NOAA Technical Memorandum NMFS-AFSC-325 doi:10.7289/V5/TM-AFSC-325 Data Report: 2015 Gulf of Alaska Bottom Trawl Survey P. G. von Szalay and N. W. Raring U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration National Marine Fisheries Service Alaska Fisheries Science Center August 2016 NOAA Technical Memorandum NMFS The National Marine Fisheries Service's Alaska Fisheries Science Center uses the NOAA Technical Memorandum series to issue informal scientific and technical publications when complete formal review and editorial processing are not appropriate or feasible. Documents within this series reflect sound professional work and may be referenced in the formal scientific and technical literature. The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries Science Center continues the NMFS-F/NWC series established in 1970 by the Northwest Fisheries Center. The NMFS-NWFSC series is currently used by the Northwest Fisheries Science Center. This document should be cited as follows: von Szalay, P. G., and N. W. Raring. 2016. Data report: 2015 Gulf of Alaska bottom trawl survey. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-325, 249 p. Document available: http://www.afsc.noaa.gov/Publications/AFSC-TM/NOAA-TM-AFSC-325.pdf Reference in this document to trade names does not imply endorsement by the National Marine Fisheries Service, NOAA. NOAA Technical Memorandum NMFS-AFSC-325 doi:10.7289/V5/TM-AFSC-325 Data Report: 2015 Gulf of Alaska Bottom Trawl Survey P. G. von Szalay and N. W. Raring Alaska Fisheries Science Center National Marine Fisheries Service National Oceanic and Atmospheric Administration 7600 Sand Point Way NE Seattle, WA 98115 www.afsc.noaa.gov U.S. DEPARTMENT OF COMMERCE Penny. S. Pritzker, Secretary National Oceanic and Atmospheric Administration Kathryn D. Sullivan, Under Secretary and Administrator National Marine Fisheries Service Eileen Sobeck, Assistant Administrator for Fisheries August 2016 This document is available to the public through: National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161 www.ntis.gov iii PREFACE This report presents data from the 2015 Gulf of Alaska groundfish survey conducted by the Alaska Fisheries Science Center of the National Marine Fisheries Service. It contains detailed descriptions of the survey planning and operations, species distribution and abundance charts, length frequency plots, tables of estimated biomass, catch per unit effort, average weight and length estimates, length frequency plots, length-weight regression parameters, lists of identified species, survey strata specifications and charts, and trawl descriptions and diagrams. v ABSTRACT Scientists of the Groundfish Assessment Program of Alaska Fisheries Science Center's Resource Assessment and Conservation Engineering (RACE) Division conducted the ninth Gulf of Alaska Biennial Bottom Trawl Survey during the summer of 2015. This survey extends to 13 the series of surveys, previously conducted every 3 years between 1984 and 1999, which constitute the time series used in stock assessments of Gulf of Alaska groundfish resources. The survey area covered the continental shelf and upper continental slope to 1,000 m in the Gulf of Alaska from Islands of Four Mountains (170°W long.) and approximately 2,800 km across the Gulf of Alaska to Dixon Entrance (133°25'W long.). The survey was conducted aboard three chartered commercial trawlers, the FV Alaska Provider, FV Sea Storm, and FV Cape Flattery. Trawl haul samples were successfully collected at 772 survey stations using standard RACE Division Poly Nor'Eastern high-opening bottom trawl nets with rubber bobbin roller gear. The primary survey objectives were to define the distribution and estimate the relative abundance of the principal groundfish species within the survey area and to collect data to estimate biological parameters useful to groundfish researchers and managers including age, growth, length-weight relationships, feeding habits, and size, sex, and age composition. The survey also collected ancillary data requested by other research groups. A total of 171 fish and 410 invertebrate species were captured in survey tows. The species with the highest total catch abundance (by weight) over the entire survey area were arrowtooth vi flounder (Atheresthes stomias), Pacific ocean perch (Sebastes alutus), walleye pollock (Gadus chalcogrammus), giant grenadier (Albatrossia pectoralis), Pacific halibut (Hippoglossus stenolepis), and Pacific cod (Gadus macrocephalus). Survey results presented here include estimates of catch per unit of effort, biomass, population size composition, and length-weight relationships, as well as charts depicting the distribution of catch for commercially important species encountered during the survey. vii CONTENTS PREFACE .................................................................. iii ABSTRACT ................................................................. v INTRODUCTION ............................................................. 1 METHODS .................................................................. 4 Survey Area............................................................ 4 Vessels ............................................................... 5 Fishing Gear ........................................................... 9 Survey Design .......................................................... 9 DataCollection Techniques ............................................... 11 CollectionandProcessingof Samples .......................................13 Abundance, Size Composition, and Length-Weight Relations ...................... 15 Survey Limitations ..................................................... 17 RESULTS .................................................................. 18 Catch Resultsby Area ...................................................20 Catch Resultsby Species .................................................22 FLATFISHES ............................................................... 23 Arrowtooth Flounder .................................................... 23 Pacific Halibut......................................................... 30 Flathead Sole.......................................................... 37 SouthernRock Sole..................................................... 44 Northern Rock Sole ..................................................... 51 Rex Sole ............................................................. 58 Dover Sole............................................................ 63 Yellowfin Sole......................................................... 72 Other Flatfishes ........................................................ 79 Alaska Plaice .................................................... 79 Starry Flounder .................................................. 79 English Sole..................................................... 76 Butter Sole...................................................... 80 ROUNDFISHES ............................................................. 89 Walleye Pollock........................................................ 89 Pacific Cod ........................................................... 96 Atka Mackerel........................................................ 103 Sablefish ............................................................ 110 Giant Grenadier....................................................... 117 ROCKFISHES.............................................................. 124 PacificOcean Perch.................................................... 124 Northern Rockfish. .................................................... 131 Rougheye Rockfish .................................................... 138 Blackspotted Rockfish.................................................. 145 Dusky Rockfish. ...................................................... 152 Dark Rockfish ........................................................ 159 Sharpchin Rockfish .................................................... 164 Shortraker Rockfish.................................................... 171 Shortspine Thornyhead.................................................. 178 viii Other Rockfishes...................................................... 185 Redstripe Rockfish .............................................. 185 Silvergray Rockfish .............................................. 185 Harlequin Rockfish .............................................. 185 Redbanded Rockfish.............................................. 186 Yelloweye Rockfish .............................................. 186 Rosethorn Rockfish. ............................................. 186 SKATES ..................................................................199 Alaska Skate ......................................................... 199 Aleutian Skate ........................................................ 199 Bering Skate ......................................................... 199 Big Skate............................................................ 200 Longnose Skate ....................................................... 200 MISCELLANEOUS SPECIES ..................................................211 Capelin ............................................................. 211 Eulachon............................................................ 211 Pacific Hake ......................................................... 211 CITATIONS ...............................................................219 APPENDIX A ..............................................................223