Search

The Mediterranean sub-population of sperm whales is believed to be isolated and is classified as Endangered on the IUCN Red List. Although there is evidence to suggest the population is declining, there is a lack of abundance data. A series of acoustic line-transect surveys were undertaken between 2004 and 2013. In 2004, 3,946km of acoustic effort was conducted in the southern Western Mediterranean basin, resulting in the detection of 159 sperm whales. While in 2007 and 2013, 10,276km of acoustic effort was conducted in the Eastern Mediterranean basin, resulting in the detection of 24 sperm whales. A pooled detection function gave an effective strip half-width of 9.8km. A correction for availability bias was made for each block based on published simulations using data on sperm whale acoustic behaviour: estimates of g(0) were 0.95–0.96. Estimated abundances were: Southern Western Mediterranean Block 634 animals [374–1,077] (95% log-normal confidence interval); Hellenic Trench Block 41 [17–100]; Central Aegean Sea Block 33 [5–203]; Herodotus Rise Block 5 [1–28] and Southern Adriatic Sea Block 2 [0–12]. Estimates for all other blocks were zero. The density of sperm whales in the surveyed Southern Western Mediterranean Block was over 17 times higher than for the surveyed Eastern Mediterranean (2.12 and 0.12 whales per 1,000km² respectively). These results, combined with an acoustic survey of the northern Ionian Sea in 2003 and aerial surveys in the northern Western Mediterranean basin in 2010–11, covered approximately 57% of the likely sperm whale habitat in the Western Mediterranean and 75% in the Eastern Mediterranean. Approximate total estimates of sperm whale abundance in the Western and Eastern Mediterranean basins based on extrapolation to the unsurveyed areas are 1,678 and 164 whales respectively. This gives an estimate for the whole Mediterranean Sea of 1,842 animals.

Rough-toothed dolphins (Steno bredanensis) form an isolated subpopulation in the Mediterranean Sea that resides only in the eastern basin. Due to the paucity of records, the conservation threats these dolphins face and their ecology and distribution are poorly understood. While most observations indicate that individuals are found in two isolated clusters in the eastern basin, we hereby present five observations -three visual, one acoustic and one stranding- that possibly extend the range of this subpopulation to the entire offshore waters of the eastern basin. The stomach content remains of the stranded individual revealed a diet based on epipelagic squids and octopods. The stranded dolphin had also consumed seven plastic bags and nine squid-like plastic fishing lures, which had caused a complete gastric blockage and probably led to the stranding. High pollution loads from macroplastics in the Mediterranean Sea may evolve into a new potential threat for this subpopulation.

While in the northern hemisphere, many studies have been conducted on the vocal repertoire of long-finned pilot whales (Globicephala melas), no such study has been conducted in the southern hemisphere. Presented here, is the first study on the vocalisations of long-finned pilot whales along the southern coast of mainland Australia. Multiple measures were taken of 2028 vocalisations recorded over five years in several locations. These vocalisations included tonal sounds with and without overtones, sounds of burst-pulse character, graded sounds, biphonations, and calls of multiple components. Vocalisations were further categorised based on spectrographic features into 18 contour classes. Altogether, vocalisations ranged from approximately 200 Hz to 25 kHz in fundamental frequency and from 0.03 s to 2.07 s in duration. These measures compared well with those from northern hemisphere pilot whales. Some call types were almost identical to northern hemisphere vocalisations, even though the geographic ranges of the two populations are far apart. Other call types were unique to Australia. Striking similarities with calls of short-finned pilot whales (Globicephala macrorhynchus) and sometimes sympatric killer whales (Orcinus orca) were also found. Theories for call convergence and divergence are discussed.

