Age and Growth of Fish
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Age and Growth of Fish
1. Definitions and metrics
2. Three primary ways to estimate growth
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Age and Growth of Fish
1. Age refers to years
• Aging fish, all fish have a birthday on January 1
- Change with spawning time (spring or fall in WI)
• Age class is the year the fish is born
• Not that all that interesting in itself, used to describe growth
- Exceptions might be maturity
2. Growth is the change in length, wet weight, or dry weight over time
• Why so many metrics?
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Different metrics of fish growth
Length
-Pros: easy, intuitive, history in angling, length rarely shrinks
-Cons: lots of change in biomass not related in length
Wet Weight
-Pros: used in large calculations (ie population biomass), metric used in production
-Cons: can take more time in field (rocking boat or wind and balance don't mix)
Dry Weight – fat weighs less then water but is way more valuable to individual. 24-72 hours at 60 degrees C (140° F)
-Pros: accurate description of individual's current state
-Cons: time intensive and must kill fish
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LOG (LENGTH)
LOG
(W
EIG
HT
)
How the metrics are related
• Length Frequency Analysis
W=.000004*L3.2603
W= 3.3287*L-12.689
W= 2.8401*L - 10.6620
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Length
Wei
ght
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3 ways to estimate growth in natural populations• Length Frequency Analysis
•Recaptures of individually marked fish
Back calculation from calcified structures
#C
augh
t
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10
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10 40 70 100 130 160 190 220 250 280
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Length Frequency Analysis
Pros: non-destructive, archived lengths
Cons: have to catch lots of fish, unknowns are high!, easy to bias sample with gear, time, or location
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10 40 70 100 130 160 190 220 250 280
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Recaptures of marked individuals
Pros: non-destructive, good individual data
Cons: have to catch TONS of fish to see a recapture
Population is 10000 fish
You catch and tag 100 fish, good effort, but
You Come back a year later.......at best maybe 60 survived....
.... so there are 54 tags in 10,000 fish
...maybe only 10% lost their tags
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Estimating growth from tagging
Pros: understand the variability in individual growth
Cons: tag loss, tagging may influence growth, behavior, or mortality, cant read tag
www.daybreakfishing.com/TaggingFish.html
www.dfg.ca.gov/.../FishTagDescriptions.htm
www.dfg.ca.gov/.../FishTagDescriptions.htm
www.dfg.ca.gov/.../FishTagDescriptions.htm
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T-bar, dart, floy tags –old school
www.fishinginpuertorico.com/page_ds10.htm
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Coded Wire Tags – new school
http://www.hafro.is/catag/myndir/cwt.jpg
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www.hpl.umces.edu/facilities/fishhatchery4.htm
www.bnl.gov/.../Herpetological_Inventories.htm
www.absc.usgs.gov/.../coho_archivetags_obj2.htm
PIT Tags – newest schoolpassive integrated transponder
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Tags for small fish
Visible Implant Elastomer
– new school
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Interpreting age from structures
• WE INTERPRET• we don't age, we don't assign ages
- seems overdone, but it is important, because it teaches you that you may be wrong, which is ok, as long as you know you might be wrong!
Cause Brian learned "the art" from Dr. John Casselman (OMNR)
2 main uses: Age and Back Calculate
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Age
12
345678
9
Age = this 358 mm largemouth bass is 10 years old
10
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Processed 76 largemouth bass
Crampton Lake (border upper penn. and WI)
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Age
Leng
th (
mm
)
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Back Calculate Growth
7
3
10
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y = 477.61x - 45.171
R2 = 0.847
y = 180.9x + 179.28
R2 = 0.7277
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0 0.2 0.4 0.6 0.8 1 1.2
Otolith Radius
Fis
h Le
ngth
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Back Calculation Age = this 358 mm largemouth bass is 10 years old
20052004200320022001200019991998199719961995YEAR
109876543210AGE
0.950.920.880.830.720.670.590.510.40.290.09RADIUS
355345338330310300284197143890LENGTH
0107820101687545489GROWTH (mm)
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Other structures used for aging
Cleithra - Esocidae (sacrifice)
arvidsfishingreport.com/
http://www.palaeos.com/Vertebrates/Bones/Dermal/Opercular.html
Opercula (sacrifice)
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www.fws.gov/midwest/alpena/rpt-stnib02.htm
Other structures used for aging
Vertebrae-Sharks (no spines, teeny otoliths)
www.pac.dfo-mpo.gc.ca/.../lingcod/ling_aging.htm
Fin Rays – anything where scales don't work and you don't want to kill the fish
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How we look at growth data ...ie figures!
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LMB Age
Me
an
Le
ng
thSize at age
How do we quantify how these populations are different?
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LMB Age
Me
an
Le
ng
thVon Bertalanffy Growth Equation
Lt L∞*(1 – e(-K*t))=Lt = length at time
't'L∞ = maximum length
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Problems with back calculation
• Lee's Phenomenon
Age Yr.Class 1 2 3 4 5 6
1 1988 90
2 1989 85 113
3 1990 78 112 139
4 1991 75 108 133 150
5 1992 66 96 129 147 160
6 1993 59 92 126 147 156 166
LENGTH AT AGE
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Understanding Vulnerability and Sample Bias
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Which fish have been taken out already
Which fish are not represented?
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Fisheries Uses of Age and Growth
• What does the age structure look like
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Age
% o
f th
e po
pula
tion
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Age
% o
f th
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pula
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Maturity
Maturity
Walleye population in Lake Nevafishd
Walleye population in Takemal Flowage
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Fisheries Uses of Age and Growth
• What if the length limit on bluegill was 150mm
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Toledo Bend
Toledo Reservoir
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Ecology of growth
20052004200320022001200019991998199719961995YEAR
109876543210AGE
0.950.920.880.830.720.670.590.510.40.290.09RADIUS
355345338330310300284197143890LENGTH
0107820101687545489GROWTH (mm)
![Page 29: Age and Growth of Fish](https://reader036.fdocuments.net/reader036/viewer/2022081503/56812ccf550346895d91881f/html5/thumbnails/29.jpg)
What ecological factors might influence that growth
Water temperature
Age
Climate or the Year
Food availability
Number of competitors
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