State of Washington Department of Fisheries PACIFIC COD (GADUS MACROCEPHALUS) IN PUGET SOUND AND ADJACENT WATERS: BIOLOGY AND STOCK ASSESSMENT BY WAYNE A. PALSSON FISH BIOLOGIST DECEMBER 1990 Technical Report Number: 112 State of Washington DEPARTMENT OF FISHERIES TECHNICAL REPORT NO. 112 Pacific Cod (Gadus macrocephalus) in Puget Sound and Adjacent Waters: Biology and Stock Assessment by Wayne A. Palsson Fish Biologist Booth Gardner Governor December 1990 ABSTRACT A stock assessment of Pacific cod was undertaken for Puget Sound. The biology of Pacific cod was reviewed to provide insights into stock structure and population dynamics. Tagging data for Puget Sound revealed that three stocks exist: a stock in the Gulf-Bellingham and San Juan Island Regions, a stock in the Strait of Juan de Fuca and Port Townsend Bay, and a stock south of Admiralty Inlet. Catch data showed that periods of high catches alternate with periods of low catches. Six of these cycles were observed since 1942 with a peak catch of 3.5 million pounds in 1980. Catches in recent years have been below the last ten-year average of 2.5 million pounds per year. Catch patterns differed among regions. The Gulf-Bellingham Management Region typically produced over half of the catch of Pacific cod during a year. Catch rates from trawl and recreational fisheries were used as an index of abundance to assess stock condition. Catch rates in most regions and fisheries were lower in the 1980s than in the 1970s, but catch rates have been stable until 1990 in the Gulf­ Bellingham Region. Catch rates for fisheries in the eastern portion of the western stock have declined, especially for the Port Townsend area. Recreational catch rates for the southern stock were higher during some years in the late 1970s and early 1980s than during recent years. The causes of the decreased catch rates are not clear. Lower catch rates corresponded to a change in oceanographic conditions but also follow a period of increased fishing effort and harvest and increased marine mammal abundance. TECHNICAL REPORTS The Technical Reports present results of completed or ongoing investigations carried out by the Department of Fisheries that are deemed of sufficient timely interest to be made available to the scientific community and the public. The contents of these reports may be reprinted, and reference to the source will be appreciated. STATE OF WASHINGTON Booth Gardner, Governor DEPARTMENT OF FISHERIES Joseph R. Blum, Director MARINE FISH PROGRAM Mark Pedersen, Assistant Director 115 General Administration Building Olympia, WA 98504 TABLE OF CONTENTS Page LIST OF FIGURES.............................................. iii LIST OF TABLES............................................... v LIST OF APPENDIX FIGURES ..................................... vii I NTRODUCT I ON. 1 REVIEW OF BIOLOGy............................................ 4 Distribution and adult ecology........................ 4 Reproductive biology and growth ....................... 8 Stock Del ineation...................................... 15 Recruitment............................................ 17 MATERIALS AND METHODS........................................ 18 Catch and Effort....................................... 18 Commercial....................................... 18 Recreational..................................... 21 Stock Delineation...................................... 21 Stock Assessment....................................... 23 Catch rates...................................... 23 Length data...................................... 27 Mortality rates.................................. 27 RESULTS. 28 Stock Deli neat ion. 28 Fi shery Hi story. 33 Commerc i a 1 . 33 Recreational..................................... 38 Catch Patterns......................................... 43 PMFC Area 4A..................................... 43 Page Eastern North Pacific............................ 48 Regional Catches in Puget Sound.................. 51 Northern stock............................. 54 Western stock.............................. 59 Southern stock............................. 66 Stock Assessment....................................... 71 Northern stock................................... 71 Western stock ................................... 78 Southern stock .................................. 88 DISCUSSION ................................................... 93 Stock Deli neat ion. 93 Catch and Effort....................................... 94 Stock Assessment....................................... 98 Stock status..................................... 98 Assessment methods ............................... 100 Recruitment...................................... 