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WF4133‐Fisheries Science
Module 4: Culture FisheriesClass 23
Housekeeping
• Now is the time to be looking for summer jobs!– State websites– USA jobs– Fisheries.org– Texas A&M
Scenario 1‐If everybody gets 200 out of 200 on the final then the lowest grade in the class = A
Scenario 2‐If everybody performs similarly to Exam II then the lowest grade in the class = C (but barely, right on the margin)
No Lab Monday @ 1pm – flooded out
• Lab @ 1pm Columbus to help MDWFP• Will try to get everybody there… if possible and weather cooperates.
Homework Due 4/22 by 5pm
• Develop 6 questions for the final exam– 2 multiple choice– 2 short answer– 2 in a format of your choice, excluding multiple choice or short answer.
– MUST Include the right answer• Email to me by due time• These will be used as the basis for the final exam & will be posted to the website for you to study from.
Final Exam
• Wednesday May 1, 2019 8am‐11am
CULTURE FISHERIES
Aquaculture is commonly used in fisheries to supplement or augment populations that are at risk to loss and mitigate for loss of habitat. There is much to be learned about the effects of stocking on fish populations.
Hatchery types
1. Commercial: profitable source of protein2. Research: optimize hatchery practices3. Enhancement: provide fish for additional
fishing opportunity4. Conservation: population recovery
Enhancement
• “Enhance” fishing opportunities• 2 types
– Put & grow– Put & take
Stocking types
1. Put & grow‐ fish are stocked at a small size & allowed to grow to harvestable size‐ assumes fish will survive & grow
2. Put & take‐ fish are raised to harvest size and stocked‐ assumes fish will be harvested
Put & grow‐
Need to understand1) Growth‐ need to understand how long it will take stocked fish to get to harvestable size2) Survival‐ need to know how many to stock to have sufficient 3) Carrying capacity
Suppose…
Time
Opening day
Size
Harvestable size
Suppose…
Time
Opening day
Abun
dance
Fish per acre
Stocking objectives
1. How many fish
2. What size by expected harvest time
Stocking tables
• How many fish to stock & when given:1) growth2) survival3) habitat
• One of the first: Embody 1927
Embody’s stocking tables
A formal approach
0
0
whereMean population densityInitial population density
Annualsurvival ( )Instantaneous mortality
Z F
AN NZ
NN
A A eZ
Estimate the number of fish to plant to get a desired mean density
An example
Suppose we have a 100 acre lake & desire to have a 300 hatchery origin fish per acre next year‐ Instantaneous mortality (Z) is 0.6‐ Fishing mortality (F) is 0.2Need to determine A A = exp(‐Z‐F)A = exp(‐0.4)A = 0.45
An example
0
0
0
0
0
0.450.6
0.6 0.45 0.60.45 0.6 0.450.60.45
300
300
300
399
AN NZ
N
N
N
N
Need to stock 399 fish per acre
A formal approach
• Estimate the number of fish to plant to get a desired mean density or biomass
0
0
1
Mean biomassInitial biomassInstananeousgrowth rateInstananeous mortality rate
g ZeP Pg Z
wherePPgZ
An example
Suppose we have a 100 hectare lake & desire to have a 75 kg per hectare hatchery origin fish per acre next year‐ Instantaneous mortality (Z) is 1.39‐ Instantaneous growth (g) is 1.61
How much to stock
0
1.61 1.39
0
0
0
0
1
1751.61 1.39
75 1.11875
1.11867.1
g ZeP Pg ZeP
P
P
P
If a fry weighs 45 grams then you need to stock 1491 fry per hectare (67.1/0.045)
Stocking sport or forage fish?
• Walleye stocking in Spirit Lake, Iowa• Managed for walleye• Spirit Lake: about 10,000 sac fry/ha stocked• Predation of stocked fish sustain artificially high adult walleye densities
State of the science
• Selecting for desirable traits (e.g., super catchables)
• Hybridization with native fish• Hybrids• Sterilization‐ triploidy• Return to creel• Lunkers‐ strains with increased growth• Stocking strategies & systems
Hatchery types
1. Commercial: profitable source of protein2. Research: optimize hatchery practices3. Enhancement: provide fish for additional
fishing opportunity4. Conservation: population recovery
Conservation
• Mitigation‐ create or maintain a run that was lost due to dams
• Supplementation‐ supplement existing runs that have experienced declines due to habitat loss/modification or overfishing
Willamette basin spring ChinookAnadromous species of conservation need
-Threatened status 1999- Anthropogenic modifications
Spring Chinook life historyRedds & eggs Parr (0+)Hatch Fry (0+)
Smolt (1)
Mini jack (2)
Jack (3)
Adult (4)
Adult (5)
Adult (6)
1950‐60s Barriers to adult migration
www.nwd‐wc.usace.army.mil
Big Cliff
Big Cliff: 1953
Foster
Foster: 1968
Cougar: 1963CougarFall Creek: 1966
Dexter: 1954
Fall Creek &
Dexter
Willamette Falls
Limited natural reproduction
www.nwd‐wc.usace.army.mil
Big Cliff: 1953
Foster: 1968
Cougar: 1963Fall Creek: 1966
Dexter: 1954 Big Cliff
Foster
Cougar
Fall Creek &
Dexter
Dexter Dam
Spring Chinook life historyRedds & eggs Parr (0+)Hatch Fry (0+)
Smolt (1)
Mini jack (2)
Jack (3)
Adult (4)
Adult (5)
Adult (6)
Fall Creek Dam
Dexter Dam
Lookout Point Dam
Hills Creek Dam
Natural production
Trap and haul
Historic spawning habitat
Historic spawning habitats
Fall Creek Dam
Dexter Dam
Lookout Point Dam
Hills Creek Dam
Natural production
Historic spawning habitat
Historic spawning habitats
Fall Creek Dam
Dexter Dam
Lookout Point Dam
Hills Creek Dam
Natural production
Historic spawning habitat
Historic spawning habitats
Another source of natural production!
Key to recovery!
Reintroduction above dams1) Trap
2) Haul
3) Outplant
Issues with conservation?
• Domestication • Reduced fitness• Unnatural selection• Behavior differences
Domestication
• Change genetics• Rapidly select for fish that excel in hatchery environment
• Shorter time scale relative to environmental variability
Reduced fitness
• Survival of hatchery origin fish may be lower than naturally produced fish
• Relative reproductive success half of natural fish (Milot et al.)
Unnatural selection
• Spring chinook return to the Imnaha River• June to September
Study area
Process
Spawning run: Week 23‐37June – mid September
Objectives‐ Get sufficient number of fish to meet hatchery quotas
Spawning Fish Collected From Wild
Expectation: no selection effect
Week
Abun
dance
Cumulative abundance
Expectation: selection effect
Week
Abun
dance
Cumulative abundance
Hatchery effects
• In some years,hatchery fisharrived earlier
• In other yearsnatural origin fish returnedearlier
Consequences Happening upstream of the Weir.
State of the science
Spawning protocols• Timing• Genetic diversity & pedigreeRearing conditions• Diet• Density• Substrate• Predators