Stranding Events of Kogia Whales along the Brazilian Coast

The genus Kogia, which comprises only two extant species, Kogia sima and Kogia breviceps, represents one of the least known groups of cetaceans in the global ocean. In some coastal regions, however, stranding events of these species have been relatively common over the last decades. Stranding provides the opportunity to investigate the biology of these cetaceans and to explore the epidemiological aspects associated with the mortality of the organisms found on the beach. A number of disturbances (including pelagic fisheries, chemical pollution, boat strikes, and noise pollution) have been confirmed to pose a particular threat to the Kogia species. However, no study has yet investigated potential relationships between environmental conditions and stranding events. Here we analyse how a collection of environmental, physical, and biological variables, such as wind, sea surface temperature (SST), water depth, and chlorophyll-a, correlate to Kogia stranding events along the Brazilian coast. The results of our statistical analyses suggest that K. sima is more likely found in warm tropical waters, which provide an explanation for the high frequency of stranding in northeastern Brazilian coast. In contrast, K. breviceps appears to have a preference for temperate and productive waters. Wind speed results to be also an important factor for predicting Kogia strandings in Brazilian coast. Additionally, literature information in combination with our own data and analyses of stomach contents confirms that oceanic cephalopods constitute the primary nutritional source of both Kogia species. By using the available information as a qualitative proxy for habitat preference and feeding ecology, our study provides a novel and comprehensive assessment of Kogia stranding data in relation to environmental conditions along the Brazilian coast.     

Distribution of cetaceans in the offshore Gulf of Mexico

In order to comprehend better the distribution of Gulf of Mexico cetaceans, all available records of whales and dolphins in the offshore Gulf were assembled and analysed. This included sightings, strandings and captures of all species, except the Bottlenose Dolphin Tursiops truncatus , from all sources, except the recently completed GulfCet project. An attempt was made to confirm species identification for each of the records. A total of 1223 records was available for analysis. Twentyseven species of cetaceans have been confirmed to occur in the offshore Gulf of Mexico. All of the baleen whales, with the possible exception of the Bryde's Whale Balaenoptera edeni appear to be extralimital in the Gulf. The Sperm Whale Physeter macrocephalus is, by far, the most common great whale in this body of water. All previous records of Common Dolphins Delphinus spp. in the Gulf are rejected as either incorrect or unreliable, and there is currently no convincing evidence that dolphins of the genus Delphinus occur in the Gulf. The Atlantic Spotted Dolphin Stenella frontalis is the only species, other than the Bottlenose Dolphin, that regularly occurs over the continental shelf. The Pantropical Spotted Dolphin Stenella attenuata is the most common species of small cetacean in oceanic waters of the Gulf, but many other species also occur there in significant numbers.     

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.     

What can cetacean stranding records tell us? A study of UK and Irish cetacean diversity over the past 100 years

There are many factors that may explain why cetaceans (whales, dolphins, and porpoises) strand. Around the UK and Ireland, over 20,000 stranding records have been collected since 1913, resulting in one of the longest, continuous, systematic stranding data sets in the world. We use this data set to investigate temporal and spatial trends in cetacean strandings and use generalized additive models (GAMs) to investigate correlates of strandings. We find a dramatic increase in strandings since the 1980s, most likely due to increases in recording effort, and the formation of formal strandings networks. We found no correlation between the numbers of cetaceans stranding each year and several potential environmental and anthropogenic predictors: storms, geomagnetic activity, North Atlantic Oscillations, sea‐surface temperature, and fishing catch. We suggest that this is because the scale of change in the variables is too coarse to detect any potential correlations. It may also highlight the idiosyncratic nature of species’ responses to external pressures, and further the need to investigate other potential correlates of strandings, such as bycatch and military sonar. Long‐term cetacean stranding data provide vital information on past and present diversity for common, rare, and inconspicuous species. This study underlines the importance of continued support for stranding networks.     

