Harvesting Technology in the Pacific Whiting, Merluccius productus, Fishery
CHARLES W. WEST
Introduction resource. Due to the poor keeping the trawl's depth could be adjusted to qualities of thc fish, whiting by keep it "on the fish," as detected by For any fishery to develop, several catches were discarded at sea or sold the ship's echosounder. interdependent factors must come as raw material for mink and pet The Cobb pelagic trawl and its together. In the simplest terms, these foods, and no interest in establishing derivative, the BCF Universal trawl, elements include: A resource capable a directed fishery developed until were used to capture large quantities of sustaining some reasonable level of 1964. At that time the Bureau of of whiting during the subsidized exploitation; adequate demand for Commercial Fisheries (BCF) started a demonstration fishery mentioned the products of the fishery; and ap demonstration fishery for whiting off above. Despite the effectiveness of the propriate harvesting technology. the coast of Washington (Nelson, Cobb and Universal trawls, there When dealing with high-volume, low 1970). The fish was delivered to a were problems inherent in their value fisheries such as the Pacific processing plant in Aberdeen, Wash., designs that have been ameliorated whiting, Merluccius productus, where it was used to manufacture fish during subsequent developments in fishery, it is particularly important to meal and fish protein concentrate. pelagic trawl design. The small mesh have efficient, economical harvesting While whiting are occasionally sizes in the forward parts of these techniques whereby large quantities of found in bottom waters and are thus large trawls contributed a great deal fish may be located and captured at available to bottom trawls, they occur of towing resistence, adversely affect minimal expense. In part, the success more commonly in large dense ing towing speed and vessel of the current fishery can be at schools in midwater. To capture them maneuverability. The abrupt (relative tributed to the development of such effectively, it was necessary to to later pelagic trawl designs) body techniques. This paper will review the develop midwater trawling techni tapers excited escape reactions among evolution of harvesting technology ques, a technology that was still the fish within the trawl, resulting in and discuss state-of-the-art gear relatively primitive as late as the excessive "gilling" in the after parts of presently in use. mid-1960's. the body of the trawl. The special The BCF Exploratory Fishing and towing warps required for the depth Evolution of Gear Types Gear Research Base in Seattle, Wash. telemetry system were expensive, and Nelson (1970) and Johnson and (later the National Marine Fisheries the electrical conductors within the High (1970) give good detailed Service (NMFS), Northwest and warps were prone to failure. descriptions of early domestic efforts Alaska Fisheries Center) undertook in Nevertheless, the contributions of to evaluate and exploit the whiting 1960 to develop a midwater trawling the BCF work should not be over resource off the coasts of California, system that was to evolve into the looked. Midwater trawling was shown Oregon, and Washington, and their Cobb pelagic trawl and its derivatives. to be an effective harvesting method discussions of gear will be summa Unlike modern midwater trawls, the for whiting, and West Coast skippers rized here. During the 1950's and early Cobb pelagic trawl (Fig. I) featured became familiar with the techniques 1960's, large incidental catches of small mesh, 76 mm (3 inches) involved. The importance of reducing Pacific whiting in bottom trawl stretched measure or less, throughout drag through trawl design was shown, fisheries targeting on flatfish and all sections of the trawl and tapered as was the desirability of taking ad Pacific cod, Gadus macrocephalus, relatively quickly from the large vantage of the behavioral charac indicated that there was a substantial mouth opening to the narrow codend. teristics of the fish. These experiences Aluminum hydrofoil doors were also demonstrated that some form of Charles W. West is with the Northwest and Alaska Fisheries Center, National Marine designed for use with this trawl. A trawl telemetry was essential to suc Fisheries Service, NOAA, 2725 Montlake pressure-sensing trawl depth telemetry cessful midwater trawling. Boulevard East, Seattle, WA 98112. Mention of system utilizing electo-mechanical Further evolution in whiting gear trade names or commercial firms does not imply endorsement by the National Marine Fisheries towing warps for depth data transmis designs came with the entrance of Service, NOAA. sion was developed. With this system, foreign fishing fleets into the fishery.
