It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.entity.IEntityFishHook;

IEntityFishHook extends IEntity. That means all functions available to IEntities also are available to IEntityFishHook.

ZenGetter	GetterMethod	Return Type
ZenGetter caughtEntity	GetterMethod caughtEntity()	Return Type IEntity
ZenGetter angler	GetterMethod getAngler()	Return Type IPlayer

SetterName	SetterMethod	Parameter Type
SetterName lureSpeed	SetterMethod setLureSpeed(lureSpeed)	Parameter Type int
SetterName luck	SetterMethod setLuck(luck)	Parameter Type int