Upgrade your spawners by placing an item frame anywhere on a spawner and placing the upgrade item into that frame. The upgrade item then gets consumed, emptying the item frame. Available upgrades:

Eye of Ender: Entity spawn count (4 Upgrades. Up to 8 entities)
Heart of the Sea: Decrease maximum spawn delay (4 Upgrades. Down to 10 seconds)
Daylight Detector: Increase spawner activation range (4 Upgrades. Up to 80 blocks)
Echo Shard: Decrease spawn range for smaller farms (3 Upgrades. Down to 1 block)
Nether Star: Disable spawned entity AI (Single upgrade)

Disable the spawner by having a redstone torch placed inside an item frame that's on the spawner. Remove the redstone torch to resume the spawner. Spawner disabled by redstone torch