47(2),1985 47 When large fleets from the U.S.S.R. first began fishing off the West Coast for whiting and Pacific ocean perch, CHAIN ON Sebastes alutus, in 1966, several dif FOOT ROPE ferent gear types were employed. Bot SYMMETRICAL ABOUT tom trawls, midwater trawls, and CENTRAL LINE midwater pair trawls were used, de pending on fishing conditions and o o vessel capabilities. While whiting and N Pacific ocean perch were the target species, incidental catches of flatfish; sablefish, Anoplopoma fimbria; Pacific cod; and other species were substantial. Between 1966 and 1976, fleets from other Eastern Bloc nations entered the fishery, using essentially the same vessel and gear types. ::E o The passage of the Fisheries Con o servation and Management Act N (FCMA) in 1976 had a profound im pact on the fishery. Catches by the foreign fleets were brought under U.S. control, and strict limits were placed on acceptable levels of by catch of many benthic species. Foreign vessels were required to ac ::E o cept U.S. fishery observers who o MATE RIALS: N prepared independent estimates of catch sizes and composition and who BODY WEB 3,,-teI8-THREAD NYLON. obtained detailed descriptions of gear COD END 3" -"'96-THREAD NYLON. types and methods used. While catch WINGS AND BOTTOM 36 THREAD. quotas for whiting remained relatively CORNER R IBLI NES 5/8"- BRAIDED generous for the foreign fleets in NYLON. CRISSCROSS RIBLINES 1/2 "- subsequent years, the restrictions :I BRAIDED NYLON. o placed on catches of other species en USE CONVENTIONAL PUCKERING couraged the foreign fleets to fish '" RINGS AND SPLITTING STRAP more selectively on whiting while ASSEMBLY. avoiding the other species. This NOTES: change in focus of effort required the ALL FOUR SIDES ARE EQUAL. :I development and adoption of more o SUITABLE FOR 630-H.P. VESSEL. o selective gear. '" OTTERBOARDS MUST BE AT LEAST By 1976, the fishing vessels in the 72 SQUARE FEET. Soviet and Polish whiting fleets were almost exclusively large independent Figure 1. - Standard 18 Cobb pelagic trawl. stern trawlers, BMRT's of the Mayakovskii class and RTM's of the Atlantik class, both with their own processing equipment and freezer then switched to strictly midwater trawl designs. Mesh sizes graduated holds. These large vessels, 270-277 operations. down from 2,400 mm stretched feet (82-85 m) overall with over 2,000 Figure 2 is a net diagram prepared measure in the wings through 1,600 horsepower (Hitz, 1970), were by a Soviet fishing master illustrating mm, 1,200 nun, 800 mm, 400 mm, capable of towing large bottom or the general configuration of the most 200 mm, to 120 mm in the belly sec midwater trawls. Most vessels fishing common type of midwater trawl used tions adjacent to the codend, which exclusively for whiting towed mid by Soviet vessels at that time. It shows was of 60 mm mesh. The large meshes water trawls, while a few towed bot design characteristics intermediate be in the foward parts of the trawl "herd tom gear until the catch quotas for in tween early midwater trawls such as ed" the fish deeper into the trawl, cidental species had been reached, the Cobb pelagic trawl and current which tapered gradually back to the
48 Marine Fisheries Review Ilvj/JI€jJlJ/ /I xopaJltfi€jJUfmul/o nenOl/Jl/utJI020 mjlono.
-/600",," 8eiljl1eshSize DimeMion$ _ 3 {,7.., x - 3.67,.,
Figure 2. - Illustration of a U.S.S.R. midwater trawl prepared by a Soviet fishing master for a U.S. foreign fishery observer. The Russian legend reads: "Pelagic trawl dimensions and characteristics."
