Recovering Whales – The role of large baleen whales in the Southern Hemisphere Ecosystem.

Programme 1: Large Whale Population Abundances and Trends.

This programme centres on recoveries of whale populations in response to protection from severe whaling pressure over the last two centuries through the assessments of absolute and relative population abundance (trend) estimates. Species, populations and stocks included within this programme are those that undertake annual migrations between summer Southern Ocean feeding grounds and winter breeding grounds in southern African waters and projects include acoustic monitoring and assessments of Antarctic blue whale populations, natural mark capture recapture history of southern right whale population abundance and trends (a project that the Unit has been carrying out for over thirty years), natural mark capture recapture history and shore – surveys of the abundance and trends of the east and west coast humpback whale stocks, and initial acoustic monitoring of seasonal presence and abundance of other baleen whales on the historical west coast whaling ground. Within this programme, the cost advantages of monitoring high-latitude species within local low-latitude waters require strong emphasis.

Programme 2 – Cetacean Trophic Ecology

Considerable former research of the Unit has centred on the breeding migrations of migratory baleen whale species, so that there is significant scope for expanding research to the feeding migrations and habits of these species. Such studies align well within the globally recognised need for an increased understanding of trophic system ecology within the Southern Ocean, particularly in light of historic human resource use in the region. It should be noted however that such Southern Ocean studies are dependent on access to cost-prohibitive dedicated research time on Southern Ocean research vessels and could only be executed through collaborations with state funded initiatives. Proposed Southern Ocean projects include an investigation of habitat use and resource partitioning of ice – edge humpback, minke and blue whales through short term tagging studies, an investigation of the sub-Antarctic feeding ecology of Southern African right whales through satellite tagging studies and stable isotope analyses.

Recent local work has identified summer feeding aggregations of both southern right and humpback whales in the southern Benguela system. In particular there appears to be some spatial-temporal segregation in feeding distributions possibly reflecting different prey types, with right whales feeding on planktonic copepods and humpbacks feeding on clupeid fish species. These is considerable scope in investigating  these local feeding aggregations through short – term dive logger and accelerometer tagging (which provides three dimensional underwater tracking) associated with echo-sounder surveys of three dimensional prey distribution. Such a project would provide an ideal springboard to gain experience for logistically difficult studies on ice-edge species discussed above. A further local trophic ecology project investigates changes in the diet of the inshore form of Bryde’s whale, a clupeid fish-eating species which is probably in direct competition with the South African pelagic sardine and anchovy fishery, and in all likelihood its prey base has been stressed by commercial fishing pressure.