DOCSLIB.ORG

Fisheries Stock Assessment User's Manual Part I

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Fisheries Stock Assessment User's Manual Part I Preface This manual was developed based on material presented during several stock assessment training courses sponsored by the Atlantic States Marine Fisheries Commission, and supplemented by class lecture notes of Dr. Joseph T. DeAlteris, Professor of Fisheries and Aquaculture, University of Rhode Island. It is intended to be used as a reference for stock assessment biologists and students, and as a course handbook for future ASMFC stock assessment training courses. ii Acknowledgments The Commission would like to thank all of those people who assisted with the stock assessment training courses including Dr. Lisa Kline (ASMFC), Dr. Alan Temple (U.S. Fish and Wildlife Service, National Conference and Training Center), Dr. Joseph T. DeAlteris (University of Rhode Island), Mr. Najih Lazar (Rhode Island Division of Fish and Wildlife), and all the presenters and lecturers (Dr. Don Orth, Virginia Tech; Dr. Joseph DeAlteris; Mr. Mark Gibson, Rhode Island Division of Fish and Wildlife; Mr. Najih Lazar; Dr. Wendy Gabriel, National Marine Fisheries Service; Dr. Jeremy Collie, University of Rhode Island; and Dr. Josef Idoine, National Marine Fisheries Service). We are grateful to the National Conference and Training Center (U.S. Fish andWildlife Service, Shepherdstown, WV) and the University of Rhode Island for assisting with the development of the training courses, and for providing access to classrooms and computer facilities. Grateful appreciation is extended to Dr. Matthew Mitro (ASMFC/Rhode Island Division of Fish and Wildlife) for reviewing the document and providing useful comments and suggestions, and Ms. Vanessa Jones (ASMFC) and Ms. Laura Lee (ASMFC) for assistance with formatting and editing. Special thanks go to Dr. DeAlteris for providing his lecture notes, time, and experience to this manual. iii Table of Contents Preface................................................................................................................................................... ii Acknowledgements ............................................................................................................................. iii List of Figures.................................................................................................................................... viii List of Tables ..................................................................................................................................... xiii Introduction to Fish Stock Assessment, Fisheries Management, Fisheries and Fishery-Dependent Data, and Research Surveys and Fishery-Independent Data Joseph T. DeAlteris and Laura G. Skrobe .........................................................................................I - 1 Background ................................................................................................................................... I - 1 Fisheries Management .................................................................................................................I - 1 Fish Stock Assessment..................................................................................................................I - 3 Fisheries and Fishery Dependent Data..........................................................................................I - 4 Hooks and Line Gear................................................................................................................I - 4 Pots and Traps..........................................................................................................................I - 5 Dragged Gear...........................................................................................................................I - 7 Seines ....................................................................................................................................... I - 9 Gillnets ................................................................................................................................... I - 11 Fishery-Dependent Data and Analyses .................................................................................. I - 12 Research Surveys........................................................................................................................ I - 13 Bibliography................................................................................................................................ I - 15 Mathematics and Biostatistics Review Joseph T. DeAlteris...........................................................................................................................II - 1 Functions......................................................................................................................................II - 1 Powers and Logarithms................................................................................................................II - 6 Transforming or Linearizing Functions .......................................................................................II - 7 Differential Calculus....................................................................................................................II - 9 Integral Calculus........................................................................................................................II - 12 Differential Equations................................................................................................................II - 14 Descriptive Statistics..................................................................................................................II - 15 Hypothesis Testing.....................................................................................................................II - 18 Fitting Models to Data ...............................................................................................................II - 19 Exercises ....................................................................................................................................II - 21 Bibliography...............................................................................................................................II - 23 Growth Joseph T. DeAlteris