Aim: Deep‐diving cetaceans are oceanic species exposed to multiple anthropogenic pressures including high intensity underwater noise, and knowledge of their distribution is crucial to manage their conservation. Due to intrinsic low densities, wide distribution ranges and limited presence at the sea surface, these species are rarely sighted. Pooling data from multiple visual surveys sharing a common linetransect methodology can increase sightings but requires accounting for heterogeneity in protocols and platforms. Location: North Atlantic Ocean and Mediterranean Sea. Time period: 1998 to 2015. Major taxa: Ziphiidae; Physeteriidae; Kogiidae. Methods: About 1,240,000 km of pooled effort provided 630 sightings of ziphiids, 836 of physeteriids and 106 of kogiids. For each taxon, we built a hierarchical model to estimate the effective strip width depending on observation conditions and survey types. We then modelled relative densities in a generalized additive modelling framework. Geographical predictions were limited to interpolations identified with a gap analysis of environmental space coverage. Results: Deeper areas of the North Atlantic gyre were mostly environmental extrapolation in the predictions, thereby highlighting gaps in sampling across the different surveys. For the three species groups, the highest relative densities were predicted along continental slopes, particularly in the western North Atlantic Ocean where the Gulf Stream creates dynamic frontal zones and eddies. Main conclusions: Pooling a large number of surveys provided the first basin‐wide models of distribution for deep‐diving cetaceans, including several data‐deficient taxa, across the North Atlantic Ocean and the Mediterranean Sea. These models can help the conservation of elusive and poorly known marine megafauna.

Population growth and economic development in Latin America has led to an increase in seismic surveying to find new marine hydrocarbon reserves. However, most countries along the Pacific, Atlantic, and Caribbean lack the standards to minimize the impact of seismic exploration on marine organisms. We searched primary and secondary literature in major databases and consulted international authorities and oil companies to provide scientific evidence of the effects of seismic surveying on fish and cetaceans in order to propose minimum guidelines to reduce disturbance to marine organisms in Latin America. The results suggest that seismic surveys can disrupt basic life-cycle activities such as movement, communication, and feeding. Typical outcomes include sub-lethal effects such as escape behavior, habituation, temporary loss of hearing, and changes in vocalization behavior. In order to mitigate these impacts, we propose that oil companies must provide authorities with an environmental impact assessment that includes survey data, array specifications, and acoustic array properties before a hydrocarbon exploration license can be granted. Standard mitigation measures such as exclusion zones, marine mammal observers, and passive acoustic monitoring must be implemented to prevent potential adverse effects. Appropriate legislation and regulations must be designed and implemented, and environmental authorities should be privy to all activities by seismic vessels. Besides relevant regulations and continued monitoring, further investigation must be conducted to evaluate the impact of these activities on marine organisms. The adoption of these proposed minimum guidelines is highly recommended to minimize seismic surveying impact on fish and cetaceans in Latin American countries.

17 pages, 7 tables, 5 figures, Distribution maps of cetaceans and seabirds at basin and monthly scales are needed for conservation and marine management. These are usually created from standardized and systematic aerial and vessel surveys, with recorded animal densities interpolated across study areas. However, distribution maps at basin and monthly scales have previously not been possible because individual surveys have restricted spatial and temporal coverage. This study develops an alternative approach consisting of: (a) collating diverse survey data to maximize spatial and temporal coverage, (b) using detection functions to estimate variation in the surface area covered (km2) among these surveys, standardizing measurements of effort and animal densities, and (c) developing species distribution models (SDM) that overcome issues with heterogeneous and uneven coverage. 2.68 million km of survey data in the North‐East Atlantic between 1980 and 2018 were collated and standardized. SDM using Generalized Linear Models and General Estimating Equations in a hurdle approach were developed. Distribution maps were then created for 12 cetacean and 12 seabird species at 10 km and monthly resolution. Qualitative and quantitative assessment indicated good model performance. Synthesis and applications. This study provides the largest ever collation and standardization of diverse survey data for cetaceans and seabirds, and the most comprehensive distribution maps of these taxa in the North‐East Atlantic. These distribution maps have numerous applications including the identification of important areas needing protection, and the quantification of overlap between vulnerable species and anthropogenic activities. This study demonstrates how the analysis of existing and diverse survey data can meet conservation and marine management needs, JJW, PGHE, JGH and SW are supported through the NERC/DEFRA funded Marine Ecosystems Research Programme (MERP: NE/L003201/1).

