Management of Small Impoundments Chapters 21 (22)

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

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”

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

Multiple Uses of Ponds Boating Fishing Livestock Bird hunting Swimming Aesthetics

Ecological Principles Trophic Relationships Productivity and Biomass

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

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

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

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.

All-Purpose Option Harvest of LMB, BG, and CC 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

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

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

Big BASS Option Reduce number of LMB 8-15 inches so remaining individuals grow large Harvest 75 LMB 8-12 in and 13 LMB 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

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

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?

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

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

“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)

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

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

“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.

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

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

Aquatic Vegetation Control Mechanical: Harvesting and Dredging Shading Draw Down

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

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

“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)

“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 harvest harvest 12” 8” trophy

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

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

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

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

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 = balanced Low = too many carnivores High = too many forage fishes

Biomass Indices: A T 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

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 balance for LMB balance for BG % of fish attractive to anglers

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

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

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

Abundance and Weight Indices Relative Weight (W r ) Measured weight (W t) / predicted or standard weight (W s )

Length-Weight Relation W = a L b 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! W s =standard weight LMB Length-Weight relation

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

W r = W t / W s 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

Standard Weight Equations Largemouth Bass: Log 10 W s = Log 10 L Bluegill: Log 10 W s = Log 10 L Channel Catfish: Log 10 W s = Log 10 L

Internet Resources State Fish and Wildlife Agencies (TX) ndex.html (VA) ndex.html Cooperative Extension Services (WV) ment/ (MS) ment/ (AL) (NY)