and Laura G. Skrobe ...................................................................................... III - 1 Introduction................................................................................................................................ III - 1 Von Bertalanffy Growth Equation............................................................................................. III - 3 Estimating Length................................................................................................................. III - 3 iv Estimating Weight................................................................................................................. III - 5 Estimating Age...................................................................................................................... III - 6 Estimating Growth Equation Parameters................................................................................... III - 6 Gulland-Holt Method............................................................................................................ III - 6 Ford-Walford Plot................................................................................................................. III - 8 Non-linear Regression Methods.......................................................................................... III - 10 Gompertz Growth Equation................................................................................................ III - 11 Exercises .................................................................................................................................. III - 12 Bibliography............................................................................................................................. III - 13 Estimation of Mortality Rates Don Orth, Najih Lazar, and Joseph T. DeAlteris ........................................................................... IV - 1 Introduction................................................................................................................................ IV - 1 Estimating Total Mortality from Catch Curve Analysis............................................................ IV - 8 Estimating Total and Fishing Mortality from Tagging Experiments....................................... IV - 10 One Time Releases or Single Census (Petersen Type) ....................................................... IV - 11 Recaptures in a Series of Years from a Single Year Release.............................................. IV - 12 Estimating Natural Mortality from Fishing Mortality and Effort Data ................................... IV - 14 Other Methods for Estimating Natural Mortality..................................................................... IV - 15 Exercises .................................................................................................................................. IV - 17 Bibliography............................................................................................................................. IV - 18 Selectivity of Marine Fish Harvesting Gears: General Theory, Size Selection Experiments, and Determination of Size Selection Curves Joseph T. DeAlteris.......................................................................................................................... V - 1 Background
Load more

Recommended publications
  • POST-RELEASE MORTALITY of SCHOOL-SIZE ATLANTIC BLUEFIN TUNA (Thunnus Thynnus) in the U.S
    W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 2013 Post-Release Mortality of School-Size Atlantic Bluefin unaT (Thunnus thynnus) in the U.S Recreational Troll Fishery Benjamin Jon Marcek College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Fresh Water Studies Commons, and the Oceanography Commons Recommended Citation Marcek, Benjamin Jon, "Post-Release Mortality of School-Size Atlantic Bluefin unaT (Thunnus thynnus) in the U.S Recreational Troll Fishery" (2013). Dissertations, Theses, and Masters Projects. Paper 1539617936. https://dx.doi.org/doi:10.25773/v5-fknv-f695 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. POST-RELEASE MORTALITY OF SCHOOL-SIZE ATLANTIC BLUEFIN TUNA (Thunnus thynnus) IN THE U.S. RECREATIONAL TROLL FISHERY A Thesis Presented to The Faculty of the School of Marine Science The College of William and Mary In Partial Fulfillment Of the Requirements for the Degree of Master of Science by Benjamin Jon Marcek 2013 APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Master of Science Benjamin'Jon Marcek Approved, by the Committee, August 2013 ihn E. Graves, Ph.D. Committee Chairman/Advisor f Mary . Fabrizio, pfct). Richard W. Brill, Ph.D. John M. Brubaker, Ph.D.
    [Show full text]
  • Salmon Wrapup
    Looking Back: Hansen seiners UNITED FISHERMEN OF ALASKA www.pacificfishing.com THE BUSINESS MAGAZINE FOR FISHERMEN n OCTOBER 2016 Salmon wrapup US $2.95/CAN. $3.95 10 • California herring reform 63126 • Pink problems IN THIS ISSUE Editor's note Wesley Loy ® Pink THE BUSINESS MAGAZINE FOR FISHERMEN INSIDE problems Just as this issue of the magazine was going to press, Alaska Gov. Bill Walk- er sent a letter asking U.S. Commerce Secretary Penny Pritzker to declare a fishery disaster for parts of the state experiencing poor pink salmon harvests this season. Walker also directed staff to promptly consider payment waivers for pink salmon fishermen holding state loans. Observer safety review • Page 6 A disaster declaration potentially could result in millions of dollars in federal relief for Alaska’s fishing industry. Alaska isn’t the only state hoping for help after a tough fishing season. California is seeking a federal disaster declaration for its crab fishery, which was hobbled last season due to an algae-related marine toxin. For sure, Alaska pink salmon fishermen had a miserable year. The state- wide harvest of about 38 million pinks was far below the preseason forecast of 90 million. Walker requested a disaster declaration for two areas that historically have Salmon wrapup • Page 8 produced large volumes of pink salmon – Prince William Sound and Kodiak. He also included two minor fisheries in his request – Chignik and Lower Cook Inlet. Curiously, the major Southeast Alaska fishery was not included in the governor’s request, even though Southeast likewise had a subpar pink salmon harvest this year.
