1

Pond Fertilization to Enhance Fish Growth

Chris Hartleb

University of Wisconsin – Stevens Point

Pond Fertilization

Most important factor limiting efficiency in pond culture is lack of knowledge on feeding

dynamics.

Fertilization can aid in first feeding by fish.

Fertilization can provide supplemental feeding.

Fertilization in Larviculture

Least understood stage.

“Green water” phase.

Influenced by:

Type & abundance of food.

Timing & weather.

Nutrients

Phytoplankton

Zooplankton

Perch

2

Inorganic Fertilization

Primary components: Nitrogen (N), Phosphorus (P), and Carbon (C).

Often used: Powdered urea (N), triple-super-phosphate (P2O5) or phosphoric acid, and agricultural lime (CaCO3).

Enhance autotrophic food webs.

(small, green algae)

Inorganic Fertilizer

Frequent application to sustain food chain.

Can be costly depending on frequency of application.

Dry ingredients must be mixed into a liquid and sprayed on pond.

Phosphorus is absorbed by pond soil, while nitrogen remains in water.

Nutrient content in bag not always same as on label.

Organic Fertilization

Various types: Animal manures (poultry, bovine, etc), and Plant material (hay, alfalfa, cottonseed, soybean meal, etc).

Directly & indirectly enhance algae & zooplankton.

Direct: Input of nitrogen, phosphorus, carbon.

Indirect: Stimulate heterotrophic food webs (bacteria decompose organics).

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Organic Fertilizer

Can be applied directly; but should be distributed.

Low cost compared to inorganics.

Longer delay between application and enhanced productivity (slow & incomplete decomposition).

Decomposition consumes oxygen.

Organic Fertilizationof Plastic Lined Ponds

(J. Morris, Iowa State Univ.)

Walleye in ponds treated with organic fertilizer were significantly longer, heavier, and had greater biomass.

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Inorganic + Organic Fertilization

Stimulate both heterotrophic & autotrophic food webs.

Inorganics compensate for variable release of nutrients by organics.

Inorganics produce rapid enrichment (algae to zooplankton).

Organics stimulate algae, bacteria, protozoans, and benthic insects for longer duration.

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Green Water (Visibility) Method

Implies green water is nutrient rich water.

Uses visibility/secchi disk to determine greenness.

Inexpensive, subjective, minimal accuracy.

Does not consider composition of algae, plankton, or impact of fertilizer on oxygen.

Difficult to establish consistent food web.

Fixed Fertilization Rate Strategy

Fertilizer is applied weekly at a selected quantity.

Requires prior knowledge of pond dynamics & fish production.

Simple; annual production of fish predictable.

Can lead to over-fertilization and is specific for each pond.

Water Chemistry Measurement

Regularly collected water samples are measured for: Total phosphorus & soluble reactive

phosphorus. Ammonia-N, Nitrate-N, & Nitrite-N. Inorganic carbon.

Organic N, P, & C. Pond-specific & can precisely measure nutrient

deficiencies.

Significant cost, technical, time consuming, & does not take into account daily fluctuations.

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Ohio State (Culver) Method

N:P ratios < 7:1 favor nitrogen-fixing blue-green algae (inedible by zooplankton & can produce toxins).

N:P ratios > 30:1 favor small green algae preferred by zooplankton.

Inorganic ratios of 600 µg/N/L and 30 µg/PO4-P/L (20:1 ratio).

Ammonia-N (NH3-N), Nitrate-N

(NO3-N), and Phosphate (PO4).

Iowa State (Morris) Method

Measure Nitrate (NO3) and Total Phosphorus (TP).

Maintain 7:1 ratio NO3:TP

Initially fertilize pond with 0.1 mg/L TP.

Algal BioassayFertilization Strategy

Based on algal nutrition limitation of N, P, & C.

Is pond & time-specific; utilizes ponds own algal community.

Uses a simple visual indicator.

Inexpensive, simple, & ecologically-based.

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Algal Bioassay Method

Water is collected weekly in clear sample bottles.

Each bottle is spiked with either N, P, C, or nothing (control), or a combination.

Bottles are placed in sunlight for 2-3 days.

Water is filtered and compared visually and ranked as 100%, 50%, or 0% rate-limiting.

Algal Bioassay Pond Samples

Water samples showing nutrient spikes.

Filtered water showing limiting nutrient.

Possible Algal Bioassay Results

Ponds

Bioassay Results Limiting Nutrient

Control N P C N+P N+C P+C N+P+C 1st 2nd

1 P

2 N

3 C

4 P N

5 P C

6 N C

7 None

8 All

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Yellow Perch Fry Objectives

Examine pond fertilization practices.

Monitor water chemistry of culture ponds.

Identify components of food chain.

Monitor growth of larval yellow perch & determine diet selection.

Methods

Sampled late April to Mid-July

Measured temperature, DO, pH, alkalinity, hardness, NH3-N, NO3-N, PO4

-3

Collected phyto- & zooplankton

Measured growth of yellow perch

Methods

Stocked prolarval yellow perch (April 20-26)

870,000 per ¼ acre Pond A

800,000 per ¼ acre Pond B

Late April to mid-June inorganic fertilizer applied weekly

Urea-N and phosphoric acid

Desired secchi depth 1.5 m

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Average Water Chemistry Conditions

in Ponds A & B for 13-14 Weeks

Pond A

pH 8.46+0.26

Alkalinity 156.5+13.2 ppm

Hardness 248.2+26.7 ppm

Secchi Depth

Pond B

pH 8.06+0.37

Alkalinity 163.3+22.8 ppm

Hardness 239.7+17.1 ppm

Secchi Depth

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Algal Biomass Summary

High diversity in both ponds (Mean = 8 genera/week)

Chlorophyta & Ochrophyta dominated

Chlorophyll a peaked in Pond A mid-June

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Pond A

Pond B

Plankton Composition in Ponds A & B

Nanno-plankton May = Nauplii, Keratella &

Plankton eggs

June = Ostracods, Keratella, Kellicottia, Plankton eggs

July = Polyarthra, Kellicottia, Brachionus, Notholca & Lecane

Net-plankton April = Brachionus, Ostracods,

Plankton eggs

May = Ostracods, Bosmina, Keratella

June & July = Ostracods, Bosmina, Keratella, Daphnia

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Weekly Diet selection (Pond A): Number of organisms per fish.

