Bottom Trawl Net Guide: Performance, Technical Features, and Applications Explained

Types of Bottom Trawl Nets

A bottom trawl net is a widely used fishing gear designed to be dragged along the seafloor to capture demersal (bottom-dwelling) species. These nets come in various designs tailored to different seabed conditions, target species, vessel sizes, and fishing strategies. Choosing the right type of trawl net significantly affects catch efficiency, bycatch reduction, fuel consumption, and environmental impact.

Flat Trawl Nets

Designed for smooth, soft seabeds such as mud, sand, or silt, flat trawl nets are ideal for deep, level ocean floors where obstacles are minimal.

Advantages

• Excellent spread and stability on even terrain
• Highly effective for catching shrimp and soft-bodied fish
• Low resistance reduces fuel consumption
• Suitable for large offshore vessels operating in expansive areas

Limitations

• Not suitable for rocky or uneven seabeds
• Prone to damage if dragged over obstructions
• Limited effectiveness in complex underwater environments

Best for: Deep-water shrimp trawling, flat continental shelves, large commercial fleets

Comparative Bottom Trawl Nets

Engineered for rugged, uneven, or rocky seabeds, these reinforced nets are built to withstand harsh conditions and navigate complex underwater terrain.

Advantages

• Reinforced structure resists abrasion and impact
• Rolls over rocks and obstacles instead of snagging
• Equipped with shielded trawl doors for protection
• Effective in areas with high structural complexity (e.g., reefs, boulders)

Limitations

• Higher drag increases fuel usage
• More expensive due to durable materials
• Bulkier design requires skilled handling

Best for: Inshore rocky zones, small to mid-sized trawlers, targeting fish hiding in crevices

Cone Trawl Nets

Featuring a conical or funnel-shaped design, these nets are versatile and efficient for catching mid-water and near-bottom swimming species.

Advantages

• Efficiently channels fish toward the codend with minimal escape
• Reduces physical damage to catch, improving survival rates for bycatch
• Effective for pelagic and semi-pelagic species like cod, mackerel, and haddock
• Adaptable to both soft and moderately rough seabeds

Limitations

• Less effective on very uneven or obstructed bottoms
• Requires precise towing speed for optimal performance
• May need additional modifications for selective fishing

Best for: Mixed-depth fisheries, eco-conscious operations, vessels of all sizes in coastal and open waters

Specialized & Ringed Trawl Nets

Advanced variations including ring trawls, grand nets, and crustacean-specific designs optimized for targeted fishing operations.

Advantages

• Ring trawls reduce clogging and improve flow through the net
• Customizable for specific species (e.g., scallops, crabs, flatfish)
• Can integrate sorting grids or escape panels for sustainability
• Higher selectivity reduces unwanted bycatch

Limitations

• Complex setup and maintenance
• Higher initial investment
• Requires training and regulatory compliance

Best for: Sustainable fisheries, selective harvesting, research vessels, and regulated zones

Type	Seabed Suitability	Target Species	Vessel Size	Key Benefit
Flat Trawl Net	Soft, level (mud/silt)	Shrimp, flounder, sole	Large offshore	High efficiency on smooth bottoms
Comparative Bottom Trawl	Rugged, rocky, uneven	Rockfish, grouper, lobster	Small to medium inshore	Durability in harsh environments
Cone Trawl Net	Soft to moderate	Cod, mackerel, hake	All sizes	Versatility and reduced bycatch
Specialized/Ringed Nets	Variable (design-dependent)	Species-specific (e.g., scallops)	Medium to large	Selective and sustainable fishing

Expert Tip: To enhance sustainability and comply with modern fishing regulations, consider integrating Bycatch Reduction Devices (BRDs) or Turtle Excluder Devices (TEDs) into your trawl net design—especially in cone and flat trawl configurations used in biodiverse regions.

Industrial Applications of Bottom Trawl Nets

While traditionally associated with commercial fishing, bottom trawl nets have evolved into versatile tools used across multiple marine industries. Their robust design, wide coverage, and ability to collect both biological and non-biological materials make them valuable assets in scientific research, aquaculture, environmental management, and underwater engineering. This expanded utility highlights their importance beyond simple harvest operations, contributing to sustainability, infrastructure development, and ocean health monitoring.