codend. As the fish moved deeper in long. Three hundred kilograms of function as the large meshes in the to the trawl, entering more and more chain were seized to the footrope to earlier Soviet designs, while offering confined spaces, the mesh sizes were open it downwards, along with an 800 still less drag-inducing surface area. reduced to enhance the herding effect, kg weight at each lower wingtip. Thus, it was possible for the same a necessary step to prevent panic Doors were round and concave for vessels to fish still larger trawls, with escape reactions in the fish as they enhanced hydrodynamic efficiency. improved fishing power. The Poles found themselves increasingly con Acoustic-link netsondes, or depth sen were the first to bring rope trawls into fined and crowded within the trawl. sors, were used to record trawl depth the whiting fishery, but the idea was By using mesh sizes just small enough at the headrope and gauge the vertical quickly picked up by the Soviets and to elicit the herding response, and opening of the trawl from the other Eastern Bloc fishing fleets, and gradually reducing the mesh sizes only headrope to the footrope. Unlike rope trawls dominated the fishery by when necessary to sustain that more modern designs, floats were 1979. response, it was possible to build used to lift the headrope, and upper Current Gear Types trawls with the very large mouth and lower bridle lengths were equal, and Fishing Practices openings necessary for capturing large 100 m from each wingtip to the door. quantities of fish while holding tow The next step in the development of Currently, the dominant Pacific ing resistance down to an acceptable whiting gear was introduced by the whiting fishery in U.S. waters is the level. This strategy of taking advan Polish fleet. Gear designers of the so-called "joint venture" fishery, tage of fish behavior in the design of German Democratic Republic (East wherein domestic catcher boats cap large, low-drag trawls is still being Germany) had developed large mid ture the fish and deliver them at sea to refined today. water trawls that employed foreign-owned vessels for processing. Other design features were similar longitudinal ropes in the wings and The details of payment procedures, to some contemporary midwater forward body sections instead of fleet organization, and disposition of trawls. The trawl was roughly rec meshes (Rehme, 1973). These ropes the processed fish vary from opera tangular in cross section, with ab led into meshes further back in the tion to operation, but the mechanics breviated wings. The headrope and body of the trawl, which then of locating and harvesting and trans footrope were of equal length, 77.4 graduated down as described above. ferring the catch are similar. m, while the breastlines were 40 m The ropes served the same herding Prior to 1978, the first year of
47(2),1985 49 operation of the joint venture fishery, proportions of the top and bottom some are of aluminum. The size and there was very little domestic fishing sections versus the sides, and tapers weight of the doors must be tailored effort targeting on whiting other than employed in the body panels. The to the towing capabilities of the the short-lived demonstration fishery goals of these refinements are to vessel, as well as matched to the gear described earlier. A few boats up and maintain or increase the mouth open to be towed. Suberkrub doors possess down the coast, of varying sizes and ings of the trawls and the herding and a number of performance charac using a variety of trawl types, con containment efficiency by taking ad teristics that have made them the tinued to catch relatively small quan vantage of the behavior of the fish, standard for the fleet. Of the com tities of whiting for delivery to shore while keeping drag to a minimum. monly used designs, they are the most based processing plants where it was Other vital considerations are efficient available in terms of spread usually made into animal food. While durability of the trawl and ease of ing power versus drag. They can be the resource available to the domestic operation. quickly and easily "tuned" for dif coastal draggers was ubiquitous and Figure 3 depicts a rope trawl design ferent fishing conditions by changing abundant, the volumes the processors used in the 1981 joint venture whiting such things as the towing point or the would buy and the prices they would fishery. More recent designs differ points of attachment for the lower pay were low, so there was little im somewhat from this to incorporate sweeplines. For example, it might be petus to develop efficient gear types refinements, and designers are under useful