    [Show full text]
  • By RAMYLEO T. PELAYO Special Project Report in Partial Fulfillment
    THE PHILIPPINE FISHERIES SYSTEM: A MANAGEMENT PLANNING PERSPECTIVE by RAMYLEO T. PELAYO Special Project Report in partial fulfillment of the requirements for the Degree of Master of Science Marine Resources Management Program College of Oceanography Oregon State University Corvallis, Oregon 1983 For Lilia and Janice ACKNOWLEDGEMENTS My study grant for a masteral program in Marine Resources Management (MRM) came from the Philippine Governments agricul- tural loan project with the United States Government. I am therefore thankful to the officials and staffs of the National Economic and Development Authority (NEDA) and the United States Agency for International Development (USAID), the projects coor- dinating agencies for their respective governments, and the Phil- ippine Council for Agriculture and Resources Research and Deve- lopment (PCARRD), the agency I work for. I am particularly indebted to Dr. Elvira 0. Tan, PCARRD Director for Fisheries Research, for recommending me for a fel- lowship. In the end, I appreciate the favorable appraisal of my graduate committee: Dr. Victor T. Neal, MRM Program Coordinator and project adviser; Prof. Robert Schoning of the Department of Fisheries and Wildlife; and Dr. William Pearcy of the College of Oceanography. Among my professors, I should thank Dr. Charles Warren for providing me with a fresh lens for viewing resource science and management. My deepest gratitude goes to Olga and Bruce Sutherland without whose generosity and friendship my experience here would not have been as meaningful and fruitful. I also give my thanks to several other people who helped me in different ways during the making of this report, especially Kathryn Boeckman, Peter Howd, Heather Fawkes, Gary Braun, Federico and Emma Valerio, Anne-Marie Fagnan, Tish Parmenter, Mark Solon, Peter Ochumba, Gustavo Montero, Taka Hirai, Bill Ratliff, and my co-workers in PCARRD, Cesar Pagdilao, Rachel Baguilat, and Ester Cortes.
    [Show full text]
  • Boat Conference Organized by the U.N
    Copiesavellshie from: SeeGrant Extension Program 6022 MoCartyHall Universityof Florida Gslnssvlila,F I.3281 1 PletW.SseOrant Cogsge le supportedhy awed of the Officeof SeeOrant, NationalOceania aad AtrnoepherieAdmlnletradon, U4. Depert- raentef Cetmmrm,grant nwahw NAESAA-~, underprovisions of the Natkmef8ee GrantCogege and ProgramsAot of 1888. This hdenaatlaals pehlldtedhy the SeeOrant Eatenekm Proipam wideh funatlons as ~ componentof the Florida CooperativeEatenslon Ssrvtse. JehuT. ggaeste,dom, In mmduetlngCoeperadve Extension work in Agriculture.Home Eoonomies, and ggerineSeieneee. State of Fkrride.U.S. gttpartnrsntef Agrharlture,UA Qspartmentof Commerse,and Soerdeof County Commiesloasm,cooperating. printed end dlstrlhutedIn ferdsemnseof the Acts of CengrWsof Stay 8 aadJune 1 1,1814. The Florida See Orant College h anEqual Employment Opportunity-Affirme- ~ eeAetkm employeraatharlmd m 'yrow4h~h, edaoatloaalkrformadon and other earvtaeeonly to individualsand InstNutlomthat ~ aoettenwithout Nacrd ta ress,eaktr, eea, or nationalorigin. I NTERNATIQNAL CONFERENCE DN DESIGN, CONSTRUCTION,AND OPERATIONOF COMMERCIAL F I SHING VESSELS Sponsored By: Florida Sea Grant College Program Society of Naval Architects and Marine Engineers, Southeast Section Florida Institute of Technology College of Science and Engineering: OceanEngineering Program Held At: Florida Institute of Technology Edi ted By: John C. Sainsbury Thomas M. Leahy Sea Grant Project No. IR/84-6 Grant No. NA 80AA-D-00038 Report Number 67 Florida Sea Grant College May 1985 Price: $10.00 ACKNOWLEDGEMENTS SPONSORS: Florida Sea Grant College Society of Naval Architects and Marine Engineers, Southeast Section Florida Institute of Technology, College of Engineering: OceanEngineering Program CONFERENCEGENERAL CHAIRMAN: Dr. JohnC. Sainsbury,Professor Chairman, Ocean Engineering Program, Florida Institute of Technology, Melbourne, Florida 32901, USA CDGRDI NATI NG COMMITTEE: Tom Col 't ins, Desco.
