Longline System Product

Overview

A longline fishing system is a mechanized platform for industrial pelagic and deep-water longlining—a fishing method where a single mainline of 4000–8000 m carries hundreds or thousands of baited hooks suspended at intervals on branchlines (snoods). The system integrates a large mainline reel with hydraulic-powered hauling and propulsion, automated or semi-automated baiting stations, and rapid catch-sorting and line-clearing equipment. Modern vessels deploy longline systems for tuna, swordfish, halibut, and other high-value species in open ocean and slope waters.

The Mainline Reel is the mechanical heart—a barrel-drum 1.2–1.8 m in diameter that stores the working length of mainline under tension. The Hydraulic Hauler, powered by a 40–80 hp marine diesel, supplies 250–280 bar pressure to a proportional or directional valve, which feeds variable-displacement motors or cylinders. This same pump can run the Line Shooter (a pneumatic or hydraulic launch tube) and auxiliary systems simultaneously. The operator controls deployment and retrieval from a sealed stainless panel with proportional joystick, pressure gauges, and solenoid valves.

Prior to deployment, crew work at the Baiting Station—a 2 m stainless table where pre-rigged snoods (branchlines with hooks) are clipped onto the mainline at spacing intervals (typically 0.5–1.5 m). Large Branchline Bins store organized snoods, bait, and gangions on deck. During haul, the mainline comes aboard and passes over the Sorting Table, where wash spray rinses slime, and rotating perforated bins allow catch to drain while crew clear the line and remove fish. All components are fabricated from stainless steel (304 grade) or epoxy-coated carbon steel to survive years of saltwater exposure.

How it Works

Deployment sequence: Bait and snood preparation occurs at the baiting station using the Hook Guide to space snoods consistently along the mainline. The line shooter is charged to 8 bar air pressure from the Shooter Air Tank. As the mainline unspools from the Mainline Reel, it feeds into the shooter barrel and is launched into the water at 15–25 m/s, deploying a wide spread of hooks ahead of the vessel's drift. The Diesel Engine idles or turns at low speed while the Hydraulic Pump circulates oil at low pressure during this phase.

Hauling phase: After soak time (4–24 hours depending on species and depth), the operator engages the hauler with the proportional joystick. The Hydraulic Pump ramps to full displacement and pressure, driving one or more Directional Valve spool to the load-lowering or load-raising port. The mainline winds back onto the reel, with Level-Wind Guide distributing it evenly to prevent rope jam or overheating. Tension is monitored via Pressure Gauge (pilot pressure on a fixed load-cell compensator) and displayed on the control panel.

Catch processing: As the mainline hauls aboard, it passes over the inclined and slopped Sorting Table, where the Wash Pump sprays fresh or recycled seawater via Spray Nozzle. Perforated Sorting Bins allow fish and organic debris to drain into the Drain Sump. Crew manually or with powered assists clear snoods from the mainline and sort catch by species, size, and condition. Empty mainline is reeled or coiled, and the cycle repeats.

Hydraulic flow and control: The Accumulator (20 L, pre-charged to 200 bar) dampens pressure spikes and provides auxiliary power for brief high-force events (e.g., snagging recovery). The Relief Valve (pilot-operated, 250 bar setting) protects the circuit. The Oil Cooler maintains oil temperature below 60 °C during extended operations. A PLC Controller in the sealed NEMA 4X Panel Enclosure manages proportional solenoid dither, interlocks (e.g., prevent shooter fire if hauler is running), and fault logging.

Standard Configurations

Small vessel (8–12 m): Single mainline reel, one shooter, manual baiting, 40 hp engine, 3000–4000 m working line.

Medium vessel (15–25 m): Dual reels or carousel feeder, hydraulic baiting assist, dual shooters, 60 hp engine, 5000–6000 m capacity.

Large vessel (>30 m): High-capacity carousel or clip-feed mainline handler, fully automated baiting machine, secondary hauler winch for branch-line tension management, 80 hp dual-engine redundancy, 7000–8000 m spool, integrated fish-hold refrigeration via Fish Hold Refrigeration chiller unit.

Maintenance and Reliability

Stainless fasteners throughout (no galvanized steel) eliminate corrosion fatigue. The Hydraulic Pump displacement and compensator are serviced annually; oil analysis detects early wear. The Mainline Reel bearings are sealed, lubricated once per season. Rope condition is visually inspected weekly; mainline is replaced when diameter decreases >10% or visible abrasion exceeds 20% surface area. The Level-Wind Guide rollers are inspected monthly and bearing surfaces are greased using waterproof NLGI 2 marine grease.

Solenoid coils on the Directional Valve and shooter solenoid are de-rated to 80% for tropical salt-spray environments. Electrical connectors use sealed pin-and-socket marine type (IEC 61076), and the PLC maintains logging of all fault codes and pilot pressure events for remote diagnostics via Ethernet.

Fishing Regulations

Longline systems are subject to catch quotas, hook-size limits (typically 8.0–10.0 mm gap), mainline diameter minima (to allow sea-turtle escape), and acoustic or electronic line-pingers in some jurisdictions. Observer placement and electronic monitoring (EM) cameras are now mandated in many fisheries. Longline systems have largely displaced older manual jig and hand-line methods due to efficiency (>1000 fish per day in rich grounds) and reduced crew fatigue.