I catch big bullies over 10cm in our river down here in Manapouri.
I get a pin and bend the sharp end round like a hook and tie thread to it and put a wriggly earth worm on the end of the hook. I then lower it into the water where they come out from under the rocks and and they see the wriggling worm and they gulp it straight away and i rip it out of the water.
I'm not sure on the type of bullies they are, we always called them cocka bullies.
Me and my brother would catch heaps in 1/2 an hour and then let them go or put them in our mothers fish pond (and of coarse get told off for doing so. she didn't want them breeding in there).
They were a brown or black or grey in colour, always different.
the smallest 1s were easiest to catch. biggest were hardest which i suppose is y they are so big.
biggest we ever caught was around 12cm at a guess. I think he is still living under the same rock. for about 2-3yrs i alway looked when i went past and sometimes seen him sitting out in the sun
So much fun though
we couldn't keep them with the crays tho as the crays would eventually eat them
gave up on the crays tho as they kept crawling out of the tank, even with a lid on it, and found them halfway thru the house the next morning if the cat didn't get them.