Restricted 2D camera movement area?

i have object(fish) move in 2d vector and when object get near camera left or right edge then camera will move so show the rest of scene (plane)…and i want to restrict camera movement for some values in left and right not every player object move to left or right the camera will move to infinite postion
i used like this:

camera.position.x = Mathf.Clamp(camera.position.x,-9,9);

where -9 camera position when camera bounds see left plane(scene) edge.
and 9 camera position when camera bounds see right plane(scene) edge.
however these two values -9,9 woks good in free aspect resolution and when i lower game resolution(for mobiles) then these values becomes wrong and camera not show all scene because camera bounds changed
what i should do to get values works in all camera resolution.??

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