Key Industrial Applications

Marine Research & Data Collection

Bottom trawl nets are essential instruments in marine biology and fisheries science. Scientists deploy them to systematically sample benthic (seafloor) ecosystems, collecting data on species composition, population density, age distribution, and overall ecosystem health. These samples help assess biodiversity, track changes due to climate change or pollution, and monitor the recovery of protected areas.

The collected data directly informs sustainable fisheries management policies, including setting catch quotas, identifying critical habitats for protection, and evaluating the effectiveness of marine reserves. By providing empirical evidence on fish stocks and ecosystem dynamics, trawl-based research supports evidence-based decision-making for long-term ocean conservation.

Seafood Harvesting & Aquaculture Support

Bottom trawling remains a primary method for harvesting commercially valuable species such as cod, haddock, flounder, shrimp, and cephalopods like squid and octopus. These operations supply global seafood markets, restaurants, and processing facilities, contributing significantly to food security and economic activity in coastal regions.

In aquaculture, trawl nets are used not only to harvest fish from open-water pens but also to collect wild broodstock for breeding programs. Additionally, they help manage natural populations near farm sites by removing predators or competitors. When operated responsibly with selective gear modifications, bottom trawls can support sustainable seafood production while minimizing ecological impact.

Underwater Construction & Infrastructure Support

Bottom trawl nets play a supporting role in underwater construction projects, including the development of artificial reefs, offshore wind foundations, and submerged habitats. They are used to clear seabed areas of debris, old fishing gear, and scrap metal that could interfere with construction or damage equipment.

Collected materials can be recycled or repurposed—such as using cleaned nets or metal fragments in reef structures—to promote circular economy practices. Furthermore, trawl operations help maintain clean work zones around underwater installations, reducing risks during installation and maintenance phases, thereby enhancing project safety and efficiency.

Biofouling and Marine Debris Collection

Biofouling—the accumulation of marine organisms like barnacles, mussels, algae, and tube worms on submerged surfaces—is both a challenge and an opportunity. While biofouling can increase drag and reduce efficiency on vessels and offshore structures, it also indicates active biological zones.

Bottom trawl nets inadvertently collect biofouled materials during operations, offering a means to study these communities or remove excessive growth from sensitive areas. More importantly, they are increasingly used to retrieve marine debris such as ghost nets (abandoned fishing gear), plastic waste, and other pollutants from the seafloor. This cleanup function supports environmental restoration, protects marine life from entanglement, and contributes to healthier ocean ecosystems.

Application	Primary Benefit	Environmental Consideration
Marine Research	Scientific data for conservation and policy	Low-impact sampling with strict protocols
Seafood Harvesting	High-efficiency catch of commercial species	Requires bycatch reduction and habitat protection measures
Underwater Construction	Cleaning and preparing seabed sites	Reduces hazards and supports sustainable infrastructure
Debris & Biofouling Removal	Marine pollution mitigation and ecosystem recovery	Actively improves ocean health and reduces plastic impact

Best Practices for Sustainable Use

Adopt Selective Gear: Use modified trawl designs (e.g., turtle excluder devices, square mesh panels) to reduce bycatch and protect non-target species.

Map Sensitive Habitats: Avoid ecologically fragile areas such as coral reefs, seagrass beds, and spawning grounds through precise GPS navigation and marine spatial planning.

Integrate with Monitoring Systems: Combine trawling with real-time sonar, cameras, and sensors to assess seabed conditions and adjust operations dynamically.

Support Circular Economy: Recycle recovered materials like scrap metal and fishing nets into new products or reef-building components.

Promote Multi-Use Operations: Combine harvesting with cleanup missions to enhance environmental stewardship and public perception.

Important: While bottom trawl nets offer diverse industrial benefits, their use must be carefully regulated to prevent habitat destruction and overfishing. Adherence to international guidelines, environmental impact assessments, and sustainable fishing certifications (e.g., MSC) is crucial. Innovations in gear technology and operational practices continue to improve the balance between economic utility and ecological responsibility.

