Build failed with an exception.

I was trying to create a new fish mod/entity and I made my own texture and model for it from blockbench. When I make a new mod everything goes fine at start then when it compiles I get an error.

:compileJava FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler error output for details.

error: incompatible types: EntityCustom cannot be converted to EntityCreature
         this.tasks.addTask(1, new EntityAIWander(this, 1));

error: incompatible types: EntityCustom cannot be converted to EntityCreature
         this.tasks.addTask(5, new EntityAIPanic(this, 1.2));

Could someone help me figure this out?