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Middle Provo River: History, Regulations, and Population Estimates

Middle Provo River: History, Regulations, and Population Estimates. Jordan Nielson. What Happened?. Pre-1997 Low flows limited food production and habitat severely restricted. Post-1997 minimum flows (125 cfs) improved food production and habitat. What Happened?. Pre-1997

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Middle Provo River: History, Regulations, and Population Estimates

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  1. Middle Provo River:History, Regulations, and Population Estimates Jordan Nielson

  2. What Happened? Pre-1997 Low flows limited food production and habitat severely restricted. Post-1997 minimum flows (125 cfs) improved food production and habitat.

  3. What Happened? Pre-1997 Low flows limited food production and habitat severely restricted. Post-1997 minimum flows (125 cfs) improved food production and habitat. • Decreased Mortality • Increased Recruitment

  4. Current regulations were implemented to protect/enhance the fishery and increase overall size of trout • Percent of large brown trout (> 380 mm) declining

  5. 1997 Mean Length – 352 mm Mean Weight – 695 g Density - 640 fish/mile Condition Factor – 1.27 2003 Mean Length – 298 mm Mean Weight – 306 g Density – 2,391 fish/mile Condition Factor – 0.97 The Evidence

  6. Regulations • 2003 • Flies and artificial lures only • Brown trout limit 2 under 15 inches • Closed to the possession of cutthroat and rainbow trout. • 2004 • Above Legacy Bridge • Flies and artificial lures only • Trout limit 2 under 15 inches • Below Legacy Bridge • General Regulations • No gear restrictions, limit 4 trout

  7. Middle Provo RiverRegulation Change Study Recap • Angler survey: • Use increased by 35% to 278 h/acre/month (2002-2007) • Harvest increased in general regulation section • Provided additional opportunity for a more diverse group of anglers • 0.91 fish/hour - Special • 0.85 fish/hour - General

  8. Middle Provo RiverRegulation Change Study Recap • Angler survey (continued): • Fly fishermen are less likely to harvest fish (65% less 02-07) • Despite education/information • Bait anglers will harvest fish • Accounted for 47% of harvest overall • Accounted for 2% of total hours overall Provo River 1937

  9. Indices • Length • Weight • Condition Factor • Proportionate Stock Density • Relative Stock Density

  10. PSD = N≥9 inches X 100 N≥6 inches 62.2 Quality

  11. RSD = N≥15 inches X 100 N≥6 inches 10.8 Memorable

  12. PSD = N≥18 inches X 100 N≥6 inches 1.2 Trophy

  13. Length Across Time • 1997 • 13.9 in • 2010 • 10.6 in • 24% Reduction

  14. Weight Across Time • 1997 • 695 g/ 1.5 lb • 2010 • 250 g/ 0.5 lb • 64% Reduction

  15. Condition Factor Across Time • 1997 • 1.27 • 2010 • 1.0 • 21% Reduction

  16. Population Density Across Time • 1997 • 640 fish/ mile • 2010 • 2783 fish/ mile • 435% Increase

  17. Middle Provo RiverRegulation Change Study Recap • Special Regulations are not serving a biological purpose • Fish populations have not been negatively impacted by the regulation change • May need a higher harvest rate to see a positive change in fish size (Donald and Alger 1989) • >20% Reduction

  18. Conclusion • General downward trend in population indices • Upward Trend in Population Numbers • Overharvest = Easy Population Manipulation • Changing angler paradigms needs to be a “grassroots” movement

  19. Goals: • Increase fish health without decreasing the ability to catch fish • Encourage angling groups to promote harvest to begin to change angler attitude

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