Caroline R. Weir

Comparative Review of the Regional Marine Mammal Mitigation Guidelines Implemented During Industrial Seismic Surveys, and Guidance Towards a Worldwide Standard

Marine mammals rely on sound for all of the fundamental biological and ecological aspects of their lives including navigation, prey location and capture, predator avoidance, and communication (including during migration and reproduction). There is increasing concern regarding the potential effects of the airgun sound produced during geophysical seismic surveys on marine mammals. Airgun arrays typically produce high amplitude sound with source levels in the region of 220–248 dB re. 1 μPa @ 1 m. The acoustic output has highest energy at relatively low frequencies of 10–200 Hz, which overlaps extensively with the low frequency sound produced by baleen whales in the 12–500 Hz bandwidth. Airgun arrays may alsoproduce significant highMarine mammals rely on sound for all of the fundamental biological and ecological aspects of their lives including navigation, prey location and capture, predator avoidance, and communication (including during migration and reproduction). There is increasing concern regarding the potential effects of the airgun sound produced during geophysical seismic surveys on marine mammals. Airgun arrays typically produce high amplitude sound with source levels in the region of 220–248 dB re. 1 μPa @ 1 m. The acoustic output has highest energy at relatively low frequencies of 10–200 Hz, which overlaps extensively with the low frequency sound produced by baleen whales in the 12–500 Hz bandwidth. Airgun arrays may alsoproduce significant high

The habitat preferences of marine mammals west of Scotland (UK)

This study used classification and regression trees (CART) to investigate and compare the habitat preferences of marine mammals in this area. Data were collected in early summer (June/July) in 2004 and 2005 and the distribution of marine mammal species was compared to 10 ecogeographic variables (EGVs). Of 13 species of marine mammals sighted during the study, there were sufficient sightings to examine the habitat preferences of seven. For all species a measure of ‘shelf tendency’ (distance to coast or water depth) was an important variable and the species could be separated into two groups, the deep-water species and the shelf species, with little overlap between them. The occurrence of both deep-water species (long-finned pilot whales and Atlantic white-sided dolphins) was also related to dynamic variables such as sea surface temperature (SST) or primary productivity. Two of the shelf species (northern minke whales and grey seals) were only linked to topographic variables and were limited to quite specific habitats. A third species (harbour porpoise) was primarily related to topographic variables, but in the shallowest waters was also related to local variation in SST. The occurrence of the final two species (common and white-beaked dolphins) was linked to SST and local primary productivity. However, while both species preferentially occurred in areas with higher productivity, the two species differed in their preference for SST, with common dolphins preferentially occurring in warmer waters and whitebeaked dolphins in colder waters.

Overt Responses of Humpback Whales ( Megaptera novaeangliae ), Sperm Whales ( Physeter macrocephalus ), and Atlantic Spotted Dolphins ( Stenella frontalis ) to Seismic Exploration off Angola

A total of 2,769 h of marine mammal observation was conducted from a seismic survey vessel off Angola between August 2004 and May 2005. A dual-source airgun array firing a total volume of either 5,085 in (Survey 1) or 3,147 in (Survey 2) in an alternate source activation sequence was active during 51% of the analysed effort. A total of 207 sightings of humpback whales (n = 66), sperm whales (n = 124), and Atlantic spotted dolphins (n = 17) was recorded. The encounter rate (sightings/h) of humpback and sperm whales did not differ significantly according to airgun operational status. The mean distance to humpback and sperm whale sightings was greater during full-array operations than during guns off, but this difference was not significant. Atlantic spotted dolphin encounters occurred at a significantly greater distance from the airgun array (p < 0.001) during full-array operations than during guns off. Positive-approach behaviour by Atlantic spotted dolphins (n = 9) occurred only during guns-off periods. There was no evidence for prolonged or large-scale displacement of each species from the region during the 10-mo survey duration. Sperm whale sightings showed a significant increase (p < 0.001) during the survey, while Atlantic spotted dolphin encounters occurred at similar rates. A decreased occurrence of humpback whale sightings (p < 0.001) corresponded with established seasonal migration out of the survey area. Contrary to expectation based on perceived sensitivity, Atlantic spotted dolphins exhibited the most marked overt response to airgun sound of the three cetacean species examined.