Product Specifications and Features of Bottom Trawl Nets

Bottom trawl nets are highly engineered fishing tools designed for durability, efficiency, and optimal performance in diverse marine environments. Their construction integrates advanced materials, hydrodynamic design, and regulatory compliance to ensure high catch rates, long service life, and sustainable fishing practices. From the choice of synthetic fibers to the geometry of trawl doors and mesh configuration, every feature plays a critical role in operational success.

Strength and Material of Construction

Modern bottom trawl nets are constructed from high-tensile synthetic fibers such as nylon (polyamide), polyethylene (PE), and polyester (PET), selected for their exceptional strength-to-weight ratio, abrasion resistance, and resilience in saltwater environments. These materials do not corrode and maintain structural integrity under prolonged exposure to seawater, UV radiation, and mechanical stress.

• Nylon offers superior elasticity and shock absorption, ideal for handling sudden loads during towing
• Polyethylene is lightweight and buoyant, reducing drag and improving fuel efficiency
• Polyester provides excellent dimensional stability and resistance to stretching under load
• All synthetic materials are significantly lighter than traditional wire nets, yet can exceed steel in tensile strength per unit weight

Technical advantage: Synthetic nets are easier to handle, store, and deploy, reducing labor and vessel strain.

Hoop and Trawl Door Design

The hoops (or otter doors) are critical components that determine the net’s horizontal spread and stability on the seabed. Their size, shape, and weight influence hydrodynamic performance, depth control, and seabed interaction.

• Larger doors create a wider mouth opening, increasing sweep area and catch potential—ideal for offshore and deep-sea operations
• Rounded or hydrofoil-shaped doors improve lift and stability at higher towing speeds and in deeper waters
• Flatter, wider doors are suited for shallow coastal zones, minimizing bottom disturbance while maintaining spread
• Adjustable or twin-door systems allow fine-tuning of net geometry based on target species and seabed conditions

Performance insight: Proper door selection enhances fuel efficiency and reduces environmental impact by minimizing unnecessary seabed contact.

Mesh Size and Selectivity

Mesh design is central to both fishing efficiency and sustainability. Bottom trawl nets use graded mesh systems—progressively smaller toward the codend—to retain target species while allowing undersized fish and non-target bycatch to escape.

• Large mesh in upper and lateral panels allows smaller fish to escape, promoting sustainable stock management
• Progressively smaller mesh toward the codend ensures retention of market-sized catch and prevents loss during hauling
• Regulatory compliance: Many fisheries require minimum mesh sizes (e.g., 100mm in EU waters) or square mesh panels to improve selectivity
• Escape panels or sorting grids (e.g., TEDs) can be integrated to further reduce bycatch of juveniles and protected species

Sustainability note: Proper mesh configuration supports ecosystem balance and helps fisheries meet international sustainability certifications.

Net Dimensions and Operational Suitability

The overall dimensions of a bottom trawl net—including length, height, and mouth circumference—directly affect its fishing capacity, maneuverability, and suitability for different vessel sizes and fishing grounds.

• Large nets (50+ meters wide) are used by industrial trawlers for maximum catch volume and deep-water operations
• Medium nets (20–40 meters) balance capacity and handling for mid-sized vessels in continental shelf zones
• Compact nets (under 20 meters) are ideal for inshore or artisanal fishing, offering ease of deployment and retrieval in confined areas
• Longer nets increase retention time, improving catch efficiency for slower-moving species

Operational tip: Matching net size to vessel power and deck space ensures safe and efficient operations.

Expert Recommendation: When selecting a bottom trawl net, prioritize a balance between durability, regulatory compliance, and target species behavior. Opt for high-quality synthetic materials with UV stabilization and abrasion-resistant coatings. Consider integrating selective gear features like square mesh panels or escape windows to future-proof operations against tightening environmental regulations and improve public perception of sustainable practices.

