One of the fisheries biologists in Iowa told me that for Iowa they calculated that grass carp have about a 2.5% mortality rate per year for the first 20 years. It increases after that. I don't know if that was for diploid or triploid carp though.
He also told me they drained a half acre pond that had exactly 10 grass carp stocked in it 21 years prior to draining. They found 10 grass carp averaging 50lbs each. Thats 1,000 lbs grass carp per acre
