Although humpback whales are among the best-studied of the large whales, population boundaries in the Southern Hemisphere (SH) have remained largely untested. We assess population structure of SH humpback whales using 1,527 samples collected from whales at fourteen sampling sites within the Southwestern and Southeastern Atlantic, the Southwestern Indian Ocean, and Northern Indian Ocean (Breeding Stocks A, B, C and X, respectively). Evaluation of mtDNA population structure and migration rates was carried out under different statistical frameworks. Using all genetic evidence, the results suggest significant degrees of population structure between all ocean basins, with the Southwestern and Northern Indian Ocean most differentiated from each other. Effective migration rates were highest between the Southeastern Atlantic and the Southwestern Indian Ocean, followed by rates within the Southeastern Atlantic, and the lowest between the Southwestern and Northern Indian Ocean. At finer scales, very low gene flow was detected between the two neighbouring sub-regions in the Southeastern Atlantic, compared to high gene flow for whales within the Southwestern Indian Ocean. Our genetic results support the current management designations proposed by the International Whaling Commission of Breeding Stocks A, B, C, and X as four strongly structured populations. The population structure patterns found in this study are likely to have been influenced by a combination of long-term maternally directed fidelity of migratory destinations, along with other ecological and oceanographic features in the region.
A total of 2 077 records of approximately 49 000 small cetaceans, including dedicated and incidental sightings and specimens, was analysed to define distribution patterns of the 28 species found within southern African waters. Distribution analyses reveal distinct component patterns, including cosmopolitan (found in all waters) and pelagic cosmopolitan (found in all pelagic waters) components, tropical, subtropical and warm temperate components of the Agulhas Current system, an Agulhas Bank component, a South and East Coast inshore component, and West Coast neritic and pelagic components. While the offshore distribution appears to be determined by water depth, possibly through distribution of the principal prey, longshore distribution appears to be determined by water temperature. The high diversity of small cetacean species found within the relatively small study region results from the wide range of zoogeographic components present. These components arise from the wide range of water temperature resulting from the warm Agulhas Current and the upwelling Benguela system.Altesaam 2 077 boekstawings van sowat 49 000 klein walvisagtiges, doelgerigte en toevallige waarnemings en eksemplare ingesluit, is ontleed om die verspreidingpatrone van die 28 spesies wat binne Suider-Afrikaanse waters aangetref word, te omskryf. Verspreidingsontledings toon duidelike patrone van komponente, met inbegrip van kosmopolitiese (in alle waters aangetref) en pelagies kosmopolitiese (in alle pelagiese waters) komponente, tropiese, subtropiese en warmgematigde komponente van die Agulhasslroomstelsel, 'n Agulhasbankkomponent, 'n Suidkus-en Ooskus-aanlandige komponent, en Weskus-neritiese en pelagiese komponente. Die aflandige verspreiding word stellig deur waterdiepte bepaal, moontlik deur die verspreiding van die hoofprooi, maar kuslangse verspreiding word skynbaar deur watertemperatuur bepaal. Die groot verskeidenheid van klein walvisspesies wat binne die betreklik klein slUdiegebied gevind word, is die gevolg van
Engraulis capensis (Gilchrist) is capable of both filter and particulate feeding, the latter being the dominant mode. Food concentrations required to initiate filter feeding were inversely related to particle size. Turning rate, swimming speed and feeding mode also depended on prey size. The anchovy switched from filtering to biting at a threshold prey size of 0.710 to 0.720 mm; the feeding mode employed by the fish on prey approximating this size depended upon prey concentration. Biting clearance rates were greater than those for filtering, and the fish fed at maximum rate over most of their prey size spectrum. These results indicate that E. capensis had adapted its feeding behaviour to maximise food intake and to minimise energy expenditure. The selective grazing of E. capensis may have a significant effect on the structure of its prey communities.
Between 5 October and 19 November 1993, 62 sightings of 155 humpback whales were made from the lighthouse at Cape Columbine South Afnca, in 3 episodes about 9 d apart For 59 groups tracked by theodolite the average d~s t a n c e offshore peaked at 2 to 2 5 km Independent information on offshore distribution was o b t a~n e d from 1112 km searched by a ski-boat in the vlclnity of Cape Columbine from which the proportions of humpback lvhale gioups In 2 strata (0 to 5 and > 5 km) fiom the shore as seen from the lighthouse did not difter from those evpected from the boat data Net directions of movement fol 51 gioups were dlstnbuted equallv to all 4 quadrants of the compass and those gioups showing a concerted directionallty of movenient were headed equally to the north and to the south Of the same 51 groups 70'X) trdvelled at net speeds of less than 1 5 km h ' Migratory indices for individual groups (average speed/net speed) ranged as high ds 82, and those ivith the lowest indices (corresponding to those most l~kely to be migrating) were distributed equally between noltherly a n d southerly di~ections Individual identlficatlon photographs taken of 27 humpback whales over 20 d revealed only 10 individuals 5 of w h~c h were reslghted on more than 1 occasion and up to 20 d apart Apparent feedlng behavloui by huinpback whales was seen on 10 occasions over 38 d and the production of reddlsh particulate faeces indicative of reccnt f e e d~n g was seen on 7 occaslons at a defecat~o n rate of 0 22 whale ' h ' Faecal samples collected contalned euphausiid ~e m a i n s (possibly Euphausla lucens) on 2 occaslons and amphipods on another Overall the data indicated that the southward migration of humpback whales expected at t h~s time of year on the west coast of South Africa had been suspended probably in response to locally abundant prey
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