Phytoplankton production in integrated fish culture high-output ponds and its status in energy flow

Ecological Engineering, 2 (1993) 217-229 Elsevier Science Publishers B.V., Amsterdam

217

Phytoplankton production in integrated fish culture high-output ponds and its status in energy flow Honglu Yao Laboratory of Aquaculture and Fish Disease, Jiangsu ProvincialFisheries Technique Extension Center, 90 Xin mo-fan Street, Nanjing 210003, China (Received 21 September 1992; accepted 1 December 1992)

ABSTRACT Primary productivity of phytoplankton in fish ponds of three different stocking patterns was analyzed. The function and status of primary productivity in the energy flow of the fish ponds was evaluated quantitatively. In ponds subjected to stocking of non-filter-feeding fish, phytoplankton net primary productivity (NPP) was 242-284, 285-292 and 303-330 GJ/ha. year when net fish output was 7.5, 11.2 and 15 t/ha.year, respectively. In ponds subjected to stocking of filter-feeding fish, NPP was 301-384, 388, and 438-493 GJ/ha.year when net fish output was 7.5, 11.2 and 15 t/ha.year, respectively. In the ponds with stocking of 50% non-filter-feeding fish and 50% filter-feeding fish, NPP was between the NPP values observed in the ponds with other stocking patterns. Percent solar efficiency was 1.4-1.5, 1.7-1.8, and 1.4-2.7% for .20%, 50%, and 100% filter-feeding fish stocking, respectively, NPP was equal to 15-27, 30, and 33-46% of energy subsidies, and 30-48, 50, and 51-60% of total energy for phytoplankton and added food. With these inputs, fish production was 2.5-3.4, 3.9-4.2, and 3.1-5.1 t/ha.year, under the three stocking patterns, respectively. INTRODUCTION As a primary producer, phytoplankton is an important factor in determining fisheries production potential in Chinese integrated fish pond culture ecosystems. Therefore, studies of phytoplankton productivity in fish culture ponds are an important step in understanding the ecology and ecological engineering of integrated fish pond cultures. H e p h e r (1962), Boyd (1973, 1982), Schroeder (1978, 1980, 1987) H e and Li (1983), Lei et al. (1983) and Z h o n g et al. (1987) have all studied phytoplankton productivity

Correspondence to: H. Yao, Laboratory of Aquaculture and Fish Disease, Jiangsu Provincial Fisheries Technique Extension Center, 90 Xin mo-fan Street, Nanjing 210003, China. 0925-8574/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved

218

H.YAO

and its relationship to other ecological factors, such as fish output in fish ponds. However, these studies lack a comparative analysis of primary productivity in Chinese integrated fish culture ponds of different stocking patterns, with different fish outputs. Therefore, we conducted quantitative research which includes dynamic dissolved oxygen measurements and energy efficiency ratios in the Chinese integrated fish culture pond ecosystems in Nanjing and Suzhou (Yao, 1988, 1990, 1991, 1992; Yao et al., 1987, 1990a,b). This study deals mainly with primary productivity in the Chinese integrated fish culture ponds of three different stocking patterns with different fish outputs, to show the status and effect of primary productivity in energy flow. The subject is of theoretical and practical significance because it can help clarify the workings of the ecosystem, particulary the algal and detrital components of the food web. In addition, the study is important in order to select the optimal model of fish cultures and to explore the best methods for water quality improvement. Understanding the primary productivity of the system can enable us to intensify management and thereby achieve high outputs, low consumption, good quality and high efficiency as well as environmental protection. MATERIALS AND METHODS The experiment was carried out from 1978 to 1988 in ten ponds. Four of the ponds (L1-L4) are located at Liujiawei fish farm, Nanjing, (31°09'N and 118°55'E), five are located at Sheng zhuang, a suburb of Suzhou (32°15'N and 120°51'E), and one (Z1) is located at Zhanshang, Zuzhou (Table 1). Average solar energy is 37578 and 45880 G J / h a . y e a r and annual average temperature was 16°C during the experimental period (data are from the local meteorological station). In the ponds of stocking pattern I, black carp (carnivorous; Mylopharyngon piceus) and common carp (omnivorous; Cyprinus carpio) were the major species and the minor species were Wuchang fish (herbivorous; Megalabrama amblycephala), grass carp ( Ctenopharyngodon idella), the filter-feeding fish, silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), silver crucian carp (Carassius auratus gibelio), and crucian carp (omnivorous; Carassius auratus) (Table 1). In the ponds of stocking pattern III, the major fish species were filter-feeding fish, such as silver carp, bighead carp, and tilapia (Sarotherodom nilotica and S. mossambica), and the minor species were common carp, crucian carp, grass carp and Wuchang fish (Table 1). In the ponds of stocking pattern II, the non-filter-feeding and filter-feeding fish each made up 50% of the original stock. In every stocking pattern, three different sizes of net outputs (7.5,

