Cetaceans in British waters

Most information on the distribution, movements and ecology of cetaceans in the N.E. Atlantic have come from whale catches mainly in the early part of this century, and from strandings records collected by the British Museum (Nat. Hist.). With the formation of the Cetacean Group in 1973, a scheme for recording live cetaceans at sea was started. This paper summarizes the results of about two thousand sightings involving nearly 25,000 individual animals between the years 1958– 1978 (but mainly from the last 10 years), and relates them to existing information collected from other sources. Difficulties of identification and potential sources of bias are discussed. Most large cetaceans are present in British waters as part of a latitudinal feeding migration whereas smaller species may be present in the N.E. Atlantic throughout the year with movements being mainly of an offshore-inshore nature. Some species are clearly very rare probably as a result of over-exploitation in the last century and early part of this century. These include the Right whale, Blue whale and probably Humpback whale. Other species are rarely recorded because their usual range is some distance from British waters. These include narwhal and White whale (from Arctic waters), Pygmy sperm whale, smaller beaked whales and Euphrosyne dolphin (from warm temperate to tropical waters). The Harbour porpoise is by far the most common and widespread species in British waters, occurring mainly in inshore waters, although it has apparently declined in certain regions (e.g. Southern North Sea, English Channel, Irish Sea) in recent years probably as a result of pollution, disturbance and/or over-exploitation of food resources. Bottle-nosed and Risso's dolphins are also widely distributed close to the coast, although the latter is restricted to the west and south coasts and the former is associated particularly with some large estuaries. Common dolphins are relatively abundant and widespread, and are more pelagic than the previous three species. White-sided dolphins have a mainly pelagic distribution centred on the Northern North Sea whilst the White-sided dolphin has a wider distribution which includes all the western seaboard. Of larger cetaceans, the Killer whale is relatively common particularly on the west coasts and the Pilot whale is locally and seasonally abundant at the north and south ends of Britain and Ireland where they probably represent distinct populations. The Bottlenose whale, Minke, Fin and Sei whales are confined to the west and north coasts, all but the Minke whale having a primarily pelagic distribution. Sperm whales although increasingly commonly stranded on British coasts, are rarely sighted in inshore waters. The west coast of Britain and Ireland are the most important regions for cetaceans whereas the Southern North Sea has the smallest number although in previous decades numbers were probably higher. Most cetacean species occur mainly in the summer months, particularly August and September, although some species, e.g. White-sided Dolphin, Pilot whale and Minke whale show peaks later in the year. A number of species show secondary spring peaks, e.g. Bottle-nosed and Common dolphins, Risso's dolphins, and Pilot whales. Present evidence suggests that only the large whales exhibit definite latitudinal migrations, all other species being resident at high latitudes although they may show offshore-inshore or possibly small latitudinal movements. Many of the movements indicated from the present analysis can be linked to the seasonal changes in food availability and to the timing and geographical location of breeding, and these are described in detail. Many concentrations of a particular cetacean species occur regularly in the same area year after year and these may often be related to spawning concentrations of a particular fish species. Variations in herd size are noted between species and within species at different times of the year. These are related to aggregations associated with feeding, breeding, and long-distance movements winch will vary according to the biology and ecology of different cetacean species.     

ABUNDANCE OF CETACEANS IN THE OCEANIC NORTHERN GULF OF MEXICO, 1996–2001

The Gulf of Mexico is a subtropical marginal sea of the western North Atlantic Ocean with a diverse cetacean community. Ship-based, line-transect abundance surveys were conducted in oceanic waters (>200 m deep) of the northern Gulf within U. S. waters (380,432 km²) during spring from 1996 to 1997 and from 1999 to 2001. Data from these five surveys were pooled and minimum abundance estimates were based on 12,162 km of effort and 512 sightings of at least 19 species. The most commonly sighted species (number of groups) were pantropical spotted dolphin, Stenella attenuata (164); sperm whale, Physeter macrocephalus (67); dwarf/pygmy sperm whale, Kogia simalbreviceps (58); Risso's dolphin, Grampus griseus (38); and bottlenose dolphin, Tursiops truncatus (24). The most abundant species (number of individuals; coefficient of variation) were S. attenuata (91,321; 0.16); Clymene dolphin, S. clymene (17,355; 0.65); spinner dolphin, S. longirostris (11,971; 0.71); and striped dolphin, S. coeruleoalba (6,505; 0.43). The only large whales sighted were P. macrocephalus (1,349; 0.23) and Bryde's whale, Balaenopteraedeni (40; 0.61). Abundances for other species or genera ranged from 95 to 2,388 animals. Cetaceans were sighted throughout the oceanic northern Gulf and, whereas many species were widely distributed, some had more regional distributions.     

