Raven, a number of years back I tied a fly for a guy down south who wanted to fly fish for them, he said the big one where he lived  eat urchins, they BLOW on them turning them over an start  EATING from there SOFT BELLYS,breaking them open an finnishing them off.
urchin fly--> if you wish to see it PM an Ill post in flyfishing section.
GOOD LUCK GOOD FISHIN