1981 1980 1978 1979 1980 1981 1979

silver carp bighead carp tilapia

III

L1 L2 L3 L3 L3 L3 L4

1982 1983 1983 1983 1984 1984 1988 1984

black carp S1 common carp $2 Wuchang fish $3 $4 $3 $5 $5 Z1

I

Stocking Major pattern stocked fish

0.53 0.60 0.80 0.80 0.80 0.80 0.33

0.43 0.60 0.44 0.47 0.44 0.96 0.96 0.61 1.6 2.7 2.6 2.6 2.6 2.6 2.7

1.9 2.6 3.0 2.5 3.0 2.5 2.5 2.9 1603 3403 4274 3316 4121 4020 4987

1814 2382 2977 2100 3819 2943 3930 3797 8001 13086 15800 16852 1864.7 19818 19472

10075 12930 15621 13126 18489 16749 23085 19050

Pond Year Area Water Amount Gross num(ha) depth of fish stocked output ber (m) fish (kg/ha( k g / h a ) year)

The general condition of fish culture ponds for this experiment

TABLE 1

6398 9684 11527 13536 14527 15799 14484

8261 10548 12644 11024 14670 13806 19155 15253 -

36 44 33 44 33 36 27 23 2 2 3

6 4 3 3

1

3 3 4 2

18 8 8 5 11 10 7 10

17 3

18 17 20 16 21 18 27 18

57 50 36 38 50 46 48

22 39 45 42 31 40 32 1

9 7 7 3 13

4

-

22 23 22 24 26 22 24

2 9 6 7 5 7 17

-

23

-

silver tilapia and bighead carp

-

1 4 1 2 0 0

1 1 2 4 4 2

0 0 0 1 1 0

2

1

7 7 8 3 5 8 7

3

crucian other carp species of fish

7~

m

o

grass carp

a

Wuchang fish

output black ( k g / h a - carp year)

common carp

Net fish Percentage of each species of fish in the total net fish output (%)

o

z

o

220

H.YAO

11.3 and 15 t of f i s h / h a . y e a r ) were planned. The data from stocking patterns I and III come from our study, and the data from stocking pattern II are from a study in Wuxi (He and Li, 1983). The light and dark bottle method was used to measure primary productivity. Measurements were carried out on sunny, cloudy, and rainy days every month. The bottles were suspended in the center of the ponds at 0.25-m intervals from 0 to 1.5 m depth and at 0.5-m intervals below 1.5 m. The time intervals between measurements varied according to the weather conditions. On cloudy and rainy days, the bottles were suspended for 4-h periods throughout the day and for 6 h after 6 o'clock in the evening. On sunny days, bottles were suspended for 2-h periods. Water temperature, water depth, weather conditions, and phytoplankton biomass were measured at the same time. Production was expressed as g 0 2 / h a or G J / h a . We assumed that 1 mg 0 2 equaled 6.1 mg of fresh phytoplankton and 14.7 J (Wang and Shen, 1981), and NPP was calculated as 80% of the gross primary productivity (GPP) of phytoplankton (Winberg, 1972). The standing crop of plankton and suspended detritus were sampled and measured qualitatively and quantitatively once or twice every month during the experimental period by standard methods. Species were identified and counted using a microscope. Their weight was calculated by the volume of each species based on a specific gravity of 1. Their energy was evaluated by multiplying the weight by an energy equivalent coefficient for each species or genus. We calculated most of these coefficients, but some were calculated by Jergensen (1980) and Yan et al. (1987). We directly measured the biomass (B) of zooplankton and benthos and then calculated production by multiplying by the annual turnover rate ( P / B coefficient) for each category of organism (300 protozoa, 42 rotifers, 22 cladoeerans, 17 copepoda, 2 aquatic oligochaetes and chironomid larvae). Their energy was estimated by multiplying the standing crop by an energy equivalent coefficient (Table 2; Yan et al., 1987). The energy of feed, and the input and output of fish were calculated using coefficients we measured with an automatic bomb calorimeter CA-3 (Table 2; Gao and Wang, 1988; Bian et al., 1991). The subsidiary energy included labor, electric power, and petroleum oil, and was converted to energy measurements based on data from China's National Standard Agency. The data for solar radiation ( C a l / c m - d a y ) came from the local meteorological station. RESULTS AND DISCUSSION The relationship among primary productivity, stocking pattern, and fish standing crop is expressed by fish output (Tables 3 and 4). These integrated