Living with dolphins: Local ecological knowledge and perceptions of small cetaceans along the Sindhudurg coastline of Maharashtra,India

Two near shore small cetaceans occur commonly along the Maharashtra coast, the Indian Ocean humpback dolphin and Indo Pacific finless porpoise. These cetaceans frequently interact with fisheries in this region due to overlap in space and resource use. Besides stranding records, little ecological information is available about these species from Maharashtra. We conducted 143 semistructured interviews to document local ecological knowledge and community perceptions of small cetaceans in 30 coastal fishing villages in Sindhudurg. Perceptions of finless porpoises were largely neutral, whereas humpback dolphins were negative. A classification regression tree (CART) analysis (root node error: 60%) showed that the annual cost of gear damage was an important predictor variable of humpback dolphin perceptions, followed by occupation (gear type) and age. Entanglements were reported for both species in large and small gill nets, and shore seines. Perceived net damage and catch loss due to humpback dolphins was six times greater than that of finless porpoises. However, finless porpoises were reportedly more frequently entangled in gear than humpback dolphins. We provide an insight into the perceptions of cetaceans in the local community and the fisheries‐cetacean interactions that shape them.     

Humpback whales washed ashore in southeastern Brazil from 1981 to 2011: stranding patterns and microbial pathogens survey

In the Southwest Atlantic Ocean the wintering breeding ground of Megaptera novaeangliae is located in northeastern coast of Brazil, mainly in the Abrolhos Bank (16°55′ S, 38°50′ W) and its surroundings. During migratory percussion, events of strandings are thought to occur. A total of 58 stranded humpback whales were recorded between 1981 and 2011 along the coast of the Rio de Janeiro state, Brazil. The number of strandings in 20 years (1992–2011) increased during the period of study, with a mean of 2.6 events per year. In 2010 a peak occurred with 13 records of strandings. Most of them occurred preferably in the southern half of the study area, or in the southeast area of Rio de Janeiro state. Three cases of entanglement were found, two of these involving calves with less than eight meters of body length. Stranding events were more frequent during winter and spring. No statistical differences were found between age categories, but 33% were classified as “dependent calf” (< 8 m length). Males stranded more often than females. Only one whale out of 16 specimens that had the stomach contents examined presented food remains, but comprising only two cephalopod beaks of the squid Doryteuthis sanpaulensis. Bacteriological survey of Vibrionaceae and Aeromonadaceae agents in three live stranded whales on the Brazilian coast indicated evidence of animal impairment that resulted or were associated with the cause of death and stranding event.     

Cetacean strandings in Costa Rica (1966-1999)

Cetacean strandings in Costa Rica are reported for a period of 33 years, with a total of 35 strandings, 13 species and 247 individuals involved. The vast majority of documented strandings occurred on the Pacific coast and correspond to single individuals (32 and 28 strandings respectively). The highest stranding number was in the period from 1990 to 1999 (n = 24). Physeter catodon (cachalot or sperm whale) is the species with the highest frequency of strandings (n = 8) and the family Delphinidae has the majority of species (n = 8) and strandings (n = 22). No other general tendencies were determined with the existing data.     

Possible Causes of a Harbour Porpoise Mass Stranding in Danish Waters in 2005

An unprecedented 85 harbour porpoises stranded freshly dead along approximately 100 km of Danish coastline from 7–15 April, 2005. This total is considerably above the mean weekly stranding rate for the whole of Denmark, both for any time of year, 1.23 animals/week (ranging from 0 to 20 during 2003–2008, excluding April 2005), and specifically in April, 0.65 animals/week (0 to 4, same period). Bycatch was established as the cause of death for most of the individuals through typical indications of fisheries interactions, including net markings in the skin and around the flippers, and loss of tail flukes. Local fishermen confirmed unusually large porpoise bycatch in nets set for lumpfish (Cyclopterus lumpus) and the strandings were attributed to an early lumpfish season. However, lumpfish catches for 2005 were not unusual in terms of season onset, peak or total catch, when compared to 2003–2008. Consequently, human activity was combined with environmental factors and the variation in Danish fisheries landings (determined through a principal component analysis) in a two-part statistical model to assess the correlation of these factors with both the presence of fresh strandings and the numbers of strandings on the Danish west coast. The final statistical model (which was forward selected using Akaike information criterion; AIC) indicated that naval presence is correlated with higher rates of porpoise strandings, particularly in combination with certain fisheries, although it is not correlated with the actual presence of strandings. Military vessels from various countries were confirmed in the area from the 7th April, en route to the largest naval exercise in Danish waters to date (Loyal Mariner 2005, 11–28 April). Although sonar usage cannot be confirmed, it is likely that ships were testing various equipment prior to the main exercise. Thus naval activity cannot be ruled out as a possible contributing factor.     

