1 / 76

Size Structure

Size Structure. Learning Objectives. Construct and interpret length-frequency distributions Describe, calculate, and interpret Swingle’s ratios Describe the development and interpretation of standardized length categories Calculate and interpret PSS indices

galya
Download Presentation

Size Structure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Size Structure

  2. Learning Objectives • Construct and interpret length-frequency distributions • Describe, calculate, and interpret Swingle’s ratios • Describe the development and interpretation of standardized length categories • Calculate and interpret PSS indices • Describe differences associated with using traditional and incremental size-structure indices • Identify the dynamic rate functions and relations with size structure indices

  3. Size Structure • Methods of measurement of fish population structure • Calculation of indices • Interpretation of structural indices

  4. Fish Length and Weight

  5. Considerations

  6. Indices

  7. Homer Swingle • Faculty member at Auburn University • One of the first to use experimental ponds to obtain insight on management • Interested in “balanced” fish populations in ponds

  8. Balance • “The interrelationships in fish populations are satisfactory if the populations yield, year after year, crops of harvestable fish that are satisfactory in amount when the basic fertilities of the bodies of water containing those populations are considered. Such populations are considered to be ‘balanced populations’ and the species within such a population are ‘in balance.’” • “Balance then denotes a condition within a population such that if 100 pounds of fish are harvested one year the correct numbers of replacements will be provided from the population so that a satisfactory poundage of fish of desirable size may be harvested in succeeding years. If the population provides too many replacements, these fish will not reach a satisfactory size for harvesting; conversely, if too few replacements are provided, the capacity of the body of water to produce will not be fully utilized and the harvestable poundage will seriously decline.”

  9. Swingle’s F/C Ratio

  10. Swingle’s F/C Ratio • F = • C =

  11. Swingle’s F/C Ratio

  12. Swingle’s F/C Ratio

  13. Swingle’s Y/C Ratio • Y = • C =

  14. Swingle’s Y/C Ratio

  15. Swingle’s Y/C Ratio

  16. Swingle’s At

  17. Swingle’s At Species Minimum weight BLG, RESF, and similar sunfishes 0.1 Crappies 0.26 LMB 0.4 Bullheads 0.3 GZS 0.5 CHCF 0.5 Gar 1.0 Buffalo 1.0 Carp 1.0

  18. Swingle’s At

  19. Swingle’s At

  20. Swingle’s At

  21. Swingle’s At

  22. Swingle’s E • Swingle’s E = • Lower bound of balanced with 1 “C” and 1 “F” species is 1.4:1 (BLG:LMB). Therefore, there is 1 pound of LMB for every 2.4 lbs of fish (100 × 1 / 2.4 = 41.6%) • LMB (balanced) = • LMB (desired)=

  23. Other Swingle Indices • A value = • I value = • S value =

  24. Jenkins and Morais Metric • AP/P ratio • AP = • P = • Plotted on a log10 vs log10 scale • Curve should be above the 1:1 line to have sufficient prey for predators

  25. Jenkins and Morais Metric

  26. Swingle Ratios and Similar Indices • Potential problems and practicality???

  27. Length-Frequency Histograms

  28. Guidelines • ROT…sample 100 fish > stock-length

  29. Guidelines • Y-axis

  30. Guidelines • X-axis are bins • “bin bias”

  31. Bin Bias

  32. Length-Frequency Indices

  33. Weithman and Anderson (1978) Gabelhouse (1984) Length Categorization

  34. Length Categorization • Stock length = • Quality length = • Preferred length = • Memorable length = • Trophy length =

  35. Length Categorization

  36. Proportional Stock Density (PSD) • Proportion of stock-length fish that are quality length or greater • PSD = 100 × (# of fish > minimum quality length / # of fish > minimum stock length) • Round to nearest whole number!

  37. PSD-WAE Example

  38. PSD-WAE Example

  39. PSD S Q S = 29 Q = 17 S = 29 Q = 17

  40. RSDs • RSD = 100 × (# of fish > specified length / # of fish > stock length) • Round to nearest whole number! • Specified length (e.g., RSD-35) • Standard length categories

  41. RSD-WAE Example Substock (< 250 mm) = 7 Stock (250 mm) = 29 Quality (380 mm) = 17 Preferred (510 mm) = 10 Memorable (630 mm) = 6 Trophy (760 mm) = 0

  42. S Q P M T PSD = 59 RSD-P = RSD-M = RSD-370 = PSD = 59 RSD-P = RSD-M = RSD-370 =

  43. Traditional versus Incremental RSDs • Traditional RSDs • Incremental

  44. RSD-WAE Example Q P M T S

  45. RSD-WAE Example SS = S-Q = Q-P = P-M = M-T = T =

  46. RSD-WAE Example Q P M T S SQ SS QP PM MT T

  47. Traditional versus Incremental RSDs • Incremental RSDs • Traditional RSDs

  48. Proportional Size Structure (PSS) • Confusion in terminology with Proportional Stock Density and Relative Stock Density

  49. Proportional Size Structure Terminology Current New PSD PSSQ RSD-Q PSSQ RSD-P PSSP RSD-M PSSM RSD-T PSST RSD S-Q PSSSQ RSD Q-P PSSQP RSD P-M PSSPM RSD M-T PSSMT

  50. Size Structure

More Related