This got me thinking - it's a question I sure don't know the answer to. And it seems that people have a lot of "opinions". So I went to the source. Straight out of the Fisheries Act:
36. (1) No one shall
( leave or deposit or cause to be thrown, left or deposited, on the shore, beach or bank of any water or on the beach between high and low water mark, remains or offal of fish or of marine animals;
Disposal of remains, etc.
(2) Remains or offal described in subsection (1) may be buried ashore, above high water mark.
I didn't find anything about dumping remains directly in the water. Maybe someone else would care to take another look.