221

PHYTOPLANKTON PRODUCTION IN I N T E G R A T E D FISH C U L T U R E PONDS

TABLE 2

Energy equivalent coefficient (MJ. kg) for fish, benthic organisms, plankton and feed Item Fish silver carp bighead carp silver crucian carp tilapia black carp grass carp Wuchang fish common carp crucian carp Benthic organisms: snail clam larvae of chironomid aquatic oligocheate Zooplankton protozoa rotifera cladocera copepod

Energy coefficient 3.53 4.15 8.01

5.06 7.95 5.31 6.27 7.02

8.01 0.83 0.65 3.85 3.85

Item Phytoplankton Organic detritus with bacteria Green fodder

Lolium multiflorum Sorghum sudansis Eichhornia crassipes Vallisneria spiralis Potamogeton crispus Hydrilla verticillata Fine feed rape seed cake soybean cake wheat bran pelleted diet

Energy coefficient 2.61 2.61 1.73 1.36

1.00 0.57 2.62 2.62 13.17 18.82 16.24 15.68 18.29

2.43 3.59 3.40 2.92

fish culture ponds are different from the intensive fish culture ponds which depend on subsidiary energy in the form of artificial foodstuffs. In the integrated ponds, the major source of energy is solar radiation which is directly used by autotrophic organisms, and indirectly by heterotrophic organisms, including bacteria, zooplankton, benthos, and fish. Both the autotrophic and heterotrophic organisms are a source of energy in the integrated fish culture ponds. The phytoplankton is directly used as the basic feed for filter-feeding fish and it allows the production of heterotrophic organisms for omnivorous fish. In addition, it produces oxygen, which is used by other organisms in the integrated fish culture ponds. Therefore, the phytoplankton play an important role in substance cycling within the ponds. The production and solar efficiency of phytoplankton varied with the stocking patterns (Table 3), with the highest efficiency measured in stocking pattern III (1.4-2.7%). The results were affected by the concentration and input of nutrients in the ponds. More artificial fertilizers were introduced to ponds with stocking pattern III because the main food source was food produced within the pond and its growth was stimulated by the input of fertilizers. In stocking pattern I, the fish were

II

1982

G1

H1 b H2 b H3 b

a

1981 1980 1979 1980 1981 1979

L1 L2 L3 L3 L3 L4

III

1977 1977 1977

1982 1983 1983 1983 1984 1984 1988 1984

$1 $2 $3 $4 $3 $5 $5 Z1

I

Year

Pond

Stocking pattern

46002 46 002 46002

47 737

43 578 37578 44 266 37578 43 577 44 266

43451 46 880 45 880 45 880 45142 45142 45 770 45142

Solar radiation total (G J / h a - year)

22532 22 532 22532

23 382

21344 18405 21682 18405 21344 21682

21282 22 472 22 472 22 472 22111 22111 22 908 22111

PAR (G J / h a " year)

270 373 408 472 517 550

413 444 611 478 862 734 918 860

Energy subsidies total (G J / h a . year)

202 283 306 365 409 428

301 310 462 344 703 554 746 689

Feed and manure (G J / h a - year)

Energy input, energy output, energy of NPP, and the ecological efficiency in integrated high-output fish ponds

TABLE 3

26 27 28

26

21 26 26 34 30 30

17 19 20 19 21 21 22 23

Oxygen (NPP) (t 0 2 / h a "year)

Ix9 Ix9

375

379 398 406

G1 156

H I 157 H2 165 H3 169

8498 10470 16973

7500

6398 9684 13536 14527 15799 14484

8261 10458 12644 11026 14670 13806 19155 15305 33 45 65 70 75 69

53 70 81 73 93 100 123 90

4560 4762 6975

(4838)

