Both the voluntary Livestock Manure Pollution Prevention Project and federal enforcement activity have been based on this subsection of the Act. Manure contains and can produce high levels of various forms of nitrogen such as ammonia and nitrites during decomposition. These materials can poison fish and fish food such as aquatic insects. Both phosphorus and nitrogen in manure can cause excessive flowering plant and algae growth. When this excessive plant growth dies and decays it can reduce the level of oxygen in a watercourse to levels below the minimum required to sustain aquatic life.
Manure also consumes large quantities of oxygen as it decomposes.
Where a large quantity of manure is suddenly deposited in a stream, fish and aquatic insects may die by suffocation. In instances where lesser amounts are deposited, the oxygen level may be reduced causing fish to avoid the area. Although potential pathogens such as bacteria, parasites and cryptosporidium may not be deleterious to fish, concerns regarding their impacts on downstream users continue to increase and often accompany the water quality concerns mentioned above. Environment Canada's Fisheries Act compliance promotion includes both voluntary and enforcement activities. Environment Canada's voluntary activities have included the Livestock Manure Pollution Prevention Project and providing guidance on the potential environmental impacts of cattle access, intensive livestock operations and other agricultural activities.