The Loch is stocked with Rainbow and Brown Trout every month during the fishing season. Besides Trout, there are Pike, Perch, Roach and Eels in the water. Kilbirnie Loch is quite unusual in that both the inlet and outlet are just a few hundred metres apart at the north shore. The chances of catching decent trout and pike are quite high toward the beginning of the season, while the water is still quite cold. Perch and Roach are more likely to be caught during the summer months.
Eels are quite common during late evening and night fishing.
Castle Semple Loch is much more enclosed than Kilbirnie Loch. The emphasis here is also very leisure orientated. There is boat and canoe hire, windsurfing etc. Part of the loch is a bird sanctuary and so fishing is prohibited at that part. There is a great deal of woodland surrounding the loch.