Crawfish traps

I have a question for you crawfish guys. How come we only eat them in the spring? Does it have to do with a season or is it something with shells hardening?
They eat them most of the year now with pond crawfish.
Spring is the traditional time, because that's when the Atchafalaya delta floods and the crawfish are caught on the flooded land. The shells do get hard late in the season, but I've seen years where the water has stayed up into the middle of the summer and a second batch has come out.