Thanks all for the advice. We ended up heading out from Kiama and headed due east for about 70km...didn't turn a reel all day on any tuna....got to the 2000 fathom mark, water temp ranged between 16.6 and 17.2 all the way. No signs of bait or schools on the sounder so we headed back in to the edge of the shelf and dropped down to the bottom. Got my first hapuka of about 7kg and was sharked a couple of times on gemfish....just caught their heads! Had a small mako at the back of the boat for about 20 minutes, but no wire trace.
All in all it was a great day on the water even though the tuna didn't turn up. My mate had 3 24kg rods on board and we also ran 2 15kg in our spread of five, so it would have been interesting to see how we'd have done if something big did turn up. Will definitely keep at it...keen to get our first decent tuna some day soon. If I'm under gunned on 15kg, I'll just have an excuse to upgrade, and I guess it will be a story to tell and a lesson learnt!
Best of luck to all who are hunting them!
bc77