when fishing around pinnacles or fishing procedures. Nonetheless, standably reluctant to divulge the to adjust the doors so that they will innovative fishermen experimented details of their latest advances, but rise quickly, pulling up the net, when over the years with large midwater this diagram illustrates the general towing speed is increased. Other ad trawls of European design, pair trawl characteristics of modern rope-trawl justments would make the doors be ing, and other measures. The coastal design. Gear builders typically offer a come less sentitive to towing speed, or draggers, operating in this and other series of similar trawls, scaled up or sink faster, or spread less if increased fisheries, gained experience with mid down to match the towing capabilities vertical openings were called for. water trawling and refined their boats of the vessel for which a particular Perhaps the paramount feature and gear. trawl is intended. uniquely characterizing the gear used With the advent of the joint One noteworthy feature of contem in the joint venture fisheries is the venture whiting fishery came an op porary rope-trawl design is the virtual detachable codend (Fig. 4). Instead of portunity that the coastal draggers absence of floats. Rather than relying having the codend sewed permanently were ready to exploit, and they moved on floats to pull the headrope up to the body of the trawl, as is usually quickly. Even_ in the first year, the ex away from the footrope, in these done, a "zipper knot" similar to the perienced Soviet whiting fishermen trawls the footrope is weighted with knot used to close feed bags is used were impressed by the efficiency of chain and detachable weights secured which allows full codends to be quick the small U.S. catcher boats, and ahead of the ends of the footrope, ly detached from the rest of the trawl. catches routinely exceeded the which pull the footrope and lower At the end of the tow, the trawl is capacities of the factory ships' pro panels downwards. To facilitate hauled back aboard until the front cessing lines. spreading, the upper and lower end of the codend has just been From the inception of the joint ven sweeplines are attached to the upper brought aboard, leaving the part con ture fisheries, the catcher boats have and lower corners of the doors, taining the fish in the water aft of the exclusively used one variation or respectively, and the lower sweeplines boat. The codend is then detached. another of the basic rope trawl design. are lengthened to allow the footrope The open end of the codend is choked Known as Polish rope trawls due to to open down and still stay directly off with a nylon line and held on the their introduction by the Polish fleet, beneath the headrope. The only floats catcher boat until, using a buoyed the original design has been refined by used on the trawl, excluding some messenger line, a tow line from the domestic gear manufacturers to suit floats sewed to the detachable cod processor boat has been brought over the needs of the joint-venture fisheries end, are found along the two top (Fig. 5) and the codend has been and is now a very efficient piece of center ropes just behind the headrope made fast to it. This done, the codend gear. When they are "on the fish," where the netsonde is attached. These is released from the catcher boat (Fig. joint-venture catcher boat skippers floats help to orient the trawl and net 6) and winched aboard the processor expect to catch between 1 and 3 tons sonde during setting and haulback, (Fig. 7), where the catch is spilled and of whiting per minute, depending on minimizing tangles. processed. Meanwhile, empty cod the size of the trawl used. Rectangular, cambered, high aspect ends may be transferred from the Refinements have been made on a ratio midwater doors, also known as processor to the catcher boat, which number of construction details, but "Suberkrub" (FAa, 1974) doors, are then resumes fishing. perhaps the most important have been the most common type by far in the There is no such thing as a "stand in the following areas: Length and joint venture fleet. While most ard" joint-venture catcher boat, as mode of attachment of the ropes, Suberkrub doors are made of steel, most of the participating vessels were
