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Gray whale (Eschrichtius robustus) sighting in Namibia (SE Atlantic) - first record for Southern Hemisphere

  • University of Cape Town/ University of Stellenbosch


Gray whale (Eschrichtius robustus) sighting in
Namibia (SE Atlantic) – first record for Southern
1. Mammal Research Institute, University of Pretoria, Pretoria, South Africa
2. Namibian Dolphin Project, Walvis Bay, Namibia
* Corresponding author:
A gray whale (Eschrichtius robustus) has been photographed in Walvis Bay, Namibia (SE Atlantic - 23°
53’ S 14° 28’ E). The animal was first seen on 04 May 2013, species was confirmed by photographs on
09 May 2013 and it has been resident around the peninsula forming the western boundary of Walvis
Bay since this time until 09 June 2013 (day of submission of paper). Comparison of photographs of the
gray whale seen in the Mediterranean sea in 2010 (Scheinin et al., 2011) clearly shows this to be a
different animal. The animal is small, estimated 11-13m in total length and is clearly skinny scoring
poorly on body condition indices for the species. A biopsy skin sample has been collected by the
authors and future analysis will allow for determination of sex and source population.
Gray whales (Eschristius robustus) historically occupied both the North Pacific and North Atlantic
Oceans. The North Atlantic (NA) population was whaled to extinction sometime around the early
1700s (Lindquist, 2000 in Scheinin et al., 2011). The southern most records in the NA are on the coast
of Florida, USA (western NA) and southern England (eastern NA) (see Scheinin et al., 2011). Gray
whales still inhabit the North Pacific (NP) with two recognised populations inhabiting the eastern and
western sides of the Ocean. The Eastern North Pacific population (ENP) ranges from breeding areas off
Baja California in Mexico to feeding areas in the Bering, Beaufort and Chucki Seas west and north of
Alaska (Weller et al., 2012). The Western North Pacific population (WNP) feeds in the Okhotsk Sea
off Sakhalin Island, Russia and in the south western Bering Sea. It’s breeding areas are not well known
but animals may migrate through waters close to the Korean Peninsula and Japan en route to a possible
breeding location in the South China Sea (see Weller et al., 2012). The ENP population has recovered
to historic carrying capacity with the population size in the region of 19 000 individuals in 2007 (Laake
et al., 2009). In contrast the WNP population is one of the smallest of any cetacean population globally
and regarded as ‘Critically Endangered’ (Reilly et al., 2012) with the estimated population size of only
130 individuals (90% Bayesian CI = 120-142) in 2008 (Cooke et al., 2008).
The two North Pacific gray whale populations are significantly differentiated by both mtDNA and
nuDNA (Lang, 2010; Lang et al., 2011). However recent observations of two individuals satellite
tagged in the WNP identified unambiguous movement of animals from the WNP population to the
ENP (Mate et al., 2011; IUCN, 2012). Subsequent comparison of photo-ID catalogues between the
ENP and WNP populations (e.g. Weller et al., 2012) has revealed considerable exchange of individuals
(n = 23 or ~15% of the WNP population) between these two areas. Increasingly, gray whales are being
seen outside of their expected ranges, particularly around the WNP which has been historically less
well studied. Sightings of gray whales have been made in the Laptev Sea and near Frans Josef Land to
the north of continental Russia, well within range of the historical Atlantic population (Ilyashenko,
2012) and suggesting that gray whales may be using an Arctic route to travel between the North Pacific
and North Atlantic Oceans. Indeed, on the 08 May 2010 a single gray whale was photographed off the
coast of Turkey in the eastern Mediterranean Sea and 22 days later photographically re-identified off
the southern coast of Spain (Scheinin et al., 2011). This is the first confirmed sighting of a gray whale
in the Mediterranean Sea, and the first record of a gray whale in the North Atlantic since the 1700s.
Furthermore, this record represents the longest vagrancy of any mammal to date, being seen in the
region of 22 000 23 500 km from their closest known population, depending the route used between
the ENP and Turkey (Scheinin et al., 2011).
