Influences of Changes in the East Australian Current on Migrating Humpback Whales, Megaptera Novaeangliae, in Queensland, Australia

Humpback whales, Megaptera novaeangliae, migrate annually from polar feeding grounds in summer to tropical breeding grounds in winter. East Australian humpback whales travel from the Southern Ocean, along the east coast of Australia, to the Great Barrier Reef (or further) to breed. Under normal conditions, the East Australian Current (EAC) flows poleward along the east coast and dominates the environment over the continental shelf. This current carries warm water from the tropics and is responsible for generating upwelling conditions on the coast and providing the majority of nutrients available for primary production. Sharp temperature changes develop at the border of the warm current and the cooler coastal and upwelled waters. However, unusual conditions were observed during May - June 2015, where a large cyclonic eddie was located offshore of the Gold Coast, resulting in a reversal of local current direction.

This study investigates relationships between humpback whale distribution and environmental conditions (including bathymetry and remotely sensed sea surface temperature, as well as their gradients) on the Gold Coast, Australia. The study was conducted from June to November, 2013-2015, encompassing both normal and unusual conditions of the EAC.

During normal conditions, humpback whales show a preference for cooler waters and in areas with a strong temperature gradient. The higher productivity in cooler upwelled water and fronts may provide the whales with a chance of opportunistic feeding, a rare occurrence on their prolonged journey. Following particular hydrodynamic features such as these, which generally run parallel to the shore, may also serve as a tool for navigation. It is predicted that significant changes in the strength, direction and/or location of currents will affect humpback whale distribution.