    [Show full text]
  • The Invention of Power Block
    Purse seines hauled by a power block http://www.fao.org/fishery/equipment/powerblock/en SIXTY ANNIVERSARY OF PATENTING POWER BLOCK - SHORT STORY ON MARIO PURATIĆ (1904-1993) Jakov DULČIĆ and Branko DRAGIČEVIĆ (AdriaMed team) Institute of Oceanography and Fisheries, Split, CROATIA POWER BLOCK-MARIO PURATIĆ Power block is a mechanized pulley used to haul in nets, purse seine, etc. During the last decades, fishermen and deck equipment manufacturers introduced various ingenious innovations aimed to reducing manpower on board and facilitating the working procedure during fishing operations. One such innovation was the power block. No single invention has contributed more to the success of purse seine net hauling than extensive line of Power Blocks. First introduced in the 1950's the Puretic Power Block line became the linch-pin in the mechanization of purse seining. Combined with fluid hydraulic power technology and new large synthetic nets, it changed the whole character of purse seine fishing. The original Puretic power block was driven by an endless rope from the warping head of a winch. Such power blocks seem to be now used rarely, if at all. Nowdays, as a rule, power blocks are driven by hydraulic pumps driven from the main or auxiliary engine. http://www.fao.org/fishery/equipment/powerblock/en POWER BLOCK-MARIO PURATIĆ Mario Puratić (Sumartin, Island Brač, Croatia, 26 June 1904. – Santa Barbara, California, USA, 6 January 1993.) – Croatian fisherman from Brač becomes and American inventor – (usually spelled Puretic or Puretich in English) Mario Puratić Birth house POWER BLOCK-MARIO PURATIĆ - born in a family of farmers and fishermen - as many of his countrymen, he left his home in 1925 to seek a better life in the United States, where he was a hard-working fisherman on large tuna purse seiners -in 1954 he invented fishing equipment that revolutionized the technology of hauling fishing nets; patent approval was on 7th Feb 1956 -- Until then fishing nets had to be manually drawn by eight to ten people, which was an extremely difficult job.
    [Show full text]
  • The New Fisherman
    WILLIAM B. McCLOSKEY, JR. THE NEW FISHERMAN Hydraulic hoses and black boxes make fishing easier, but exact a price. We took hail and spray in our faces and crouched buoy of the first crab pot: barely a minute's search monkey-style to keep pace while working the gear on for a 2-foot pink buoy hidden in rolling seas during a a pitching deck glazed with ice. The wind blew a snowstom. straight 35 knots and gusted 60. Up through the Despite the weather, we worked all night, black hydraulic block zipped a crab pot-a 7-foot-square waves that could obliterate us towering over our by 3-foot steel-framed cage. Seven hundred pounds deck; worked without stop through all the daylight empty, it would now weigh 1000 to 2500 pou~ hours and on through the next night until about 2 depending on the number of king crabs insi£ Its AM. At last, peeling off our raingear but nothing else, trip up from the seafloor 60 fathoms below took we groaned to our bunks. about a minute. The pot surfaced in a froth of purple By the first grey light, the skipper had the wheel crab shapes and water. We braced it at the rail again. He slowed the engine, a standard signal. Our waiting for the proper boat motion, and swung it fishermen's discipline responded with feet back into aboard, holding tight to prevent a wild swing. Then it damp boots, salt-clammy raingear over our clothes. was teamwork on the run, to prepare the line and And so for seven days, until our tanks were filled.
