For those of u who have the s.i. ff can yal tell me wut to look for to b able identify crappie from other fish... I can tell if I run into a bunch of trash fish e.g. carp and gar... I also can tell wen I find balls of bait fish but can't seem to make out the crappie... I have a hummingbird 598 si and di... also I know this is pretty elementary but how do u see the thermocline line w this unit... thanks in advance for the help!!