Bream Lab: Relative Weight

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Bream Lab Relative Weight

• BIOL 3500L
• Dr. Christopher Kodani

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Learning Objectives (for Lab Quiz)

• Calculate relative weight
• Explain
• Relative weights, below 0.8, from 0.8 to 1.0,
  above 1.0
• Why using fish board is important
• Discuss example from Florida Fish Wildlife
• Identify largemouth bass, bluegill, warmouth,
  redbreast sunfish, channel catfish
• Discuss linear and non-linear regression

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Shelfords Tolerance Curve

• Note Y-axis Performance
• Could be some measure of condition
• Speed of animal
• Height of plants
• of offspring

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Relative Weight

• For fish, condition measured as Relative Weight
• Ratio of actual weight to standard weight
• Similar to Body Mass Index for humans
• CDC website http//www.cdc.gov/nccdphp/dnpa/bmi/ad
  ult_BMI/about_adult_BMI.htm

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Standard Weight

• What a fish should weigh
• Depends upon
• Size of fish
• Species
• Other factors (region, sex, reproductive
  condition)
• Available in literature
• Georgia Adopt-a-Lake Manual
• Alabama Cooperative Extension http//www.aces.edu/
  pubs/docs/A/ANR-1193/

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Fish Measurements

• Florida Fish and Wildlife http//floridafisheries.
  com/Fishes/measure.html
• Ignore girth, we only want length
• Use fish board!

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Calculating Relative Weight

• Actual weight / standard weight
• If you like, you can x100 for percentage

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Identifying Fish

• These could be present in Swan Lake
• Channel Catfish
• Look like a cat!
• Largemouth Bass
• Two distinct dorsal fins
• Sunfishes a.k.a. bream (two dorsal fins merged)
• Bluegill
• All black ear tab
• Redbreast sunfish
• Has very long ear tab
• Warmouth
• Stripes on face

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Fish ID Study Resources

• Texas Parks http//www.tpwd.state.tx.us/landwater/
  water/aquaticspecies/inland.phtml
• Virginia Fish Wildlife http//www.cnr.vt.edu/efi
  sh/families/centrarchidae.html
• NC State University http//www.ces.ncsu.edu/nreos/
  wild/fisheries/topics/fishidentification.html
• Tennessee Wildlife Resources Agency
  http//www.ces.ncsu.edu/nreos/wild/fisheries/topic
  s/fishidentification.html
• Florida Fish and Wildlife http//www.ces.ncsu.edu/
  nreos/wild/fisheries/topics/fishidentification.htm
  l

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Actual Research Example

• Florida study shows flooding may improve some
  fishs condition
• Florida Fish and Wildlife http//www.floridamarine
  .org/features/view_article.asp?id24545
• Note box and whiskers plot

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For Your Notebooks

• Frequency Distribution Tables (separate species)
• Body mass
• Total length
• Relative weight
• Make histograms (separate species)
• One for length
• One for body mass
• Scatter Plot (all fish on one)
• Mass vs. length
• Plus standard lab write up in your notebook, by
  next lab (10 points)

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Frequency Distribution

• An organized, summarized list of measurements
• Tells number within each interval
• Ex Ages of people in a group

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Frequency Distribution Example

• Bluegills (cm) 8.83, 9.25, 8.77, 10.38, 9.31,
  8.92, 10.22, 7.95, 9.74, 9.51, 9.66, 10.42,
  10.35, 8.82, 9.45, 7.84. 11.24, 11.06, 9.84, 10.75

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Histogram
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Scatter Plot
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Mean

• Mean average
• Not the only measure of centrality!
• Also median and mode!
• Example
• Bluegills (cm) 8.83, 9.25, 8.77, 10.38, 9.31,
  8.92, 10.22, 7.95, 9.74, 9.51, 9.66, 10.42,
  10.35, 8.82, 9.45, 7.84. 11.24, 11.06, 9.84, 10.75

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Mode

• Mode most common category
• Bluegills (cm)
• 8.83, 9.25, 8.77, 10.38, 9.31, 8.92, 10.22, 7.95,
  9.74, 9.51, 9.66, 10.42, 10.35, 8.82, 9.45, 7.84.
  11.24, 11.06, 9.84, 10.75

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Median

• Median the middle one (for odd sample size)
• Or average of the two in the middle for even
  sample size

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Regression

• Makes a best fit line for data
• We can use MS Excels Graph Wizard function
• Enter length into column A
• Enter body mass into column B
• Use Graph Wizard to graph of bluegill weight vs.
  length

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Linear vs. Non-Linear Regression

• Linear regression
• Assumes straight-line relationship
• y mx b
• Non-linear regression
• Uses other equations for line
• Y a bx cx2
• In Excel, click on line
• Add trendline
• Choose linear or power
• Options
• Show equation
• Show r2