Metlakatla Scallop Farm Anchoring System

Final Report

Coastal Shellfish Corporation

AIMAP 2011-P13

Introduction

Deep water shellfish farming sites are situated in a higher energy environment than that experienced in shallow water sites. This means that the anchoring system must be more robust and installed at a greater depth within the ocean bottom sediments. Coastal Shellfish Corporation (Coastal Shellfish) has introduced an innovative anchoring system for deep water shellfish farms and is comparing its effectiveness to the traditional anchoring system used in British Columbia's shellfish aquaculture industry.

The “wedge” anchor is widely employed in the Chilean shellfish aquaculture industry in soft-bottom ocean environments. Its wedge shape, the low center of gravity and special position of the handles, that allow a good combination of forces, make this anchor more stable on soft substrates compared to standard concrete blocks. The wedge anchor is designed with a 60 degree front face that submerges into the bottom sediments as the anchor line works resulting in more holding power compared to traditional concrete blocks.

At 1.5 tonnes, the wedge anchors are lighter and more easily transported compared to the traditional 2-4 tonne concrete blocks, reducing logistics costs compared to the traditional system. Wedge anchors use less concrete than standard concrete blocks. Wedge anchors are more cost effective than traditional concrete‐block anchors enabling increased scallop production with lower infrastructure costs.

This anchor was also designed to work with no need for any additional metallic gear that makes it very simple to handle at a much cheaper cost. These lower capital costs associated with farm expansion will result in reduced production costs.

Wedge anchors can be used as a single unit at each end of a long line as well as two or more working together on sites that are exposed to hard weather conditions. Their shape and position of the rope “handle” allow a very efficient force combination making two 1.5-tonne anchors work much better than one 3-tonne one.

Once the wedge anchoring system has been fully tested at the Metlakatla scallop farm under north coast winter conditions and a cost-benefit analysis has been completed benchmarking the wedge anchor system with the traditional concrete anchor system, the further expansion of the Coastal First Nations' scallop farms will be based on the most cost-effective, productive anchoring system. Implementing this new technology will improve scallop production systems and help to reduce production costs.

A scallop grading platform is required at the Metlakatla farm to handle the logistics of increased scallop production, which will result in increased productivity, reduced production costs and increased scallop production. This expansion of BC's farmed scallop production is an Aquaculture Innovation and Market Access Program (AIMAP) priority for aquaculture species diversification in the Pacific Region.

Methodology

Coastal Shellfish hired a professional marine engineer to improve the design of the new anchoring system for the loads imposed by the oceanic conditions at the Metlakatla scallop farm site. The objective was to ensure proper engineering for site‐specific conditions to mitigate the risk of storm damage to farm equipment and scallop stocks.

Blueprints were produced detailing the design specifications and lay‐out for the anchoring systems to be installed at the Metlakatla scallop farm site. This design was approved by Transport Canada.

Coastal Shellfish hired a Prince Rupert contractor to build forms for the wedge anchors and construct a total of 120 anchors. The cost of each 1.5-tonne wedge anchor was $425.

A tug and barge company operating out of Prince Rupert was hired to transport and install the wedge anchors at the Metlakatla farm site. A total of 52 wedge anchors were installed as a first phase, using GPS positioning, with two anchors at each end of the 150-meter longlines. Five longlines have been installed so far.

Other project equipment purchased with AIMAP funds included the following:

Longline Buoys –2,944 buoys were purchased from K-Marine in Peru (the quantity that fit into one 40-foot shipping container). Important specifications are as follows:

• Injection molding
• High resistance to impact
• High resistance on working pressure (up to 50 meters depth – 5 Atmosphere)
• Two ears for rope knotting

Buoys must meet these specifications due to the working conditions of the long lines, installed below the water surface.

Scallop Grading Machine for juvenile scallops was purchased from Koshin Trading Co in Japan, the dealer for HAMADE Manufacturer based in Japan. The important specifications are as follows:

• Stainless steel construction
• Special design for marine conditions
• Three grading levels for three different scallop sizes
• Grading screens from 10 mm to 45 mm
• Interchangeable grading screens

Going Forward

Coastal Shellfish intends to build and install a Scallop grading platform at the Metlakatla scallop farm. The objective is to improve farm productivity and reduce production costs by installing a unique floating platform that can handle a large increase in farmed scallop production. The final design and equipment set-up will be influenced by the results of another ongoing Coastal Shellfish AIMAP Project, AIMAP 2011-P12.

Coastal Shellfish will document the cost‐effectiveness of the wedge anchoring system for the site‐specific oceanic conditions at the Metlakatla farm and compare it to the traditional concrete‐block anchoring system.

Conclusion

The anchoring system at the Metlakatla farm was only recently installed and has not yet been subjected to a severe winter storm as can be experienced on the north coast of British Columbia.

Coastal Shellfish will produce a follow-up report after anchor performance is documented and conclusions are reached.