One Broken Anchor Chain, Entire Cage of Fish Escapes: A Comprehensive Guide to Anchor Chain Selection in Aquaculture

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Oct 07, 2025

One Anchor Chain Break, Massive Fish Escape: Guide to Anchor Chain Selection

Introduction: Anchor Chain Selection—The Invisible Lifeline That Determines Aquaculture Success

Amidst the raging winds and waves of the Norwegian fjords, or under the impact of the cold snap in southern Chile, a single broken anchor chain can cause a school of salmon worth millions of euros to escape within hours. Anchor chains are not only tools for securing cages but also a core line of defense against natural risks, safeguarding aquaculture profits.

According to the 2023 White Paper on Aquaculture Facility Safety published by the Norwegian Ministry of Fisheries and Seafood (Fiskeri- og havbruksnæringen), 68% of the salmon escapes in Norway from 2018 to 2023 that were due to broken anchor chains were directly related to improper selection, with an average loss of over 1.8 million euros per incident. Statistics from the Aquaculture Stewardship Council Chile show that cage drifting caused by anchor chain corrosion in southern Chilean waters accounted for 42% of the escapes that year. As an anchor chain manufacturer, we understand that scientific anchor chain selection can reduce risk by 90%, while a poor choice can undo ten years of hard work. Drawing on real-world examples, this article provides key anchor chain selection strategies for salmon farmers in Norway and Chile.

I. The Cost of Improper Anchor Chain Selection: Examining Risks from Real Case Studies

Case 1: Lerøy Seafood Farm in Norway – Disaster Caused by Insufficient Diameter
Incident: In December 2021, during a force 14 storm, the cages of Lerøy Seafood in the Tromsø waters, Norway, broke due to an insufficient anchor chain diameter (the original 20mm U2 alloy steel chain should have been 25mm). This resulted in the escape of 150,000 salmon.
Loss: Direct economic losses amounted to €2.4 million, with an additional €450,000 in ecological compensation required (the escaped fish hybridized with wild salmon, leading to genetic contamination). Data source: Norwegian Ministry of Fisheries and Seafood, "2021 Aquaculture Accident Investigation Report" (Report No.: NO-FISH-2021-042).
Root cause: To save costs, the farmer selected a smaller-diameter anchor chain, failing to consider the extreme tensile forces experienced during winter storms in the area (the measured tension reached 160 kN, while the breaking load of a 20 mm diameter chain is only 120 kN).


Case 2: Cermaq Chile - "Hidden Fracture" Caused by Material Corrosion
Incident: In May 2020, at Cermaq Chile's cages in the Punataki waters, the failure to replace the worn galvanized anchor chain coating led to the corrosion and perforation of the U2 alloy steel base material in the salt spray environment. This caused the cages to drift into the shipping channel, allowing 100,000 salmon to escape.
Loss: Direct losses amounted to €1.7 million, with an additional €250,000 fine for blocking the shipping channel. Data source: Chilean Aquaculture Association's "2020 Aquaculture Safety Audit Report" (Report No.: CL-ASC-2020-018).
Root cause: Farmers failed to comply with the standard of "testing corrosion rates every two years" (Article 4.3 of the Chilean "Regulations for Aquaculture Facilities"). The actual anchor chain corrosion rate reached 25% (the safety threshold is ≤15%).


Industry data confirms this:
Statistics from the Norwegian Ministry of Fisheries and Seafood show that incorrect anchor chain selection resulted in 68% of runaway incidents annually, of which 43% were due to insufficient diameter and 25% to material corrosion.

The Chilean Aquaculture Association's 2023 report indicates that 76% of anchor chain-related incidents were caused by farmers not conducting regular corrosion testing.


Fish in cages in aquaculture

II. The Relationship and Importance of Insurance and Anchor Chain Selection

Discussing the Reasonableness of the Insured Amount
Using insurance to hedge risks is essential. Anchor chain insurance provides coverage for fish escape, equipment loss, and ecological damage caused by anchor chain breakage, reducing the financial burden on farmers in the event of an accident. Without insurance, farmers would be fully responsible for losses in the event of an anchor chain breakage, potentially leading to severe financial consequences such as bankruptcy. In 2023, Nordlaks Farm in Norway insured its farm and received €1.5 million in compensation for losses of €1.8 million due to anchor chain breakage. Compensation rules for losses caused by anchor chain breakage may vary between different insurance companies and different insurance products. Please consult your local insurance company for specific details.


