Researched the subject, found out that cod spawn during spring-summer periods coinciding with flooding and water temps above 16c. sugested season is between Sep-Nov though Im unsure if it applies to all states. I explored the upper Stanly Rv which flows directly into Somerset Dam, but cant say that there was much life there, plenty of structure however the water hight and flow was pathetic pobably due to agricultural practices. Some Crimson spot rainbow fish were there which is reasuring, as Im not happy with the constant spread of Gambusia (Mosquito fish) in our water ways. Information was sourced from (Field guide to the freshwater fishes of Australia. G.R Allen, S.H Midgley, M. Allen.) A great book which I recommend to all Keen fresh water fishing enthusiasts.