On the 04 May 2013 a gray whale was seen in Walvis Bay, Namibia (23° 53’ S 14° 28’ E; Fig. 1) by
marine tour operators. The whale was reported to local researchers soon after (authors SE and TG
Namibian Dolphin Project, who were offsite at the time) and the species was confirmed from
photographs taken on the 09 and 11 May 2012 (Fig 2). The whale has been seen by tour operators
almost every day since this time until the 09 June 2013 (last available data prior to submission). On 06
June 2013, the NDP team were able to collect further confirmatory photographs and a skin sample from
the animal. The whale was estimated visually (relative to the size of the boat) to be between 11-13m in
total length, suggesting it may be a juvenile.
Concern was raised by researchers familiar with gray whales that the animal appeared in poor body
condition (P. Clapham, Jim Darling pers comm.). Using the photographs to assess body condition, the
animal would score a 1 (poorest of 3 states) for post-cranial condition and a 1 (of 2) for lateral flank
condition on the body condition scale developed by Bradford et al. (2008); it was not possible to assess
scapular condition.
All sightings of the whale have occurred near to shore (<1km) around (both east and west of) Pelican
Point, the sand spit forming the west side of Walvis Bay (Fig. 1). Although no clear signs of feeding
were observed by the research team on the 06 June 2013 (e.g. no patrolling through patches of prey,
lunge feeding or mud plumes resulting from bottom feeding), the whale has most often been reported to
be milling in a small area <1km2 when encountered by tour operators. The area around Pelican Point is
one where mixing occurs between currents leaving the bay and oceanic waters to the west which
appears to create an area of high productivity. Both Heaviside’s dolphins (Cephalorhynchus heavisidii)
and common bottlenose dolphins (Tursiops truncatus) are often seen feeding in this area (Elwen et al.,
2011, in review.; Leeney et al., 2011) presumably on teleost fish. Although no data are available on the
density of smaller prey such as krill or copepods around Pelican Point, krill has been seen washed up
on the beach along this area suggesting prey suitable for the gray whale is available in the area.
However, the bottom type in this area is a thick black mud, low in oxygen and rich in sulphur and
unlikely to provide much nutrition for the whale.
To our knowledge, this is the first report of a gray whale in the South Atlantic and Southern
Hemisphere as a whole, and it is likely one of the longest distances moved by any mammal (cf.
Scheinin et al., 2011). Given the relative sizes of the ENP and WNP populations, it is most probable
that the whale originates from the ENP population. Analysis of the genetic sample and a thorough
comparison with existing catalogues should provide further insight in the origin of this whale.
Although it may be in poor body condition, its residency for over a month within an area of known
high productivity suggests it is feeding in the Walvis Bay area.
The Namibian Dolphin Project Research team (SE, TG, NT, RHL) would like to thank the Willi
Deetleefs for reporting the whale, Jeanne Meintjies for confirming date records, Orlanda Sardinha and
John Paterson for sharing their photographs with us and Jean-Paul Roux (Ministry of Fisheries and
Marine Resources) for his support of our work. The NDP has been funded by a series of small grants
from the Rufford Small Grants Foundation, British Ecological Society, the Mohammed Bin Zayed
Foundation and the Nedbank Go Green Fund of Namibia. Research was conducted with permission
from the Namibian Ministry of Fisheries and Marine Resources. Thanks to Tim Collins for presenting
this paper to the IWC
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Figure 1. Walvis Bay, Namibia showing bathymetry, the location of the harbour, the Pelican
Point peninsula and the area (blue line) where all sighting of the gray whale have occurred to
Figure 2. Images showing the head and left flank of the gray whale encountered in Walvis Bay
Namibia on the day it was photographically confirmed (05 May 2013) and one month later (06
June 2013)
... Today, the Gray whale does not occur along the South Africa coast potentially due to the colder sea surface temperatures of the oceans off the coast today and the change in the coastal configuration. There was a sighting of a young Gray whale (Eschrichtius robustus) (11-13 m) off the Namibian coast in the southeastern Atlantic in 2013 which is the first sighting of Eschrichtius in the south Atlantic and the southern hemisphere (Elwen and Gridley 2013). The animal was in a relatively poor condition but was sighted in the highly productive region of Walvis Bay area and was thought to be feeding (Elwen and Gridley 2013). ...
