Every 6 or 7 years, the chinaman jackets turn up in plague proportions outside.
I noticed earlier this year that some very small ones were in Gunnamatta Bay in Port Hacking, the first for some time. When the small ones turn up in side the bays, then some bigger ones appear outside, too small to eat, then larger ones will be around later, being big enough to eat.
When they are in plague proportions outside, they will eat anything that swims past them - hooked flatties, each other if hooked, or anything not fast enough to swim away from the pack, and they do swim in a pack, in bigger numbers than piranha and they have the mentality of piranha. I have killed one or 2 and thrown them into the water, and other jackets will appear in their hundreds to eat their own kind - do not fall overboard. ?
A couple of larger jackets I caught some years back had just attacked and eaten a blue spotted ray - one jacket had the whole tail in it's fat guts, with just a few chew marks along the tail, and the other jacket had sections of the body in it's fat guts, including an eye that was still intact.