This study looks at the progression of maturity of a single cohort of carp in Lake Sorell Tasmania. The ability of these fish to reproduce is an important consideration for the Carp Management Program (CMP) with the goal of eradication of this contained population. All fish captured are assessed on maturity with macroscopic gonad staging. The most undeveloped gonads were classified stage one through to the most developed being stage four. Fish of the same age have shown considerable difference in the development of the gonads with only 2.22% stage four running males and 0.42% stage four running females in the 2015/2016 season. The 2015/16 season represents carp in their sixth year of growth. Historically, females in Lake Sorell reached stage four at a minimum fork length of 353mm. Seventy five percent of stage three females are less than 350mm as of the 2015/16 season. It is this limited number of large fish that is restricting maturation in Lake Sorell. Low water temperatures along with selecting for fast growing fish using larger mesh gill net throughout the CMP has limited the numbers of fish capable of maturing to stage four. The small percentage (estimated <3%) of remaining carp are also the slowest growers of the cohort. This has created a population with limited numbers of mature carp. It assists with reducing spawning risk though makes targeted fishing using spawning aggregations difficult.