Management of Small Impoundments

1. Management of Small Impoundments Chapters 21 (22)

2. Introduction • Pond = small impoundment • <0.4 ha – 40 ha • 0.2 ha – 2.4 ha (AFS Central States Pond Management Work Group) • Dam constructed to impound water • Various water sources • Springs, streams, precipitation, runoff

3. Introduction • Usually privately owned • Farm ponds • Livestock water • Irrigation • Most numerous in central and southeast • Important contribution to sportfishing • Rarely regulated as a “water of the US”

4. Management Philosophy • Sustained or improved fishing quality • High catch rates and above-average sizes

5. Multiple Uses of Ponds • Boating • Fishing • Livestock • Bird hunting • Swimming • Aesthetics

6. Ecological Principles • Trophic Relationships • Productivity and Biomass

7. Ecological Principles • Carrying capacity: max mass or density supported over a certain time period • K Density Fish Size

8. Ecological Principles • Average Fish Size varies as a function of overall pond productivity and population density

9. Ecological Principles • Influence of Aquatic Vegetation • Increased primary productivity • Decreased predator foraging efficiency • Decreased harvest efficiency • Dense prey populations • Stunted predator populations

10. Pond Types and Management Options • Warmwater • Bass and bluegill, sometimes catfish • Fall, winter, spring trout (summer kills) • Most Common and Most research • Coldwater • Trout, usually stocked • Coolwater • Rare; Walleye, hybrid striped bass, perch, etc.

11. All-Purpose Option • Harvest of LMB, BG, and CC • 30-38 cm (12-15 in) slot limit for LMB after 4 years • Reduces mid-size BG and allow some BG to reach 8 in • Harvest 75 LMB per ha (8-12 in) • Harvest BG and CC at will • Importance of LMB slot limit • Over harvest = Over population of BG • Release slot fish and smaller = Over population and stunting of LBM

12. Harvest Quota Option • Due to problems with length limits • Set harvest independent of length • Quota on number or weight per time • Difficult: • Need accurate record keeping • Tend to overharvest larger LMB and underharvest small LMB • Harvest BG and CC at will • Harvest 3-10 times the amount of LMB • C/R after quota is reached

13. Panfish Option • Big panfish instead of LMB • 15 in min length for LMB • Abundance of 8-15 in LMB reduce BG density • Large BG survive and grow > 8 in • Small LMB generally • May compete with BG (remove some) • Easy: unmanaged ponds tend to move in this direction

14. Big BASS Option • Reduce number of LMB 8-15 inches so remaining individuals grow large • Harvest 75 LMB 8-12 in and 13 LMB 12-15 in per ha per year • Release all LMB > 15 inches (except bucket mouths) • Stock gizzard shad as prey for large LMB • Catch rate is low but sizes are large • Larger ponds • Numerous small BG may reduce recruitment of LMB

15. Catfish Only Option • In muddy or small ponds • No structure for spawning or they overpopulate and stunt • Fathead minnow prey • Unrestricted harvest • Restocking to replace harvested fish

16. Black Bass Only Option • Shallow, weedy ponds with too much cover (BG stunting) • Feed on crayfish, bugs, own young • Need several year classes stocked • Prevents development of dominant year class • Inefficient use of pond resources?

17. Trout Options • Coldwater ponds—spring fed • Usually rainbow trout • Easy to control by stocking rates (won’t reproduce in standing water—brook trout will) • Must Restock • Become accustomed to formulated fish foods • Fee-fishing ponds

18. “All Purpose” Recipe • Initial Pond Survey • Population Status • Electrofishing and seining • Assess population “balance” • Alkalinity • Aquatic Weeds

19. “All Purpose” Recipe • Kill the Pond • Initial Stocking • Forage species (bluegill, shell crackers, fat head minnows) • Predator species (largemouth bass) • Stocking Rates • Supplemental Stocking • Essential in large ponds (>2 acres) • Threadfin shad, golden shiners)

20. “All Purpose” Recipe • Liming • Essential if pH < 7 and Alkalinity < 20 ppm • Agricultural limestone • Why useful?

21. “All Purpose” Recipe • Fertilization • Can triple productivity • Can cause unwanted algal blooms • Once started, difficult to stop • Granular, water soluble, liquid

22. “All Purpose” Recipe • Supplemental Feeding • Dramatically increase size and growth of BG and LMB. • Only recommended if Trophy Bass is the management objective. • Same negatives as fertilizer.