... There was a sighting of a young Gray whale (Eschrichtius robustus) (11-13 m) off the Namibian coast in the southeastern Atlantic in 2013 which is the first sighting of Eschrichtius in the south Atlantic and the southern hemisphere (Elwen and Gridley 2013). The animal was in a relatively poor condition but was sighted in the highly productive region of Walvis Bay area and was thought to be feeding (Elwen and Gridley 2013). Although further analysis was still to be carried out it was thought that this individual originated in ENP (Elwen and Gridley 2013). ...
... The animal was in a relatively poor condition but was sighted in the highly productive region of Walvis Bay area and was thought to be feeding (Elwen and Gridley 2013). Although further analysis was still to be carried out it was thought that this individual originated in ENP (Elwen and Gridley 2013). ...
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Hondeklip Bay is a Zanclean, early Pliocene, locality in the Northern Cape Province of South Africa. Cetacean fauna from Hondeklip Bay includes the mysticetes: Balaenopteridae indet. (sp. 1), cf. Eschrichtius sp., Balaenopteridae indet., cf. Plesiobalaenoptera, Balaenidae indet., and the odontocetes: Physeteroidea indet, cf. Livyatan, and an unidentified neonate delphinid. Hondeklip shares a seal and cetacean taxon with Langebaanweg, which is 430 km to the south. Cf. Eschrichtius sp. from Hondeklip Bay is the first description of the taxon from South Africa and it also has the first balaenid described from South Africa. Its cetacean fauna also strengthens the links of South Africa’s west coast with the Atlantic of Europe and North America, and eastern North and South Pacific.
... In some baleen whales, there can be vast distances between suitable seasonal breeding and feeding habitats, necessitating long annual migrations, and the grey whale (Eschrichtius robustus) is an extreme example (known to migrate as much as 8500 km between breeding and feeding grounds). Here, we investigate the origins of the first grey whale ever recorded in the South Atlantic [1] to better understand the process and context of long-distance migrations. ...
... Photographic documentation (e.g. figure 1) suggested poor body condition and although it remained in a very localized area, no feeding was clearly observed [1]. We sequenced the nuclear genome (to 19.8X coverage, also providing the mitochondrial genome; NCBI accession no. ...
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We use genomics to identify the natal origin of a grey whale found in the South Atlantic, at least 20 000 km from the species core range (halfway around the world). The data indicate an origin in the North Pacific, possibly from the endangered western North Pacific population, thought to include only approximately 200 individuals. This contributes to our understanding of Atlantic sightings of this species known primarily from the North Pacific, and could have conservation implications if grey whales have the potential for essentially global dispersion. More broadly, documenting and understanding rare extreme migration events have potential implications for the understanding of how a species may be able to respond to global change.
... The grey whale, Eschrichtius robustus, once inhabited both the Pacific and Atlantic Oceans. Originally described from fossil remains from Gräso, Sweden by Lilljeborg (1861), the species has since been extirpated from the North Atlantic and is today found only in the Pacific Ocean (Jefferson et al. 2015), although two vagrants have been recorded recently in the Atlantic (Scheinin et al. 2011;Elwen & Gridley 2013) and a further live animal was recorded off Rabat, Morocco in March 2021. Radiocarbon dating and historical accounts suggest that the species was extirpated from the North Atlantic within the last 300 years, probably because of human hunting (Mead & Mitchell 1984;Bryant 1995, Kitchener et al. 2008. ...