For fish parts & fish food = Number of fish that contained each item.

Date

Diet Item 5/9 5/16 5/23 5/30 6/6 6/13 6/20 6/27 7/3 7/11

N 50 50 50 50 30 50 50 50 50 50

# Empty 0 0 3 3 0 5 27 14 17 5

Plankton eggs 1.28 3.20 2.34 42.38 88.77

Brachionus 0.36 0.16 0.16

Daphnia 0.34 0.10 0.14 0.36

Keratella 4.00 10.88 63.06 86.90

Kellicottia 0.20 0.58 0.36 0.02

Bosmina 0.54 0.44 0.36 1.64 0.57 0.04 0.08 0.44

Ostracods 0.16 4.76 21.06 34.98 10.47 0.76 0.76 7.58 3.24 1.02

Copepodite 0.04

Misc 0.73 0.42 0.32 0.10

Diptera 1.92 0.12 0.10

Chironomid 0.10 0.02 0.04 0.02

Fish parts X (3) X (5)

Fish food X (1) X (2) X (3) X (41)

Pond A Diet Selection

May 9 - June 6 (5 weeks)

Plankton eggs Keratella Ostracods

June 13

Diptera

June 20 – July 3 (3 weeks)

Ostracods

July 11

Fish feed

Weekly Diet selection (Pond B): Number of organisms per fish.

For fish parts & fish food = Number of fish that contained each item.

Date

Diet Item 5/2 5/9 5/16 5/23 5/30 6/6 6/13 6/20 6/27 7/3

N 50 50 50 50 48 50 50 50 50 50

# Empty 0 1 5 1 1 0 6 22 23 18

Yolk sac feeding 50 14

Nauplii 1.80 0.20 0.42 0.04

Copepodite/

Cyclopoid copepod

0.46/0.0

1.42/

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0.00/

3.00

Plankton eggs 0.32 0.02 1.56 2.23 1.63 3.09

Bosmina 0.14 1.35 18.14 32.83 23.32 0.02 2.50

Keratella 0.18 0.60

Daphnia/

Ceriodaphnia

0.48/

0.00

1.98/

3.56

0.00/

11.06

0.06/

0.00

Closterium 0.06 0.02 4.73 0.02 23.66 36.06

Chydorus 0.04 2.39

Misc 0.16 0.10 0.02 0.14 0.44

Ostracods 11.02 1.50 6.88 2.94

Fish parts X (2)

Fish food X (6) X (1)

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Pond B Diet Selection

May 2 – May 9 (2 weeks)

Yolk sac Nauplii

May 6

Copepodites

May 23 – June 6 (3 weeks)

Bosmina Ceriodaphnia

June 13

Ostracods

June 20

Bosmina

June 27 – July 3 (2 weeks)

Closterium

Pond fertilization schedule showing fertilizer applied to Pond A

Date Urea-N

(lbs)

Phosphoric acid

(oz)

PO4-P

(ug/L)

NH3-N

(ug/L)

NO3-N

(ug/L)

N:P

4/23 25 15

5/1 25 15

5/7 25 14

5/9 4 30 0 12:1

5/14 30 14

5/16 7 20 333 50:1

5/20 15 6

5/23 7 40 533 82:1

5/28 0 11

5/30 4 120 133 63:1

6/6 7 280 133 59:1

6/13 13 50 200 19:1

6/20 21 0 233 11:1

6/27 19 40 433 25:1

7/3 11 40 300 31:1

Pond fertilization schedule showing fertilizer applied to Pond B

Date Urea-N

(lbs)

Phosphoric acid

(oz)

PO4-P

(ug/L)

NH3-N

(ug/L)

NO3-N

(ug/L)

N:P

4/23 25 15

5/1 25 15

5/7 35 14

5/9 6 0 233 39:1

5/14 35 14

5/16 13 20 366 30:1

5/20 12 10

5/23 10 30 1300 133:1

5/28 0 11

5/30 20 170 100 14:1

6/6 20 80 100 9:1

6/13 27 20 166 7:1

6/20 14 10 166 13:1

6/27 21 20 366 18:1

7/3 21 0 333 16:1

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Growth (TL) of Larval Perch from Ponds A & B

Date

5/6/02 5/20/02

6/3/02 6/17/02

7/1/02 7/15/02

Length

(m

m)

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y = 5.4097e0.2124x

r2 =0.96

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Length

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m)

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y= 4.4376e0.2061x

Pond A

Pond B

Growth (wet weight) of Larval Perch from Ponds A & B

Date

5/6/02 5/20/02 6/3/02 6/17/02 7/1/02

Weig

ht (

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-0.2

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r2 = 0.95

y = 0.0003e 0.7453x

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Weig

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-0.5

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y = 0.0009e 0.7474x

r2 = 0.97

Pond A

Pond B

Conclusions

Application of fertilizer based on transparency to establish “green water” not a good indicator of pond fertilization or trophic cascade.

Diet shift by larval perch evident after 4 weeks in culture ponds.

Early growth was strongly temperature dependent. Poor survival related to low density of preferred prey. Late season variability in growth related to diet and feed

training.