An area in the central North Sea was surveyed in November 2011 in order to estimate the abundance and density of harbour porpoises (Phocoena phocoena). A total of 2833 km of pre-determined trackline were acoustically surveyed, of which 28% included visual effort. The poor sighting conditions during the survey limited visual effort and demonstrated the advantage of using acoustic techniques for studying harbour porpoise in winter months. Absolute abundance and density estimates were calculated from acoustic encounter rates using estimates of probability of detection and mean group size. The density of harbour porpoises in the west of the survey area was almost double that in the east, with UK waters to the south-west of the Dogger Bank having the highest density of the area surveyed. The overall acoustic encounter rate was higher than most other surveys in the North Sea. The mean density across the survey area of 0.63 (95% CI 0.27–1.52) individuals km−2and distribution of porpoises was similar to that documented in the summer suggesting that high abundance of harbour porpoises in the west of the North Sea is not confined to summer months. This information is particularly relevant given plans for the construction of a large offshore wind farm on the UK section of the Dogger Bank; the resulting impacts, including acoustic disturbance from pile driving, will potentially affect substantial numbers of harbour porpoises.

Several species of deep-diving odontocetes, including beaked whales, sperm whales and pilot whales, are associated with steep continental slope habitat in the northeast Atlantic, where they feed on cephalopods and meso-bathypelagic fish. Some species such as sperm whales are listed as vulnerable by the IUCN red list, whilst many beaked whale species are listed as data deficient, therefore, understanding their habitat is key for their successful conservation. A six-day survey was carried out in November 2017 to characterise the habitat of deep-diving odontocete species in this region by sampling multiple aspects of the ecosystem, from oceanographic features through to prey and predator distributions. Sampling of odontocete occurrence was carried out using both visual and acoustic surveys, supported by ten stations that sampled conductivity, temperature, fluorescence and zooplankton; at five of these stations, fish and cephalopod communities were also sampled during dusk and dawn to a maximum depth of 356 m. Results showed that temperature, salinity, and fluorescence were stable throughout the study area. Zooplankton were dominated by copepods, fish were dominated by myctophids, whilst cephalopods were dominated by Todarodes sagittatus and two Histioteuthis spp. Pilot whales, sperm whales and Sowerby's beaked whales were detected both acoustically and visually, along with other delphinids in large numbers, providing evidence that the study covered rich foraging habitat for these species, especially along the 1000 m–2000 m deep continental slope.

A small population of humpback whales breeds around the Cape Verde Islands off West Africa. These whales exhibit a boreal seasonality, albeit two months later than that in the West Indies. Based on aseasonal observations of humpback whales and calves, Hazevoet et al. (2011) postulated that whales with an austral seasonality may also breed in Cape Verdean waters. Regions known to host breeding and calving whales from both hemispheres are rare, e.g. Costa Rica in the North Pacific. Here we present evidence consistent with this scenario in Cape Verde, using results from acoustic, molecular genetic and visual surveys. In April 2014, an SM2M+ underwater autonomous recorder (Wildlife Acoustics) was deployed to a depth of 600 m to record for 10 months, 100 km north of São Nicolau (N 17.6°, W 24.3°) over the abyssal plain (depth 3000 m). Analysis of 1539 hrs of recordings revealed humpback whale song during both austral and boreal spring, with absences in July and October to November. The percentage of positive detection hours conformed to a bimodal distribution, peaking in April (63%) and again in August (29%). In September 2014, 1182 km of visual survey effort was conducted from a sailing vessel throughout the archipelago, resulting in 9 encounters with a total of 12 humpback whales including 2 mother-calf pairs. Two adults were biopsy sampled, both exhibiting haplotypes (xx bp length D-loop fragments?) typical of whales sampled in the Southern Ocean. Further evidence of breeding behaviour is required to establish whether Cape Verde constitutes a breeding ground for whales with an austral seasonality. However, using three lines of evidence (acoustics, visual encounters and molecular genetics), our results build a stronger case for this scenario.

