3.0 Fish Cage Moorings

3.1 Anchor Leg Assembly:

The anchor leg assembly links the grid corner ring and square rope grid to the 1000 kg Sampson anchor. The components of each of the four anchor mooring legs are listed in Table 2,

and shown (in a not to scale assembly drawing of the original anchor mooring leg without the load cell and 7/8 inch chain) in Figure 3.

The mooring is positioned (anchor picked up to relax the mooring and pulled to retention the mooring) and the anchor lowered to the bottom during deployment by a crown line attached to the back end of the Samson anchor. The crown line components are listed in Table 3 and shown (in a not to scale assembly drawing of the original crown line assembly) in Figure 4. The modifications for the addition of the short the sections of steamer chain to add compliance to the spar buoy while handling from the Nobska’s trawl winch is shown in Figure 5.

3.3 Bridle Line Assembly:

The cage is attached to the four anchors and grid lines with four bridle line assemblies. The components of each bridle line assembly are listed in Table 4, and shown in (a not to scale assembly drawing of the bridle lines) in Figure 6.

As part of the instrumentation of the mooring and fish cage to understand its performance, verify modeling efforts, and to assist new, and optimized mooring designs, nine load cells were placed at critical locations in the mooring. One was placed between each of the anchor lines and the grid corner rings. These load cells have internally recording data loggers that are serviceable by divers. The Northeast corner of the mooring was thought to be most critical to monitor because this is the prevailing direction of winter storms. Therefore, additional load cells were placed in this mooring leg. Two were mounted on the fish cage rim where the cage bridle-lines attached. Three additional load cells were added at the grid corner rope ring, so that the tension in all lines on the Northeast corner would be monitored. The critical element of this configuration is the collection of four load cells at the corner ring.

The "to scale" horizontal section through the grid corner ring is shown in Figure 7. It shows the angle that the lower bridle line makes when the cage is in the up and down positions. A top view of the four load cells at this corner is shown in Figure 8. Note that to simplify cable configuration, the recorder is mounted in the lower grid line, rather than the anchor line. The wires from the four load cells must run across or along the grid ring to the recorder. The main difficulty with making this configuration reliable is preventing the electrical cables from chafing, becoming entangled, or overstretched while allowing the lines connected to the grid corner rope ring to move with the weather and grid configuration. This means that the cables can move in three dimensions, and a hint of the motion what must be accounted for is shown in the section from anchor line to lower bridle line in Figure 9.