Catching Grass Shrimp?

Anyone know how and when the best time is to harvest grass shrimp? They were available commercially her in southeastern MA, for a while but seem to have disappeared (at least from bait shops). I know they're still around cause some oldtimers are using them to catch white perch. Any

In Texas, old timer bait fishermen drag a large fine meshed dip net trough the weeds next to the bank and harvest them that way. They probably start to hatch in the late spring for y'all. To get more information, you might try doing a web search usind the latin species name. I've had good luck doing this in that often references to dissertations and published works by professional bioligists are made available to the public on the www. Yopu can learn some very useful and surprising things this way.