Results are presented from the first systematic visual and acoustic line-transect survey for harbour porpoises in the Thracian Sea, northern Aegean Sea. During the vessel survey, undertaken in summer 2013, porpoises were observed on nine occasions and detected acoustically 16 times, with a total of 21 distinct encounters recorded. Harbour porpoises were encountered in three discrete blocks: north of the Island of Thasos, Greece; south and west of the city of Alexandroupolis, Greece; and in Saros Bay, Turkey. Saros Bay exhibited the highest relative acoustic encounter rate of harbour porpoises, and porpoises were observed visually there on two occasions 14 days apart, in small groups, one of which included a mother-calf pair. A comprehensive review of stranding records is also presented. The three areas identified as harbour porpoise habitat in this study coincide with the highest number of recorded stranded animals. This paper is the first to report free-swimming harbour porpoises in the Aegean Sea since 1993, and the first time ever in Turkish Aegean waters. Now that the presence of harbour porpoises has been documented, international cooperation towards long term monitoring and management measures are urgently required in order to conserve this vulnerable population.

The Levantine Basin (LB) is still considered a void as regards its cetacean fauna: species population abundance and distribution patterns are unknown, and even the list of species and their regional status have so far not been finalized. In an effort to fill the knowledge gap, we present original data collected in the LB over the years 1993-2009. The data relies on strandings, bycatch victims and on incidental and dedicated-survey sightings. We supplement these by reviewing available information on cetacean occurrence in the LB, prior to and including the above period. We believe that the following list and suggested status is a comprehensive updated regional inventory: Species with a 'regular' status include the common bottlenose dolphin, striped dolphin, common dolphin, Risso's dolphin and rough-toothed dolphin, as well as Cuvier's beaked whale; 'visitors' include false killer whale, sperm whale, minke whale and fin whale; Indo-Pacific humpback dolphin, humpback whale and killer whale are designated 'vagrants'. The only common Mediterranean species notably absent is the long-finned pilot whale. Indeed, despite its profound oligotrophicity, the diversity of cetacean species in the LB equals that in the western basins, and due to the relatively lower anthropogenic impact that it sustains, it should receive its share of resources and efforts towards conserving this diversity.

1.The bottlenose dolphins of Doubtful Sound, New Zealand are a declining population at the southern limit of the species' range, exposed to impacts from tourism and habitat modification. Patterns in apparent annual survival were analysed from photographic resightings of naturally marked adults (1990 to 2008) and calves within the first year of life (1994 to 2008) using capture-recapture models. 2.The most parsimonious model for adults provided a time-invariant, sex-invariant estimate of survival (ϕa(1990–2008)=0.9374; 95% CI: 0.9170–0.9530), marginally lower than prior estimates for wild bottlenose dolphins. 3.The most parsimonious model for calves indicated a significant time-variant decline in survival from an estimate similar to other populations (ϕc(1994–2001)=0.8621; 95% CI: 0.6851–0.9473) to a current estimate that is, to our knowledge, the lowest recorded for free-ranging bottlenose dolphins (ϕc(2002–2008)=0.3750; 95% CI: 0.2080–0.5782). 4.Information theoretic evidence ratios suggested that observed patterns in calf survival were 22 times more likely to be explained by a decline coincident with the opening of a second tailrace tunnel for a hydroelectric power station than by a decline in any other year or across multiple years. 5.Projections using an age-structured stochastic population model indicated that the current level of calf survival was unsustainable (population decline: 100% of model runs; population extinction: 41.5% of model runs) and was a key factor in the observed population decline in Doubtful Sound. Copyright © 2008 John Wiley & Sons, Ltd.

