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2005 Bottom Trawl Survey of the Eastern Bering Sea Continental Shelf

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Alaska Fisheries Science Center National Marine Fisheries Service U.S DEPARTMENT OF COMMERCE AFSC PROCESSED REPORT 2007-01 2005 Bottom Trawl Survey of the Eastern Bering Sea Continental Shelf January 2007 This report does not constitute a publication and is for information only. All data herein are to be considered provisional. This document should be cited as follows: Lauth, R, and E. Acuna (compilers). 2007. 2005 bottom trawl survey of the eastern Bering Sea continental shelf. AFSC Processed Rep. 2007-1, 164 p. Alaska Fish. Sci. Cent., NOAA, Natl. Mar, Fish. Serv., 7600 Sand Point Way NE, Seattle WA 98115. Reference in this document to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. Notice to Users of this Document This document is being made available in .PDF format for the convenience of users; however, the accuracy and correctness of the document can only be certified as was presented in the original hard copy format. 2005 BOTTOM TRAWL SURVEY OF THE EASTERN BERING SEA CONTINENTAL SHELF Compilers Robert Lauth Erika Acuna Bering Sea Subtask Erika Acuna Lyle Britt Jason Conner Gerald R. Hoff Stan Kotwicki Robert Lauth Gary Mundell Daniel Nichol Duane Stevenson Ken Weinberg Resource Assessment and Conservation Engineering Division Alaska Fisheries Science Center National Marine Fisheries Service National Oceanic and Atmospheric Administration 7600 Sand Point Way N.E. Seattle, WA 98115-6349 January 2007 ABSTRACT The Resource Assessment and Conservation Engineering Division of the Alaska Fisheries Science Center conducts annual bottom trawl surveys to monitor the condition of the demersal fish and crab stocks of the eastern Bering Sea continental shelf. The standard study area, surveyed each year since 1979, encompasses a major portion of the eastern Bering Sea shelf between the 20-m and the 200-m isobaths and from the Alaska Peninsula north to approximately the latitude of St. Matthew Island (60°50'N). In 2005, two chartered trawlers, the 40-m FV Arcturus and the 40-m FV Aldebaran, again surveyed this area. Demersal populations were sampled by trawling for 30 minutes at stations centered in a 20 × 20 nautical mile grid covering the survey area. At each station, species composition of the catch was determined. Length distributions and age structure samples were collected from ecologically and commercially important species. Three-hundred and fifty-three of the 356 standard survey stations were sampled. Walleye pollock, yellowfin sole, and rock sole dominated fish biomass estimates (10.1 metric tons combined). A total of 219 invertebrate species were identified in the survey. Survey results presented in this report include relative fishing powers of the survey vessels, abundance estimates for fish and invertebrates, geographic distributions of important fish species and size composition of principal fish species. Surface and bottom temperatures recorded at each sampling station are also presented. Appendices provide station data, species listings, and detailed results of analyses of abundance and biological data of the sampled populations. iii CONTENTS INTRODUCTION ...........................................................................................................................1 METHODS Survey Area and Sampling Design......................................................................................3 Survey Stations Sampling Design........................................................................................4 Survey Vessels and Sampling Gear .....................................................................................8 Data Collection ..................................................................................................................11 Data Analysis.....................................................................................................................16 Special Studies...................................................................................................................17 RESULTS Station Data........................................................................................................................19 Environmental Conditions .................................................................................................19 Relative Fishing Powers of Survey Vessels.......................................................................24 Relative Abundance of Individual Fish Species ................................................................25 Estimated Biomass of Major Fish and Invertebrate Groups..............................................25 Northwest Stations.............................................................................................................26 Abundance, Distribution, CPUE, and Size Composition of Principal Species and Species Groups ............................................................32 Walleye pollock .................................................................................................................34 Pacific cod..........................................................................................................................38 Yellowfin sole....................................................................................................................42 Rock sole (grouped)...........................................................................................................46 Flathead sole (grouped)......................................................................................................50 Alaska plaice......................................................................................................................54 Greenland turbot ................................................................................................................58 Arrowtooth flounder ..........................................................................................................62 Kamchatka flounder...........................................................................................................66 Pacific halibut ....................................................................................................................70 Bering skate .......................................................................................................................74 v Alaska skate .......................................................................................................................76 Warty sculpin.....................................................................................................................78 Great sculpin ......................................................................................................................80 Plain scupin........................................................................................................................82 Bigmouth sculpin...............................................................................................................84 Wattled eelpout ..................................................................................................................86 Shortfin eelpout..................................................................................................................88 Marbled eelpout .................................................................................................................90 Sturgeon poacher ...............................................................................................................92 Bering poacher...................................................................................................................94 Butterfly sculpin.................................................................................................................96 Eulachon ............................................................................................................................97 Capelin ...............................................................................................................................98 Pacific herring...................................................................................................................99 CITATIONS ................................................................................................................................101 APPENDIX A: List of Species Encountered.............................................................................................105 APPENDIX B: Station Data......................................................................................................................117 APPENDIX C: Rank Order of Relative Abundance of Fish and Invertebrates........................................133 APPENDIX D: Population Estimates by Sex and Size Groups for Principal Fish Species......................145 vi INTRODUCTION The eastern Bering Sea continental shelf supports one of the most productive groundfish and crab fisheries in the world (Bakkala 1993). Since 1970, groundfish such as walleye pollock (Theragra chalcogramma), yellowfin sole (Limanda aspera) and Pacific cod (Gadus macrocephalus) have been the primary target species among commercial catches. Although many species of groundfish are caught commercially, the most abundant has been the walleye pollock with catches ranging from 0.9 to 1.5 million metric tons (t) for the past 30 years (North Pacific Fishery Management Council 2002). Since 1971, the National Marine Fisheries Service (NMFS) Resource Assessment and Conservation Engineering
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