SPATIOTEMPORAL PREDICTION MODELS OF CETACEAN HABITATS IN THE MID-WESTERN NORTH ATLANTIC OCEAN (FROM CAPE HATTERAS, NORTH CAROLINA, U.S.A. TO NOVA SCOTIA, CANADA)

Habitat prediction models were developed for 13 cetacean species of the mid-western North Atlantic Ocean: beaked whale, fin whale, humpback whale, minke whale, pilot whale, sperm whale, bottlenose dolphin, common dolphin, Risso's dolphin, spotted dolphin, whitesided dolphin, and harbor porpoise. Using the multiple logistic regression, sightings of cetaceans during the 1990–1996 summer (June-September) surveys were modeled with oceanographic (sea surface temperature, monthly probability of front occurrence) and topographic (depth, slope) variables for the same period. Predicted habitat maps for June and August were created for each species using a Geographical Information System. The predicted habitat locations matched with current and historic cetacean sighting locations. The model also predicted habitat shifts for some species associated with oceanographic changes. The correct classification rate of the prediction models with 1997–1998 summer survey data ranged from 44% to 70%, of which most of the misclassifications were caused by false positives ( i.e. , absence of sightings at locations where the models predicted).     

DIETS OF FIN, SEI, AND SPERM WHALES IN BRITISH COLUMBIA: AN ANALYSIS OF COMMERCIAL WHALING RECORDS, 1963–1967

Diets of fin ( Balaenoptera physalus ), sei ( Balaenoptera borealis ), and sperm whales ( Physeter macrocephalus ) were estimated from the stomach contents of individuals killed along the British Columbia coast from 1963 to 1967. The dominant prey types of fin whales were euphausiids, with minor contributions from copepods and fish. Sei whale stomachs contained primarily copepods in three years, whereas euphausiids or a variety of fish dominated the diet in the other two years. Sperm whales consumed primarily North Pacific giant squid ( Moroteuthis robusta ), but secondary prey differed between males and females. Female sperm whales frequently consumed ragfish ( Icosteus spp.) and other fish, whereas the male diet also contained rockfish ( Sebastes spp.). The high abundance of euphausiids along the British Columbia coast likely contributed to the presence of a summer resident population of fin whales. The high abundance of large copepods farther north probably influenced the migration of sei whales through the offshore waters of British Columbia. Sperm whale stomach contents differed by sex reflecting location and possibly breeding behaviors.     

Cetaceans of Southeast Alaska: distribution and seasonal occurrence

Aim To assess the distribution, group size, seasonal occurrence and annual trends of cetaceans. Location The study area included all major inland waters of Southeast Alaska. Methods Between 1991 and 2007, cetacean surveys were conducted by observers who kept a constant watch when the vessel was underway and recorded all cetaceans encountered. For each species, we examined distributional patterns, group size, seasonal occurrence and annual trends. Analysis of variance (anova F) was used to test for differences in group sizes between multiple means, and Student’s t‐test was used to detect differences between pairwise means. Cetacean seasonal occurrence and annual trends were investigated using a generalized linear model framework. Results Humpback whales (Megaptera novaeangliae) were seen throughout the region, with numbers lowest in spring and highest in the fall. Fin whale (Balaenoptera physalus) and minke whale (Balaenoptera acutorostrata) distributions were more restricted than that reported for humpback whales, and the low number of sightings precluded evaluating seasonal trends. Three killer whale (Orcinus orca) eco‐types were documented with distributions occurring throughout inland waters. Seasonal patterns were not detected or could not be evaluated for resident and offshore killer whales, respectively; however, the transient eco‐type was more abundant in the summer. Dall’s porpoise (Phocoenoides dalli) were distributed throughout the region, with more sightings in spring and summer than in fall. Harbour porpoise (Phocoena phocoena) distribution was clumped, with concentrations occurring in the Icy Strait/Glacier Bay and Wrangell areas and with no evidence of seasonality. Pacific white‐sided dolphins (Lagenorhynchus obliquidens) were observed only occasionally, with more sightings in the spring. For most species, group size varied on both an annual and seasonal basis. Main conclusions Seven cetacean species occupy the inland waters of Southeast Alaska, with distribution, group size, seasonal occurrence and annual trends varying by species. Future studies that compare spatial and temporal patterns with other features (e.g. oceanography, prey resources) may help in identifying the key factors that support the high density and biodiversity of cetaceans found in this region. An increased understanding of the region’s marine ecology is an essential step towards ensuring the long‐term conservation of cetaceans in Southeast Alaska.     

