This ritual is used to show your gratitude to the spirits after a good catch. To perform it, you must sacrifice a raw fish. Note that it does not matter how big the fish is, nor how heavy it is. It is similar to the Sacrifice For a Newly Killed Animal in that it only raises your relationship with the spirits and nothing else.
Performing this ritual too many times will result in a message saying 'This feels meaningless', which gives no relationship boost with the spirits.