There are plenty of huge carp in Lake Ontario just like you will find in many of the other Great Lakes. If you are looking to target carp, try fishing the parts of the lake that have access to rivers and bays. As these waters warm in the late spring / early summer, you will usually get a shot at targeting some of these giant fish in larger numbers and in fairly shallow waters. From summer through fall, they can be hit or miss, but if you enjoy carp fishing, there is always somewhere to go to target them as long as the water stays above that 60 degree range. You can catch them in cooler water, but it becomes a little more difficult for most anglers.