SPC/Fisheries21/WP. 30 7 August 1989 ORIGINAL : ENGLISH SOUTH PACIFIC COMMISSION , 21ST REGIONAL TECHNICAL MEETING ON FISHERIES (Noumea, New Caledonia, 7-11 August 1989) VERTICAL LONGLININQ -, ;< ' THE CONCEPT,' TRIALS, AND PRESENT STATE OF DEVELOPMENT P ,' . j.'. •...;...•....•''•*•• by PAUL MEAD SPC MASTERFISHERMAN DEEP SEA FISHERIES DEVELOPMENT PROJECT GEAR DEVELOPMENT SUB-PROJECT (Vava'u, Tonga) r 660/89 * SPC/Fisheries21/WP. 30 Page 2 Introduction Simply put, a vertical longline consists of a length of mainline suspended near vertical in the water column by a weight at one end and a float at the other, with a number of baited branchlines attached at regular intervals. It permits focussing fishing effort through a band of depth in a single small area, in contrast to more traditional and widespread horizontal longlining which distributes effort over an expanse of ocean. The notion of a vertical longline surfaced during a country assignment in Yap in 1979. It came about after losing several large fish while trolling outside and along the reef in the area of an extremely steep drop-off. The heavy strikes were confined to that area, and occurred mainly at early morning or late afternoon. The intention of that first vertical longline was to focus fishing effort in these "hbles." The method of those first attempts was to go up-current, lower the longline, and then drift the bait through the holes over a range of depth. ' Since those first trials in Yap, the fishing method and gear configurations have evolved substantially, due to a greater understanding of the geaf and how it responds to a variety of fishing1 and catching situations, and also because much more is known about the behavior of the targetted fish. Vertical longlining moved through a progression of stages and locations before the Gear Development Sub-Project was set up in Vava'u in 1986. It's in Tonga vertical longlining developed to the point it is now - one complementary with local technology, efficiently gets lots of gear in the water, and is generally affordable for local economies. This presentation will briefly track the history and stages of vertical longlining and test fishing trials, list the pertinent findings along the way that helped direct its development, and then focus on present technology and operations of recent work in Tonga. History Yap (1979). This was the first attempts at vertical longlining, and as mentioned above, the idea was to fish more hooks in holes along the reef where large tunas might dwell. This first time only 1 vertical longline was fished, and the gear was set after dark. A parachute was deployed as a sea anchor to slow the boat's drift through the target area. The longline was 8 mm kuralon mainline with 20 - No.10/0 Sampo swivels spliced in (for branchline attachments) at 8 fathom intervals. Branchlines consisted of a locking snap swivel fastened to a 3 fathom length of 250 lb. test monofilament line that terminated in a No.5 Mustad tuna circle hook. If fish struck while the line was being deployed they were fought to the surface and hauled onboard. The first complete haul yielded 4 sharks and 2 dogtooth tuna. Fishing was curtailed at 4 am, and the night's catch was 12 sharks, 2 dogtooth tuna, and 1 large barracuda. Nlue (1982). After that single night of effort in Yap, vertical longlining wasn't tried again until 1982 in Nuie. There vertical longlining was associated with fish aggregating devices (FADs). On first trials fresh flying fish were used as bait, and the longline was set on a FAD after dark and soaked all night. An early morning check revealed no catch, so the line was left to soak through the day, until 4:30 that afternoon. The day set only produced 1 large blue shark. It was decided to postpone further trials until a better bait was available. • SPC/Fisheries21/WP.30 Page 3 In the meantime the gear was modified. Fisheries Division had a large supply of shark clips, the swivels used,ta.attach the snoods, or branchlines, to the mainline were replaced with shark clips. Instead of clipping thesnood through the lower eye of the swivel, branchlines were snapped directly onto the jnainline just above the splice that joined each swivel to the mainline. ^ • \- ^ Sometime after the gear was modified, large schools of Decapterus were noticed gathered around one of the FADs. Light handlines and a fish trap were used to catch enough for use as bait and trials, were, started up again-i The masterfisherman and one other crew, in a 12* aluminium boat, made an early morning run to the FAD, tied off, and set the longline. After the morning's bite finished*,th©catch totaled 5 yellowfin (11 kgs each) and 3 dolphin fish (6 kg average). None of the ifish was caught deeper than 90 fathoms. Another gear innovation was experimented with: mainline without swivels was tried, Branchline positions were marked, with cord. The idea was