Their reproduction is somewhat unusual. All Barramundi fish start out as males. It takes them about three to four years to mature.
Then, after another year or two, usually at around age five, they change gender and become female. So the small fish you catch are male. The bigger the fish the more likely it is to be a female.
The females produce eggs which hatch within 20 hours and the larvae grow rapidly. It takes a Barramundi fish about three years to reach more than 2 kilos.
At six years of age a Barramundi fish will have reached a size of over 5 kilos and will almost certainly be female.