I think it is still debated Ronnie. I had read 8 years/72" and 80+ inches before...
from:
http://www.nmfs.noaa.gov/fishwatch/s...uefin_tuna.htm
"Reaches reproductive maturity: Late – western Atlantic bluefin tuna first spawn at age 8 and are believed to take longer to reach maturity than bluefin tuna in the eastern Atlantic. Recent studies indicate most bluefin are sexually mature by about 12 years."
Other thing's I've read said as young a 5 years.