The grey whale, Eschrichtius robustus, occurred in the Atlantic Ocean until c.300 years ago, having been extirpated probably owing to hunting by humans. Three records of fossil grey whale bones were known previously from Cornwall and Devon in the 18th and 19th centuries. Morphological identification to species of cetacean remains from palaeontological and archaeological sites is problematic, because the bones are often fragmentary or have been modified by humans. The application of ancient DNA analysis and collagen fingerprinting (ZooMS) allows the identification of fragmentary and modified cetacean bone to species and/or generic level, thus offering new opportunities to understand the exploitation of cetaceans by human coastal communities. Analyses of cetacean bone from Orkney and Shetland have identified for the first time the presence of grey whale at archaeological sites in Scotland, extending the geographical range of records in Britain. These findings confirm for the first time that the seas around Scotland were part of the range of the grey whale in the eastern North Atlantic, thereby linking records of this species (from southern Scandinavia, the Northern Isles of and southwest Britain, the southern North Sea and Netherlands, to the Iberian Peninsula and Morocco) over a similar latitudinal range that the species still occupies in the Pacific Ocean.
... This movement could be a case of overshooting on a mis-orientated or reverse migration. This is a phenomenon well documented in birds (Howell et al., 2014) and may help define other extralimital occurrences of cetaceans such as an Antarctic minke whale (Balaenoptera bonaerensis) reported in the North Atlantic (Glover et al., 2010) and gray whales (Eschrichtius robustus) reported in the North and South Atlantic, respectively (Elwen & Gridley, 2013;Scheinin et al., 2011). The drivers of such movements are varied and largely unknown, but temporary yet significant disturbances to the Earth's magnetosphere caused by solar storms are known to disrupt navigation in cetaceans (Ferrari, 2017). ...
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Bowhead whales occur in the Arctic year-round. Their movements are largely correlated with seasonal expansions and reductions of sea ice, but a few recent extralimital sightings have occurred in the eastern and western North Atlantic and one was also documented in the western North Pacific over 50 years ago. Here we present details of a juvenile bowhead whale that was photographed and filmed from above and below the water while it was skim-feeding in Caamaño Sound, BC, Canada on May 31, 2016. This sighting occurred over 2000 km southeast from the nearest known range for this species in the Bering Sea at a time that most bowhead whales in that region would have been migrating northeast. This sighting represents the first and only documentation of a bowhead whale in the eastern North Pacific to date.
... The opening up of the Arctic Ocean between the North Pacific and North Atlantic, may have led to the grey whale occurring again in the Atlantic after a gap of almost four hundred years, with confirmed sightings of the species in the Mediterranean Sea off Israel and Spain, in May-June 2010 (Scheinin et al., 2011), and off Namibia in South-west Africa in May and June 2013 (Elwen and Gridley, 2013). ...
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... For example, Caperea, previously only known from the Southern Hemisphere, surprisingly occurred in the Northern Hemisphere as well [39]; Herpetocetus, once thought to exist only prior to the Pleistocene, unexpectedly survived well into the Pleistocene [40]; Eschrichtius, unable to recover its western Pacific population partly due to the unknown breeding site, likely used southern part of the Taiwan Strait for breeding and nursing calves [22]; and two extremely large species, blue and fin whales (Balaenoptera musculus and B. physalus), were first discovered and adequately documented from the Pleistocene [7,41], further complicating their evolutionary history as B. musculus × physalus pair represents one of the most common hybridizations in marine mammals [42]. As climate change proceeds and unusual occurrences seem to happen more frequently [43][44][45], more effort into searching Pleistocene sediments, in both overlooked [46] or even well-sampled areas [47], should bring more surprises alive and guide us how to respond to global climate change. ...