Hearing loss in stranded odontocete dolphins and whales

The causes of dolphin and whale stranding can often be difficult to determine. Because toothed whales rely on echolocation for orientation and feeding, hearing deficits could lead to stranding. We report on the results of auditory evoked potential measurements from eight species of odontocete cetaceans that were found stranded or severely entangled in fishing gear during the period 2004 through 2009. Approximately 57% of the bottlenose dolphins and 36% of the rough-toothed dolphins had significant hearing deficits with a reduction in sensitivity equivalent to severe (70-90 dB) or profound (>90 dB) hearing loss in humans. The only stranded short-finned pilot whale examined had profound hearing loss. No impairments were detected in seven Risso's dolphins from three different stranding events, two pygmy killer whales, one Atlantic spotted dolphin, one spinner dolphin, or a juvenile Gervais' beaked whale. Hearing impairment could play a significant role in some cetacean stranding events, and the hearing of all cetaceans in rehabilitation should be tested.     

SEASONAL PATTERNS IN THE ABUNDANCE AND DISTRIBUTION OF CALIFORNIA CETACEANS, 1991–1992

This study presents a detailed seasonal comparison of the abundance and distribution of cetaceans within 100-150 nmi (185-278 km) of the California coast during 1991 and 1992. The results of a shipboard line-transect survey conducted in July-November 1991 ("summer") were compared to those from aerial line-transect surveys conducted in March-April 1991 and February-April 1992 ("winter"). Using a confidence-interval-based bootstrap procedure, abundance estimates for six of the eleven species included in the comparison exhibited significant (α= 0.05) differences between the winter and summer surveys. Pacific white-sided dolphins ( Lagenorhynchus obliquidens ), Risso's dolphins ( Grampus griseus ), common dolphins ( Delphinus spp.), and northern right whale dolphins ( Lissodelphis borealis ) were significantly more abundant in winter. The abundance of blue whales ( Balaenoptera musculuss ) and gray whales ( Eschrichtius robustus ) reflected well-documented migratory patterns. Fin whales ( B. physalus ) were significantly more abundant during summer. No significant differences in seasonal abundance were identified for Dall's porpoises ( Phocoenoides dalli ), bottlenose dolphins ( Tursiops truncatus ), killer whales ( Orcinus orca ), sperm whales ( Physeter macrocephalus ), or humpback whales ( Megaptera novaeangliae ). Significant north/south shifts in distribution were found for Dall's porpoises, common dolphins, and Pacific white-sided dolphins, and significant inshore/offshore differences were identified for northern right whale dolphins and humpback whales.     

Insights into the population structure of blue whales in the Eastern North Pacific from recent sightings and photographic identification

Blue whales were widely distributed in the North Pacific prior to the primary period of modern commercial whaling in the early 1900s. Despite concentrations of blue whale catches off British Columbia and in the Gulf of Alaska, there had been few documented sightings in these areas since whaling for blue whales ended in 1965. In contrast, large concentrations of blue whales have been documented off California and Baja California and in the eastern tropical Pacific since the 1970s, but it was not known if these animals were part of the same population that previously ranged into Alaskan waters. We document 15 blue whale sightings off British Columbia and in the Gulf of Alaska made since 1997, and use identification photographs to show that whales in these areas are currently part of the California feeding population. We speculate that this may represent a return to a migration pattern that has existed for earlier periods for eastern North Pacific blue whale population. One possible explanation for a shift in blue whale use is changes in prey driven by changes in oceanographic conditions, including the Pacific Decadal Oscillation (PDO), which coincides with some of the observed shifts in blue whale occurrence.     

