I wonder if varying the feed the HSB receive could be useful in controlling those variable crappie numbers.
Years with a good crappie spawn - withhold HSB feed; HSB eat more crappie.
Years with a poor or no crappie spawn - feed the HSB.
This would give an additional control state (how rarely - thankfully - I get to use Control Theory here!

) to go with varying HSB numbers and direct reduction of crappie numbers via angling or traps(?) in the crappie equation.