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Status of Lake Whitefish Populations In Lake Superior

Status of Lake Whitefish Populations In Lake Superior. Mike Petzold Upper Great Lakes Mgmt Unit, Ontario, M.N.R. For Mar. 2002, Annual Meeting of the Lake Superior Committee. Acknowledgments. M. Ebener (CORA) B. Mattes (GLIFWC) Members of LSTC. Introduction. Habitat

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Status of Lake Whitefish Populations In Lake Superior

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  1. Status of Lake Whitefish PopulationsIn Lake Superior Mike Petzold Upper Great Lakes Mgmt Unit, Ontario, M.N.R. For Mar. 2002, Annual Meeting of the Lake Superior Committee

  2. Acknowledgments • M. Ebener (CORA) • B. Mattes (GLIFWC) • Members of LSTC

  3. Introduction • Habitat • Harvest and Effort History • Management Guidelines • Current Status • Recommendations

  4. Known and Historic, Lake Whitefish Spawning and Nursery Areas Thunder Bay Kaministikwia R. Michipicoten R. St. Louis Estuary Isle Royale Bete Grise Bay Keewenaw Bay Apostle Is. Whitefish Bay From Bronte et al, unpublished manuscript

  5. Ontario Annual Whitefish Catch Distribution Whitefish Habitat CATCH (T) 0 . 5 0 1 . 0 0 2 . 0 0 4 . 0 0 8 . 0 0 1 6 . 0 0 3 2 . 0 0

  6. Total Harvest in Metric Tons 2 0 0 0 CATCH (T) 1 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 8 9 9 9 9 9 9 9 9 9 9 9 8 0 1 2 3 4 5 6 7 8 9 9 9 0 0 0 0 0 0 0 0 0 0 9 YEAR MI MN ON WI

  7. Total Effort (large mesh gillnet equivalents) 3 0 0 0 0 2 0 0 0 0 LARGE MESH GILLNET EFFORT (KM) 1 0 0 0 0 0 1 1 1 1 1 1 9 9 9 9 9 9 5 6 7 8 9 9 0 0 0 0 0 9 YEAR MI MN ON WI

  8. ONTARIO LARGE MESH GILLNET, BY MESH DEPTH 1 0 0 9 0 8 0 7 0 6 0 5 0 PERCENT 4 0 3 0 2 0 1 0 0 5 6 7 8 9 0 0 0 0 0 0 0 YEAR OTHER MESH DEPTH < 18 18 19-25 30-36 50 >50

  9. COMMERCIAL CATCH PER KM OF LARGE MESH GILLNET 1 9 0 1 8 0 1 7 0 1 6 0 1 5 0 1 4 0 1 3 0 1 2 0 CPUE KG/KM 1 1 0 1 0 0 9 0 8 0 7 0 6 0 5 0 4 0 3 0 1970 1980 1990 2000 YEAR WI MI ON

  10. Catch per km of gillnet for Western Ontario Zones 6 0 0 5 0 0 4 0 0 CPUE (KG/KM) 3 0 0 2 0 0 1 0 0 0 0 7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 0 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 YEAR Zone 7 9 1

  11. Geometric Mean CPUE Whitefish Bay (April-Sept.) 1 1 0 1 0 0 9 0 8 0 7 0 6 0 KG PER KM 5 0 4 0 3 0 2 0 1 0 0 7 4 7 6 7 8 8 0 8 2 8 4 8 6 8 8 9 0 9 2 9 4 9 6 9 8 00 YEAR ZONE ON-3 3 ON-3 4 Data plotted where effort >25 km

  12. ESTIMATED SPAWNING BIOMASS - EASTERN MICHIGAN Data from M. Ebener, CORA

  13. Management Guidelines/Objectives • Extractions of 0.51 kg/ha (water < 73 m) Busiahn(1990) • Total annual mortality (adults) between 60 and 65% Busiahn(1990) • Maintain self-sustaining populations within range of abundance observed between 1990-1999 (Draft Fish Community Objectives, 2001).

