Condition

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Condition

description

Condition. Learning Objectives. Describe condition and different methods for measuring or indexing condition Calculate and interpret length-weight relationships Describe the advantages and disadvantages of different methods for describing condition Describe the RLP technique - PowerPoint PPT Presentation

Transcript of Condition

Page 1: Condition

Condition

Page 2: Condition

Learning Objectives• Describe condition and different methods for

measuring or indexing condition• Calculate and interpret length-weight relationships• Describe the advantages and disadvantages of

different methods for describing condition• Describe the RLP technique• Calculate and interpret different condition indices• Describe relations of condition to rate functions

Page 3: Condition

Power Function

• W = aLb

• b >• b < • b =

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Length (mm)

0 100 200 300 400 500 600

Wei

ght (

g)

0

500

1000

1500

2000

2500

3000

3500

Length-Weight Relationships• Strong relationship between length and

weightIowa SMBR 2 = 0.99P = 0.0001

Weight = 0.00000639 (Length)3.123

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Logarithm Rules

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Logarithm Rules

• Multiplication inside the log can be turned into addition outside the log, and vice versa

• Division inside the log turned into subtraction (denominator is subtracted) outside, and vice versa

• An exponent inside log moved out as a multiplier, and vice versa

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Power Function

• So, if W = a Lb

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Length-Weight Relationship

Length (mm)

0 100 200 300 400 500 600

Wei

ght (

g)

0

500

1000

1500

2000

2500

3000

3500

log10 length (mm)

1.8 2.0 2.2 2.4 2.6 2.8

log 1

0 w

eigh

t (g

)

0

1

2

3

4

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log10 length (mm)

1.8 2.0 2.2 2.4 2.6 2.8

log 1

0 w

eigh

t (g

)

0

1

2

3

4

Length-Weight Relationship

Iowa SMBr 2 = 0.99P = 0.0001

log10 (W) = -5.033 + 3.057 log10 (L)

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Condition

• So…weight can be predicted from length

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Length (mm)

0 100 200 300 400 500 600

Wei

ght (

g)

0

500

1000

1500

2000

2500

3000

3500

Condition

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Indices of Condition

• Fulton condition factor • Relative condition factor • Relative weight

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Fulton Condition Factor

• K = • C =

• KTL, KSL

• CTL, CSL

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Fulton Condition Factor

KTL =

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Fulton Condition Factor

• Condition factors vary for the same fish depending on whether you estimate K or C

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Relative Condition Factor

• Compensates for differences in body shape

• Kn =

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Relative Condition Factor

log10 length (mm)

1.8 2.0 2.2 2.4 2.6 2.8

log 1

0 w

eigh

t (g

)

0

1

2

3

4Iowa SMBr 2 = 0.99P = 0.0001

log10 (W’) = -5.033 + 3.057 log10 (L)

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Relative Condition Factor

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Relative Condition Factor

• Average fish of all lengths and species have a value of 1.0 regardless of species of unit of measurement

• Limited by the equation used to estimate W’– Communication is hindered among agencies

• Also, tend to see systematic bias in condition with increasing length

• To help alleviate these problems and to improve utility of the condition indices, relative weight (Wr) was derived

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Relative Weight

• Wr = 100 x (W/Ws)

• log10 (Ws) = a’ + b log10 (L)

– Note: a’ = log10 (a)

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Relative Weight

• First equation was for LMB using data from Carlander (1977)– Compiled weights and a curve was fit to the

75th-percentile weights to develop the Ws equation

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Regression-Line-Percentile (RLP)

• Obtain length-weight data from populations across the distribution of the species

• Fit log10-transformed length-weight equation to obtain estimates of a’ and b for each population

• Estimate weight of fish at 1-cm intervals (from minimum and maximum lengths in data set) for each population

• Obtain the 75th-percentile weight for each 1-cm length group

• Fit an equation to the 75th-percentile weights

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Regression-Line-Percentile (RLP)

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Regression-Line-Percentile (RLP)

Flathead catfishn = 4 populations

log10 length (mm)

1.8 2.0 2.2 2.4 2.6 2.8 3.0

log 1

0 w

eigh

t (g

)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

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Regression-Line-Percentile (RLP)

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Regression-Line-Percentile (RLP)

n = 74

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Regression-Line-Percentile (RLP)

• Obtain the 75th-percentile weight for each 1-cm length group

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Regression-Line-Percentile (RLP)

log10 length (mm)

2.0 2.2 2.4 2.6 2.8 3.0 3.2

log 10

wei

ght

(g)

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0log10 (Ws) = -5.542 + 3.230 log10 (length)Minimum length = 130 mm

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Relative Weight—SMB Example

Minimum length = 150 mm

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Relative Weight

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Relative Weight

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Relative Weight

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Relative Weight

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Relative Weight

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Relative Weight

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Relative Weight

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Relative Weight