Insurance Requirements for Chain Classification Certification
Typically, insurance requires that the chain be certified by a classification society. Classification society certification is an authoritative endorsement of the quality, performance, and safety of the anchor chain. Anchor chains certified by classification societies meet stringent standards and specifications in design, manufacturing, and material selection, making them more resilient to the various challenges of the marine environment and reducing the probability of accidents such as breakage. To mitigate risk, insurance companies often prefer to insure certified, reliable anchor chains or offer more favorable premiums.

III. Four Core Dimensions of Anchor Chain Selection: The "Golden Rule" of Scientific Decision-Making

Dimension 1: Diameter and Breaking Load—Hard Indicators for Matching Environmental Tension
Calculation Method: Anchor Chain Breaking Load (kN) ≥ Maximum Environmental Tension (kN) × Safety Factor (3 - 5 recommended)

Norwegian Fjords: Winter storm forces can reach 120 - 180kN, so choose a 25mm Φ U2 alloy steel chain (breaking load 220kN, safety factor 3.7).

Southern Chile: Cold currents and tidal forces can combine to create forces of 80 - 120kN, so choose a 22mm Φ chain (breaking load 160kN, safety factor 4).
Case Comparison:
After upgrading its anchor chain diameter from 20mm to 25mm in 2022, Norway's SalMar Farm saw a 91% reduction in escape incidents (Source: SalMar's 2022 Sustainability Report).
After Chile's AquaChile switched to a 22mm chain in 2021, the chain breakage rate dropped from three per year to zero (Source: AquaChile's Internal Audit Report).
Key Point: An insufficient diameter can cause the anchor chain to be unable to withstand the tensile forces in the actual environment, easily leading to breakage and causing serious damage such as fish escape. The appropriate diameter of anchor chain must be selected based on the environmental tensile forces and safety factors.


Dimension 2: Material and Corrosion Resistance - The "Lifeline" Against the Marine Environment
Advantages of U2 Alloy Steel:

· Composition: An alloy containing manganese, nickel, and chromium, with salt spray corrosion resistance 60% higher than ordinary carbon steel (certified by DNV GL for C5 - M corrosion resistance).

· Lifespan: Up to 8 - 10 years in Norwegian waters and 6 - 8 years in Chilean waters (compared to 3 - 5 years for ordinary carbon steel chains).

· Cost-Effectiveness: Full-Life Cycle Costs Are 45% Lower Than Ordinary Carbon Steel Chains (2023 Cost Analysis Report by the Norwegian Fisheries Research Institute).
A Real-World Comparison:
Mowi Farm in Norway switched to U2 chain in 2019 and has maintained it for eight years, achieving a corrosion rate of only 12%. A neighboring farm using ordinary carbon steel chain experienced a corrosion rate exceeding 20% after three years, forcing premature replacement (Data Source: Mowi's "Facility Maintenance Records 2019 - 2023").
Key Points: Different environmental factors, such as salinity and humidity, affect anchor chain corrosion to varying degrees, necessitating the selection of a material with appropriate corrosion resistance. U2 alloy steel offers significant advantages in corrosion resistance and cost-effectiveness.


Dimension 3: Redundant Design and Emergency Response—From Passive Remediation to Active Prevention and Control
Dual Anchor System:
The main anchor chain bears 80% of the tension, while the secondary anchor chain (one diameter smaller) serves as a backup, automatically taking over if it breaks. After implementing this system at Grieg Seafood Farm in Norway in 2020, escape incidents decreased by 92% (data source: Grieg's "2020 Safety Improvement Report").
Intelligent Monitoring:
Integrated tension sensors provide real-time overload warnings (e.g., triggering an alarm when the tension exceeds 150kN).
After implementing this system at Cermaq in Chile in 2021, the response time to anchor chain breaks was reduced from 2 hours to 15 minutes (data source: Cermaq's "2021 Technology Upgrade Report").
Key Points: Redundant design and intelligent monitoring can effectively reduce the risk of anchor chain breaks, improve emergency response capabilities, and minimize losses.


Dimension 4: Analysis of Current Chain Diameter Selection
According to data on Chinese marine aquaculture chains exported to Norway and Chile from 2022 to 2025, current chain diameters are all above 30 mm. This is due to the following considerations:

· Coping with more severe environmental conditions: With global climate change, the marine environment is becoming more complex and extreme, and the intensity of natural forces such as storms and currents may increase. Larger diameter anchor chains have a higher breaking load and can better withstand these stronger environmental forces, ensuring cage stability and aquaculture safety.