    [Show full text]
  • RECENT USE of FISH AGGREGATING DEVICES in the EASTERN TROPICAL PACIFIC TUNA PURSE-SEINE FISHERY: 1990-1994 (Revised March 1996)
    RECENT USE OF FISH AGGREGATING DEVICES IN THE EASTERN TROPICAL PACIFIC TUNA PURSE-SEINE FISHERY: 1990-1994 (Revised March 1996) (This is a revised copy of Administrative Report LJ-95-14) By Wesley A. Armstrong and Charles W. Oliver Southwest Fisheries Science Center P.O. Box 271 La Jolla, California 92038-0271 March 1996 ADMINISTRATIVE REPORT LJ-96-02 Contents Page List of Figures....................................................................................................................................ii List of Tables.................................................................................................................................... iii INTRODUCTION............................................................................................................................1 LOGS ...............................................................................................................................................2 FADS................................................................................................................................................4 FAD INVESTIGATIONS: 1990-1992 .............................................................................................6 FAD INVESTIGATIONS: 1993-1994 .............................................................................................7 DOLPHIN-SAFE QUESTIONNAIRE.............................................................................................8 SKIPPER A's FADs: Drifting FADs: Construction and Deployment..........................................................................9
    [Show full text]
  • The Effects of Seasonal Variations, El Niño-Southern Oscillation, and Climate Change on the Tuna-Dolphin Association
    University of San Diego Digital USD Theses Theses and Dissertations Winter 11-25-2019 The effects of seasonal variations, El Niño-Southern Oscillation, and climate change on the tuna-dolphin association Caitlynn Birch University of San Diego Michael D. Scott Inter-American Tropical Tuna Commission Zhi-Yong Yin University of San Diego Lisa T. Ballance Oregon State University Follow this and additional works at: https://digital.sandiego.edu/theses Part of the Aquaculture and Fisheries Commons, Marine Biology Commons, and the Terrestrial and Aquatic Ecology Commons Digital USD Citation Birch, Caitlynn; Scott, Michael D.; Yin, Zhi-Yong; and Ballance, Lisa T., "The effects of seasonal variations, El Niño-Southern Oscillation, and climate change on the tuna-dolphin association" (2019). Theses. 40. https://digital.sandiego.edu/theses/40 This Thesis: Open Access is brought to you for free and open access by the Theses and Dissertations at Digital USD. It has been accepted for inclusion in Theses by an authorized administrator of Digital USD. For more information, please contact [email protected]. UNIVERSITY OF SAN DIEGO San Diego The effects of seasonal variations, El Niño-Southern Oscillation, and climate change on the tuna-dolphin association A thesis submitted in partial satisfaction of the requirements for the degree of Master of Science in Environmental and Ocean Sciences by Caitlynn Amber Birch Thesis Committee Michael D. Scott, PhD., Chair Lisa T. Ballance, PhD. Zhi-Yong Yin, PhD. 2019 i Copyright 2019 Caitlynn Birch iii ACKNOWLEDGEMENTS First and most of all, I would like to thank Dr. Michael Scott for his incredible expertise, assistance, guidance and patience throughout the course of this project and thesis.
    [Show full text]
  • FAO Fishery Country Profile
    FISHERY COUNTRY PROFILE Food and Agriculture Organization of the FID/CP/USA United Nations PROFIL DE LA PÊCHE PAR PAYS Organisation des Nations Unies pour l'alimentation et l'agriculture RESUMEN INFORMATIVO Organización de las Naciones Unidas para February 2005 SOBRE la Agricultura y la Alimentación LA PESCA POR PAISES t THE UNITED STATES OF AMERICA I. General geographic and economic data Land and Water Area[ii]: Land: 9,631,418 sq. km // water: 469,495 sq km EEZ area (to 200 miles) [iii]: 3.36 million sq. nm = 11.5 million sq. km Length of coastline[iv]: 19,924 km Population (2005) [v]: US: 295,184 // World: 6,410,524,000 GDP (2004) [vi]: US$ $11,815 billion Per Capita GDP (2003)[vii] US$ 37,898 Agriculture (Farms) GDP (2003) [viii]: US$ 84.8 billion, 0.8 % of total US GDP Forestry, Fishing, & Hunting GDP (2003) Combined US$ 29.1 billion, 0.3 % of US GDP [ix] II. Fisheries data (2003) [x] Production Imports Exports Food Per supply caput sup.* mt in live weight - except mollusks kg/year Fish for direct 3,420,000 4,390,000 2,450,000 5,360,000 26.8 human consumption Fish for animal 900,000 310,000 620,000 590,000 4.2 feed and other purposes TOTAL 4,320,000 4,700,000 3,070,000 5,950,000 31.0 * Per capita supply excludes exports, is live weight, and includes military abroad 1. Estimated employment Primary sector: The number of vessels greater than 5 net tons with commercial fishing documents is about 36,150 (2005)[xi]In an internal NMFS analysis of commercial fishing craft that were licensed and actively fished during 2004, there were about 19,350 vessels and 17,300 boats.
