so take out larger fish if they are not female? until i reach 30lb/acre total? is there a good way to tell male from female?

the 5.1 lb fish was definately a female. all the other fish caught were small and i killed these. total weight harvested is ~21 lbs. 280 lbs to go.

it was confirmed to me this weekend that we have crappie in the pond. i hadnt caught one, but someone caught several large crappie 2 years ago. this is bad, right? 10 acre pond.