· Increasing aquaculture scale and density: The salmon aquaculture industry continues to grow, with increasing aquaculture scale and density, and the number and weight of fish in the cages have also increased accordingly. This places higher demands on the load-bearing capacity of anchor chains. Larger diameter anchor chains provide more reliable anchoring and support, preventing chain breakage caused by fish movement or the weight of the cages themselves.

· Long-term cost-effectiveness: Although larger diameter anchor chains have a higher initial purchase cost, their greater durability and reliability can reduce replacement frequency and maintenance costs in the long term. They can also effectively reduce losses caused by chain breakage, such as fish escape and equipment damage, thereby improving the overall economic benefits of aquaculture.

· Improving industry standards and regulations: To ensure the safety and sustainability of the aquaculture industry, relevant industry standards and regulations may impose stricter requirements on anchor chain diameter and other performance indicators. To meet these standards and avoid the risk of non-compliance, fish farmers will choose larger diameter anchor chains.
Key Points: Choosing a larger diameter anchor chain is a comprehensive consideration of multiple factors, including the environment, aquaculture scale, costs, and industry standards. This helps ensure the long-term stability and economic benefits of aquaculture.

IV. Special Considerations for Anchor Chain Selection in Norway and Chile

Criteria for Choosing Girdleless and Stud Chains:
Differences in Aquaculture Environments:

· Norway: The currents, winds, and waves in the Norwegian fjords are relatively complex and unique. Girdleless chains may be more flexible in adapting to environmental changes under certain currents and load conditions, reducing friction and jamming between the yokes and other components, and lowering the risk of breakage. For example, in environments subject to frequent lateral currents, the smoothness of girdleless chains may be more conducive to maintaining overall structural stability.

· Chile: The waters of southern Chile may experience different current patterns and marine life activity. The yokes in stud chains may help to enhance the stability of the connection between the chain and the cage, preventing excessive swaying or displacement of the cage in complex marine environments. Furthermore, the structural characteristics of a stud chain may be more suitable for handling the friction caused by large sand particles or marine debris that may occur locally, reducing wear on the chain surface.

Aquaculture Methods and Cage Structures:

· Norway: Norwegian salmon aquaculture may tend to favor large-scale, intensive cage farming, which requires high flexibility and adaptability in anchor chains. The simple structure of a studless chain may be easier to integrate with modern aquaculture equipment and monitoring systems, meeting the needs of efficient aquaculture management.

· Chile: Chilean aquaculture methods and cage structures may differ from those in Norway, with greater emphasis on securing and stabilizing the cages in specific waters. The stud ring design of a stud chain may help better distribute tension, allowing the cages to maintain a relatively stable position under wind and wave conditions from different directions, and reducing additional stress on the anchor chain caused by cage swaying.

Key Point: The differences in anchor chain selection between Norway and Chile may be related to their respective aquaculture environments, aquaculture methods, and cage structures, and should be considered based on actual conditions.

Ⅴ. Our Solution: Full Service from Selection to Insurance

As an anchor chain manufacturer, we provide the following services to salmon farmers in Norway and Chile:

Customized Selection Tool: 

Input marine environmental parameters (wind speed, current velocity, salinity) to automatically generate recommended anchor chain diameters and materials (based on DNV GL-certified models).
We also provide weight recommendations relative to offshore anchors and sardine anchors, ensuring a better anchoring system.


Full Lifecycle Management:

Installation Guidance: Provide technical solutions and guide our professional installation team through on-site commissioning to ensure balanced anchor chain tension.

Regular Inspection: Fish farm owners are advised to undergo free annual inspections for corrosion and cracking, and replacement recommendations are provided (in compliance with Norwegian NORSOK standards and Chilean CL-ASC regulations).

Classification Society Certification Guarantee: We can provide certifications from major classification societies such as LR, DNV, and BV upon request, making it easier for customers to insure their fish farms.

Conclusion: Choosing the right anchor chain means choosing the right future.

In the game of salmon farming, anchor chain selection is a balancing act between cost and safety: saving one cent on the anchor chain could mean 100 cents more in losses. Through scientific selection (diameter, material, redundant design) and insurance hedging, you can transform the risk of anchor chain breakage from an "inevitable event" to a "controllable accident."


Choose us, and choose a "safety chain" that never breaks.

(Data sources: "2023 Aquaculture Safety White Paper" by the Norwegian Ministry of Fisheries and Seafood, "2023 Aquaculture Safety Audit Report" by the Chilean Aquaculture Association, DNV GL certification reports, and internal client reports)


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


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