Bait Loss From Halibut Longline Gear Observed From a Submersible

WILLIAM L. HIGH

Introduction During July 1978 National Oceanic longline gear. A self-contained and Atmospheric Administration battery-powered acoustic transmitter Demersal longline gear is fished (NOAA) scientists conducted a series was attached near the gear anchor for along the west coast of the United of dives using the chartered submersi­ the submersible pilot to locate the States for Pacific halibut, Hippoglossus ble Nekton Gamma to study longline groundline. While the pilot maintained stenolepis; sablefish, Anoplopoma gear and predation on bait. The study a course parallel to the groundline and, fimbria; and spiny dogfish Squalus was conducted in Frederick Sound, when possible, 2-3 feet (0.6-0.9 m) off acanthias. Little information is avail­ Alaska, adjacent to the northwest shore bottom, we attempted to view each able on the behavior of fish around the ofKupreanof Island. Our objective was hook. Observations, voice recorded on gear and bait, bait durability on hooks, to view from the Nekton Gamma de­ magnetic tape, included presence or ab­ predators other than the target species, mersal halibut longline gear on com­ sence of bait on hooks, predators pres­ and other factors. Usually the gear is mercial fishing grounds. When we were ent or eating the bait, fish species fished in deep water, quite inaccessible near the bottom, we observed I) the hooked or near the bait, and whether the to direct view or remote data collecting behavior of fish before, during, and hook was fishing or snagged. We systems. Consequently most conclu­ after they attacked the bait on the photographed the gear, predators, and sions drawn as to catch per unit effort, hooks, 2) other predators of the bait, fish with an externally mounted 35-mm bait or hook effectiveness, predation on and 3) length of time the bait, either underwater camera. bait and catch, and competition by var­ Pacific herring, Clupea harengus pal­ ious species are derived after the gear is lasi, or octopus, Octopus dofieini, 're­ Results retrieved. mained on the hooks. Four dives were made to view the sea Skud and Hamley (1978) reported floor and longline gear. The sea floor Methods upon experiments conducted by the In­ composition varied from gravel to ternational Pacific Halibut Commission Two typical halibut longline skates, boulders rising 5-6 feet ( 1.5-1.8 m) off (IPHC) to measure catch with relation composed of 250-fathom (fm) (458-m) bottom and equally long. The large to soak (time left on the bottom) and groundline with I3-foot (4.0-m) hook boulders presented some hazard to the bait loss. They reported that bait loss spacing (IPHC, 1978) were fished from submersible, especially when it was occurred while the gear was being set the NOAA RV John N. Cobb at depths necessary to travel down current. Un­ and from feeding by target species and from 165 feet (50.3 m) to 540 feet fortunately, the current on the bottom by other predators. (\64.6 m). The gear was set slowly could not be predicted from the direc­ without a chute to reduce the possible tion or magnitude of the surface cur­ loss of bait from hooks during the set. rent. The skates were baited with large her­ We were able to view the Iongline ABSTRACT-During July 1978 the ring pieces (from frozen blocks) except gear and fish readily from the submer­ submersible Nekton Gamma was used by for one skate having herring and fresh sible. Fish did not appear frightened National Oceanic and Atmospheric Admin­ octopus pieces on alternate hooks. during these or other survey dives. On istration (NOAA) investigators to observe Following the set, the John N. Cobb the contrary, halibut followed us sev­ halibut longline gear in Alaskan waters. Rate of Pacific herring, Clupea harengus stood by to assist the Nekton Gamma if eral times until we could count as many pallasi, bait loss to predators was higher it became entangled with the halibut as 15 (Fig. 1). Halibut dispersed slowly than of octopus, Octopus dofleini, baited after the submersible settled to the sea hooks. Species of fish caught included floor, whereas sculpins occasionally Pacific halibut, Hippoglossus stenolepis; William L. High is with the Northwest and gathered in moderate numbers (well arrowtooth flounder, Atheresthes stomias; Alaska Fisheries Center. National Marine sculpins, family Cottidae; rockfishes. fam­ Fisheries Service, NOAA, 2725 Montlake over 50 individuals) while we were mo­ ily Scorpaenidae; and others. Boulevard East, Seattle, WA 98112. tionless.

26 Marine Fisheries Review Figure I.-Both halibut and sculpin were attracted to the submersible. Note swimming halibut in the upper left with two others nearly obscured behind it.

Bait Loss Figure 2.-Loss of herring and octopus bait from longline hooks in relation to length of time after the gear had been set. Strong tidal current on the bottom precluded our prompt arrival at the gear 100~~ _ I . 16* site to observe whether the setting pro­ cess contributed to bait loss. Con­ c ~ 80 sequently our first view of the hooks .3 ~ was 30 minutes or more after the set. o Even after this short period, crab and ~ § 60 ~ shrimp were actively feeding on the c 'c baited hooks. Because the International .~ Pacific Halibut Commission studies ~ 40 showed that few baits were lost to the c. ~ normal setting process and our gear sets o were carefully done to avoid bait loss, we concluded that all observed bait loss I20 ~ (; was from predators (Fig. 2). The ob­ I .. In(Jlcate~ [he number of hooks observed served gross bait loss rate exceeded a 50 0'----"'-----'----'-----'-----'----'----'-1 138 _1, percent loss within 5 hours reported by 30 60 90 120 150 180 210 1020 Skud and Hamley (1978). Hooks with Length of time after set of gear (minutes) fish were excluded from the tabulation.

