management of small impoundments chapters 21 (22)
TRANSCRIPT
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Management of Small Impoundments
Chapters 21 (22)
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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
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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”
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Management Philosophy
Sustained or improved fishing quality
High catch rates and above-average sizes
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Multiple Uses of Ponds Boating Fishing Livestock Bird hunting Swimming Aesthetics
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Ecological Principles
Trophic Relationships Productivity and Biomass
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Ecological Principles
Carrying capacity: max mass or density supported over a certain time period
K Density Fish Size
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Ecological Principles
Average Fish Size varies as a function of overall pond productivity and population density
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Ecological Principles
Influence of Aquatic Vegetation Increased primary productivity Decreased predator foraging
efficiency Decreased harvest efficiency Dense prey populations Stunted predator populations
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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.
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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
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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
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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
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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
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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
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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?
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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
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“All Purpose” Recipe
Initial Pond Survey Population Status
Electrofishing and seining Assess population “balance”
Alkalinity Aquatic Weeds
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“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)
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“All Purpose” Recipe
Liming Essential if pH < 7 and Alkalinity < 20
ppm Agricultural limestone Why useful?
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“All Purpose” Recipe Fertilization
Can triple productivity Can cause unwanted algal blooms Once started, difficult to stop Granular, water soluble, liquid
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“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.
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“All Purpose” Recipe
Aquatic Vegetation Control Optimum level at 20% in TX
reservoir Optimum level at 36% in IL pond
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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
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Aquatic Vegetation Control Mechanical:
Harvesting and Dredging Shading Draw Down
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Aquatic Vegetation Control
Chemical: Herbicides Copper sulfate Nutrients stay Depletes DO Effective, quick,
cheap in small impoundments
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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
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“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)
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“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
No harvestharvest harvest
12”8”trophy
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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
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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
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Balanced Fish Populations
Indices to assess balance Biomass Indices Length-Frequencies Indices Abundance-Weight Indices
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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
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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
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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
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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
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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
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Comparing PSD and RSD Pop 1
PSD = 50 RSD-38 = 0
PSD = quality size/stock sizeRSE = other size/stock size
Pop 2 PSD = 50 RSD-38 = 15
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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
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Abundance and Weight Indices
Relative Weight (Wr) Measured weight (Wt) / predicted or
standard weight (Ws)
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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
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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
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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
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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
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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_Manage
ment/index.html (VA)
Cooperative Extension Services http://www.wvdnr.gov/Fishing/FarmPondMgmt.sht
m (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)