Pond Fertilization to Enhance Fish Growth. Pond Fertilization. Fertilization in Larviculture. Chris Hartleb University of Wisconsin Stevens Point

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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. Perch Zooplankton Phytoplankton Nutrients 1

2 Inorganic Fertilization Primary components: Nitrogen (N), Phosphorus (P), and Carbon (C). Often used: Powdered urea (N), triple-superphosphate (P 2O 5) or phosphoric acid, and agricultural lime (CaCO 3). 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). 2

3 percent occurence total length (mm) 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 Fertilization of Plastic Lined Ponds (J. Morris, Iowa State Univ.) Walleye in ponds treated with organic fertilizer were significantly longer, heavier, and had greater biomass /7/21 5/17/21 5/29/21 6/5/ 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. 3

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. 4

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 > 3:1 favor small green algae preferred by zooplankton. Inorganic ratios of 6 µg/n/l and 3 µg/po 4-P/L (2:1 ratio). Ammonia-N (NH 3-N), Nitrate-N (NO 3-N), and Phosphate (PO 4). Iowa State (Morris) Method Measure Nitrate (NO 3) and Total Phosphorus (TP). Maintain 7:1 ratio NO 3:TP Initially fertilize pond with.1 mg/l TP. Algal Bioassay Fertilization 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, & ecologicallybased. 5

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 1%, 5%, or % 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 6

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, NH 3 -N, NO 3 -N, PO 4-3 Collected phyto- & zooplankton Measured growth of yellow perch Methods Stocked prolarval yellow perch (April 2-26) 87, per ¼ acre Pond A 8, 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 7

8 mg Clorophyll a /m 3 Lake Water Secchie Depth (m) Average Water Chemistry Conditions in Ponds A & B for Weeks Pond A ph Alkalinity ppm Hardness ppm Secchi Depth Pond B ph Alkalinity ppm Hardness ppm Secchi Depth /11 4/25 5/9 5/23 6/6 6/2 7/4 4/11 4/25 5/9 5/23 6/6 6/2 Algal Biomass Summary High diversity in both ponds (Mean = 8 genera/week) Chlorophyta & Ochrophyta dominated Chlorophyll a peaked in Pond A mid-june.3.25 Pond A Pond B /3 6/6 6/13 6/2 6/27 7/4 7/11 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 8

9 Weekly Diet selection (Pond A): Number of organisms per fish. For fish parts & fish food = Number of fish that contained each item. Diet Item 5/9 5/16 5/23 5/3 6/6 6/13 6/2 6/27 7/3 7/11 N # Empty Plankton eggs Brachionus Daphnia Keratella Kellicottia Bosmina Ostracods Copepodite.4 Misc Diptera Chironomid 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 2 July 3 (3 weeks) Ostracods June 13 Diptera 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. Diet Item 5/2 5/9 5/16 5/23 5/3 6/6 6/13 6/2 6/27 7/3 N # Empty Yolk sac feeding 5 14 Nauplii Copepodite/ Cyclopoid copepod.46/. 1.42/../ 3. Plankton eggs Bosmina Keratella.18.6 Daphnia/ Ceriodaphnia.48/. 1.98/ 3.56./ /. Closterium Chydorus Misc Ostracods Fish parts X (2) Fish food X (6) X (1) 9

10 Pond B Diet Selection May 2 May 9 (2 weeks) Yolk sac Nauplii June 13 Ostracods May 6 Copepodites June 2 Bosmina May 23 June 6 (3 weeks) Bosmina Ceriodaphnia June 27 July 3 (2 weeks) Closterium Pond fertilization schedule showing fertilizer applied to Pond A Urea-N (lbs) Phosphoric acid (oz) 4/ / / PO 4 -P NH3-N NO3-N (ug/l) (ug/l) (ug/l) N:P 5/ :1 5/ / :1 5/ / :1 5/ / :1 6/ :1 6/ :1 6/ :1 6/ :1 7/ :1 Pond fertilization schedule showing fertilizer applied to Pond B Urea-N (lbs) Phosphoric acid (oz) 4/ / / PO 4 -P NH3-N NO3-N (ug/l) (ug/l) (ug/l) N:P 5/ :1 5/ / :1 5/ / :1 5/ / :1 6/ :1 6/ :1 6/ :1 6/ :1 7/ :1 1

11 Growth (TL) of Larval Perch from Ponds A & B 6 5 y = 5.497e.2124x r 2 =.96 Length (mm) Pond B y= e.261x 5/6/2 Pond A 5/2/2 6/3/2 6/17/2 7/1/2 7/15/2 Length (mm) r 2 = /6/2 5/2/2 6/3/2 6/17/2 7/1/2 Growth (wet weight) of Larval Perch from Ponds A & B y =.9e.7474x r 2 =.97 Weight (g) Pond B /6/2 5/2/2 6/3/2 6/17/2 7/1/2 7/15/ y =.3e.7453x r 2 =.95 Pond A Weight (g) /6/2 5/2/2 6/3/2 6/17/2 7/1/2 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. 11