Spatial and temporal trends in the distribution of harbour porpoises, white-beaked dolphins and minke whales off Aberdeenshire (UK), north-western North Sea

Most North Sea cetacean species are wide-ranging and consequently poorly studied. Spatial and temporal trends in the distribution of the harbour porpoise Phocoena phocoena, white-beaked dolphin Lagenorhynchus albirostris, and minke whale Balaenoptera acutorostrata were assessed at a coastal North Sea study area in Aberdeenshire, Scotland. Between March 1999 and October 2001, cetacean data were collected using both land- and vesselbased survey methods. A total of 174 sightings of these three cetacean species was recorded during approximately 330 h of combined survey effort (228 h land-based and 102 h vessel-based). Harbour porpoises were present throughout the year with peak occurrence during August and September. The presence of white-beaked dolphins and minke whales was strictly seasonal, with a peak in occurrence during August. The fine-scale distribution of all three species varied within the study area, with an apparent preference for sections of coast adjacent to deeper water. Most porpoise calves and juveniles were recorded between June and September, when 35% of harbour porpoise groups contained immature animals. The proportion of calves amongst porpoise sightings was higher during June than any other month. White-beaked dolphin calves were present in 32% of groups, and occurred in all three months that the species was recorded. Group size was higher in white-beaked dolphin pods containing immature animals. The strong seasonality in occurrence of all three species may relate to requirements for breeding habitat, movements of shared prey species and/or inter-specific competition with other species.

Temperature-based summer habitat partitioning between white-beaked and common dolphins around the United Kingdom and Republic of Ireland

The white-beaked dolphin (Lagenorhynchus albirostris) and short-beaked common dolphin (Delphinus delphis) are two of the most abundant delphinid species in shelf waters around the United Kingdom (UK) and Republic of Ireland (ROI) in the summer season (May - October). As these two species have similar habitat preferences and diets, it might be expected that they would partition their otherwise shared niche to reduce the potential for competition at this time of year. This study used 569 sightings of the two species, collected from shelf waters (<200 m water depth) in the summer season between 1983 and 1998, to investigate whether there is evidence of widespread niche partitioning based on water temperature in this area. Below 13°C, white-beaked dolphins were dominant with 96% of sightings comprising this species. In contrast, above 14°C, 86% of sightings comprised common dolphins. A classification tree analysis found that of the four eco-geographical variables analysed (water depth, seabed slope, seabed aspect and sea surface temperature), temperature was the most important variable for separating the occurrence of the two species. These results are consistent with widespread temperature-based niche partitioning between white-beaked and common dolphins in shelf waters around the UK and ROI. As temperature is important in determining the relative distribution of these species, the range of the white-beaked dolphin might be expected to contract in response to increasing sea temperature resulting from global climate change, while that of the common dolphin may expand.

West Africa's Atlantic Humpback Dolphin (Sousa teuszii): Endemic, Enigmatic and Soon Endangered?

Atlantic humpback dolphins (Sousa teuszii) are endemic to nearshore West African waters between Western Sahara and Angola. They are considered Vulnerable by the International Union for Conservation of Nature based on restricted geographic range, low abundance and apparent decline in recent decades. We review the human activities most likely to affect the species and consider appropriate conservation actions. Bycatch (incidental capture) in gillnets is the greatest immediate threat. Deaths from entanglement have been documented in Mauritania, Senegal, Guinea-Bissau, Guinea and the Republic of the Congo. In Namibe Province, Angola, 4.8 artisanal fishing boats and two gillnets per km were observed in some areas within 1 km of the coast and gillnets are deployed regularly inside bays used by dolphins. Other concerns include the ‘marine bushmeat’ trade, habitat loss/degradation, overfishing, marine pollution, anthropogenic sound and climate change. Conservation challenges include a paucity of scientific data on the species, and widespread human poverty within most range states, resulting in high dependence on artisanal fisheries. Recommended conservation and research priorities include: (1) distribution and abundance surveys in known and potential range states, (2) bycatch monitoring programmes, (3) education/awareness schemes, and (4) protection of core areas via reduction/elimination of nearshore gillnetting.

Examining the importance of Aberdeenshire (UK) coastal waters for North Sea bottlenose dolphins (Tursiops truncatus)

Using land- and vessel-based surveys, data on the relative abundance, distribution and habitat use of bottlenose dolphins (Tursiops truncatus) in Aberdeenshire waters were collected between 1999 and 2001. Bottlenose dolphins were present throughout the year, with peak abundance during the months of March to May. The occurrence of calves was seasonal, with the proportion of calves highest during the spring months. Foraging behaviour was recorded mainly in the vicinity of Aberdeen harbour. Dolphins photographed in Aberdeenshire waters were successfully matched and con¢rmed as Moray Firth animals. The results of the present study suggest that Moray Firth bottlenose dolphins utilize Aberdeenshire waters more frequently than previously reported. Aberdeen harbour is apparently an important feeding area, and Aberdeenshire waters are regularly used by mother^ calf pairs. This has important management implications since this area of coastline does not currently form part of the designated Special Area of Conservation (SAC) for this population.