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Abstract Current patterns of biological distribution result from the deep past. Of particular interest, some closely related species appear at high latitudes of both hemispheres, but not in between, a pattern known as antitropical distribution. However, the timing, pathway, and drivers of antitropical distributions remain mostly unknown. Here we describe a new fossil, a left tympanic bulla (part of the ear bones), from the Middle/Late Pleistocene (0.78–0.01 mya, but not excluding the possibility of Holocene in age, as the specimen was dredged from the sea bottom and the geological horizon remains uncertain) of Taiwan. The tympanic bulla is diagnostic in baleen whales, and this specimen shows morphological features that are identical to extant Eubalaena, including: relatively large size (the anteroposterior length is 117 mm); rectangular outline in medial view; short anterior lobe, judging from the remaining of the lateral furrow; squared anterior margin; prominent transverse crease on the involucrum; transversely compressed in anterior view; well-developed and rounded outer lip; and parallel involucral and main ridges. Although incomplete, the morphological characters and overall similarity to extant Eubalaena allow a reliable taxonomic assignment to Eubalaena sp. The occurrence of a Pleistocene Eubalaena on the southern margin of the western North Pacific is the first balaenid fossil evidence indicative of the biotic interchange between two hemispheres leading to the origin of antitropical distribution in the Pleistocene; alternatively, this specimen might merely represent an extra-limital record of the North Pacific Eubalaena. Furthermore, this find suggests that the Eubalaena interchange, being one of the largest species displaying antitropical distribution pairs in the history of life, likely took place along the western Pacific. Notably, this does not preclude the Eubalaena interchange from other routes, such as the eastern Pacific or the Atlantic Ocean, and future finds should test the scenario for the biotic interchange between Northern and Southern Hemispheres of Eubalaena.
... We suspect this could be an example of an extralimital occurrence of H. ampullatus. Considering the recent sightings of the gray whales in the Mediterranean or in Namibia 36,37 , the possibility of vagrant individual navigate through the Northwest passage during summer should be studied. ...
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... Like the pygmy right whale, the gray whale Eschrichtius robustus is restricted to a single hemispherein this case, the North Pacific, with the North Atlantic population having gone extinct in the eighteenth century [8]. Likewise, all known fossil eschrichtiids are also from the Northern Hemisphere [9][10][11][12][13][14]. Yet, there was a single sighting of a gray whale in the Southern Hemisphere [15] in Namibia, around latitude 13°S. This remarkable extralimital occurrence is comparable to the Gambia Caperea and, along with additional examples of equatorial crossings by other mysticete species [16,17]), suggesting that faunal exchange between both hemispheres may be more frequent, or may be in the process of becoming more frequent, than commonly thought. ...
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... Although recent studies have elucidated their paleodiversity (Bisconti and Varola, 2006;Bisconti, 2008;Whitmore and Kaltenbach, 2008), the fossil record of the Eschrichtiidae is relatively sparse, and their evolutionary history remains unclear. The modern gray whale, Eschrichtius robustus, is presently found only in the North Pacific, though vagrant individuals have been sighted outside its established ranges (Scheinin et al., 2011;Elwen and Gridley, 2013). Three modern gray whale populations have been recognized: a large eastern North Pacific stock, a very small, remnant western North Pacific stock, and an extinct Atlantic stock (Rice, 1998;Jefferson et al., 2008). ...
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Whales and dolphins (cetaceans) are streamlined mammals that spend all their lives in water. Their earliest ancestors evolved more than 50 million years ago from even‐toed hoofed mammals like hippos and cows. Modern cetaceans range through all oceans and from the tropics to the polar regions. Even so, they belong to just two major clades: baleen whales (mysticetes) and toothed whales (odontocetes). Mysticetes include the largest animals on Earth and are characterised by keratinous, comb‐like baleen plates which they use to filter feed on tiny prey. By contrast, odontocetes use a form of biosonar (echolocation) to target single fish and squid. The vast majority of the 92 recognised living species belong to just three families: oceanic dolphins, beaked whales and rorquals. Key Concepts Whales and dolphins evolved from even‐toed hoofed mammals. They spend all their lives in water and show key aquatic adaptations like streamlined bodies, baleen, echolocation and suction feeding. They include the largest and, apart from humans, the brainiest animals on Earth. Most belong to just three major families: oceanic dolphins, beaked whales and rorquals. Advances in fossil sampling are beginning to reveal global patterns in whale evolution, including a major turnover event around 23 Ma.
