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.