How can I detect a Gameobject touching another gameObject without using collider2D's?

I have fish gameObjects that have colliders2D so that I can click and move them. I added fish food with Collider2D's but it was hard for me to click on the fish. After I disabled the fish food collider2D it was easier to click on the fish. Is there an alternative when detecting two gameObjeccts without colliders?

So far I got this. But its not working well when I tried the drag version

 public class FishClicker : MonoBehaviour {
 
     public LayerMask whatIsFish;
 
     public float clickRadius = 0.1f;
 
     void Update() {
 
         if (Input.GetMouseButtonDown(0)) {
             var mousePos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
             var hit = Physics2D.OverlapCircle(mousePos, clickRadius, whatIsFish);
 
             if (hit != null) {
                 var fish = hit.GetComponentInParent<Fish>();
 
                 if (fish != null) { fish.DoClickThing(); }
             }
         }
     }
 }