Hi ubnt
I catch my share of mullet for bait in castnet, sometimes targeting sometimes as bycatch. Though I'd say I've never noticed a pattern, caught them before and after sunrise, high and low tide. A few specific conditions do stand out though, I think they usually hold high in water column, spook easy with boat traffic and head to shore, and on runout tides hang around run-off, drop off points. When struggling for bait Il walk/ cast up stream maybe every few metres ahead of me shallow, then again out deeper to cover ground. If quiet and undisturbed you can find mullet in ankle deep water foraging. Keep throwing you'll catch something!
Jono4500's post in toowoon bay central coast nsw was marked as the answer