Conference Paper
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Previous studies have documented genetic differentiation between gray whales in the eastern and western North Pacific on the basis of both mtDNA haplotype and microsatellite allele frequencies. In these studies, the eastern North Pacific (ENP) population of gray whales has been represented by a sample set comprised primarily of samples from animals that stranded along the migratory route. Recent studies assessing population substructuring of gray whales within the ENP have resulted in the collection and analysis of additional samples from ENP gray whales feeding north of the Aleutian Islands (n=106 sampled individuals). Here we update previous assessments of genetic differentiation between ENP and western North Pacific (WNP) gray whales using these additional ENP samples and samples collected from whales (n=142 individuals) feeding off the northeastern coast of Sakhalin Island, Russia. In addition, comparison of the mtDNA haplotype, sex, and genotypes (8 to 13 loci) of all analyzed samples (n=380) was used to identify samples with identical genetic profiles, and these genetic matches were used to infer movements of individuals between areas. Consistent with the results of previous studies, significant levels of differentiation were found between WNP and ENP gray whales using both mitochondrial (e.g., Sakhalin versus Chukotka, FST = 0.082, p<0.0001; ФST = 0.037, p<0.001) and nuclear (e.g., Sakhalin versus Chukotka, FST =0.010, p=0.001; FST' = 0.037, p=0.001) markers (n=8 loci). Seven pairs of samples shared identical genetic profiles, including one match between an animal sampled off the coast of San Diego and an animal taken in the Chukotka hunt, four matches between animals biopsied on the Sakhalin feeding ground and animals biopsied off southeastern Kamchatka, and two matches between animals biopsied on the Sakhalin feeding ground and animals biopsied off the coast of southern California. While the significant levels of genetic differentiation support demographic independence and a degree of reproductive isolation between whales feeding in the WNP and the ENP, the putative movements detected here, in combination with information derived from photo-identification comparisons and telemetry studies, suggest that some of the animals summering off Sakhalin overwinter in the ENP in at least some years. Given that recent records document gray whales in Japanese waters during winter and spring, these results suggest that population structure in gray whales may be more complex than previously believed, such that not all of the animals which feed off Sakhalin share a common wintering ground, or that some animals may switch between wintering grounds. Thus, the number of gray whales remaining in the WNP year-round may be lower than previously thought, highlighting the need for additional studies focusing on identifying migratory routes and wintering ground(s) used by gray whales in the WNP
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Brief information on the biology and conservation status of Gray whales in the coastal waters of Chukotka is summarized
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The western North Pacific (WNP) population of gray whales Eschrichtius robustus is redlisted by the IUCN as Critically Endangered. As part of a long-term study on whales off Sakhalin Island, Russia, photo-catalog comparisons of gray whales in the western and eastern North Pacific (ENP) were undertaken to assess population mixing. These comparisons in -volved 2 ap proaches: (1) a systematic comparison of the WNP 'Sakhalin Catalog' to an ENP 'Pacific Northwest Catalog' that consisted of images from the northwest coast of North America and (2) a non-systematic comparison of the WNP 'Sakhalin Catalog' to an ENP 'Laguna San Ignacio Catalog' that consisted of images from central Baja California, Mexico. The Sakhalin to Pacific Northwest comparison consisted of 181 and 1064 whales, respectively, and resulted in 6 matches (3 males, 2 females, and 1 whale of unknown sex). All sightings of 'Sakhalin whales' in the Pacific Northwest occurred off southern Vancouver Island, British Co -lum bia, Canada. The Sakhalin to Laguna San Ignacio comparison consisted of 181 and 2514 whales, respectively, and re sulted in 4 matches (2 males and 2 fe -males). As the Pacific Northwest and Laguna San Ignacio catalogs represent only a small fraction of the total estimated number of individuals in the ENP population (~19 000), it is likely that more WNP/ENP ex change has occurred than was detected by these photo-catalog comparisons. Although these matches provide new records of movements between the WNP and ENP, recent observations of gray whales off Japan and China suggest that not all gray whales identified in the WNP share a common wintering ground.