February 1980 27 Figure 3.-A portion ofdemersallongline with a gangion and hook is shown on the sea floor. Two shrimp of the type seen covering many baits were apparently attracted to the bait.

While one could reasonably assume hooked. Of56 fish we observed hooked hand, produced few fish caught during that bait was available when the fish during the several dives, 14 (25 per­ the early soak. While we recognize that became hooked, our observations cent) were missing from the gear on the the data are meager, it does suggest that showed that eight fish were hooked at subsequent survey. Six of IO (60 per­ the catch rate of hooks with octopus bait locations where previously the hook cent) arrowtooth flounder, Atheresthes is low. Octopus bait was apparently was without bait. We offer no explana­ stomias, were missing, whereas only 5 less attractive to small feeding inverte­ tion for this anomaly. of 26 (19 percent) Pacific halibut were brates, and because the flesh is tough, Shrimp, hermit crab, and brachyuran missing. We thought these fish escaped the bait remained on the hooks over a (true) crab were the most abundant ob­ or were removed by larger predators. A long period resulting in a catch similar served predators on herring-baited large skate, Raja binoculata, became to that with herring bait. Therefore, hooks in Frederick Sound (Fig. 3). hooked where we previously observed when halibut longline gear must have a Often we could not see the herring bait an arrowtooth flounder. Other species long soak, octopus bait will remain beneath a mound of feeding animals. observed hooked included sculpin, available for a longer time than herring. Octopus baits, on the other hand, family Cottidae; yelloweye rockfish, When the gear soak is short, octopus only once appeared to have an animal Sebastes ruberrimus; Pacific cod, offers no advantage. feeding on them. Our observations Gadus macrocephalus; salmon shark, Some hooked fish were detected at a suggested that herring, though fragile, Lamna ditropis; and shortspine thorny­ distance greater than 65 feet (19.8 m) was more attractive to predators. head rockfish, Sebastolobus alascanus . because their escape efforts caused The catch of fish on herring-baited considerable movement of the Fish Catches hooks increased in a decreasing rate groundline. On one occasion, a hooked Some fish passed near the baits with­ with soak during the first 3 hours until halibut swam more than 8 feet (2.4 m) out apparent interest while other fish most herring bait was gone from the offbottom carrying the groundline onto were seen to strike at the bait or become hooks (Fig. 4). Octopus, on the other our submersible. Deft maneuvering

28 Marine Fisheries Review 40 fishermen are faced with the selection - Herring balled hooks I of a best balance of bait type and length Io Octopus baited hooks I • of soak. c 30 ID ~ Strong near-bottom currents and un­ .e predictable movements of the ground­ .c • 20 line caused by hooked fish presented £ .~ • o some potential hazards to the submersi­ -'" • • 0 ble. 0 • I 10 • • • Acknowledgments o o OL.....I..----L_-L_.L----L_--'-----L_...L----'_---'-- -:-' These observations made by the au­ 20 40 60 80 100 120 140 160 180 200 1020 thor, Lou Barr (NMFS Northwest and Length of rime after set of gear (minutes) Alaska Fisheries Center, Auke Bay Laboratory), and submersible pilots, Rick Olsen and Rex Horton, were made Figure 4.-Catch of fish on herring- or octopus-baited hooks at time intervals following gear set. possible by the combined efforts of all members of the Project Sea Sub re­ search team. The team included Cap­ tain Larson, Field Party Chief Robert Loghry, and crew of the NOAA RV John N. Cobb, the crew of the submer­ cleared the line but the incident pointed soak, more than 80 percent of the her­ sible Nekton Gamma, and Captain Jeff up a potential hazard to a submersible ring was consumed whereas only about Hendricks and his crew aboard the char­ operating near gear considered to be 15 percent of the octopus was missing tered vessel Antares. The submersible lying quietly on the ground. from the hooks. Catch of fish on charter was provided by the NOAA herring-baited hooks in the first 2 hours Manned Undersea Science and Summary of soak was much higher than for Technology Office. Our observations of longline halibut octopus-baited hooks. A decreasing hooks in Frederick Sound, Alaska, catch rate for herring with soak is as­ Literature Cited baited with Pacific herring or octopus, sociated with the rapid bait loss. Al­ International Pacific Halibut Commission. 1978. show that predators such as fish, though the data are meager, they The Pacific halibut: Biology, fishery, and man­ agement. Int. Pac. Halibut Comm., Tech. shrimp, hermit crab, and brachyuran suggest that because ofthe longer reten­ Rep. 16:21-24. crab contribute to a rapid loss of herring tion of octopus bait on the hook, the Skud, B. E., and J. M. Hamley. 1978. Factors bait. Herring bait attracted far greater catch in long soaks is similar to that of affecting longline catch and effort: I. General review, II. Hook spacing, III. Bait loss and numbers of invertebrates than did fresh herring. Therefore, on grounds with competition. Int. Pac. Halibut Comm., Sci. octopus and, as a result, after a 2-hour many actively feeding invertebrates, Rep. 64, 66 p.

February 1980 29