A guide to marine aquaculture Gear: From the anchor to the cage

The expansion of marine aquaculture is a key piece of the blue economy, but its success and sustainability fundamentally depend on one choice: the right gear. From the stability of an anchor on the seabed to the resilience of a net in the open sea, every component plays a crucial role. A well-planned culture system design not only ensures the containment and welfare of the species but also optimizes operations and minimizes environmental risks.

Based on the comprehensive “Technical Guide to Marine Aquaculture Gear,” published by the NOAA Fisheries Southeast Regional Office, this article offers a detailed and accessible overview of the systems and technologies that define modern aquaculture. We will explore everything from basic components to specialized structures for mollusks, macroalgae, and finfish, culminating in the innovations that will shape the future of the sector.

Knowing the right gear for each job

The guide identifies the appropriate gear for different types of marine aquaculture, describing the relevant advantages, disadvantages, and considerations for installation, maintenance, and harvesting. Illustrations of gear types, glossaries of key terms, and descriptions of shellfish, seaweed, and fish species offer a comprehensive overview for resource managers.

“This type of document is extremely useful for resource managers,” explains Tori Spence, a regional aquaculture coordinator for NOAA Fisheries. “There is a wide diversity of gear used for aquaculture in the ocean, and these gear types can be complex, even if some aspects are common to other maritime applications. It’s helpful to have a repository for resource managers where they can consult aquaculture-specific information and make decisions to ensure that gear is appropriate, safe, and reliable across the country.”

This resource will also benefit aquaculturists. As Rusty Grice, manager of the Auburn University Shellfish Lab, explains to farmers, “The largest and most significant line item in your business plan’s budget is infrastructure. Once you have committed to a particular type of gear, it is expensive to reinvest in another.” This guide minimizes the risk of farmers having to reinvest, as everyone involved can understand the performance of different systems in various environmental settings.

Fundamental components of marine culture systems

Every aquaculture system, regardless of its complexity, is built upon a foundation of common components designed to withstand the dynamics of the marine environment. Stability and structural integrity depend on the correct selection and combination of these elements.

Anchors and mooring systems: The foundation of all cultivation

Anchors are essential for maintaining the position and tension of any structure in the water. The choice depends on the seabed substrate, expected loads, and system design. The three main types are:

• Drag Embedment Anchors: These bury themselves into the seafloor when dragged horizontally, offering high holding power in soft bottoms.
• Direct Embedment Anchors: Such as helical or screw-in types, these are inserted vertically into the seabed and support both vertical and horizontal loads.
• Deadweight Anchors: Typically, concrete blocks, their holding capacity comes primarily from their mass. They are useful on rocky bottoms where other anchors cannot penetrate.

Ropes, chains, and nets: structure and containment

These elements form the “skeleton” and “skin” of the culture systems.

• Ropes and Lines: Made from synthetic fibers like nylon, polyester, and polypropylene, they are used for mooring, connecting components, and as a cultivation substrate. Their UV resistance and elasticity are key factors.
• Chains: Usually made of galvanized or stainless steel, they connect anchors to mooring lines, add weight to maintain the system’s shape, and manage tension.
• Nets: Crucial for containing the cultured species and protecting them from predators. They can be made of flexible fibers or more rigid materials like copper alloy mesh, which also has antifouling properties.

Buoys and connectors: Buoyancy and connection

• Buoys: These provide the necessary buoyancy to keep gear at the desired depth. There are surface buoys (to mark boundaries or float structures), subsurface buoys (to keep mooring lines elevated off the bottom), and compensator buoys (to absorb wave energy and relieve tension).
• Connectors: Hardware such as shackles, thimbles, and corner plates ensures the robust connection of components, distributing loads and guaranteeing the structural integrity of the entire system.

Specialized gear for bivalve farming

The farming of bivalves like oysters, clams, and mussels is predominant in coastal zones and utilizes a wide variety of systems adapted to each species and environment.

