Jigging cod requires torque, something that spinning reels don't have. Sailfishing is a finnese sport, unlike cod fishing, and spinning rods are conducive to throwing a live pilchard or ballyhoo when need be. I have seen people bottom fish with spinning rods, but I wouldn't want to be reeling up 12 or 16 ounces jigs on one. Just my $.02.
Gamakatsu
Gamakatsu