Feature	Common Options	Performance Benefit	Typical Use Case
Material	Nylon, PE, Polyester	Durability, flexibility, corrosion resistance	All environments, especially saltwater
Door Shape	Rounded (hydrofoil), Flat, Twin	Improved spread and stability	Deep sea vs. shallow water
Mesh Size (Codend)	80–120 mm (regulated)	Target species retention	Demersal fish (cod, haddock, etc.)
Mesh Type	Diamond, Square, Hexagonal	Selectivity and escape efficiency	Bycatch reduction compliance
Net Width	10–60+ meters	Coverage and catch volume	Inshore to offshore trawling

Additional Considerations

• Wear Protection: Reinforced edges, net guards, and anti-abrasion coatings extend lifespan in rocky or rough seabed conditions
• Hydrodynamic Efficiency: Streamlined net design reduces drag, lowering fuel consumption and emissions
• Repairability: Modular construction and standardized mesh patterns allow for easier on-board repairs
• Monitoring Integration: Modern nets can support sensors for real-time data on catch composition, temperature, and net position
• Environmental Impact: Responsible design minimizes seabed disturbance and bycatch, supporting eco-certifications like MSC

How to Choose the Right Bottom Trawl Net: A Comprehensive Buyer’s Guide

Selecting the appropriate bottom trawl net is crucial for maximizing catch efficiency, minimizing environmental impact, and ensuring long-term durability under harsh marine conditions. Whether you're outfitting a new vessel or upgrading your current gear, understanding the key selection criteria will help you make an informed decision tailored to your fishing operation. This guide explores the most important factors to consider when purchasing a bottom trawl net, from design and materials to vessel compatibility and maintenance.

Safety & Sustainability Note: Always comply with local fisheries regulations and environmental guidelines. Overly aggressive trawling on sensitive seabeds can damage ecosystems and lead to legal penalties. Consider using turtle excluder devices (TEDs) or bycatch reduction grids where applicable to promote sustainable fishing practices.

Key Factors to Consider When Choosing a Bottom Trawl Net

• Net Design: Matching Shape to Seabed Conditions

  The shape of your trawl net significantly influences its performance across different ocean floors and target species. Selecting the right design ensures optimal drag, stability, and catch retention.

  • Cone Nets: These are the most versatile and widely used designs. Their tapered structure allows for smooth water flow and efficient concentration of fish toward the codend. Ideal for mixed-species fisheries and variable seabed types, cone nets are easier to deploy and retrieve, making them excellent for coastal and mid-depth operations.
  • Flat Trawl Nets: Designed for deep, open waters with soft, sandy, or muddy bottoms. Their wide, horizontal mouth provides broad coverage, increasing sweep efficiency. However, they should be avoided in rocky or uneven terrain as they are prone to snagging and abrasion damage.
  • Comparative (or Rigid) Bottom Trawl Nets: Engineered for rugged, irregular, or rocky seabeds. These nets often feature reinforced bobbins, rollers, or protective tires along the footrope to glide over obstacles without tearing. Their robust construction minimizes downtime due to repairs and maximizes operational uptime in challenging environments.
• Net Features: Optimizing Catch Efficiency and Selectivity

  Modern trawl nets come with specialized features that enhance productivity, reduce bycatch, and improve fish survival—especially important for live transport or regulated species.

  • Mouth and Codend Design: Nets with a larger codend (back opening) allow for higher catch volume and reduce overcrowding, which can minimize fish stress and physical damage. However, size must be balanced with mesh regulations to avoid illegal retention of undersized species.
  • Front Configuration: A closed-front net prevents fish from escaping during towing, ideal for maximizing yield in dense schools. In contrast, open-front designs (such as those with sorting grids or escape panels) allow non-target species or undersized fish to exit, supporting sustainable practices and reducing sorting time onboard.
  • Species-Specific Enhancements: For shrimp and shellfish, look for nets equipped with small-mesh liners, "shrimp doors" (which close during retrieval to retain catch), or turtle excluder devices. For delicate species like flatfish or juvenile cod, inclusion panels with larger mesh can reduce bruising and mortality.
  • Expandable Nets: These adaptable systems feature adjustable wings or extendable sections, allowing fishermen to modify the net’s footprint based on sea conditions, target density, or regulatory requirements. They offer flexibility in dynamic fishing environments.
• Material and Maintenance: Ensuring Durability and Longevity

  The choice of material directly affects the net’s strength, weight, resistance to wear, and overall lifespan. Proper maintenance is equally critical to preserving performance and minimizing operational costs.

