Transcript Management of Small Impoundments

Management of Small
Impoundments
Chapters 21 (22)
Introduction
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Pond = small impoundment
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<0.4 ha – 40 ha
0.2 ha – 2.4 ha (AFS Central States Pond
Management Work Group)
Dam constructed to impound water
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Various water sources
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Springs, streams, precipitation, runoff
Introduction
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Usually privately owned
Farm ponds
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Livestock water
Irrigation
Most numerous in central and southeast
Important contribution to sportfishing
Rarely regulated as a “water of the US”
Management Philosophy
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Sustained or improved fishing quality
High catch rates and above-average
sizes
Multiple Uses of Ponds
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Boating
Fishing
Livestock
Bird hunting
Swimming
Aesthetics
Ecological Principles
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Trophic Relationships
Productivity and Biomass
Ecological Principles
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Carrying capacity: max mass or density
supported over a certain time period
K
Density
Fish Size
Ecological Principles
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Average Fish Size varies as a function of
overall pond productivity and population
density
Ecological Principles
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Influence of Aquatic Vegetation
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Increased primary productivity
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Decreased predator foraging efficiency
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Decreased harvest efficiency
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Dense prey populations
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Stunted predator populations
Pond Types and Management
Options
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Warmwater
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Coldwater
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Bass and bluegill, sometimes catfish
Fall, winter, spring trout (summer kills)
Most Common and Most research
Trout, usually stocked
Coolwater
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Rare; Walleye, hybrid striped bass, perch,
etc.
All-Purpose Option
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Harvest of LMB, BG, and CC
30-38 cm (12-15 in) slot limit for LMB after 4
years
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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
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Over harvest = Over population of BG
Release slot fish and smaller = Over population
and stunting of LBM
Harvest Quota Option
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Due to problems with length limits
Set harvest independent of length
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Quota on number or weight per time
Difficult:
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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
Panfish Option
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Big panfish instead of LMB
15 in min length for LMB
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Small LMB generally
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Abundance of 8-15 in LMB reduce BG density
Large BG survive and grow > 8 in
May compete with BG (remove some)
Easy: unmanaged ponds tend to move in this
direction
Big BASS Option
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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
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Catch rate is low but sizes are large
Larger ponds
Numerous small BG may reduce recruitment of
LMB
Catfish Only Option
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In muddy or small ponds
No structure for spawning or they
overpopulate and stunt
Fathead minnow prey
Unrestricted harvest
Restocking to replace harvested fish
Black Bass Only Option
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Shallow, weedy ponds with too much
cover (BG stunting)
Feed on crayfish, bugs, own young
Need several year classes stocked
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Prevents development of dominant year
class
Inefficient use of pond resources?
Trout Options
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Coldwater ponds—spring fed
Usually rainbow trout
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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
“All Purpose” Recipe
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Initial Pond Survey
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Population Status
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Electrofishing and seining
Assess population “balance”
Alkalinity
Aquatic Weeds
“All Purpose” Recipe
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Kill the Pond
Initial Stocking
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Forage species (bluegill, shell crackers, fat
head minnows)
Predator species (largemouth bass)
Stocking Rates
Supplemental Stocking
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Essential in large ponds (>2 acres)
Threadfin shad, golden shiners)
“All Purpose” Recipe
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Liming
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Essential if pH < 7 and Alkalinity < 20 ppm
Agricultural limestone
Why useful?
“All Purpose” Recipe
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Fertilization
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Can triple productivity
Can cause unwanted algal blooms
Once started, difficult to stop
Granular, water soluble, liquid
“All Purpose” Recipe
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Supplemental Feeding
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Dramatically increase size and
growth of BG and LMB.
Only recommended if Trophy
Bass is the management
objective.
Same negatives as fertilizer.
