Scallops are very sensitive to extremes in temperature and humidity. Make sure that your work flow minimizes air exposure and temperature swings; water baths and sun shading are helpful, especially on very hot, cold, or windy days. Unlike oysters, scallops will not tolerate fresh water rinses. Bio fouling control can be accomplished through physical removal such as scraping or pressure washing, or by air-drying the equipment.
Longline design and materials
Longlines vary in length and materials but have some elements in common. Scallop longlines generally require 60 feet (18m) of depth or greater to function properly, and to accommodate nets and lines.
Moorings and mooring lines
Anchors for longlines include screw-type anchors, dead weights, and modified kedge-type anchors. Screw/helical anchors are easy to deploy, but should only be used where the sediment will definitely support the long line, as failure will lead to lost gear. Deadweight such as granite blocks may be more expensive, but will provide a measure of security as long as they are properly deployed and matched to the holding power needed. A modification of kedge anchors is used commonly in Japan and has been tried in Maine with some success. They must be matched well to holding power needed and sediment, and the long line may move or tangle if the anchors fail in heavy weather.
Mooring lines are set commonly at 3:1 to 5:1 scope, with appropriate shackles and chain at the anchor end to provide sea keeping and to dampen shock loads.
Longline (or backline)
Longlines are commonly 24mm (1") in diameter and made of polypropylene, which has relatively low stretch. Longlines are submerged typically 10 –25'below the surface to allow vessel traffic over the line and to place the culture gear below the zone of heaviest fouling.
Tension buoys are attached where the mooring line joins the long line ends. Hard plastic, submersible buoys of 75lbs (34kg) buoyancy are commonly used, sometimes in groups of three or more. Tension buoys help maintain the shape of the long line and can help identify the end of the long line, although they are submerged most of the time.
Marker buoys are placed periodically along the longline. Their purpose is somewhat to help maintain a level profile in the longline, but more to act as an indicator of when to add more compensator buoys, as the crop grows and becomes fouled over time. The marker buoys also alert mariners to the presence of the longline, and can be used to raise specific portions of thelong line when needed.
Compensation buoys maintain proper buoyancy, and a horizontal profile along the line. There is a balance to be struck; too much flotation will bring the entire longline to the surface where it can present a navigation hazard, and not enough flotation will result in culture gear that might rest on the bottom, where it will abrade and allow predators to climb up the lines.
As a balance to buoyancy compensation, weighted drop lines to the seabed are often used. Weights might be concrete, stone, or even bags filled with sand, and might range from 50 to 200 lbs.
Site selection for any species is a critical decision, and the factors that influence this decision are complex. However, some of the basics that relate to scallop farming include the following: correct temperature and salinity; feed availability; ability to access the site; proper flow and exposure to extreme conditions; depth; presence of competing uses, such as fishing; seabed composition and ability of moorings to remaining place; type, degree, and seasonality of fouling; and frequency and degree of harmful algal blooms in the area. Growers may find it helpful to list out the various considerations and take notes about how one site compares to another.