Fisheries - Enviro Dynamics Namibia

F I S H E R I E S , M A M M A L S A N D S E A B I R D S S P E C I A L I S T S T U D Y
/ subtropical offshore habitats (elsewhere in the world) and would therefore be more likely to
occur (if at all) both further offshore and in the more northerly extent of Namibian waters, than
the cold temperate conditions characterising the Namibian coast. Stranding or skeletal records of
southern bottlenose whales, rough toothed dolphin and Gervais’ beaked whale have been
recorded from the Namibian coast, although the level to which these may be extra-limital records
is unknown. There are no data on the population status of these species off the southern African
coast.
The main species characteristics and relevance to the MLA are outlined herewith and also listed
in Appendices 1a – 2 and 3.
4.3.2 Mysticete (baleen) whales (Appendix 1a - 2)
Blue whales : Two forms of blue whales are recorded from the Southern Hemisphere. Antarctic
or true blue whales (Balaenoptera musculus intermedia) migrate from summer feeding grounds
within the southern ocean (near the Antarctic ice edge) to winter calving grounds in temperate
waters, although little is known of their definite destination in winter (Mackintosh 1966). Pygmy
blue whales (B. m. brevicauda) are recorded from the southern Indian Ocean. Harmer (1931)
noted on the basis of the peak of the catches being sharper off Moçamedes (now Namibe),
Angola, than Walvis Bay, Namibia, that Angola was closer to the northern point of the blue whale
migration than Walvis Bay. The seasonality of catches of blue whales from the southern African
west coast suggests that the majority of blue whales migrate northwards through southern
Namibian waters between May and July to Angolan waters (July and August) and return
southwards after August.
Although no offshore distribution patterns were recorded off Namibia, catches of blue whales in
waters 65 to 95 kilometres offshore of the South western Cape coast of South Africa suggest that
the migration occurs off the continental shelf slope (in waters of depths of between 2000 and
3500 metres). Furthermore, catches of blue whales off the southern Africa west coast generally
occurred after catches of humpback whales which suggest that blue whales occurred in offshore,
deeper waters than humpback whales. Olsen (1915) however noted that off the Western Cape,
large schools moved inshore from the north between June and August.
Blue whales are unlikely to pass in or near the MLA
Fin whales (B. physalus) : Like blue whales, little is known of the winter migration destinations of
fin whales. Gambell (1985) noted that fin whale migrations occur after blue whale migrations, but
precede those of sei whales. Harmer (1931) reported that catches off the Western Cape had a
bimodal distribution (with maxima in May – July and October – November). Fin whales have been
recorded in catches from Walvis Bay and Angola (Harmer 1929), and off Gabon in 1934 (Budker
and Collignon 1952), and although no seasonal maxima are provided, these records show
migrations to the north of the Western Cape.
If the shelf edge is taken as 200 m, most of the fin whales should pass inshore of the mining area.
Although the offshore distribution of fin whales in southern Namibia is unknown, there is some
suggestion that the species migrates along the continental shelf edge (Macintosh 1966).
Final Report
Namibian Marine Phosphate (Pty) Ltd.
Page 37