ACOUSTIC DETECTIONS OF SINGING HUMPBACK WHALES IN DEEP WATERS OFF THE BRITISH ISLES

From October 1996 through September 1998, we used bottom-mounted hydrophone arrays to monitor deep-water areas north and west of the British Isles for songs of humpback whales ( Megaptera novaeangliae ). Singing humpbacks were consistently detected between October and March from the Shetland-Faroe Islands south to waters west of the English Channel. Temporal and geographic patterns of song detections, and movements of individually tracked whales, exhibited a southwesterly trend over this period, but with no corresponding northward trend between April and September. These results, together with a review of historical data from this area, suggest that the offshore waters of the British Isles represent a migration corridor for humpbacks, at least some of which summer in Norwegian (and possibly eastern Icelandic) waters. The migratory destination of the detected animals remains unknown, but the limited data suggest that these whales are bound primarily for the West Indies rather than historical breeding areas off the northwestern coast of Africa. Humpbacks detected in British waters after early to mid-March probably do not undertake a full migration to the tropics. These data provide further evidence that singing is not confined to tropical waters in winter, but occurs commonly on migration even in high latitudes.     

The first baleen whale marine protected area proposed for Bryde's whales in the Beibu Gulf,China

The establishment of marine protected areas (MPAs) for cetaceans is an important strategy to mitigate human disturbance and protect biodiversity. Despite abundant cetacean species, there are only a few MPAs dedicated to cetacean conservation in China, all of which are for inshore dolphins. Bryde's whales, the only nearshore baleen whale population in mainland China, are conflicting with intensive human activities, yet an effective conservation strategy is lacking. This study used species distribution models to analyze distribution patterns and suitable habitats of Bryde's whales in the Beibu Gulf and proposes the first baleen whale MPA in China. Our results showed Bryde's whales have a seasonal distribution pattern in the Beibu Gulf, and that the waters around Weizhou Island and the southeastern coast of Vietnam were their core habitats. The seasonal nighttime light data indicated a negative relationship between the number of ship lights and Bryde's whale sightings and suggest that Bryde's whales might be threatened by fisheries. We proposed an MPA based on the results, suggesting that the waters within 20 km around Weizhou Island should be declared a protected area. Furthermore, we recommend that anthropogenic activities in the waters around Weizhou Island are better managed to reduce negative impacts on marine life.     

The peculiarities of foraging migrations of the Korean-Okhotsk gray whale (<Emphasis Type="Italic">Eschrichtius robustus</Emphasis>) population in russian waters of the Far Eastern seas

Photographic identification of the Korean-Okhotsk gray whale Eschrichtius robustus population has been conducted since 2002 by researchers of the Institute of Marine Biology at the Far East Branch of the Russian Academy of Sciences (IMB FEB RAS), with financial support provided by Exon Neftegas, Ltd. and Sakhalin Energy Investment Co., in order to study the migration features and biology of this species. In 2008, photo-ID studies were carried out in two areas, off the northeastern coast of Sakhalin Island and off the southeastern coast of Kamchatka. As a result of the studies, 122 whales known from the Sakhalin gray whale catalogue were photographed. Of them, 97 individuals were registered off Sakhalin, 24, off Kamchatka, and one whale was observed at both sites. In addition, 25 more gray whales that had not been sighted off Sakhalin Island before were found off the coast of Kamchatka. Based on these photographic materials, the whales physical and skin conditions were also analyzed. Cases of sightings of gray whales in areas that are remote from their traditional summer and fall feeding grounds in the Far Eastern seas of Russia are discussed.     

