Caulmert have recently secured planning permission for the upgrading of an existing fish pass in a watercourse which is within a Special Area of Conservation (SAC) and a Site of Special Scientific Interest (SSSI) within Snowdonia National Park. A fish pass (also known as a fish ladder, fish way or fish steps), is a structure on or around artificial barriers (such as dams and locks) to facilitate diadromous fishes’ natural migration. Most fish pass’s enable fish to pass around the barriers by swimming and leaping up a series of relatively low steps (hence the term ladder) into the waters on the other side. The velocity of water falling over the steps has to be great enough to attract the fish to the ladder, but it cannot be so great that it washes fish back downstream or exhausts them to the point of inability to continue their journey upriver.
In this instance, the approved development involves the removal of the existing fish pass and the construction of a rock ramp to allow Atlantic salmon to pass through the watercourse even at low water levels.