Just spoke to our lecturer, it is not known whether ALL leeries head up to Natal to spawn, as some big ones stick around down here. The sardine run definitely does play a role in their life cycle though.
Apparently genetic studies are currently underway to determine whether there are separate populations in southern Africa.
Also, leeries don't nessessarily need estuaries as nursery areas, they can grow up in sheltered bays too, which explains the west coast/ namibian/ angolan populations, although rivers like the Kunene are important.
The other thing was that it is HIGHLY unlikely that leeries spawn in closed estuaries, no matter how big the system. Recruitment occurs during overtopping events.
Grunter eggs were found in the closed St. Lucia system, but it is not known whether these would survive, as they also have a pelagic planktonic phase. The fish may just have spawned because they were trapped.
My weekly update....
Regards
Carl
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