Deep pelagic night longlining off Dondra Trench: yellowfin tuna drift currents and circle hooks?

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Liam Cetacean880 rep

How do artisanal multi-day offshore fishing boats deploy 30-mile drifting longlines across the southern continental drop-off to target yellowfin and swordfish?

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6 Answers from travellers

Accepted Answer

Offshore longline fisheries operating out of Mirissa and Beruwala target pelagic apex predators over the deep Dondra submarine trench where depths exceed 2,000 meters. Vessels deploy mainline monofilament lines stretching 25 to 40 nautical miles, suspended 15 to 40 meters deep with buoy floats. Setting occurs at dusk (6:00 PM to 9:00 PM) to target nocturnal feeding migrations of Yellowfin Tuna (Thunnus albacares) and Swordfish (Xiphias gladius). Vessels bait branches with whole flying fish or illuminated chemical lightsticks, utilizing non-offset 16/0 circle hooks that hook fish cleanly in the jaw corner, dramatically reducing mortality of non-target sea turtles.

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Capt Roshan Whale1870 rep

Vessels must maintain continuous radar and AIS watch; the longline drift corridor intersects the heavy international commercial container shipping lane off Dondra Head.

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Liam Cetacean880 rep

Department of Fisheries regulations mandate satellite Vessel Monitoring Systems (VMS) on all multi-day craft to prevent unauthorized incursions into foreign EEZ waters.

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Capt Roshan Sea1720 rep

Hauling begins before sunrise at 3:30 AM using hydraulic line-haulers; captured tuna are bled, eviscerated, and packed in crushed ice slurry below 1°C within 15 minutes.

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Marco Pelagic910 rep

Deploying bird-scaring tori lines during line setting prevents pelagic shearwaters and petrels from diving on baited hooks behind the boat transom.

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Swell heights in the trench increase dramatically during monsoon transitions, requiring heavy ballast trim to prevent vessel rolling during manual deck processing.

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Dr Anouk Marine1890 rep

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