LONG-RANGE MOVEMENTS OF SOUTH ATLANTIC RIGHT WHALES EUBALAENA AUSTRALIS

Abstract: Movements of southern right whales between Gough Island and South Africa, and between Argentina and Tristan da Cunha, southern Brazil, and South Georgia are documented through matching of six photoidentified individuals. These include the resighting of a male in a mid-oceanic locality some 4,424 km away from (and 11 yr after) its last sighting in a coastal area where it had been seen in six of the preceding eight years, a female photographed in mid-Atlantic resighted with a calf in a coastal nursery area 2,769 km away, resightings of females with calves in different nursery areas 2,051 km apart in different years, and the first example of a link between a coastal nursery area and a feeding ground in high latitudes. The possible implications of these movements for estimates of calving interval and survival rate based on resightings in coastal waters are discussed. The potential for intermingling between populations on either side of the South Atlantic seems greater than was previously considered likely from a comparison of animals photographed in coastal waters.     

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.     

TRENDS IN THE INSHORE RIGHT WHALE POPULATION OFF SOUTH AFRICA, 1969–1987

Results of annual aerial surveys of the right whale population along the southern coast of South Africa from 1971 to 1987 are analysed. About 91.5% of cows with calves and 82% of unaccompanied adults on the South African coast in spring are found within the standard survey area, with some indications that the range is expanding up the west coast. In the nearshore region, most right whales (90%) are found within 1.85 km, and all cows with calves within 0.93 km, of the coast. Within the standard survey area, specific areas of concentration can be predictably identified, both for cows with calves and unaccompanied adults. Although total counts (and counts expressed per hour flown) have increased overall, by a best estimate of 6.8% (95% CL 4.6, 9.0) per year from 1971 to 1987, some concentration areas for both classes have failed to show an increase over the same time period. Photographic flights since 1979 have permitted the movements of individually identified adult females to be monitored between successive calves. In at least one concentration area for which no overall increase between 1971 and 1987 was apparent (Mossel Bay), a large net emigration rate was found, nearly all of which involved a shift to the main nursery area to the west, off De Hoop. Reasons for the dissimilar dynamics of different concentration areas are not yet known.     

Does disappearance mean extirpation? The case of right whales off Namibia

Right whales off Namibia were severely depleted by early 19th century whaling, and rarely featured in modern whaling catches in the 1920s. Aerial surveys of the Namibian coastline from 1978 and onwards revealed increasing numbers of right whales, but few cow‐calf pairs. Aerial surveys off South Africa since 2009 showed a major decline in the availability of animals without calves. Twenty individual matches were made between 94 whales photographed off Namibia/Northern Cape in 2003–2012 and 1,677 photographed off South Africa in 1979–2012. Eight were adult females that calved in South African waters, but only one was also seen with a calf off Namibia. Twelve out of 13 individuals off Namibia with distinctive dorsal pigmentation were first seen as calves off South Africa. These results strongly indicate connectivity between the two regions, while the presence off Namibia of three adult females from the South African population in the season in which they are believed to conceive suggests that there is unlikely to be any genetic differentiation between the two areas. We conclude that the reappearance of right whales off Namibia represents range expansion from South Africa rather than the survival of a few remnants of an originally separate stock.     

Characterization of tetranucleotide microsatellite loci and development and validation of multiplex reactions for the study of right whale species (genus Eubalaena)

A North Atlantic right whale (Eubalaena glacialis) genomic library was developed and screened with a (GATA)₈ probe to identify tetranucleotide microsatellite loci. Sixteen characterized loci were polymorphic in North Atlantic and/or South Atlantic (Eubalaena australis) right whales, 12 being polymorphic in E. glacialis, and 15 in E. australis. Fourteen of these were combined with 21 other previously identified loci for a suite of 35 loci which can be used to increase resolution of genetic analyses of these species. Multiplex reactions were developed for genotyping samples at these loci, providing a method that is rapid, reliable and cost‐effective.     

RATES AND POTENTIAL CAUSES OF MORTALITY IN NORTH ATLANTIC RIGHT WHALES (EUBALAENA GLACIALIS)

North Atlantic right whale mortality rates range from 2% to 17% over the first four years of life. Sources of mortality in this population include ship collisions, entanglements, and natural causes. A combined analysis of stranding data, entanglement records, and photographic information indicates that approximately one third of all right whale mortality is caused by human activities. Anthropogenic sources of right whale mortality may be a significant factor inhibiting growth in the North Atlantic population.     

Is there spatial segregation between reproductive groups of southern right whales along the coastline of southern Brazil?

Santa Catarina State, in southern Brazil, is an important breeding ground for the southern right whale and it is possible to record mother-calf pairs and unaccompanied adults that migrate to this coast to either give birth, mate, or socialize. From the geographical position of the sightings, spatial segregation was evaluated between mother-calf pairs and unaccompanied whales. Using GAM, we analyzed 15 years of aerial survey data from 2003 to 2018. The study area (780 km²) was divided into 500 × 500 m grid cells. Whale count per grid cell was modeled using a set of explanatory variables. The explanatory variables of latitude, coast distance, seabed, and maximum SST were selected for both classes. However, coast type was also selected for unaccompanied whales, while coast linearity and bathymetric slope were additionally selected for mother-calf pairs. The response curves fitted by models indicated a certain degree of spatial segregation, by which mother-calf pairs remained closer to the coast, where the curve peak is reached at 500 m from the coast, compared to unaccompanied whales where the curve peaked near 1,000 m from the coast. Also, unaccompanied whales more frequently appeared in the southern boundaries of the study area, at latitudes south from 28.4°S.