abandoned after losing several large fish. Hooked fish wrapped the snood around and around the mainline and then got off. f Cook Islands (1983). In Rarotonga in 1983 local fishermen had already devised their own method of "vertical longlining" around FADs. Their gear usually consisted of a single hook dropped from a.single,fjpat and fished, at depths between 30 and 60 fathoms. Law banned boats from tieing up to FAD*>sq fiahermeamotored 3 r40Q meters uprcurrent, dropped their line, and drifted past. Lines were hauled about 3-400 meters from the FAD on the down-current side. The Cook Islands was the first spot that two vertical longlines were fished simultaneously, tethered together with;a piece .of floating line. Difficulties with obtaining bait, exceptionally cool winter temperatures, and an El Nino, all combined to confound trial attempts and disrupt the regular seasonal appearance of tunas. Although a new gear innovation arose, few fishing trials were executed. Table 1. Results from vertical longlining test fishing around a FAD in Niue Month No. of Trips Catch .... ~ ~~ 12 yellowfin r Nov 5 3 albacore 6 dolphinfish •. *. 17 yellowfin ... Dec 6 6 albacore , 17 yellowfin Jan 7 3 albacore 1 bigeye 447 yellowfiyellow! n Feb 5 2 albacoralbacoi e 3 bigeye SPC/Fisheries21/WP. 30 Page 4 Fyi (1984). A much more determined approach to developing vertical longlinirig took place during &e Gear Development Project's attachment to Fiji. A Fiji 28 "fo6ter"was the fishing {ttatformyattd several'trip* to a FAD east of Bequa Island with the kuralon longhne prbthiced seVeral large yellowfin and albacore. Even so, the gear was bulky, and careful handling of the line was required because of the limited space onboard the 28 foot vessel. Several points emerged during early operations: ; ; --< •>;. • !v- -?rM'«--<•• |ls,.. ,;, • ,, < •. : /-.-,• •' •>' • •• ..,-•.;•••••,.•. •••- -• • •••-,; > ••'•'**•>• vl« !•'"«:'• .1. Wire snoods were ineffective aftd were more difficult to handle compared to hyloh; s .;'.; 2. A single species of shark was dominant around FADS, but it could be depleted with several days of intense fishing. If the FAD was not fished for 2-3 weeks the process had to be repeated; -•••'. 3. Tuna hook-ups increased if bait was hooked with the Japanese or Cook Island method instead of hooking through the eyes; -; i; hon; : < r 4. No.3 tuna circle hooks weren't strong enough to hold big fish. Forced to switch to #48 !.••••••, r. • BKN, and even some big fish straightened that size; •''•'" I' -I • O i /•':• > 5. Steady heavy surges of big tuna could undo or break the improved cinch knot. The * palomar knot was more dependable, although more difficult to tie in heavy nylon;': 1 ;. :••..• • >•••••• ;- i-,->!ii.L!? "••;• •'•• 6. If longlines were set after dark, squids stripped the baits in less than an hour; !...•.••-•! •,- >'!••-...•' , , '. •• • ' ' "••:"'. '.'<! A'.:\y. '••'•! 7. Before sunrise, yellowfin could be caught in the upper 40 fathoms ofwater;'' '»'>'' 8. After sunrise hookups of most tuna species occurred in water deeper than 30-40 fathftms; 9. Birds working around FADs almost always indicated that fish could be caught; -.;..,,, • . .. .-•..- ••••• •-• •: - '!• ••• U .? ••>"<'; I" 10. A large bait, such as a 1-3 kg skipjack or rainbow runner worked good as a bottom bait; 11. Light line (150 lb test) and smaller hooks (No. 5 Mustad tuna circle hooks) worked good from the surface to 70 fathoms during daylight hours; particularly for dolphinfish and rainbow runner; ,|f1 Several gear innovations were experimented with. The mainline was varied between braided nylon, Super Toto, and nylon monofilament. These alternatives were considered because kuralow mainline was particularly bulky. All three of the lines tested occupied much less deck space than the kuralon, but each was also difficult to haul by hand* A Sarnoan handreel was modified to get around the problem. The only modification required was to replace the terminaF insulator on the lever arm with a 6" nylon pulley to permit the swivels to pas* through. Every reel was capable of storing a single vertical mainline drop. Several drops occupied much less space than the same lengths of kuralon, and the reels were much easier; to load, unload, and store. Additionally, since small diameter line is less affected by current it hangs more near vertical inthe water column1 and also only requires a small sinker. Space saving organisation of snoods was also implemented. Snoods were stored on plastic handcaster spools. It was quickly discovered after trying to land a large 1 SPC/Fisheries21/WP. 30 Page 5 bigeye th^ 50-100 fathoms of backing was necessary on the reels because the fish would sound rapidly once hauling commenced. , Over the cpwrse of several.country assignments it was .shown that vertical longlining worked, especiajjyjin area%,of, known or, likely concentrations of tuna.