Spawning and recruitment of barramundi in estuaries.

[Douglas]

After a stuttering start, lets have a look at the spawning element which is different to the recruitment element although one is a consequence of the other.

Firstly I suggest that you have a look at the story of coral spawning on the GBR.

There are some similarities to be seen in that both are mass events and the timing is different for different parts of the coastline. This is reflected in differing spawning closures between the east coast and the Gulf of Carpentaria spawning periods for barramundi due to differing local circumstances.

Lets simply look at the east coast area and the Fitzroy in particular although places like Burnett and Mary will have differences.

What's been found to date.

Spawning (release of eggs from the big females) coincides with slack water on a big tide usually at night as the tides tend to be bigger at night.

Big tides mean stronger run to distribute the eggs.

The females are attended by thousands of males (younger and smaller) whose job it is to fertilise the released eggs. They have 1 hour to do that job. After that, the eggs "harden" and will not produce.

What that means is that both the females and the males have to be close together due to the 1 hour constraint on fertilisation.

That means they have to congregate.

Have an interruption here. Be back in a minute.