Middle Provo River:History, Regulations, and

Population Estimates

Middle Provo River:History, Regulations, and

Population Estimates

Jordan NielsonJordan Nielson

What Happened?What Happened?Pre-1997Low flows limited food production and habitat severely restricted.

Pre-1997Low flows limited food production and habitat severely restricted.

Post-1997 minimum flows (125 cfs) improved food production and habitat.

Post-1997 minimum flows (125 cfs) improved food production and habitat.

Pre-1997Low flows limited food production and habitat severely restricted.

Pre-1997Low flows limited food production and habitat severely restricted.

Post-1997 minimum flows (125 cfs) improved food production and habitat.

Post-1997 minimum flows (125 cfs) improved food production and habitat.

What Happened?What Happened?

1. Decreased Mortality

2. Increased Recruitment

1. Decreased Mortality

2. Increased Recruitment

0

5

10

15

20

25

30

1997 2000 2003

• Current regulations were implemented to protect/enhance the fishery and increase overall size of trout

• Percent of large brown trout (> 380 mm) declining

• Current regulations were implemented to protect/enhance the fishery and increase overall size of trout

• Percent of large brown trout (> 380 mm) declining

The EvidenceThe Evidence• 1997

– Mean Length – 352 mm

– Mean Weight – 695 g– Density - 640

fish/mile– Condition Factor –

1.27

• 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

• 2003– Mean Length – 298

mm– Mean Weight – 306 g– Density – 2,391

fish/mile– Condition Factor –

0.97

RegulationsRegulations• 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

• 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

Middle Provo RiverRegulation Change Study Recap

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

• 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

Middle Provo RiverRegulation Change Study Recap

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

• 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

IndicesIndices• Length• Weight• Condition Factor• Proportionate Stock Density• Relative Stock Density

• Length• Weight• Condition Factor• Proportionate Stock Density• Relative Stock Density

PSD = N≥9 inches X 100

N≥6 inches

62.2Quality

RSD = N≥15 inches X 100

N≥6 inches

10.8Memorable

PSD = N≥18 inches X 100

N≥6 inches

1.2Trophy

Length Across TimeLength Across Time

• 1997– 13.9 in

• 2010– 10.6 in

• 24% Reduction

• 1997– 13.9 in

• 2010– 10.6 in

• 24% Reduction

Weight Across TimeWeight Across Time

• 1997– 695 g/ 1.5 lb

• 2010– 250 g/ 0.5 lb

• 64% Reduction

• 1997– 695 g/ 1.5 lb

• 2010– 250 g/ 0.5 lb

• 64% Reduction

Condition Factor Across Time

Condition Factor Across Time

• 1997– 1.27

• 2010– 1.0

• 21% Reduction

• 1997– 1.27

• 2010– 1.0

• 21% Reduction

Population Density Across Time

Population Density Across Time

• 1997– 640 fish/

mile• 2010

– 2783 fish/ mile

• 435% Increase

• 1997– 640 fish/

mile• 2010

– 2783 fish/ mile

• 435% Increase

Middle Provo RiverRegulation Change Study Recap

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

• 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

ConclusionConclusion• General downward trend in population

indices • Upward Trend in Population Numbers• Overharvest = Easy Population

Manipulation• Changing angler paradigms needs to

be a “grassroots” movement

• General downward trend in population indices

• Upward Trend in Population Numbers• Overharvest = Easy Population

Manipulation• Changing angler paradigms needs to

be a “grassroots” movement

Goals:Goals:• Increase fish health without

decreasing the ability to catch fish

• Encourage angling groups to promote harvest to begin to change angler attitude

• Increase fish health without decreasing the ability to catch fish

• Encourage angling groups to promote harvest to begin to change angler attitude