Anchor Chain for Deep-Sea Fish Farms Guide

Introduction: The Real Cost of Getting It Wrong 

In the rough waters off Norway or the exposed coasts of Chile, a broken anchor chain is not just equipment failure—it’s a business disaster. A single escape can cost millions in lost fish, fines, and reputation damage. 

Publicly reported industry data shows that for over a decade, a significant portion of anchor chain-related escape incidents in Norway have been linked to improper chain selection, with average losses reaching several million euros per incident. In Chile, corrosion-related failures account for a major portion of escapes each year. These failures share common causes: undersized diameter, ignored wear, and lack of regular inspection. 

Drawing on real cases and our supply experience, this guide outlines practical anchor chain selection strategies for salmon farmers and aquaculture operators.  

Part I: Lessons from Real Incidents 

Case 1: Norway – Undersized Chain in a Winter Storm 

In 2021, a Norwegian farm suffered a cage failure during a severe winter storm. The anchor chain broke under extreme tension, leading to a large escape. Investigation revealed that the chain diameter was undersized for the site’s actual environmental loads—the measured tension during the storm exceeded the chain’s rated breaking load. The operator had chosen a smaller diameter to save initial cost, without accounting for the site’s winter storm history. 

Lesson: Diameter selection must be based on site-specific maximum environmental tension, not standard recommendations or budget alone. 

Case 2: Chile – Corrosion Leading to Hidden Failure 

In 2020, a Chilean farm lost thousands of salmon when corroded chains failed during routine conditions. The galvanized coating had worn through, allowing saltwater to attack the base material. The farm had not conducted regular corrosion testing as required by local regulations. By the time the failure occurred, the chain had lost over 20% of its original diameter—well beyond the safety threshold. 

Lesson: Regular inspection and corrosion testing are not optional. They are the difference between catching a problem early and losing a cage.  

Part II: Diameter and Grade Selection 

There is no one-size-fits-all answer. Diameter depends on water depth, wave climate, wind patterns, and seabed conditions. 

From our supply experience:

- Farms use a wide range from 16mm to 44mm, with 28mm to 36mm being the most common sizes for aquaculture mooring.

- For exposed sites with long fetch and strong currents, stud link chain is preferred—it provides higher strength (30%+ more than studless) and better resistance to deformation.

- For sheltered sites, studless chain is lighter, cheaper, and sufficient for moderate conditions. 

Grade:

- Most fish farms use U2 (AM2) . It’s the right balance of strength and cost.

- U3 is more common for ship anchor chains, not fish farming. Recommending U3 for aquaculture is usually over-specifying and adds unnecessary cost. 

Our advice: Let sea conditions decide—not the price list. If your site is exposed, invest in the right diameter and grade. If you’re unsure, share your site data and we’ll help you calculate. 

Part III: Surface Treatment – Black Paint or Galvanized?

Black paint is the most common choice for aquaculture chains. It provides adequate protection at lower cost and works well for seasonal cages that are inspected and maintained regularly. 

Hot-dip galvanizing is often requested, but we recommend caution for smaller diameters. For chains under 20mm, we do not recommend hot-dip galvanizing—the high-temperature process can reduce tensile strength. For larger diameters, galvanizing is an option if specifically required. 

Our recommendation: Black paint for most aquaculture chains. Galvanizing only for larger chains where the customer understands the trade-offs and has a specific need for extended corrosion protection. 

Part IV: Regular Inspection – What to Check and When

The incidents above share one thing in common: the failure was avoidable. 

| Inspection Item | Why It Matters             | Recommended Frequency |

| Diameter wear | Chain loses strength as it wears | Annually (or per local regulation) |

| Corrosion / pitting | Weak points lead to sudden failure | Annually |

| Galvanized coating condition | Once worn, base metal corrodes quickly | Every 2 years |

| Shackles and connectors | The weakest link in the system | Before each season / every use | 

Part V: Certification – Not Optional 

For farms in regulated markets (especially Norway), certification is a requirement for: 

- Insurance – Insurers require valid product certificates for mooring components.

- Compliance – Authorities require documented chain quality to prevent escapes.

- Financing – Some equipment financing agreements require certified chain. 

We supply chains with LR, ABS, DNV, BV, CCS, NK, KR, RMRS, RINA, and IRS certification. If your project requires a specific class society, let us know and we’ll provide the matching certificate. 

Part VI: Procurement Checklist 

Before you place your order, confirm these details: 

- Chain diameter (16mm – 44mm, with 28mm – 36mm most common)

- Grade (U2 – standard for fish farms)

- Type (stud link / studless – based on sea conditions)

- Length (customized per site design)

- Surface treatment (black paint recommended for under 20mm)

- Certification (LR / ABS / DNV / BV / CCS / etc.)

- Accessories (shackles, swivels, end links) 

 Summary 

- Stud link for exposed sites, studless for sheltered sites.

- U2 is the standard—U3 is rarely used in aquaculture.

- Black paint for chains under 20mm—galvanizing can reduce strength.

- Design for worst-case conditions, not average.

- All accessories must match chain certification.

Based on 20 years of experience in aquaculture mooring—from design and manufacturing to supply and certification.

More Links:

Deep-sea Trend of Marine Aquaculture and Anchoring Solutions

The Core Role of Anchor Chains in Aquaculture

Anchoring Analysis of Deep Water Wind-wave Resistant Net Cage