Oyster farming systems: From bottom to surface

• On-bottom systems: These use bags or cages anchored directly to the seabed. It is a lower-cost method but is more exposed to benthic predators and sedimentation.
• Off-bottom systems: These keep the oysters suspended in the water column but close to the bottom. The “rack and bag” system is a classic example, where bags of oysters are placed on table-like structures. This improves water flow and reduces predation.
• Suspended and floating systems: This category includes suspended longlines, from which bags or cages hang from a horizontal rope. Also notable are floating systems like “flip bags,” which use tidal action to rotate the bags, helping to clean the oysters and give them a deeper, more marketable shape.

Techniques for clam and geoduck farming

Clam farming is mostly done on the bottom, where seed is planted directly in the substrate or inside polyester mesh bags. They are often covered with protective netting to prevent predation. For geoduck, PVC pipes or hard mesh tubes are inserted into the sediment to protect the delicate seed during its initial growth phase.

From mussels to scallops: Suspension culture

• Mussels: Taking advantage of their ability to attach to substrates, they are grown on vertical “dropper lines” that hang from floating horizontal longlines. The seed can be collected naturally or placed in biodegradable cotton “socks” that are wrapped around the line. Culture rafts are also common, especially on the U.S. West Coast, functioning as floating platforms from which the lines hang.
• Scallops: Their cultivation is more delicate. It involves a spat collection phase in “spat bags” followed by a transfer to grow-out systems like “pearl nets” (conical nets) or “lantern nets,” which are multi-tiered structures suspended from longlines.

Innovations in Seaweed Farming

The cultivation of macroalgae, such as kelp, requires systems that keep the plants near the surface for adequate sun exposure.

• Longline systems: This is the most common method. It can be a simple horizontal culture line anchored at its ends or more complex grid-like or “array” systems with multiple parallel culture lines. The algae grow directly on these lines.
• Towards offshore cultivation: To operate in more exposed waters, advanced designs like catenary systems are being developed. These use curved lines or spreader bars to maintain uniform tension throughout the structure, reducing the number of anchors and allowing the system to self-adjust to changing ocean conditions.

Technology for marine fish farming: Culture cages

Marine fish farming relies on net pens or cages that contain the fish while allowing water circulation.

• Flexible floating cages: These are the most common, especially in sheltered waters. They use circular collars made of high-density polyethylene (HDPE) pipe for flotation, from which the containment net hangs.
• Rigid floating cages: These are massive steel structures, often hexagonal or square, designed to withstand open-sea conditions. They can be so large that they function as stable work platforms.
• Semi-submersible cages: This is the key technology for offshore aquaculture. These cages, both flexible and rigid, can be submerged to avoid high surface energy during storms or to seek optimal water conditions. Buoyancy control is achieved using ballast tanks that are filled with water to submerge the cage or with air to raise it.

The future of aquaculture gear: Integration and sustainability

Innovation is ongoing, seeking more efficient systems with a lower environmental impact.

Integrated Multi-Trophic Aquaculture (IMTA)

IMTA, also known as “3D Ocean Farming,” involves co-cultivating species from different trophic levels. For example, fish cages (which release nutrients) are combined with macroalgae culture lines (which absorb inorganic nutrients) and molluscs (which filter organic matter). This synergy reduces the farm’s environmental footprint and diversifies production.

Towards minimum-impact aquaculture

Future research aims to reduce reliance on certain materials and minimize risks. Technologies such as “on-demand” or ropeless gear, inspired by trap fisheries, are being explored to reduce the risk of marine mammal entanglement. Likewise, there is great interest in developing gear with biodegradable materials, such as nets or bags, to decrease plastic pollution.

Conclusion

The selection of gear in marine aquaculture is a strategic decision that impacts the economic viability, operational efficiency, and environmental sustainability of any project. As the NOAA technical guide demonstrates, the sector has a diverse and constantly evolving technological arsenal, from traditional methods refined over decades to cutting-edge innovations designed to conquer the challenges of the open ocean. Understanding these tools is the first step toward building a more productive aquaculture industry that is in harmony with the marine ecosystem.

Reference (open access)
Feldman, L. E., Shields, J., Gray, L., Bowden, M., & Sunny, R. (2025). Technical Guide to Marine Aquaculture Gear (NOAA Technical Memorandum NMFS-SER-11). U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Regional Office. https://doi.org/10.25923/8kw5-2023

Milthon Lujan

Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.