5044 8587 10943 11710 13547 11514

2115 2577 3265 2981 3851 4032 4920 4266 24 28 48 53 60 52

9 10 13 14 16 17 21 18

Filtering-feeding fish output mud carp Energy fresh (G J / h a weight year) (kg/ha. year)

1.7 1.8 1.8

1.6

1.4 2.1 1.8 2.7 2.1 2.0

1.1 1.3 1.3 1.3 1.5 1.4 1.4 1.5

5.9 5.9 8.4

(7) c

7.9 10.0 12.4 10.8 13.7 11.8

3.6 3.5 4.6 4.7 5.1 5.5 6.3 5.5

Transforming Transforming ratio of P A R ratio of NPP to to NPP (%) filter-feeding fish (%)

a In Sonda, Gyangdong Province, in which the major fishes are mud carp and bighead carp (Zhong, 1987). b In Wuzi, Jiangsu Province (He, 1983). c Mud carp and bighead carp.

II

242 284 292 285 304 308 328 330

301 384 388 493 348 441

L1 L2 L3 L3 L3 L4

III

101 118 121 119 126 128 136 137

Energy (G J / h a . year)

Fish fresh weight (kg/hayear)

Phytoplankton fresh weight (t/ha. year)

Energy (G J / h a . year)

Net fish output

NPP

125 160 161 205 182 183

S1 $2 $3 $4 $3 $5 $5 Z1

I

Stocking pattern/ pond

0.10 0.10 0.15

0.11 0.21 0.18 0.29 0.28 0.24 (0) c

0.04 0.04 0.06 0.06 0.07 0.08 0.09 0.08

Ecological efficiency from P A R energy to filter-feeding fish (%)

224

H.YAO

fed more food produced outside of the ponds, therefore less fertilizer was used in these ponds. The input of inorganic nitrogen to the ponds of stocking pattern Ill (1.5-7.8 mg/1) was greater than the inputs to the other ponds (0.7-4.1 mg/1). The net production of phytoplankton in the ponds of stocking patterns I, II and III was greatest in the ponds with the highest designed fish output (15 t f i s h / h a . y e a r ; Table 3). These results show that the correlation between fish output ( t / h a . y e a r ) and NPP ( G J / h a . y e a r ) in the same stocking pattern is positive and significant. The correlation coefficients and regression equations are: stocking pattern I: r = 0.88(n = 8, P < 0.01)

and

NPP = 1.1678X + 197.02

and

NPP -- 3.241X+ 216.15

stocking pattern III: r = 0.88(n = 6, P < 0.05)

In other words, NPP increased with increased fish output in the ponds of similar stocking pattern. In Israel, in integrated fish culture ponds fertilized with cow and chicken manure, and stocked with common carp, silver carp, and tilapia, the phytoplankton GPP was 10-50 kg C / h a . day (about 33-166 kg O 2 / h a . day) in spring and fall, and 40-80 kg C / h a . day (about 133-266 kg O 2 / h a . day) in summer (Hepher, 1962; Schroeder, 1978) and the fish average production was 30-32 k g / h a , day in the fish growing season. The phytoplankton GPP is about 495 G J / h a . y e a r and NPP is about 395 G J / h a . y e a r . These results are similar to ours from pond L1 in Nanjing, pond $5 and pond G1. The fish output in the Israeli study was also similar to ours (Table 3). In ponds located in Alabama, USA, in which the fish output was half of that in Israel, the average GPP (10-30 kg C / h a . day) was also only about half of that in Israel (Boyd, 1982). In tilapia ponds in West Java, Indonesia which were fertilized with chicken manure, fish production was only 65% of that in Alabama (Hansen et al., 1991). Silver carp, bighead carp, and silver crucian carp are typical fitter-feeding fish which feed on plankton, suspended and decayed organic detritus, and bacteria; tilapia feeds on all of these as well as on sessile algae and sedimented detritus and plankton; mud carp (Cirrhina molitorella) feeds mainly on detritus (Yan and Yao, 1989; Liu and He, 1992). The integrated fish culture pond ecosystem's algal-detrital food web is composed of algae, bacteria, zooplankton and filter-feeding fish, and the web is based on phytoplankton production in the ponds. NPP directly affects filter-feeding fish and their output.

