The rigging of trawl gear is a vital component in the fishing industry, especially for commercial vessels targeting species such as shrimp, cod, pollock, and other bottom-dwelling or midwater fish. Proper rigging not only enhances the effectiveness of the trawl net but also ensures that it functions efficiently while minimizing bycatch and environmental impact. Rigging must account for the type of trawl, the fishing ground conditions, and the target species. In this topic, we’ll explore the various elements that go into successful trawl gear rigging and why it plays such a critical role in modern fishing operations.
Understanding Trawl Gear
What is a Trawl?
A trawl is a conical fishing net that is dragged through the water behind a boat, either along the sea floor (bottom trawling) or in midwater (pelagic trawling). The mouth of the trawl is kept open by trawl doors, and the net is typically towed by one or more vessels. Trawling is one of the most productive methods in commercial fishing, capturing a wide variety of species in large volumes.
Main Components of Trawl Gear
Before diving into rigging specifics, it’s important to understand the main components involved:
- Trawl doors: These are large, hydrodynamic panels that hold the net open horizontally.
- Bridles: These cables connect the trawl doors to the net, distributing the towing force evenly.
- Headline and footrope: The headline is the top line of the net with floats, while the footrope lies along the seabed and may have rollers or chains.
- Codend: The tail end of the net where fish are collected.
- Otter boards: Another term for trawl doors, sometimes used interchangeably.
Steps in Rigging Trawl Gear
1. Selecting the Right Trawl Net
The first step in rigging is choosing the correct net for the fishing operation. The mesh size, net dimensions, and material strength must align with the targeted species and fishing location. Bottom trawls typically require stronger nets due to contact with rough seabeds, while pelagic trawls may use lighter materials.
2. Attaching the Trawl Doors
Trawl doors are critical for spreading the net open during towing. These must be rigged correctly based on vessel horsepower, desired spread width, and water depth. The angle of attack and weight of the doors determine how well the net opens and remains stable during operation.
3. Installing Bridles and Sweeps
Bridles connect the trawl doors to the wings of the net. These need to be equal in length and tension to ensure balanced towing. Sweeps or ground gear may also be attached to guide fish toward the mouth of the net. For bottom trawls, the sweeps often include chains or rollers to protect the net from abrasion and damage.
4. Adding Floats and Weights
To achieve the correct vertical opening, floats are attached to the headline while weights or chain links are added to the footrope. This balance determines the height of the net and ensures that it opens effectively in the water column or along the seabed. Improper weighting can cause poor performance or increased bycatch.
5. Codend Installation and Strengthening
The codend must be strong enough to hold large volumes of fish. It is typically reinforced with additional meshes or cover nets. Codends can also include devices like grids or square mesh panels to allow juvenile fish to escape, reducing bycatch and promoting sustainable fishing practices.
Specialized Rigging Techniques
Rock Hopper Gear
When trawling in rocky or uneven seabeds, standard footropes may become snagged or damaged. Rock hopper gear includes large rubber discs or rollers attached to the footrope, allowing it to roll over obstructions. This rigging method is essential for maintaining net integrity in harsh conditions.
Twin Trawling
Twin trawling involves towing two trawl nets simultaneously, usually from the same vessel. This setup requires a twin rig system with additional winches and carefully balanced gear. Twin trawling increases catch efficiency but also demands precise rigging to prevent entanglements and uneven towing.
Semi-Pelagic or Off-Bottom Trawling
This method targets fish that live slightly above the seafloor. The trawl is rigged so that only the footrope barely touches the bottom while the headline rides higher in the water column. This technique requires careful float and weight adjustment to maintain the desired height and avoid seabed damage.
Safety and Maintenance Considerations
Regular Inspections
Trawl gear endures considerable stress, especially in deep waters or during long towing sessions. Routine checks should be made for net tears, weakened knots, and damaged floats or chains. Any damage should be repaired immediately to prevent gear failure during operations.
Safe Handling Practices
Rigging and deploying trawl gear involves heavy machinery and sharp tools. Proper training is essential to minimize risks. Crew members should wear protective gear, follow safety protocols, and communicate clearly during rigging and hauling operations.
Environmental Impact Reduction
Rigging gear with bycatch reduction devices (BRDs) and turtle excluder devices (TEDs) helps reduce the impact of trawling on non-target species. These additions are often required by regulation and are crucial for maintaining a sustainable fishery.
Benefits of Proper Trawl Rigging
Increased Catch Efficiency
When trawl gear is properly rigged, it increases the likelihood of targeting the desired species effectively. It ensures that the net opens correctly and that fish are funneled into the codend with minimal loss.
Reduced Gear Damage
Using the right rigging setup protects the gear from unnecessary wear and tear. This saves time and money on repairs and helps extend the lifespan of expensive components such as nets and trawl doors.
Better Fuel Efficiency
A well-rigged trawl net creates less drag, allowing the vessel to tow with less resistance. This translates to reduced fuel consumption and lower operating costs, which is especially important in long-haul commercial fisheries.
Compliance with Regulations
Adhering to rigging standards ensures compliance with local and international fishing laws. Regulations may mandate certain rigging types, mesh sizes, or exclusion devices, and meeting these requirements is essential for avoiding penalties and maintaining fishing licenses.
The rigging of trawl gear is not a one-size-fits-all operation. It demands careful planning, precise execution, and ongoing maintenance. Each component, from trawl doors to codends, must be chosen and adjusted based on the fishing environment and target species. Whether you’re operating in deep-sea conditions or coastal waters, understanding how to rig trawl gear effectively is essential for sustainable, efficient, and safe fishing practices. With continued innovation and responsible practices, the future of trawl fishing can balance productivity with environmental stewardship.