At around twenty acres, Harlock is the largest of a chain of three water supply reservoirs on the high ground to the west of Ulverston. The fishing on the reservoir is controlled by Barrow Angling Club who manage this water as a brown trout fishery.

The fishing is best in the first half of the season and slows somewhat over the summer months when the peak of any activity will be late in the evening as fish respond to hatches of sedge. There is a particularly good olive hatch on Harlock from mid May through into mid June when sport can be fast and furious at times. Fishing usually picks ups again for the last few weeks of the season.

Water levels may fluctuate significantly and the fishery is open to the prevailing wind but nevertheless it can provide very good sport typical of upland brown trout fishing.