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The western gray whale population (Eschrichtius robustus) is critically endangered and its potential for recovery is uncertain. Along with other natural and anthropogenic threats, western gray whales are susceptible to nutritional stress, known from regular observations of individual whales in compromised body condition. Thus, the ability to visually quantify the relative body condition of free-ranging western gray whales and evaluate how this condition varies seasonally and annually is needed. A photo- identification study of western gray whales on their feeding ground off the northeastern coast of Sakhalin Island, Russia, produced a large dataset of digital, film, and video images of 150 identified individuals from 1994 to 2005. These images were utilized to visually assess the body condition (i.e., good, fair, poor) of western gray whales by evaluating the relative amount of subcutaneous fat in three body regions presumed to reflect reductions in body condition. Multinomial logistic regression for ordinal responses was used to evaluate the effects of year, month, whale class, and sex on the body condition of western gray whales. Although the correlation between observations of individual whales has not yet been accounted for, significant findings of the analysis indicate that: 1) the body condition of whales varied annually and seasonally; 2) the body condition of whales improved as each feeding season progressed; and 3) lactating females were in relatively poorer body condition nursing calves in comparatively better body condition. Additional work is needed to refine the statistical analysis. Investigating the causes and consequences of compromised body condition in western gray whales is important for understanding the health and viability of this population.
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A population assessment of the western gray whale (Eschrichtius robustus) was conducted using the photoidentification data collected off Sakhalin Island under the joint Russia-U.S. programme from 1994 to 2005. This is an update of the assessment by Reeves et al (2005) which used data up to 2003, fitted to the same, individually-based population model. New median estimates of key population parameters (with 90% Bayesian confidence intervals) are 0.986 (0.975 - 0.995) for the adult survival rate; 0.72 (0.60 - 0.83) for the survival rate from calf to yearling; 3.0% per annum (2.1% - 4.2%) for the average annual rate of population increase over 1994-2005; 0.43 (0.37 - 0.50) for the female sex ratio and 122 whales (113 - 131) for the 1+ (non-calf) population size in 2006. The updated assessment is more optimistic than the Reeves et al assessment. This is mainly due to reduced calving intervals observed in recent years, implying a higher reproductive rate. The modal calving interval has shortened from 3 years to 2 years in the most recent seasons, which is consistent with reduced disturbance from industrial activity during 2002-04. Forward projections of the population model to 2030, assuming no additional mortality or disturbance to reproduction, indicate a high probability (>99%) of population increase. Three whales (all female) were killed in fishing nets on the coast of Japan in 2005 during the northward migration. Projections of the female population incorporating extra mortality at the 2005 level indicate a high probability (~75%) of population decline and a substantial risk (>25%) of extirpation by 2030. It is important to avoid any further human-caused deaths in this depleted population.
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Hydrogen sulphide eruptions with their typical turquoise discolorations at the water surface are a unique phenomenon along the Namibian coastline. The remote sensing techniques of ocean colour sensors and microwave scatterometers were used for the investigation of such events. The studies with ocean colour sensors showed that the turquoise discolorations near the Namibian coast were neither linked to dust deposition into the water column by desert storms nor to the reflection of bright material in shallow water areas. In addition, other coloured marine events like algae blooms and river outflows were differentiable from the hydrogen sulphide eruptions by their special optical properties. Quasi-true colour images and spectral identification methods were utilised to monitor and investigate the spatial and temporal distribution of sulphide events. In the past years, they were sometimes and locally limited discovered. Newest remote sensing observations including our own investigations have established that the occurrence of sulphide events is more frequent and longer lasting. The north-westerly direction of propagation and their velocity between 12 cm s-1 and 15 cm s1 were derived from an event on 14 April 2004. Lastly, the microwave scatterometer remote sensing was applied to investigate the relation of sulphide events to oceanographic conditions. The events from May 2004 were clearly related to strong coastal upwelling.