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Figure 3. - Plan of a typical rope wing trawl used in the 1981 joint venture whiting fishery by vessels of 700-1,000 horsepower. DETACHABLE CODEND FOR PACIFIC WHITING Joint Venture Fishery Adjacent riblines on end hooked together with shackles Heavy Hammerlock Specifications LENGTH 60 ~ DIAMETER 5 _ Fly meshes and MA TERI ....L 1 layer a01J01e poIvethylene / z;pper knots 3-1/2"M 3(0,\ long. 140M arouno R1BllNES 4 1-1/4" oameler 1l'y100 roDe. Intermediate CON1AiNER LINES 17 t"1/4"dlamele. nylon IT aro.n:1. CAPACITY ~ Ions. CHAFING GEAR 'Hula Sku1" 3/4 01 he way atCU'lC1 anaChed near rings 0<"11'( Figure 4. - Detachable codend details. Figure 5. - Buoyed tow line being streamed back Figure 6. - Codend full of fish being towed from from a joint-venture processing ship to a catcher a catcher boat to a processing ship. boat. originally built with other fisheries in will be made to describe the most typical boat fishes its primary trawl mind. Consequently, deck gear and common features of a joint-venture from a net reel mounted just aft of the layout vary considerably from boat to boat. Many of the catcher boats were house. Spare trawls and/or empty boat within the constraints laid down built for the coastal bottom-trawl codends may be stored on the after by the requirements of midwater fisheries, and are about 80 feet (24 m) net reel(s), mounted above the deck trawling. Having said this, an attempt long with a 24-foot (7 m) beam. A on a stern gantry. Some kind of 52 Marine Fisheries Review Figure 7. - Full codend be A-frame or boom arrangement ing winched up the ramp of the processing ship, a facilitates handling the gear on deck, Soviet BMRT factory and accessory gilson winches, splitting trawler. Note the "Suber winches, outhauls, deck cranes, krub" trawl doors hanging catheads, etc., will be found in at the stern, and the various combinations. Conventional spherical trawl doors stacked on deck forward of trawl winches are most common, the ramp area. carrying warps of Ys - Ys inches (16-22 mm) in diameter, although some boats are installing the more advanced "constant-tension" winches of Euro pean design. Main engines of 750-1,000 horsepower are most com mon in the 75-90 foot (23-27 m) vessels, with more powerful engines found in some of the larger Alaska king crab vessels that have been con verted to trawling. Kort nozzles, aftercoolers, and other means of boosting towing performance are be ing installed throughout the fleet, the goal being to pull the largest possible trawl that can be towed at 3 knots or more. The joint-venture catcher boats rely heavily on electronic aids to maximize their catching efficiency (Fig. 8). Sonar systems of varying degrees of sophistication are used to locate schools of fish. Driving the boat over a selected school, the skipper uses the echosounder to get information on school depth, density, and composi tion. There is a trend toward in creased use of color sounders because of the added ease of interpretation of the echo information. For even finer resolution of within-school density distributions an acoustic device known as a "memo-scope" may be employed. With the memo-scope, selected portions of individual echo pulses may be expanded and exam ined in detail, yielding information about target density within a fairly small area. Loran-C navigation systems provide precise positioning information, especially when coupled to an automatic plotter unit, either paper or video. Using a plotter it is easy to record the exact locations of Figure 8. - The bridge of the Colintino Rose 1I, a typical modern joint-venture promising fish traces while scouting catcher boat. Note the numerous electronic aids visible here. for fish. Once a specific school has been targeted and the gear has been set, electronic aids continue to guide the 47(2),1985 53 fishing process. The echosounder in systems, weather facsimile receivers, echosounders are used to gain addi dicates the approximate depth to and radars. tional information about school depth which the trawl should be set in order While the joint venture fishery is and density. Additional information to intercept the fish. The netsonde on the dominant fishery for Pacific on within-school density patterns can the trawl provides immediate infor whiting, other fisheries do exist. be obtained with memo-scopes mation on the trawl's performance Small-scale shore-based fisheries con and/or color sounders. Automatic and its position within the water col tinue to operate up and down the plotters coupled to the ship's Loran-C umn. Echoes from fish above or coast, usually involving smaller, older systems are valuable for recording the below the netsonde's headrope trans vessels employing an assortment of locations of schools when scouting for ducer allow the skipper to adjust the trawl types. The whiting vessels fish. While fishing, netsondes of depth of the trawl for maximum delivering to processors in Oregon various kinds provide essential infor catch, especially useful when the fish and California use rope trawls