  • Synthetic Fibers: High-quality nylon and polyethylene are the preferred materials due to their exceptional resistance to saltwater, UV degradation, and abrasion. They are lightweight compared to older natural fiber nets, reducing fuel consumption and easing handling during deployment and retrieval.
  • Corrosion Resistance: Unlike metal components, synthetic nets do not rust or corrode, making them ideal for prolonged exposure to seawater. However, metal fittings (such as rings, shackles, and chains) should be stainless steel or galvanized to prevent failure.
  • Reinforced Construction: Pay close attention to stress points—seams, corners, and attachment zones should be double-stitched or reinforced with webbing. Look for nets with abrasion-resistant coatings or protective sleeves on high-wear areas like the groundline and headline.
  • Maintenance Practices: Regular inspection and cleaning after each use extend net life significantly. Rinse with fresh water to remove salt and debris, dry thoroughly before storage, and repair any tears or weak spots immediately. A well-maintained net can last years longer than a neglected one, improving cost-efficiency and reducing downtime.
• Compatibility with Vessel and Fishing Conditions

  Even the best-designed net will underperform if it's not properly matched to your vessel’s capabilities and operational environment.

  • Vessel Size and Power: Larger vessels with higher towing capacity can handle wider, heavier nets designed for deep-sea or offshore trawling. Smaller boats require lighter, more compact nets that match engine output and winch strength to avoid strain or instability.
  • Fishing Zone: Inshore and coastal waters often have complex seabed topography, requiring maneuverable nets with protective features. Offshore operations in deep, open waters benefit from large, flat nets optimized for consistent bottom contact over soft sediments.
  • Target Species: Different fish behaviors call for specific net shapes. Bottom-dwellers like flounder, halibut, or cod respond well to spreader bars and flat trawls that maintain a stable mouth height. Pelagic species such as mackerel or herring are better caught with cone-shaped nets that create a funneling effect through the water column.
  • Integration with Existing Gear: Ensure the net’s rigging, attachment points, and towing lines are compatible with your current winches, cables, and monitoring systems. Mismatched components can lead to inefficiencies, safety hazards, or equipment damage.

Selection Factor	Ideal Use Case	Avoid When...	Recommended Add-Ons
Cone Net	Coastal fishing, mixed species, variable seabeds	Targeting only deep-water flatfish on soft bottoms	Sorting grids, acoustic sensors
Flat Trawl Net	Deep offshore trawling on sandy/muddy seabeds	Operating near reefs, rocks, or hard substrates	Groundline rollers, sonar telemetry
Rigid/Comparative Net	Rugged, rocky, or uneven sea floors	Fishing in soft, open waters with minimal obstacles	Protective tires, breakaway links
Expandable Net	Changing conditions, multi-species fisheries	Fixed regulatory zones with strict gear limitations	Hydraulic spreaders, GPS integration
Small-Mesh Liner	Shrimp, prawns, or small demersal species	Targeting larger fish or operating in bycatch-sensitive areas	Turtle excluder devices (TEDs)

Expert Tip: Before finalizing a purchase, consult with experienced fishermen in your region or request a trial deployment from the manufacturer. Real-world testing in your typical fishing grounds can reveal performance nuances not apparent from specifications alone.

Final Recommendations for Buyers

• Always verify that your chosen net complies with local fisheries regulations regarding mesh size, bycatch mitigation, and seabed impact.
• Invest in high-quality, certified nets from reputable suppliers—even if the upfront cost is higher, long-term savings in repairs and replacements justify the investment.
• Train crew members on proper net handling, deployment, and maintenance procedures to maximize efficiency and safety.
• Keep detailed logs of net usage, repairs, and performance to inform future purchasing decisions.
• Consider integrating digital monitoring tools (like net sensors or GPS tracking) to optimize trawling patterns and improve catch reporting accuracy.

Choosing the right bottom trawl net is not a one-size-fits-all decision. It requires careful evaluation of your vessel, target species, fishing environment, and sustainability goals. By prioritizing durability, compatibility, and smart design features, you can enhance your catch rates, reduce operational costs, and contribute to more responsible fishing practices. When in doubt, seek advice from marine gear specialists or fisheries advisors to ensure your investment supports both profitability and environmental stewardship.

