Longlines are used worldwide to grow everything from scallops to seaweed. These systems are preferred in high exposure areas. They are productive and flexible enough to handle a variety of shellfish species as well as a range of culture systems. In a longline system, the farmer anchors a length of line at both ends, attaches a flotation and hangs culture systems on the line.
Nursery rearing as well as grow-out can be accomplished on longlines. Trays, tube modules and bags or cages can be hung in deep water for nursery rearing of clams, oysters or scallops. Seeded lines or socks (with adequate predator protection) are commonly suspended from longlines. Scallops are frequently grown-out on sunken longlines, in suspended lantern nets, or ear-hung directly on a down-line.
Layout of a longline system depends on site characteristics. The most significant feature, from a security and stability perspective, is availability of shore to anchor one end of the longline. In some locations, both ends can be fixed to the shore. Anchoring both ends in deep water may be done at sites where shore anchoring is not possible or desirable.