The reason that the swan is not eating and lethargic is that it is starving from being able to eat without pain. The line and hook may be preventing him from swallowing or eating. You have to be extremely careful that you do not cause more harm when pulling out the hook. If the hook is embedded in the soft tissue of the mouth, tongue or especially in the beak, you have to be extremely careful or you can break the beak and he will die from not being able to eat. The best thing to do is to contact a veterinarian or a wildlife rehabilitator (if they can treat a swan in your area without being mandated by law to kill it) to help with the extraction. The swan may also need an antibiotic shot to prevent infection from the hook. If the assistance of a veterinarian or wildlife rehabilitator is not possible, then you will need to carefully remove the hook. You would do this by cutting the barbs and pulling the hook back through, similar to how you would remove an embedded hook from your finger. Hopefully, you can find a veterinarian that can help. In any case, the swan will die from infection and starvation if it is in pain and entangled in a line and hook. Please let us know how this situation progresses. The Regal Swan