Is tank cycled???

Hi i have 50 gallon
i started on 10/25/2015 with piece of raw salmon in tank...
ammonia went from 0ppm to over 4ppm
then nitrite from 0ppm to over 5ppm
now ammonia and nitrite are 0ppm and Nitrate 0ppm
is my tank cycled???
PH is 7.8
thank you...