Pesticides, herbicides, and fertilizers from your yard get washed into storm drains when it rains, and from there into creeks and rivers and then into the Delaware Bay. Antifreeze, coolant, car wash detergent, even fragments from tires and brake pads that end up on roadways become part of the runoff that is carried by rain into storm drains and beyond. All of these materials make water unfit for fish to live in.
Trout feed on macros and other insects unlucky enough to get too near to the water.
Adult trout sometimes feed on other types of fish. This is all part of the cycle of life in freshwater. Besides the fish that live all their lives in fresh water lakes, rivers, or streams, there are many types of fish that migrate upstream from the sea. These species are anadromous fish. They begin life in freshwater, go downstream to the ocean for most of their lives, and return to their birthplaces in rivers and streams when it is time to spawn.