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Static acoustic monitoring is a cost-effective, low-effort means of gathering large datasets on echolocation click characteristics and habi- tat use by odontocetes. Heaviside’s dolphins (Cephalorhynchus heavisidii) were monitored using an acoustic monitoring unit, the T-POD, in July 2008 at a site of known high abundance for this species in Walvis Bay, Namibia. The T-POD successfully detected clicks from Heaviside’s dol- phins, and these clicks were detected in the 120 to 140 kHz frequency range. A distinct diel pattern to the hourly mean inter-click interval was observed, with higher values during daylight hours than at night, suggesting that click trains are produced at faster rates at night time. There was no apparent diel pattern in the proportion of buzz trains pro- duced, however. A diel pattern in click activity was observed, with many more detection-positive minutes per hour recorded between dusk and dawn, and vocalization activity dropping to low levels in the middle of the day. This corresponded with visual observations made on abundance of dolphins in the study area. These results suggest that Heaviside’s dolphins use this site primar- ily during the night. Static acoustic monitoring proved to be an effective technique for monitoring patterns of habitat use by Heaviside’s dolphins.
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On 8 May 2010, a gray whale was sighted off the Israeli Mediterranean shore and twenty-two days later, the same individual was sighted in Spanish Mediterranean waters. Since gray whales were last recorded in the North Atlantic in the 1700s, these sightings prompted much speculation about this whale's population origin. Here, we consider three hypotheses for the origin of this individual: (1) it represents a vagrant individual from the larger extant population of gray whales found in the eastern North Pacific; (2) it represents a vagrant individual from the smaller extant population found in the western North Pacific; or (3) it represents an individual from the previously thought extinct North Atlantic population. We believe that the first is the most likely, based on current population sizes, on known summer distributions, on the extent of cetacean monitoring in the North Atlantic and on the results of a performed route analysis. While it is difficult to draw conclusions from such singular events, the occurrence of this individual in the Mediterranean coincides with a shrinking of Arctic Sea ice due to climate change and suggests that climate change may allow gray whales to re-colonize the North Atlantic as ice and temperature barriers to mixing between northern North Atlantic and North Pacific biomes are reduced. Such mixing, if it were to become widespread, would have implications for many aspects of the marine conservation and ecology of these two regions.
Conventional wisdom has held that eruptions of toxic hydrogen sulphide that occur from time to time in the ocean off southwestern Africa were rather isolated near-coastal features, limited both in extent and in ecosystem-scale consequences. Now, however, it has become possible to identify sulphide outbreaks by satellite remote sensing. This new capability appears to lead to a complete revision of the conventional view, with some eruption episodes being observed to affect areas of ocean surface exceeding 20,000 km2. The occurrences are also seen to be more frequent and longer lasting than previously supposed. Example sequences of Sea-viewing Wide Field of View (SeaWiFS) images are presented to indicate general classes of eruption types that are observed and to support discussion of potential eruption mechanisms. Certain methodological problems in interpreting effects on local productivity are outlined. Spatial configurations of eruptions indicate that simple upward advection in the upwelling process may not be a sufficient explanation for the range of eruption characteristics experienced. Eruptions seem often to be coincident with one of two contrasting types of atmospheric weather situation: either (1) increased intensity of wind driven coastal upwelling, or (2) indications of passage of a low pressure weather cell (e.g. interruption of coastal upwelling, sudden warming of the sea surface, rainfall in the hinterland). Such a pattern may imply that related lowering of hydrostatic pressure at depth may tend to trigger incipient eruptions. It also suggests an episodic mechanism driven by the buoyancy introduced by the effervescence of gases trapped by hydrostatic pressure within the sea-floor sediments. Connotations of these phenomena to the local ecology and to that of the entire Benguela Current regional ecosystem would appear to be major. Their relevance to the valuable but extremely variable fishery resource populations of the region, which have undergone drastic declines in recent decades, is likely to be high.