The East Australian Current usually brings warm water south from the equator, along the east coast of Australia to Tasmania and even further south; but sometimes it diverts eastward to New Zealand. It carries hitchhikers from tropical waters along with it, and some of them end up at the Poor Knights Islands. I've never before seen trigger fish in other than tropical waters; but this one was at Northern Arch, more than 35 degrees from the equator, in 62 F water. The dive guides told us that they are not unusual.
Triplefins like to congregate above dips in the bottom below the kelp. No doubt they seek protection, companionship, and perhaps even love -- as we humans do in our own groups.
The kelp in New Zealand resembles the sea palms we see in the Channel Islands. The invertebrates underneath are at least analogous to those we see on hardbottom under macrocystis forests.