KILLER WHALES, ORCINUS ORCA, IN THE SOUTHEASTERN BERING SEA: RECENT SIGHTINGS andPREDATION ON OTHER MARINE MAMMALS

An unusual number of killer whales appeared in inshore waters of the southeastern Bering Sea in summer 1989 and 1990. Multiple sightings occurred in Bristol and Kuskokwim bays where killer whales had been seen only rarely in previous years. Three animals became stranded on mud flats in Kuskokwim Bay but were able to free themselves on a high tide. Killer whales were observed interacting with salmon, harbor seals, Steller sea lions, walruses, and beluga whales. Detailed observations were made of killer whales attacking belugas in the Naknek River. Local conditions and behavioral adaptations may reduce the susceptibility of belugas to killer whale predation. Continued killer whale activity in this area would be unlikely to affect fish resources, but might have some influence on beluga whales.     

Distribution and abundance of fin whales (Balaenoptera physalus) in the western Mediterranean sea during the summer

A sightings survey was conducted in the summer of 1991 in the western Mediterranean to describe the distribution of fin whales and to estimate their absolute abundance during the summer feeding season. Fin whales were only found in the Liguro-Provençal basin, in deep waters (mean depth 2,360, S.E.: 46.8 m), beyond the continental shelf. The highest densities of fin whales were found in relatively cool waters (mean = 23.9°C), and water in areas in which fin whales were found was significantly cooler than that in areas without fin whales. Patterns of distribution of whales, with remarkably high densities in the feeding grounds, and composition of schools, which were found to be smaller than in other regions, suggest that food resources for the species in the north-western Mediterranean feeding grounds occur at higher densities but are more patchily distributed than in other fin whale feeding grounds so far studied. Abundance was estimated as 3,583 individuals (S.E.: 967; 95% CI: 2,130-6,027).     

Vocal activity of tropical dolphins is inhibited by the presence of killer whales,Orcinus orca

Research has suggested killer whale (Orcinus orca) predation may affect cetacean vocal behavior; however, few data exist to test this hypothesis. Data collected during 40,976 km of visual and acoustic shipboard surveys in the tropical Pacific Ocean, including 1,232 detections of 13 species, were examined to determine if changes in dolphin vocal activity could be attributed to the presence of killer whales. Generalized linear models and Random Forest analyses were used to test the hypothesis that dolphin vocal activity was related to the distance and time to the nearest killer whale sighting. Both results show that dolphin vocalizations were inversely correlated with the temporal proximity of killer whales (P < 0.05). Despite the relative rarity of killer whales in the tropics, they appear to influence vocal behavior of nearby dolphin schools. This disruption in communication may not significantly impact interactions necessary for survival in tropical waters where killer whale density is low. However, in temperate climates, where increased productivity supports a greater abundance of killer whales, this interruption in communication may have a greater impact. The lower incidence of whistling dolphins in temperate waters may be related to the greater abundance of killer whales in these areas.     

BLUE WHALE (BALAENOPTERA MUSCULUS)DISTRIBUTION IN THE EASTERN TROPICAL PACIFIC

The distribution of blue whales, Balaenoptera musculus , in the eastern tropical Pacific (ETP) was analyzed from 211 sightings of 355 whales recorded during research vessel sighting surveys or by biologists aboard fishing vessels. Over 90% of the sightings were made in just two areas: along Baja California, and in the vicinity of the Costa Rica Dome (a large, stationary eddy centered near 9°N, 89°W), with the rest made along the equator near the Galapagos islands, the coasts of Ecuador and northern Peru. All sightings occurred in relatively cool, upwelling-modified waters. Because these areas are the most productive parts of the ETP, and have relatively large standing stocks of euphausiids, it seems possible that blue whales select low latitude habitats which permit foraging. The waters off western Baja California were occupied seasonally, with a peak in sightings coinciding with the spring peak in upwelling and biological production. The Costa Rica Dome area was occupied year round, suggesting either a resident population, or that both northern and southern hemisphere whales visit, with temporal overlap. The modal group size was one for all areas and seasons, but the frequency of groups with two or more whales was significantly higher in sightings made near the Galapagos Islands and the coast of Ecuador and northern Peru.     