Cetacean research in the southern African subregion: a review of previous studies and current knowledge

Cetacean research, in terms of the number of papers, and areas for which data are available, has expanded considerably in the southern African subregion in the past decade, especially in the South-West Indian Ocean. We review cetacean research within this subregion from the 1800s to the present to provide an overview of findings, investigate trends and identify knowledge gaps. Data are presented separately for large whales (those subject to commercial whaling) and smaller cetaceans, and are separated by era and ocean basin. Over 550 peer-reviewed papers and books were identified relating to research on cetaceans within the subregion. More than half (284) have been produced since 1990 and 193 relate specifically to South African waters. The most-studied species are those that are most accessible due to their coastal distributions (southern right whale Eubalaena australis: 45 papers, humpback whale Megaptera novaeangliae: 31 papers, killer whales Orcinus orca: 27 papers, Indo-Pacific bottlenose dolphin Tursiops aduncus: 30 papers, Indo-Pacific humpback dolphin Sousa chinensis (plumbea form): 25 papers) and/or were hunted commercially (sperm whale Physeter macrocephalus: 25 papers). Identified conservation concerns vary throughout the subregion, but include bycatch and directed hunts, oil and gas development, ecotourism activities, shifts in prey resources, and noise and chemical pollution. The inshore stocks of Brydes whales Balaenoptera edeni, the Indo-Pacific humpback dolphin and the Atlantic humpback dolphin S. teuszii were identified as the populations of highest conservation concern, although there are considerable knowledge gaps relating to deep-water species and almost no data (even on species occurrence) are available for several areas and countries.

Records of Fraser's dolphin Lagenodelphis hosei Fraser 1956 from the Gulf of Guinea and Angola

Although Frasers dolphins Lagenodelphis hosei are considered to inhabit deep tropical waters worldwide, their occurrence in the tropical eastern Atlantic Ocean from the Gulf of Guinea southwards to Angola is only represented by two specimen records from Ghana. During cetacean surveys carried out concurrently with geophysical seismic surveys off Nigeria in 2004 and off Angola in 2007 and 2008, a pod of 150 probable Frasers dolphins was videoed 130 km south of Nigeria and schools of 120 and 60 animals were photographed 170 km and 140 km respectively off the coast of Angola. All records occurred in deep water (>1 000 m). Cetacean bycatch was monitored at six artisanal Ghanaian fishing ports between 1998 and 2000. Four Frasers dolphin specimens comprising one adult, one juvenile and two calves were photographed at two ports. Drift gillnets were identified as the probable cause of mortality for at least two specimens. Two sightings of Frasers dolphins off Angola provide the first at-sea records for the Gulf of Guinea region and, together with bycaught specimens, confirm new southern and eastern distribution limits for the species within the Atlantic Ocean. Further information is required on the status of Frasers dolphins and the potential impact of fisheries bycatch on this species within the Gulf of Guinea.

A Long-Term Opportunistic Photo-Identification Study of Bottlenose Dolphins (Tursiops truncatus) off Aberdeen, United Kingdom: Conservation Value and Limitations

The waters of the Inner Moray Firth were designated a Special Area of Conservation (SAC) in 2005 for the conservation of the bottlenose dolphin (Tursiops truncatus) in northeast Scotland. However, the long-term conservation of this population requires monitoring throughout its entire known range. Opportunistic photo-identification of bottlenose dolphins occurred during 65 cetacean surveys conducted between 1999 and 2008 in the coastal waters of Aberdeenshire. A total of 88 bottlenose dolphin photo-identification encounters resulted in one to 45 animals identified per survey. The minimum annual total population size based on marked animals alone was 62 individuals, and the discovery curve indicated that the population has not yet been adequately sampled. Of 40 highly distinctive adult animals, the annual sighting rate ranged from 0.167 (seen in one year only) to 1.000 (seen every year). The cumulative monthly sighting rate varied from 0.091 (photographed in one month only) to 0.636 (photographed during seven of the 11 combined survey months in the 2001 to 2008 study period). The overall seasonal occurrence of dolphins off Aberdeenshire peaked during May and June, when 65% of distinctively marked animals were recorded per month (combined data for 2001 to 2008). Eighty-four percent of distinctively marked dolphins were matched with those photographed in the Inner Moray Firth, while 93% were matched with those photographed in the southern Outer Moray Firth. Despite its opportunistic nature, the photo-identification study provided valuable information on a population of bottlenose dolphins in a poorly studied part of their range. The high percentage of matches with dolphins from the Moray Firth SAC indicates that over half of the known northeast Scotland population uses the Aberdeenshire region, and some individuals do so regularly. The frequent occurrence off Aberdeen of bottlenose dolphins from a protected SAC has repercussions for the conservation and management of the population and for the effectiveness of the SAC for their longterm protection.