Australian Bass Reproduction Facts
Australian Bass start their migration to the estuaries in mid to late winter where they breed.
For those in the northern hemisphere, and you know who you are, Winter is reversed as is summer in the southern hemisphere. Winter begins at the beginning of June as Summer begins in the Northern Hemisphere. Be mindful of this when booking fishing trips to southern hemisphere destinations.
The northern Australian Bass populations begin their migration followed by the Victorian populations.
Juvenile Australian Bass, or fingerlings as they are known as in Australia, move back upstream when they reach 2 inches (about 5cm).
The male Australian Bass school together waiting for the females to appear. Once the females arrive, spawning begins with each female releasing several thousand eggs. As the females release their eggs, the males fertilize them. Australian Bass eggs are free floating.
When the fry hatch, they are very small. The size of the egg is no more than one millimeter in diameter.
At 3 months, the Australian Bass develop pigmentation as they reach 20 mm in length (approximately 3/4 of an inch).
The exact timing of migration, the beginning of spawning, varies from river to river and from state to state as is the case with most fresh water fish.
In experimental pools, spawning began when water dropped to as low as 9C degrees. However the optimal temperature range for the survival range of 7 day old bass larvae is between 16C and 20C (approximately 61F and 68F). The survival rate drops off significantly around 12C.
Therefore, spawning starts as early as June and can begin as late as October.
In recent years drought has caused water levels to drop. This has meant that the migration of Australian Bass occur earlier than the historic average as the waterways loose their heat quicker. As a result many adult Australian Bass cannot, or have not migrated downstream to spawn. This has caused a reduction in population sizes.
Additionally most of the freshwater lakes and dams on the eastern drainage are stocked with bass for recreational fishing and in order to keep these populations up, they need to be continually restocked. However, even these inland lakes and reservoirs are low on water.
Restrictions on Catch
The Australian government enforced a zero bag limit from June 1, 2009 until August 31 that covered Australian Bass and estuary perch from all rivers and estuaries, which is essentially closed fishing for these species. This policy was enforced after a 3 year study and public consultations.
While the ban was lifted on September 1, 2009, there were still many restrictions left in place. Anglers are permitted 2 Australian Bass or estuary perch per person. This restriction applies to both species or a combination of both. In rivers, the limit goes further in that only one fish may be kept that’s over 35 cm in length (approximately 14 inches). For more information check out this link dpi.nsw.gov.au
The reason for the zero bag limit is a continued trend in the decline of fish stocks due to dozens of dams built within their distribution and further exasperated due to persistent drought conditions over the past decade.
It’s hoped that the zero bag limit will help increase fish stock levels, though it’s unlikely to return to stock levels of 1950’s population due to the amount of human engineering along the south-east coast of Australia.