Association between pygmy right whales (Caperea marginata) and areas of high marine productivity off Australia and New Zealand

Abstract

Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata.     

RIGHT WHALES (EUBALAENA GLACIALIS) ON JEFFREYS LEDGE: A HABITAT OF UNRECOGNIZED IMPORTANCE?

North Atlantic right whales ( Eubalaena glacialis ) are known to spend the majority of the year between the Great South Channel southeast of Cape Cod, and the Nova Scotian shelf. We examined sightings of right whales on and around Jeffreys Ledge, a 54-km-long glacial deposit off the coast of northern Massachusetts, New Hampshire, and Maine. Sightings on Jeffreys Ledge were extracted from three data sets: (1) a systematic survey of the entire northeastern continental shelf between 1979 and 1982, (2) whale-watch and research-cruise sighting data from 1984 to 1997, and (3) a collaborative database of sightings collected by organizations conducting right whale research and all other available sources. Each database supported two seasonal sighting peaks. During summer (especially July and August) sightings were primarily of mother-calf pairs. Several cow-calf pairs were seen over several days to weeks. Several females were resighted in more than one year, but only when calves were present. During October, November, and December, sightings included all age classes, surface-feeding behavior was frequently observed, and some animals were resighted over several weeks. Given the relatively reduced sighting effort during fall, this number of sightings is surprising. During the 20 yr of observations, 52 of 374 photo-identified North Atlantic right whales (13.9%) were seen at least once on Jeffreys Ledge. We suggest that Jeffreys Ledge may be a more important right whale habitat than previously believed, and that it may play an important role in annual movements and distribution of this population.     

Spatiotemporal patterns of marine mammal distribution in coastal waters of Galicia, NW Spain

The spatial and seasonal distribution of cetaceans and possible links with environmental conditions were studied at the Galician continental shelf. Data were collected between February–August 2001 and June–September 2003 during opportunistic surveys onboard fishing boats. Seven species of cetaceans were identified from 250 sightings of 6,846 individuals. The common dolphin (Delphinus delphis) was by far the most frequently sighted and the most widely distributed species. Spatiotemporal trends in cetacean distribution and abundance, and their relationships with environmental parameters (sea depth, SST and chlorophyll-a) were quantified using generalised additive models (GAMs). Results for all cetaceans were essentially the same as for common dolphins alone. Modelling results indicated that the number of common dolphin sightings per unit effort was higher further south. The number of individual common dolphins seen per sighting of this species (i.e. group size) was however higher in the north and west of the study area, higher later in the year and higher in 2001 than in 2003. In contrast, the number of common dolphin calves seen (per sighting of this species) was higher in the south. Models including environmental variables indicated larger common dolphin group sizes in deeper waters and at higher chlorophyll concentrations (i.e. in more productive areas). There was also a positive relationship between survey effort and group size, which is probably an artefact of the tendency of the survey platforms (fishing boats) to spend most time in areas of high fish abundance. Numbers of common dolphin calves per sighting were found to be higher in shallower waters. The results are consistent with common dolphins foraging mainly in deeper waters of the Galician continental shelf, while more southern inshore waters may represent a nursery area.     

POPULATION CHARACTERISTICS AND MIGRATION OF SUMMER AND LATE-SEASON HUMPBACK WHALES (MEGAPTERA NOVAEANGLIAE) IN SOUTHEASTERN ALASKA

A total of 326 humpback whales (Megaptera novaeangliae) were individually identified in southeastern Alaska during five summer seasons (July to September) and four late seasons (November to February) spanning the years 1979 to 1983. Peak numbers of whales were found late in August or early in September. Whales arrived 1–2 wk later in 1982 than in 1981. Whales sighted in both the summer and late seasons of 1981 and 1982 remained about 3.7 mo and one whale remained for at least 4.9 mo. Humpback whales from southeastern Alaska wintered in Hawaiian or Mexican waters, but generally did not travel to other feeding regions. The most rapid migratory transit between Hawaii and southeastern Alaska was 79 d. Based on mark-recapture analyses of the photographic data, we estimate a population of 270–372 whales in the southeastern Alaska feeding herd.