    [Show full text]
  • Subsistence, Commercial, and Recreational Fisheries
    p. 567-594. In: The Ecology of Marine Fishes: California and Adjacent Waters. 2006. L.G. Allen, D.J. Pondella, and M. H. Horn (eds.). University of California Press, Berkeley, 670 pp. C HAPTER 22 Subsistence, Commercial, and Recreational Fisheries MILTON S. LOVE Introduction occurred during the late Pleistocene, at least 12,000 years before the present (BP) (Erlandson et al., 1996; Rick, 1999). The marine fisheries of California extend back thousands of Many of these early subsistence communities utilized an years and encompass many dozens of species. This chapter extremely wide range of marine and terrestrial animals and describes the broad trends in these fisheries from the time of plants. And while these earliest settlers captured fishes as the first aboriginal fishermen to the present day. We can only part of their diet, shellfish were usually more important paint with a broad brush and we will leave the mass of catch (Erlandson, 1991, 1994; Warren, 1968). However, it is clear statistics and other detailed analyses for such technical works that there was a great deal of variability in the food habits of as Leet et al. (2001). the first California residents. For instance, fishes contributed It is important to note that over the years landings in both 50–65% (edible meat) to the diets of the inhabitants of Daisy the recreational and commercial fisheries have been quite Cave, San Miguel Island, a site dated to at least 12,000 BP volatile. As noted by Thomson (2001), “Landings tend to (Rick, 1999). increase with stock abundance, as fish are easier and less costly Fish species central to the diets of coastal peoples varied to locate and harvest when they are at higher levels of abun- with location.
    [Show full text]
  • Technical Report Number 3 0 Appendixes A,B, & C
    ~“&+?a . g#E#,~ fJJ)py . ~~ Technical Report Number 30 Appendixes A,B, & C A,a@()~3 I Socioeconomic Studies Program Sponsor: Bureau of Land Management Northern and Western Gulf of Alaska Petroleum Development Scenarios Commercial Fishing Industry Analysis The United States Department of the Interior was designated by the Outer Continental Shelf (O(X) Lands Act of 1953 to carry out the majority of the Act’s provisions for administering the mineral leasing and develop- ment of offshore areas of the United States under federal jurisdiction. Within the Department, the Bureau of Land Management (BLM) has the responsibility to meet requirements of the National Environmental Policy Act of 1969 @_EPA) as well as other legislation and regulations dealing with the effects of offshore development. In Alaska, unique cultural differences and climatic conditions create a need for developing addi- tional socioeconomic and environmental information to improve OH deci- sion making at all governmental levels. In fulfillment of its federal responsibilities and with an awareness of these additional information needs, the BLM has initiated several investigative programs, one of which is the Alaska OCS Socioeconomic Studies Program (SESP). The Alaska OCS Socioeconomic Studies Program is a multi-year research effort which attempts to predict and evaluate the-effects of Alaska OCS Petroleum Development upon the physical, social, and economic environ- ments within the state. The overall methodology is divided into three broad research components. The first component identifies an alterna- tive set of assumptions regarding the location, the nature, and the timing of future petroleum events and related activities. In this component, the program takes into account the particular needs of the petroleum industry and projects the human, technological, economic, and environmental offshore and onshore development requirements of the regional petroleum industry.
    [Show full text]
  • References Technological Aspects of the Modern Norwegian Purse Seine
    NORWEGIAN PURSE SEINE TECHNOLOGY 225 net is then shot. Sometimes two boats cooperate. In that tons, whereas the smallest open boats seldom exceed case, one of the boats equipped with an echo sounder 50 metric tons each. stays above the school until the second one has shot the net around it. Small mechanical purse winches are commonly available. Sometimes, in the case of smaller References boats, manual winches are used. During pursing, the vessels have to be anchored in order to stay clear of the ANON Records of catches. Aegir, 1961-69. net. In the case of cooperation of two boats, the search JAKOBSSON, J Recent developments in Icelandic Herring Purse boat sometimes purses· by steaming with one end of the 1964 Seining- In Modern Fishing Gear of the World, 2, purse line away from the catch boat. Power blocks are pp. 294-305. London. not generally used. (Personal communication from Hjortur Fjeldsted, Akureyri.) THORSTEINSSON, G Fangrnethoden in der Kabeljaufischerei. The season starts in late April and lasts as long as 1965 Protokolle zur Fischereitechnik, Vol. IX, pp. 288-381. schools can be found, usually until late July. If the fish THORSTEINSSON, G Icelandic purse seines with double is scattered, the vessels take up other fishing gear, such 1970 leadline- Construction and experience. FAO Techni­ as handlines or Danish seines. The average catch of cal Conference on Fish Finding, Purse Seining and boats above 20 GT is in most years more than 200 metric Aimed Trawling. Reykjavik. (See p. 273 ff.) Technological Aspects of the Modern Norwegian J. Hamre, 0.
    [Show full text]