In southern African waters, information about species distribution and habitat
preferences of many cetacean species is limited, despite the recent economic growth
that may affect them. We determined the relative importance of eight environmental
variables (bathymetry, distance to shore, slope, chlorophyll-a, salinity, eastwards sea
water velocity, northwards sea water velocity and sea surface temperature) as drivers of
seasonal habitat preferences of Bryde’s whales (Balaenoptera brydei), humpback whales
(Megaptera novaeangliae), southern right whales (Eubalaena australis) and sperm
whales (Physeter macrocephalus). Using presence only data from multiple sources, we
constructed predictive species distribution models (SDMs) consisting of ensembles
of seven algorithms for these species during both summer and winter. Predicted
distribution for all cetaceans was high in southern Africa and, in particular, within
the South African Exclusive Economic Zone (EEZ). Predictive models indicated a
more pronounced seasonal variation for humpback, sperm and southern right whales
than for Bryde’s whales. Southern right whales occurred closer to shore during winter,
humpback whales were more likely to occur along the east coast in winter and the west
coast in summer, and sperm whales were more concentrated off the shelf in winter.
Our study shows that ensemble models using historical, incidental and scientific data,
in conjunction with modern environmental variables, can provide baseline knowledge
on important environmental drivers of cetacean distribution for conservation purposes.
Results of this study can further be used to help develop marine spatial plans and identify
important marine mammal areas.
Around 176 500 whales were killed in the sub-Antarctic waters off South Georgia
(South Atlantic) between 1904 and 1965. In recent decades, whales have once again become summer visitors, with the southern right whale (SRW) ...
Best, Peter B.; Photopoulou, Theoni(Public Library of Science, 2016-04-07)
The presence of crater-like wounds on cetaceans and other large marine vertebrates and
invertebrates has been attributed to various organisms. We review the evidence for the
identity of the biting agent responsible for ...