Spatio-temporal analysis of cetacean strandings and bycatch in a UK fisheries hotspot

Marine vertebrate strandings data can provide insights into the long-term dynamics of cetacean populations, and the threats they face. We investigate whether the spatio-temporal patterns of cetacean strandings around Cornwall, SW Britain, have changed in the past century. Analysis of strandings from 1911 to 2006 (n = 2,257) show that, since the mid-1970s, the relative frequency of strandings of common dolphins (Delphinus delphis), harbour porpoises (Phocoena phocoena) and pilot whales (Globicephala melas) has increased significantly. Seasonal peaks in strandings frequencies are apparent, between December and March for harbour porpoises and common dolphins, and between November and January for pilot whales. There were significant positive trends in the number of common dolphin and harbour porpoise strandings, as a proportion of total strandings, over time. Strandings of common dolphins, porpoises and all other species occur more frequently on the south coast of Cornwall. A total of 415 cetaceans were subject to full veterinary necropsy to determine cause of death, between 1990 and 2006, and 253 (61%) of these individuals were determined to have died due to bycatch in fishing gear. Analyses of industrialised fishing pressure in UK waters show the seas around Cornwall to be one of the most heavily fished areas of the UK. We suggest a number of factors that could be responsible for the recent increases in cetacean strandings in southwest UK waters in recent years, including survey effort, as well as abundance and range shifts that are potentially linked with climate change. Although detectable levels of bycatch rate have not increased over time, fisheries interactions are in significant part responsible for mortality patterns and are worthy of more detailed investigation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The application of GIS and spatiotemporal analyses to investigations of unusual marine mammal strandings and mortality events

In 2006–2007, an unusually high number of harbor porpoises (Phocoena phocoena) stranded along the Washington and Oregon coastlines. Spatiotemporal analyses were used to examine their ability to detect clusters of porpoise strandings during an unusual mortality event (UME) in the Pacific Northwest using stranding location data. Strandings were evaluated as two separate populations, outer coast and inland waters. The presence of global clustering was evaluated using the Knox spatiotemporal test, and the presence of local clusters was investigated using a spatiotemporal scan statistic (space–time permutation). There was evidence of global clustering, but no local clustering, supporting the hypothesis that strandings were due to more varied etiologies instead of localized causes. Further analyses at subregional levels, and concurrently assessing environmental factors, might reveal additional geographic distribution patterns. This article describes the spatial analytical tools applied in this study and how they can help elucidate the spatiotemporal epidemiology of other UMEs and assist in determining their causes. More than one spatial analytical technique should be used if the study objective is to detect and describe clustering in time and space and to generate hypotheses regarding causation of marine mammal disease and stranding events.     

Estimating At-Sea Mortality of Marine Turtles from Stranding Frequencies and Drifter Experiments

Strandings of marine megafauna can provide valuable information on cause of death at sea. However, as stranding probabilities are usually very low and highly variable in space and time, interpreting the results can be challenging. We evaluated the magnitude and distribution of at-sea mortality of marine turtles along the Pacific coast of Baja California Sur, México during 2010–11, using a combination of counting stranded animals and drifter experiments. A total of 594 carcasses were found during the study period, with loggerhead (62%) and green turtles (31%) being the most common species. 87% of the strandings occurred in the southern Gulf of Ulloa, a known hotspot of loggerhead distribution in the Eastern Pacific. While only 1.8% of the deaths could be definitively attributed to bycatch (net marks, hooks), seasonal variation in stranding frequencies closely corresponded to the main fishing seasons. Estimated stranding probabilities from drifter experiments varied among sites and trials (0.05–0.8), implying that only a fraction of dead sea turtles can be observed at beaches. Total mortality estimates for 15-day periods around the floater trials were highest for PSL, a beach in the southern Gulf of Ulloa, ranging between 11 sea turtles in October 2011 to 107 in August 2010. Loggerhead turtles were the most numerous, followed by green and olive ridley turtles. Our study showed that drifter trials combined with beach monitoring can provide estimates for death at sea to measure the impact of small-scale fisheries that are notoriously difficult to monitor for by-catch. We also provided recommendations to improve the precision of the mortality estimates for future studies and highlight the importance of estimating impacts of small–scale fisheries on marine megafauna.     

