may experience higher levels of energetic stress during the migration fast. The relationships we developed between body lipid and length can be used to inform bioenergetics and ecosystem models when such detailed information is not available.

scholarly journals Distribution and abundance of large whales in Norwegian and adjacent waters based on ship surveys 1995-2001

2009 ◽  
Vol 7 ◽  
pp. 31 ◽  
Author(s):  
Nils Øien
Keyword(s):  
Species Abundance ◽  
Humpback Whale ◽  
Humpback Whales ◽  
Physeter Macrocephalus ◽  
Sperm Whales ◽  
Species Identity ◽  
Independent Observer ◽  
Abundance Estimates ◽  
Partial Area ◽  
Fin Whales

The abundances of large whale species are presented for the northeast Atlantic from near-complete survey coverage in 1995 and from multiple partial-area surveys during 1996-2001. These Norwegian shipboard surveys were generally conducted with 2 independent observer platforms, except for single-platform surveys during part of 1995. Tracking procedures implemented for minke whales – Balaenoptera acutorostrata (the target species) meant that the surveys had to be conducted in passing mode, and there were therefore only limited opportunities for closing on sightings to determine species identity and school size. Abundance estimates for large whale species (fin – Balaenoptera physalus, humpback – Megaptera novaeangliae and sperm whales – Physeter macrocephalus) were obtained by combining sightings from both platforms, and applying standard distance sampling techniques to the smeared and truncated perpendicular distances for each species. Abundance estimates for the 2 survey groupings (1995 and 1996-2001) summarised over comparable areas were: fin whales, 5,034 (cv 0.209) and 6,409 (cv 0.18); humpback whales, 1,059 (cv 0.248) and 1,450 (cv 0.29); and sperm whales, 4,319 (cv 0.199) and 6,207 (cv 0.22). The estimated cv’s are likely underestimates and specifically the combined partial-area survey cv’s do not include additional variance due to possible distributional shifts between years. Inclusion of a new survey stratum north of Iceland (block NVS) in the later set of surveys revealed a high additional abundance there of fin whales 3,960 (cv 0.538) and humpback whales 3,246 (cv 0.512). The high humpback whale estimate for this stratum confirms the Icelandic survey findings of a large humpback whale population summering in that area.

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