“All Purpose” Recipe
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Aquatic Vegetation Control
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Optimum level at 20% in TX reservoir
Optimum level at 36% in IL pond
Aquatic Vegetation
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Natural Succession of lentic systems
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Depressions accumulate material
Increased organic matter and nutrients
Cultural Eutrophication
Ponds become increasingly susceptible
to nuisance algae and vegetation
Aquatic Vegetation Control
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Mechanical:
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Harvesting and Dredging
Shading
Draw Down
Aquatic Vegetation Control
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Chemical: Herbicides
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Copper sulfate
Nutrients stay
Depletes DO
Effective, quick, cheap
in small
impoundments
Aquatic Vegetation Control
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Biological
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Grass carp
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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
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May inhibit additional algal growth
Mechanism uncertain: fungal chemicals?
Nutrients stay
“All Purpose” Recipe
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Aerators and Destratifiers
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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)
“All Purpose” Recipe
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Harvest Control
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Limit over harvest
Maintain population “balance”
Minimum length limits
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Low recruitment situations
Protects individuals until they reach maturity
Slot Limits
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High recruitment where minimum length limits will lead
to overpopulation and stunting
Grows bigger fish
Must harvest small fish
8”
harvest
12”
No harvest
harvest
trophy
Balance and Population
Analysis
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Are stocked ponds really in balance?
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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
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Diversity of habitat
Sustained source of water
Prey diversity
Balanced Fish Populations
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Characteristics
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Continual reproduction of predator and
prey
Diversity of prey for all predators
High growth rates
Harvestable fish in proportion to pond
fertility
Balanced Fish Populations
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Indices to assess balance
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Biomass Indices
Length-Frequencies Indices
Abundance-Weight Indices
Biomass Indices: F:C Ratio
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Total weight of all forage fishes (F) /
total weight of all carnivorous fishes (C)
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3-6 = good
1.4-10 = balanced
Low = too many carnivores
High = too many forage fishes
Biomass Indices: Y:C ratio
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Total weight of forage fishes small
enough to be consumed by the average
sized carnivore / Total weight of all
carnivorous fishes (C)
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1-3 = good
0.02-5 = balanced
Low = too many carnivores
High = too many forage fishes
Biomass Indices: AT value
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Total availability value
% that is “harvestable”
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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
Length-Frequency Indices:
Proportional stock Density (PSD)
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# fish of a given species greater than or
equal to quality length / # fish greater than
or equal to stock length X 100
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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
Length-Frequency Indices:
Relative stock Density (RSD)
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# fish of a given species greater than or
equal to length you want / # fish
greater than or equal to stock length X
100
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Must ID the size you want
Special case of PSD
More sensitive to recognizing quality of the
stock
Comparing PSD and RSD
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Pop 1
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PSD = 50
RSD-38 = 0
PSD = quality size/stock size
RSE = other size/stock size
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Pop 2
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PSD = 50
RSD-38 = 15
PSD and RSD: Size Categories
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Base on percentage of world record
lengths
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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
Abundance and Weight
Indices
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Relative Weight (Wr)
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Measured weight (Wt) / predicted or
standard weight (Ws)
Length-Weight Relation
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W = aLb
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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
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Equation for a line!
Ws =standard weight
LMB Length-Weight relation
W=aL
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b=3
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Isometric growth
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b
Growing in all directions in proportion
Shape is not changing (rare)
b≠3
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Allometric growth
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Growing faster in girth than length or vise versa;
changing shape
More common growth
Old fish grow more in girth than length
Wr = Wt / Ws
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Do fish weight what they should
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< 85 = underweight and too abundant
100 = in balance with food supply
> 105 = too plump; pond can support
more fish
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
Internet Resources
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State Fish and Wildlife Agencies
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http://www.tpwd.state.tx.us/fish/infish/ponds/ (TX)
http://www.dgif.state.va.us/fishing/Pond_Management/i
ndex.html (VA)
Cooperative Extension Services
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http://www.wvdnr.gov/Fishing/FarmPondMgmt.shtm
(WV)
http://msucares.com/wildfish/fisheries/farmpond/manage
ment/ (MS)
http://www.aces.edu/pubs/docs/A/ANR-0577/ (AL)
http://www.dnr.cornell.edu/ext/fish/pond1.htm (NY)