THREE MASS STRANDINGS OF SPERM WHALES (PHYSETER MACROCEPHALUS) IN SOUTHERN AUSTRALIAN WATERS

One hundred and fifteen sperm whales (97 female, 15 male, 3 unknown sex) were involved in three mass stranding events during the month of February 1998 along the west and northwest coastlines of Tasmania, Australia. Sixty-six of these whales stranded at Ocean Beach, Strahan; 35 at Greens Beach, Marrawah; and 11 at Black River Beach, Stanley. The remaining whales stranded singly along the coastline. Three mass strandings of this species in such close temporal proximity have not been reported in this area before, and this is the first time that data have been comprehensively collected from complete or near-complete groups of sperm whales from Tasmanian waters. Adult females dominated the three stranding groups. Total lengths ranged from 417 to 1,200 cm and ages ranged from 0.75 to 64 yr. Four females were lactating and four fetuses were found amongst the groups. Stomach contents were dominated by pelagic cephalopods.     

Overview of sperm whale Physeter macrocephalus mortality events in the Adriatic Sea, 1555–2009

• 1 In the Mediterranean Sea, the sperm whale Physeter macrocephalus is one of eight regular cetacean species. Poor knowledge of its ecology and status, together with suspected decline in numbers, make studies of historical and present occurrence especially relevant. Long‐term time series of stranding events are the most reliable data to provide a scientific framework for testing hypotheses that seek to explain the mechanisms responsible for cetacean strandings.
• 2 We present a comprehensive overview of cases of sperm whale mortality and human response to such events encompassing five centuries (1555–2009) within a portion of the Mediterranean Sea that offers a wealth of historical information – the Adriatic Sea.
• 3 A total of 36 mortality events were validated, involving 68 animals. Two findings of skeletal materials are also reported. The geographic distribution of strandings within the basin clearly was uneven: 44% of records (n = 16) were clustered along a 280km portion of the western Adriatic coast. A relatively high number of mortality events occurred along gently sloping sandy beaches away from suitable sperm whale habitat.
• 4 Until the first half of the 20th century, live‐stranded animals were routinely killed: all but one cases with known human response elicited killing attempts. Starting from the 1980s, killing was replaced by efforts to rescue the animals.
• 5 Mass strandings of sperm whales have occurred since historical times in the Adriatic Sea. Mortality events involving multiple individuals accounted for at least 17% of the total sample (6 of 36 mortality events). At least 29% of live strandings (6 of 21) involved more than one individual.
• 6 This study contributes a long‐term dataset based on careful validation of historical information, suitable for hypothesis testing aimed at investigating spatial and temporal correlates of sperm whale strandings – particularly live strandings – as a clue to their causes.

     

Parasitism as a factor (?) in single strandings of southern California cetaceans

From 1970 to 1976 a total of 91 cetaceans was examined for parasites and associated pathology. Sixty of the animals were found stranded along a 100-mile section of southern California coastline while 31 were taken at sea. Parasites from 5 species of cetaceans are reported along with their possible role as a contributing factor in stranding behavior.     

Evaluating postintervention survival of free‐ranging odontocete cetaceans

Until recently, few data were available for evaluating postintervention survival of free‐ranging cetaceans receiving aid from humans through: rescue from stranding, with rehabilitation and release; rescue, rehabilitation and release of debilitated or entangled individuals that had not beached; rescue of entangled animals with immediate release; and rescue, transport, and release of out‐of‐habitat animals. Advances in medical diagnosis, husbandry and therapy have improved survival of rehabilitation cases, and advances in radio‐telemetry have improved postrelease monitoring. In total, 69 cases (1986–2010) were evaluated, involving 10 species of odontocete cetaceans with release data. Findings suggested a success criterion of surviving at least six weeks postrelease is useful in evaluating intervention strategies. No species had better success than others. Stranded beached cetaceans were less successful than free‐swimming rescued animals. Rehabilitated animals were less successful than those released without rehabilitation. Mass stranded dolphins fared better than single stranded animals. Old age, diminished hearing ability, and lack of maternal care were factors in several unsuccessful cases. Success is not clearly related to rehabilitation duration. Retaining healthy individuals from mass strandings until all animals are ready for release may reduce success for some. Transport durations for unsuccessful cases were greater than for successful cases.     

