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Middle Provo River Regulation Impact Study: Enhancing Trout Population Trends Post-1997

Explore the effects of post-1997 regulations on Middle Provo River trout population. Discover how minimum flows improved food production and habitat, resulting in decreased mortality and increased recruitment. Dive into data showing changes in trout size, weight, density, and conditions factors pre and post regulations. Analyze angler behavior shifts and the need for potential changes in regulations to impact fish size positively. This study emphasizes promoting sustainable fish health and angler attitudes through strategic management.

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Middle Provo River Regulation Impact Study: Enhancing Trout Population Trends Post-1997

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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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