  14. Commercial Fish Regulations • Individual Transferable Quotas (Ontario) • Seasons and/or Licence Limits (Tribal Fisheries, States) • Gear Restrictions (all agencies)

  15. Mean Annual Yield in kg/ha, Lake Superior, 1998-2000 DATA FROM B. MATTES, 2001 REPORT TO THE GLFC Kg/ha 0 . 0 0 0 - 0 . 0 0 2 0 . 0 0 2 - 0 . 0 9 0 . 0 9 - 0 . 2 5 0 . 2 5 - 0 . 3 1 0 . 3 2 - 0 . 5 3 0 . 5 4 - 2 . 1 3 9

  16. 6.8 11.5 7.7 10.0 8.3 8.7 63% 7.8 55% 7.9 59% 9.4 55% 8.0 49% 7.6 69% [33%] 7.7 35% [36%] 7.4 38% [51%] 8.7 49% 8.2 56% Mean Age (top number) and Annual Mortality (bottom), 1997-2000 from Catch Curve 7.5 47% [62%] Note: Number in brackets is mortality of age 8 fish from Catch at Age Analysis

  17. Age Distribution in Commercial Gillnets THUNDER BAY (ON-1) 2 0 1 9 1 8 1 7 1 6 1 5 1 4 1 3 AGE 1 2 1 1 1 0 9 8 7 6 5 4 3 2 0 7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 YEAR

  18. MEAN FORK LENGTH(CM) FROM LARGE MESH GILLNETS 5 3 5 2 5 1 5 0 4 9 Mean Fork Length (cm) 4 8 4 7 4 6 4 5 4 4 4 3 0 0 7 7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 YEAR WFS-7 Mgmt. Unit ON-1 ON-33

  19. Percent Mature in Commercial Catch, Whitefish Bay 1 0 0 9 9 9 8 9 7 9 6 9 5 PERCENT MATURE 9 4 9 3 9 2 9 1 9 0 8 9 8 8 9 1 9 2 9 3 9 4 9 5 9 6 9 7 9 8 9 9 0 0 YEAR WFS-7 WFS-8

  20. PROPORTION FEMALES MATURE BY LENGTH 1 . 0 0 . 9 0 . 8 0 . 7 0 . 6 PROPORTION MATURE 0 . 5 0 . 4 0 . 3 0 . 2 0 . 1 0 . 0 4 0 5 0 6 0 7 0 TOTAL LENGTH-CLASS (CM) Mgmt. Unit WFS-7 WFS-6 ON-33 WFS-8

  21. MEAN TOTAL LENGTH - AGE 7 6 2 6 1 6 0 5 9 5 8 5 7 5 6 5 5 5 4 TOTAL LENGTH (CM) 5 3 5 2 5 1 5 0 4 9 4 8 4 7 4 6 0 5 0 5 0 5 0 7 7 8 8 9 9 0 YEAR ON-1 ON-33 WFS-7

  22. Stock Status Summary • Abundance is high in most zones, likely a consequence of stocks rebuilding after removal of effort when lake trout fishery collapsed in 1950s • Mortality below 60-65% guideline in most zones • Harvest composed mainly of mature fish • Average harvest weight has been increasing or is static in many zones • Prognosis is good for lake whitefish in most areas

  23. However, • Extractions, lake-wide, approach Historic maximum • Exceed 0.51 kg/ha in Whitefish Bay, Thunder Bay, Black Bay, and S. Pukaskwa • Abundance declining in Whitefish Bay (WFS-7, WFS-8, ON-33, ON-34)

  24. Recent Applications • Statistical Catch-at-age-analysis (CORA) • Simulations and Projections (CORA) • Habitat Mapping (MN, CORA-Whitefish Bay) • Food Web Modelling (ECOSIM)

  25. Recommendations Implement: • Index Fisheries to Acquire • relative abundance estimates • maturation rates, fecundity, growth • Methods to Delineate Stock • Habitat Mapping • Spawning and nursery areas • Refine and Develop Models • Seek ways to reduce lake trout by-catch

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