Factors Affecting Harp Seal (Pagophilus groenlandicus) Strandings in the Northwest Atlantic

The effects of climate change on high latitude regions are becoming increasingly evident, particularly in the rapid decline of sea ice cover in the Arctic. Many high latitude species dependent on sea ice are being forced to adapt to changing habitats. Harp seals (Pagophilus groenlandicus) are an indicator species for changing high-latitude ecosystems. This study analyzed multiple factors including ice cover, demographics, and genetic diversity, which could affect harp seal stranding rates along the eastern coast of the United States. Ice cover assessments were conducted for the month of February in the Gulf of St. Lawrence whelping region from 1991–2010 using remote sensing data, and harp seal stranding data were collected over the same time period. Genetic diversity, which may affect how quickly species can adapt to changing climates, was assessed using ten microsatellite markers to determine mean d ² in a subset of stranded and by-caught (presumably healthy) seals sampled along the northeast U.S. coast. Our study found a strong negative correlation (R ² = 0.49) between ice cover in the Gulf of St. Lawrence and yearling harp seal strandings, but found no relationship between sea ice conditions and adult strandings. Our analysis revealed that male seals stranded more frequently than females during the study period and that this relationship was strongest during light ice years. In contrast, we found no significant difference in mean d ² between stranded and by-caught harp seals. The results demonstrate that sea ice cover and demographic factors have a greater influence on harp seal stranding rates than genetic diversity, with only a little of the variance in mean d ² among stranded seals explained by ice cover. Any changes in these factors could have major implications for harp seals, and these findings should be considered in the development of future management plans for the Arctic that incorporate climate variability.     

Assessing the relationship between cetacean strandings (<Emphasis Type="Italic">Tursiops truncatus</Emphasis> and <Emphasis Type="Italic">Stenella coeruleoalba</Emphasis>) and fishery pressure indicators in Sicily (Mediterranean Sea) within the framework of the EU Habitats Directive

Cetacean strandings are a constant phenomenon that occurs on coastlines; mortality is related to several factors but commercial fishing is considered one of the main pressures, in the Mediterranean, that can impact small cetacean species such as common bottlenose dolphin (Tursiops truncatus) and striped dolphin (Stenella coeruleoalba). Since all eight species of cetaceans residing in the Mediterranean Sea are listed in the Habitats Directive, there is a legislative and management need to survey and report their conservation status every 6 years. The aim of this study was to assess the relationship, in Sicily, between strandings of two species and the fishery capacity, using records from 1995 to 2012. Positions and densities of all the strandings were compared with values of engine power from all the fishing vessels registered in 48 Sicilian ports. In addition, the relationship between strandings and the wild population at sea was investigated. Results showed that trends of fishing capacity and strandings both decreased, with a strong positive association. Trends were also confirmed when data were grouped into “6-year periods” or into different geographical sub-areas. Strandings were clustered near ports with higher fishing capacities; S. coeruleoalba records were distributed more homogenously along the coastline compared to T. truncatus, whose strandings were mostly distributed on the southern coastline, where the fishing capacity of bottom otter trawls was greater. The ratio between the two cetacean species was similar both for strandings and at-sea populations. Results show that fishing capacity is a pertinent indicator of pressure/threat to small cetacean species, and stranding records could complement at-sea data to assess population status within the framework of EU Directives.     

Assessing Disease and Mortality among Small Cetaceans Stranded at a World Heritage Site in Southern Brazil

Cetaceans are considered environmental sentinels and their health often reflects either anthropogenic or natural spatio-temporal disturbances. This study investigated the pathological findings and mortality of small cetaceans with the aim of detecting hazards and monitoring health trends in a high-biodiversity area. Between 2007 and 2012, 218 stranded cetaceans were recorded on the Paraná coast, southern Brazil. Fifty-seven (26.1%) of these animals, including 50 Sotalia guianensis, 2 Pontoporia blainvillei, 2 Stenella frontalis, 1 Stenella longirostris, 1 Tursiops truncatus and 1 Globicephala melas were necropsied and samples were collected for histopathology. Causes of death were determined in 46 of the 57 (80.7%) animals and most (30 or 65.2%) were ascribed to anthropogenic activities, including fisheries bycatch (28/30) and trauma (2/30). The remaining 16 fatalities were considered natural, and attributed to pneumonia (10/16), emaciation (3/16), septicemia (1/16), neonatal pathology (1/16) and choking via food obstruction (1/16). Irrespective of the cause, bronchointerstitial pneumonia, associated with parasitism, lymphadenitis and membranous glomerulonephritis were common findings among all fatalities. These results suggest, that while anthropogenic activities are a leading cause of cetacean strandings in Paraná, underlying pre-existing diseases may contribute towards deaths. Although the studied area is considered a biosphere reserve by UNESCO, complex anthropogenic and natural interactions might be occurring, increasing cetacean susceptibility to hazards. This study may help facilitate developing an effective conservation plan for coastal cetaceans focusing on reducing fisheries interactions, habitat degradation and pollution as mechanisms for ultimately increasing species resilience.