Spring is the best time to plan a trout-fishing trip to Algonquin Park. That’s when the water is coldest, but still open, and the fish are in the rapids and in the shallows. As the water warms, trout in the lakes retreat to the thermocline at about 15 feet deep, while river trout hold up in deep pools or near cold-water springs, making them much more challenging to catch. Things pick up again in the fall but spring is prime time. Note: Due to the late ice-out, spring fishing conditions in 2019 could go until July.