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Nechako (SG-5) and Upper Fraser (SG-4) White Sturgeon

Nechako (SG-5) and Upper Fraser (SG-4) White Sturgeon. Overview. Two populations Nechako and Upper Fraser Distribution Population Status Biological Description Threats Unknowns. Nechako Oct-2005. Nechako SG-5. Upper Fraser SG-4. Upper Fraser SG-4.

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Nechako (SG-5) and Upper Fraser (SG-4) White Sturgeon

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  1. Nechako (SG-5) and Upper Fraser (SG-4) White Sturgeon

  2. Overview • Two populations • Nechako and Upper Fraser • Distribution • Population Status • Biological Description • Threats • Unknowns Nechako Oct-2005

  3. Nechako SG-5 Upper Fraser SG-4

  4. Upper Fraser SG-4 • Stable Stock Structure/Ongoing Recruitment • Substantial numbers of juveniles • Small adult population • Juv. >50cm) 630109 Adults 18529 • Genetically distinct • from Nechako/ lower Fraser • Slow growth late maturity • low productivity habitat (relatively few salmon) • Summer temps peak 10-14 oC

  5. Threats/ Mortality • Few if any significant sources of direct human caused mortality • no guided fishing, low levels of sport fishing • Little development in the Upper Fraser River • no dams, • some agriculture, little bank encroachment, rip-rap or loss of side-channel habitat on the upper Fraser)

  6. NechakoSG-5

  7. Nechako SG-5 • Ageing Stock/ Ongoing Recruitment Failure • Few juveniles (n<20 50 cm to 1-m since ‘95) • Small population (570 150) mostly adults • Genetically distinct (mDNA/) from Upper Fraser • Slow Growth/ low productivity habitat • Largest < 3m growth 5.9 cm/year to 30 years, • 4.0 cm/year ages 30 to 50 • Late maturity ~40 years for females

  8. Age Distribution –Comparison through time Young fish dominant in 1980-82 catch. Older fish more abundant in 1995-99 catch.

  9. Discharge Pre/post Regulation Mean Daily Nechako River Flow at Vanderhoof

  10. Spawning • One confirmed spawning event at Vanderhoof • May 18, 2004 (22 adults in area) • Low discharge- 131 m3/s (declining limb) • Mean 13.9 oC Max 16.0 • Shallow depth 2.9- m, flow 1.02-1.26 m/s • 400 hrs egg mats/ kick netting • captured one larvae, 3 eggs

  11. Spawning • Other Congregations • 30-60 fish in 2003 (May 26) • 2002 (no visuals, just telemetry) • River conditions similar • 2005 no congregation • June 8 (n=4 ~ 1-m fish) • discharge 350-400 m3/s\

  12. Threats • Ongoing mortality in net fisheries • Uncertainty around recruitment failure • Spawning reach at Vanderhoof • Over winter sites (rkm 116, 125) • Summer feeding areas Stuart River confluence Critical Habitat

  13. Unknowns • Cause(s) of recruitment failure • Full extent of distribution • Mortality rates • Habitat and other factors allowing limited recruitment • Other spawning locations

  14. Potential solutions • Conservation hatchery at Vanderhoof • Coldwater release facility at Kenny Dam

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