If the offal and cleaning discards are eaten by the scavengers then it becomes food. However if there are uneaten items then they will naturally decompose and that area of the pond may experience slightly increased filamentous algae growths due to excess nutrients. One might then decide to use a herbicide to kill the excess unsightly algae in a fequently used area. Not dumping the discards back into the pond would have probably prevented the excessive localized algae growth and a use of herbicides.
Removing fish and not throwing discards from fish cleaning back into the pond is a way to slow down the eutrophication process of a water body. Fish contain large amounts of bound nutrients obtained from the food web of the aquatic system, removing fish or anything that grew within the pond is a method of removing significant concentrations of nutrients from the pond and slowing its aging process. Fish and animals grown in a water body typically contain a lot more phosphorus (primarily in protein) compared to plant matter. Phosphorus is the primary nutrient responsible for eutrophication. Make your own conclusions.