The distribution of harbour porpoises Phocoena phocoena in southern Europe and along the Atlantic African coast is poorly understood, with tentative assessments suggesting a discrete West African population with a northern limit around the Straits of Gibraltar. This study describes visual and acoustic surveys for porpoises in Atlantic waters of North-West Africa in spring 2005 between latitudes of 20°N and 37°N. During this period, 276h of acoustic data were collected in all sea states (from 3 125km of trackline) and 60h (824km) of visual effort was conducted in Beaufort sea states of three or less. Harbour porpoises were seen three times on the survey trackline and on four additional occasions off the trackline. The four individuals seen in Agadir Bay (30°N) represent the northernmost living porpoises reported from the Atlantic African coasts and the first sightings of porpoises reported in Moroccan waters. In addition, 31 acoustic detections were made on the survey trackline, of which 23 were made between Dakhla (24°N) and Cap Barbas (22°N). Fishing activities off North-West Africa are intense, ranging from small-scale artisanal gillnetters to international freeze-trawlers. Further monitoring of the status of this little known and isolated population is required for effective conservation management. Keywords: acoustics; distribution; harbour porpoise; Phocoena phocoena; West Africa African Journal of Marine Science Vol. 29 (3) 2007: pp. 403-410

Sei whale calls have been documented on very few occasions and never in the Azores Archipelago, an area transited by this species during their migration to northern latitudes in spring and early summer. Using a combination of video range tracking (VRT) and acoustic methods, vocalizations are described from an encounter with two sei whales in April 2012 off Pico Island, Azores. Recordings analyzed post-survey revealed 53 low frequency downsweep calls with average maximum frequencies of 100 Hz [standard deviation (SD = 14 Hz)] down to 37 Hz (SD = 8 Hz) over 1.21 s (SD = 0.33 s). Apparent source levels of 177 dB (SD = 5 dB) root-mean-square (rms) re 1 μPa were recorded. Vocalizations were attributed to the pair of sei whales encountered using a combination of the VRT data and differences in arrival time of calls at the hydrophones. These calls are similar to those reported from sei whales off New England and similar to those recorded off Hawaii. The growing body of acoustic data on sei whale vocalizations may contribute to the understanding of this species' distribution and population identity; key information is needed to guide future conservation efforts for this species.

Quantification of the vocal repertoire of a species is critical for subsequent analysis of signal functionality, geographical variation, social relevance, and transmission. While signal repertoires have been documented for numerous animal species, detailed descriptions for the cetaceans are rare. This study describes the vocalizations of free-ranging bottlenose dolphins resident to the waters of Fiordland, New Zealand. The field recordings presented in this paper were made using both audio band and broadband apparatus. Subsequent classification of vocalizations using multivariate parameters enabled a quantification of the entire vocal output of the focal animals. These results were used to propose a meaningful repertoire of signals employed by this species. A total of 12 individual signal types were described, comprising four broad structural classes: "tonal," "single bursts," "click bursts," and "repeat bursts." The proposed repertoire will allow subsequent investigation into vocal behavior. It appears that the successful description of a species' repertoire is dependent on the use of appropriate recording systems, a high number of representative recordings with good signal-to-noise ratio, and subsequent validation of the original classification system.

More than 12 studies of different bottlenose dolphin populations, spanning from tropical to cold temperate waters, have shown that the species typically lives in societies in which relationships among individuals are predominantly fluid. In all cases dolphins lived in small groups characterised by fluid and dynamic interactions and some degree of dispersal from the natal group by both sexes. We describe a small, closed population of bottlenose dolphins living at the southern extreme of the species' range. Individuals live in large, mixed-sex groups in which no permanent emigration/immigration has been observed over the past 7 years. All members within the community are relatively closely associated (average half-weight index>0.4). Both male–male and female–female networks of preferred associates are present, as are long-lasting associations across sexes. The community structure is temporally stable, compared to other bottlenose dolphin populations, and constant companionship seems to be prevalent in the temporal association pattern. Such high degrees of stability are unprecedented in studies of bottlenose dolphins and may be related to the ecological constraints of Doubtful Sound. Fjords are low-productivity systems in which survival may easily require a greater level of co-operation, and hence group stability. These conditions are also present in other cetacean populations forming stable groups. We therefore hypothesise that ecological constraints are important factors shaping social interactions within cetacean societies.