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).
3
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.
0
10
20
30
40
50
60
70
80
90
100
05/07/2001 05/17/2001 05/29/2001 06/05/2001
perc
ent
occure
nce
0
4
8
12
16
20
24
28
32
36
40
44
48
tota
l le
ngth
(m
m)
Daphnia
Copepod
Dipteran
Length
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.
4
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.
5
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.
6
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
7
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
8
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
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
4/11
4/25 5/
95/
23 6/6
6/20 7/
4
Se
cch
ie D
ep
th (
m)
0
0.5
1
1.5
2
2.5
3
3.5
4/11
4/25 5/
95/
23 6/6
6/20
Algal Biomass Summary
High diversity in both ponds (Mean = 8 genera/week)
Chlorophyta & Ochrophyta dominated
Chlorophyll a peaked in Pond A mid-June
0
0.005
0.01
0.015
0.02
0.025
0.03
5/30 6/
66/
136/
206/
27 7/4
7/11
mg
Clo
rop
hyll a
/m
3 L
ak
e W
ate
r
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
9
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/
0.00
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)
10
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
11
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)
0
10
20
30
40
50
60
y = 5.4097e0.2124x
r2 =0.96
Date
5/6/02 5/20/02 6/3/02 6/17/02 7/1/02
Length
(m
m)
0
5
10
15
20
25
30
35
40
r2 = 0.95
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 (
g)
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
r2 = 0.95
y = 0.0003e 0.7453x
Date
5/6/02 5/20/02
6/3/02 6/17/02
7/1/02 7/15/02
Weig
ht (g
)
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
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.