Frequently Asked Questions (FAQs) About Bottom Trawl Nets

Q1: What is a bottom trawl net?

A1: A bottom trawl net is a specialized fishing gear designed to be towed along the seafloor to capture demersal (bottom-dwelling) fish and other marine species such as shrimp, cod, haddock, and flatfish. The net is typically shaped like a cone or a bag, with a wide mouth that gradually narrows into a closed end known as the "codend," where the catch is collected.

These nets are engineered to skim the ocean floor, using weighted ground ropes and otter boards (trawl doors) to keep the mouth open horizontally and vertically. While effective for commercial fishing, their use raises ecological concerns due to potential seabed disturbance and bycatch of non-target species.

Q2: How does a bottom trawl net work?

A2: Bottom trawl nets are deployed from fishing vessels and dragged across the seabed at controlled speeds. The operation involves several key components:

• Trawl Doors (Otter Boards): Large, rectangular panels that spread the net horizontally as they are pulled through the water, creating a wide opening.
• Headline and Groundline: The top rope (headline) and bottom rope (groundline) maintain vertical openness. The groundline often includes chains or bobbins to bounce over rough terrain and herd fish into the net.
• Net Body: A funnel-shaped structure that guides fish toward the codend.
• Codend: The final section of the net where fish are retained. It’s often made with smaller mesh to prevent escape.

As the boat moves forward, fish and other marine life in the path of the net are swept inside. Because the catch is brought aboard relatively quickly, the fish remain fresh, minimizing spoilage and allowing for efficient sorting on deck without significant quality loss.

Q3: What are the key features of a bottom trawl net?

A3: Modern bottom trawl nets are designed with durability, efficiency, and environmental considerations in mind. Key features include:

• Durable Materials: Constructed from high-strength synthetic fibers like nylon, polyethylene (PE), or polyester, which resist abrasion, UV exposure, and saltwater corrosion.
• Adjustable Mesh Sizes: Mesh dimensions can be customized to target specific species and sizes, helping to reduce the capture of juvenile fish and improve selectivity.
• Variety of Sizes and Configurations: Nets come in multiple dimensions to suit different vessel sizes, fishing depths, and target species—from small coastal trawlers to large offshore factory ships.
• Bycatch Reduction Technologies: Many modern trawl nets incorporate features such as square mesh panels, sorting grids (e.g., Turtle Excluder Devices or Bycatch Reduction Devices), and escape windows to allow non-target species to exit safely, minimizing ecological impact.
• Reinforced Stress Points: Critical areas like the wings, belly, and attachment points are reinforced to withstand heavy loads and prolonged use on rough seabeds.

Q4: What factors should be considered when choosing a bottom trawl net?

A4: Selecting the right bottom trawl net involves balancing operational efficiency, environmental responsibility, and vessel compatibility. Important considerations include:

• Net Design:
  • Cone (or Round) Nets: Highly versatile and easier to handle, ideal for mixed-species fisheries and variable seabed conditions. Suitable for both shallow and moderate depths.
  • Flat (or Sieve) Nets: Better suited for deep, open waters with soft, flat seabeds. Their broad, flat structure allows for efficient coverage over large areas, especially in industrial-scale operations.
• Functional Features:
  • Larger net openings increase catch capacity and improve the likelihood of capturing fish alive and undamaged.
  • Effective closure mechanisms (e.g., drawstrings or locking codends) prevent fish from escaping during retrieval.
  • Expandable sections or adaptive panels help manage fast-swimming or agile species that might otherwise evade the net.
• Material and Durability: Choose abrasion-resistant, repairable fabrics to extend service life. Reinforcing high-wear zones (like the belly and footrope) ensures structural integrity and reduces maintenance costs over time.
• Vessel and Operational Compatibility: The net must match the boat’s towing power, winch capacity, storage space, and typical fishing grounds. It should also align with the target species’ behavior and habitat to maximize efficiency and minimize environmental impact.

Consulting with fisheries experts or net manufacturers can help tailor the design to specific needs, ensuring optimal performance, sustainability, and regulatory compliance.