This winter we have observed some spectacular dolphin feeding behaviour, particularly dolphins chasing and catching yelloweye and sea mullet. Both mullet species take advantage of the high productivity in the estuary to feed, but are not reliant on estuaries as part of their life cycle. Mullet has been considered abundant in the Peel-Harvey for thousands of years.
Historically the Noongar community in the area gathered each winter at the mungah fishtrap on Serpentine to harvest sea mullet as it moved downstream to more saline waters escaping the freshwater runoff. In the 1870’s, the first commercial fishermen arrived and started fishing for mullet in the Peel-Harvey. Today mullet is caught in both commercial and recreational fisheries for bait and for human consumption. Mullet appears to be part of the dolphins’ diet throughout the year. We typically observe them feeding on mullet up in the rivers, in the shallows of the Peel-Harvey and in Dawesville Cut.
Interestingly, the estuary resident dolphins appear to use a different strategy to catch mullet than the dolphins that spend a lot of time in Dawesville Cut. Be it in shallow or deep water, the estuary dolphins use a ‘tail whack’, a quick manoeuvring of their body and tail fluke to create a sound and a large splash. This is thought to stun and disorient the fish making it easier to catch.
Often the force of impact has mullet flying out of the water. In shallow waters the tail whack is typically preceded by a rooster tail, so called due to the sheet of water trailing off the dolphin’s dorsal fin as it swims fast along the surface chasing fish. We have also observed dolphins hydroplaning along the sandy beaches in pursuit of the mullet.
In stark contrast to tail whacks and shallow water chases, the dolphins of Dawesville Cut chase a school of mullet along the canal and rock walls where the fish try and seek refuge. Usually the dolphin manages to separate one fish from the school and then chases the lone fish along the wall appearing to tire it out until it can be easily caught, or snatch it quickly as it tries to escape.