102 Causes of Stock Decline ................................ 103 Environmental .........•.......................... 103 Fisheries effects ................................ 107 Further Research and Recommendations................... 110 SUMMARY. III ACKNOWLEDGEMENTS............................................. 113 LITERATURE CITED............................................. 114 APPENDIX FIGURES............................................. 123 ; ; LIST OF FIGURES Figure Page 1. Pacific Marine Fisheries Commission (PMFC) statistical areas along the British Columbia and Washington coasts. 2 2. Marine fish management regions of Puget Sound (PMFC Area 4A)......................................... 3 3. Minor statistical areas of the inside waters of British Columbia (after Westrheim 1987)................ 7 4. Marine fish catch reporting areas of Puget Sound ....... 20 5. Salmon Catch Record Areas (SCRAs) of Washington State .. 22 6. Historical Pacific cod catches in Puget Sound by trawl, set net, other commercial, and recreational gears. .. 44 7. Annual Pacific cod trawl catches along the U.S. coast and southern Vancouver Island (V.I.) and British Columbia waters north of Vancouver Island, 1956-1988 ............................................... 50 8. Pacific cod trawl catches by PMFC area: (A) Coastal areas; (B) Inside areas .................... 52 9. Annual Puget Sound Pacific cod catches by management region, 1955-1987...................................... 55 10. Annual catches of Pacific cod in the Gulf-Bellingham Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ............................. 56 11. Annual catches of Pacific cod in the San Juan Islands Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ............................. 57 12. Average monthly trawl catches (1978-1987) in each Puget Sound Management Region .......................... 58 13. Average monthly recreational catches (1978-1987) in each Puget Sound Management Region ..................... 60 14. Annual catches of Pacific cod in the Juan de Fuca Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ............................. 62 iii Figure 15. Annual catches of Pacific cod in the West Juan de Fuca Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ..............•.............. 63 16. Annual catches of Pacific cod in Port Townsend Bay (WOF Area 250 and Admiralty Inlet (WOF Area 25B) by trawls and set nets, 1970-1987 ...•..•.................. 64 17. Annual catches of Pacific cod in the Central Puget Sound Management Region south of Admiralty Inlet by trawl, set net, and sport gears, 1970-1987 ............. 67 18. Annual catches of Pacific cod in the South Puget Sound Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ..........•.................. 68 19. Annual catches of Pacific cod in the Hood Canal Management Region by trawl, set net, other commercial, and sport gears, 1970-1987 ................. 69 20. Trawl and recreational catch rates for the northern cod stock: (A) Trawl; (B) Recreational ................ 74 21. Annual mean lengths (by fishery years) for Pacific cod trawl samples, 1970-1988: (A) Northern Puget Sound; (B) Southern Puget Sound ......................•....•... 80 22. Trawl and recreational catch rates for the western cod stock: (A) Trawl; (B) Recreational ................ 82 23. Annual mean lengths (by fishery years) for Pacific cod set net samples by management region, 1970-1988 ........ 86 24. Annual mean lengths (by fishery years) for Pacific cod recreational samples, 1970-1988: (A) Northern Puget Sound; (B) Southern Puget Sound........................ 87 25. Trawl and recreational catch rates for the southern cod stock: (A) Trawl; (B) Recreational-central SCRAs; (C) Recreational-southern SCRAs .....•........... 89 26. Puget Sound climate index, based upon snowfall and sea surface temperatures (after Ebbesmeyer et ale 1988) .... 105 iv LIST OF TABLES 1. Growth parameters estimated from Pacific cod stocks .... 12 2. Total and natural mortality rates for Pacific cod ...... 13 3. Significant fishery months for recreational and trawl fisheries.............................................. 25 4. Modified results of Pacific cod tagging studies: Percent recoveries escaping fishery during tagging ..... 30 5. Frequency of parabranchial lesions on Pacific cod in Washington State .................................... 32 6. Annual trawl hours in each Puget Sound Management Region and the Port Townsend area, 1970-1988 ........... 37 7. Annual set net landings in each Puget Sound Management Region and the Port Townsend area, 1970-1988 ........... 39 8. Annual number of angler trips made by all anglers in each Puget Sound Management Region, 1970-1987 .......... 41