23. “All Purpose” Recipe • Aquatic Vegetation Control • Optimum level at 20% in TX reservoir • Optimum level at 36% in IL pond

24. Aquatic Vegetation • Natural Succession of lentic systems • Depressions accumulate material • Increased organic matter and nutrients • Cultural Eutrophication • Ponds become increasingly susceptible to nuisance algae and vegetation

25. Aquatic Vegetation Control • Mechanical: • Harvesting and Dredging • Shading • Draw Down

26. Aquatic Vegetation Control • Chemical: Herbicides • Copper sulfate • Nutrients stay • Depletes DO • Effective, quick, cheap in small impoundments

27. Aquatic Vegetation Control • Biological • Grass carp • Non-native, illegal in some states • Escape hatcheries and reproduce • Triploid variety infertile • Can completely eliminate vegetation, eat invertebrates (crayfish) • Nutrients stay (convert macrophytes to phytoplankton) • Barley Straw • May inhibit additional algal growth • Mechanism uncertain: fungal chemicals? • Nutrients stay

28. “All Purpose” Recipe • Aerators and Destratifiers • Often necessary in fertilized ponds or ponds that receive high nutrient runoff. • Avoid stratification and extremely low oxygen levels. • Expensive (especially with increasing gas prices)

29. 8” 12” trophy No harvest harvest harvest “All Purpose” Recipe • Harvest Control • Limit over harvest • Maintain population “balance” • Minimum length limits • Low recruitment situations • Protects individuals until they reach maturity • Slot Limits • High recruitment where minimum length limits will lead to overpopulation and stunting • Grows bigger fish • Must harvest small fish

30. Balance and Population Analysis • Are stocked ponds really in balance? • Likelihood declines with ponds that are simple are artificial • Artificial ecosystems? Must manage hard to get what you want • Big aquarium? • Ponds with a natural assemblage within a natural habitat are more likely to be a self-sustainable ecosystem • Diversity of habitat • Sustained source of water • Prey diversity

31. Balanced Fish Populations • Characteristics • Continual reproduction of predator and prey • Diversity of prey for all predators • High growth rates • Harvestable fish in proportion to pond fertility

32. Balanced Fish Populations • Indices to assess balance • Biomass Indices • Length-Frequencies Indices • Abundance-Weight Indices

33. Biomass Indices: F:C Ratio • Total weight of all forage fishes (F) / total weight of all carnivorous fishes (C) • 3-6 = good • 1.4-10 = balanced • Low = too many carnivores • High = too many forage fishes

34. Biomass Indices: Y:C ratio • Total weight of forage fishes small enough to be consumed by the average sized carnivore / Total weight of all carnivorous fishes (C) • 1-3 = good • 0.02-5 = balanced • Low = too many carnivores • High = too many forage fishes

35. Biomass Indices: AT value • Total availability value • % that is “harvestable” • Total weight of harvestable fish / total weight of all fish • Need to define minimum weight harvestable • 60-85% = good • Low = stunted • High = too many big carnivores

36. Length-Frequency Indices: Proportional stock Density (PSD) • # fish of a given species greater than or equal to quality length / # fish greater than or equal to stock length X 100 • Quality Length – size most anglers like to catch • Stock Length – size at which fish reach sexual maturity, minimum “recreational” length • 40-70 balance for LMB • 20-60 balance for BG • % of fish attractive to anglers

37. Length-Frequency Indices: Relative stock Density (RSD) • # fish of a given species greater than or equal to length you want / # fish greater than or equal to stock length X 100 • Must ID the size you want • Special case of PSD • More sensitive to recognizing quality of the stock

38. Pop 1 PSD = 50 RSD-38 = 0 PSD = quality size/stock size RSE = other size/stock size Pop 2 PSD = 50 RSD-38 = 15 Comparing PSD and RSD

39. PSD and RSD: Size Categories • Base on percentage of world record lengths • Stock Length = 20-26% of the world record length for the species (LMB 20 cm) • Quality Length = 36-41% (LMB 30 cm) • Preferred Length (LMB 38 cm) • Memorable Length (LMB 51 cm) • Trophy Size = 80% (LMB 63 cm) • Table 21.1

40. Abundance and Weight Indices • Relative Weight (Wr) • Measured weight (Wt) / predicted or standard weight (Ws)

41. Length-Weight Relation • W = aLb • Exponential relationship • W is a function of L to some power • a (constant) and b are parameters from L vs W relation • log W = log a + b log L • Equation for a line! • Ws =standard weight LMB Length-Weight relation

42. W = a L b • b = 3 • Isometric growth • Growing in all directions in proportion • Shape is not changing (rare) • b ≠ 3 • Allometric growth • Growing faster in girth than length or vise versa; changing shape • More common growth • Old fish grow more in girth than length

43. Wr = Wt / Ws • Do fish weight what they should • < 85 = underweight and too abundant • 100 = in balance with food supply • > 105 = too plump; pond can support more fish

44. Standard Weight Equations Largemouth Bass: Log10 Ws = -5.528 + 3.273 Log10 L Bluegill: Log10 Ws = -5.374 + 3.316 Log10 L Channel Catfish: Log10 Ws = -5.800 + 3.294 Log10 L

45. Internet Resources • State Fish and Wildlife Agencies • http://www.tpwd.state.tx.us/fish/infish/ponds/ (TX) • http://www.dgif.state.va.us/fishing/Pond_Management/index.html (VA) • Cooperative Extension Services • http://www.wvdnr.gov/Fishing/FarmPondMgmt.shtm (WV) • http://msucares.com/wildfish/fisheries/farmpond/management/ (MS) • http://www.aces.edu/pubs/docs/A/ANR-0577/ (AL) • http://www.dnr.cornell.edu/ext/fish/pond1.htm (NY)