I do not know anything about this. Contact Diana Andrews, the Fisheries Supervisor in that district. She should be able to shed some light on this topic. 870-367-3553
On a side note, this is a common rumor that we hear about other lakes when a game species population is in decline. The public wants to blame it on something that we (AGFC) did, rather than except that fish populations go up and down (especially crappie). If I had a guess, I would say this is the case for Grand as well.