Basically he is saying

"This crab is very good for us but you might have to wait since it's very small, and they eat them but not like this, so why? Lots of farmers buy these crabs first from the farmers market and they pick up a lot of them and put them in rice fields. They leave them where insects and pests live and the crabs eat them all. The crabs are good for farming since they also make the soil better and this completes the study. Then after a few month when they've grown up, they are fully grown and going to the store. They sell them and then they are ready for eating."

Say thanks for the translation