for the mation on trawl position and catch have moved between the time they most part, with the exception of a few rates. were detected on the vessel's echo vessels using bottom trawls. Draggers sounder and the time the trawl ar involved in the Puget Sound, Wash., Acknowledgments rives. Additionally, variations in the whiting fishery depart from this A number of individuals and intensity of the fish traces passing norm. One vessel uses a smaller ver organizations made substantial con below the headrope indicate the quan sion of the "2/3 Cobb pelagic trawl" tributions during the preparation of tity of fish entering the trawl, an index described by Johnson and High this report. Captains Carl Burlesci, A. of catch rate. (1970), with an 18.3 m (60-foot) Geiser, and Lyle Yeck gave generous Wireless netsondes, which rely on headrope, 18.3 m breastlines, and an ly of their time while describing their an acoustic link to transmit informa 18.3 m footrope. Two other fisher catcher vessels and their operational tion via a hydrophone mounted either men use two-seam bottom trawls of practices in the joint-venture fisheries. on the ship's hull or a towed fin, are their own design, incorporating 108 The Gourock Division of Wire Rope the most common type found in the mm (4Y4-inch) mesh in the forward Industries, Ltd., furnished plans for a joint venture fleet. The more expen panels and with a 21.3 m (70-foot) rope trawl, and Northeastern Trawl sive "third-wire" netsondes, using a headrope and a 27.4 m (90-foot) Systems, Inc., provided information wire from the netsonde to the ship for footrope. from which the detachable codend il data transmission, are favored by Recently joint-venture fisheries for lustration was drawn. Marine some skippers because neither vessel whiting have gotten underway in Resources Company and the NMFS maneuvers nor water conditions can Canadian waters. No preferred trawl Foreign Fisheries Observer Program disrupt the data link, and current type has yet emerged within this fleet, provided other illustrative material. third-wire systems can provide as a number of different modern mid Dennis Lodge of Clatsop Community desirable additional information un water trawl designs are being College, Astoria, Oreg., and Ben available with current wireless employed. Otherwise, the vessels and Jones and Fred Wathne of the NMFS systems. In particular, the catch-load fishing practices are similar in most Northwest and Alaska Fisheries indicators available as accessories respects to the U.S. joint-venture Center, Seattle, Wash., reviewed the with some third-wire systems have operations already described. manuscript and made many helpful proven their value. With knowledge Summary suggestions. Carol Hastings helped of the quantity of fish in the codend, with the figures. the skipper can shorten or extend the The harvesting technology in the tow to get a catch of the preferred Pacific whiting fishery is in a state of Literature Cited size, usually 25-30 tons. Additionally, rapid evolution, particularly in the FAO. 1974. Otter board design and per by comparing the rate at which the joint venture fisheries. As fast as im formance. Food Agric. Organ. U.N., Dep. codend is filling up with the rate at proved trawls and electronic instru Fish., Rome. FAO Fish. Man., 82 p. which fish pass below the netsonde's ments become available and prove Hitz, C. R. 1970. Operation of the Soviet trawl neet off the Washington and Oregon headrope unit, the skipper can detect their worth, they are quickly adopted coasts during 1966 and 1967. In Pacific hake, escape reactions among the fish throughout the fleet. At present, most p. 53-76. U.S. Fish Wild!. Serv., Circ. 332. Johnson,L.J.,andW. L. High. 1970. Mid within the trawl and alter his opera boats use recent versions of Polish water trawling equipmenl and fishing tech tions accordingly. rope trawls spread with Suberkrub nique for capturing whiting off the coast of In addition to the equipment pelagic doors. Catch rates between I Washington and Oregon. In Pacific hake, p. 77-102. U.S. Fish. Wild!. Serv., Circ. 332. described above, joint venture boats and 3 tons per minute are relatively elson, M. 0., 1970. Pacific hake fishery in carry the usual assortment of other easy to attain with well-tuned gear. Washington and Oregon coastal waters. In navigation, communications, and Extensive use is made of Pacific hake, p. 43-52. U.S. Fish Wild!. Serv., Cir. 332. safety gear, such as SSB, CS, and sophisticated electronic aids. Sonars Rehme, W. 1973. Multi-purpose pelagic VHF radios, satellite navigation are used to locate schools of fish, and trawls. World Fish. 22(9):70-71. 54 Marine Fisheries Review