225

P H Y T O P L A N K T O N P R O D U C T I O N IN I N T E G R A T E D FISH C U L T U R E PONDS

6O0 =

500

400 300 Y=236 + 3.9 X E

I00

Z

0

n=14, r-~.95 I

I

I

I

I

I

I

0 10 20 30 40 50 60 70 Net yield of silver carp, bighea~t, Tilapia and silver crucian carp (GJ ha" ~yr-~)

Fig. 1. The relationship between phytoplankton net primary productivity and net yield of silver carp, bighead carp, tilapia, and silver crucian carp in integrated fish ponds.

As the data in Table 3 show, the ecological efficiency of NPP to fish was usually higher in the ponds of stocking pattern III (filter-feeding fish) than in the ponds with stocking patterns I and II. The transforming efficiency from NPP to the net fish output increased with increasing fish output in ponds of similar stocking pattern with different levels of fish output. The correlation coefficient for the total output of silver carp, bighead carp, tilapia, and silver crucian carp or mud carp ( G J / h a . year) NPP ( G J / h a . year) is 0.948 (n = 14, P < 0.01) and the regression equation is NPP = 3.85X + 236.42 (Fig. 1). It is estimated that about half of the NPP in these ponds could be utilized by filter-feeding fish. Based on a food coefficient between phytoplankton and filter-feeding fish of about 20 (He, 1983) and the utilizable amount of NPP by filter-feeding fish, estimated above, it is estimated that the potential output of filter-feeding fish from NPP is 2.5 to 3.4 t / h a . year with stocking pattern I, 3.9 to 4.2 t / h a . y e a r with stocking pattern II, and 3.1 to 5.1 t / h a . year with stocking pattern III, which constitutes 18 to 30%, 25 to 46%, and 29 to 50% of total fish output in the three stocking patterns, respectively (Table 4). The reasonable input of fish feed is a management goal in integrated fish culture ponds. The input of foodstuff can directly transform to non-filtering fish output (Table 4). The ratio of feed input to non-filtering fish is about 4 in these ponds.

a b c d

H1 H2 H3

II

8 497 10 471 16 972

6120 4477 17 747 11378 14527 17 694 21436

18049 22678 30801 23 457 42755 34 805 48 462 38 895

(kg/ha)

Input

Feed

5 374

1530 1 119 1937 2845 3631 4 424 5 359

4512 5669 7790 5 864 10689 8 701 12115 9 723

32

20 18 20 21 25 28 47

55 54 61 53 73 63 63 64

79 83 84

82 78 63 80 81 102 91 92

50 59 61 59 63 64 68 69

(t/ha)

(kg/ha)

total (%)

Consumed by fish

Converted to fish Output percent of

NPP

3 936 4133 4 221

4118 ¢ 3899 d 3132 3 992 4030 5120 4 556 4 580

2517 2952 3031 2 964 3153 3 205 3 407 3 433

Output (kg/ha)

46 39 25

59 c 52 d 49 41 30 35 29 32

30 28 24 27 21 23 18 23

percent of total (%)

Converted to fish

At Dirsel, Israel, the major stocked fish are tilapia, silver carp, and common carp (Schroeder, 1978). At Sonde, Gyangdong Province, the major stocked fish are mud carp and bighead carp. Mainly tilapia and silver carp (Schroeder, 1978). Mainly mud carp and bighead carp.

1977 1977 1977

7000 7500 6398 9 684 13536 14527 15 798 14 484

D1 a G1 b L1 L2 L3 L3 L3 L4

III

!978 i982 1981 1980 1979 1980 1981 1979

8260 10548 12644 11026 14670 13 806 19155 15 253

1982 1983 1983 1983 1984 1984 1988 1984

$1 $2 $3 $4 $3 $5 $5 Z1

Total

I

Year

fish (kg/ha) output

Pond

patterns

Stocking

7 378

2883 2071 2147 2 755 6661 5775 6 819 4 545

1231 1926 1920 2197 828 1899 3 633 2 096

Output (kg/ha)

43

41 28 34 39 49 40 43 31

15 18 15 20 6 14 19 14

percent of total (%)

zooplankton and benthic organisms converted to fish

Detritus with bacteria,

Fish output (expression of fish production) produced by feed, algae and detritus with zooplankton and benthic organisms in the ponds of stocking patterns I - I I I

TABLE 4

,.< > 0

-r

b-J tO

PHYTOPLANKTONPRODUCTIONININTEGRATEDFISHCULTUREPONDS SUNLIGHT

~

~

I,~...t'-' ~ ' ~ -I ~

14

227

,'

water- in

,

'- .

_1

Fig. 2. The energy flow pathways in an integrated fish culture pond in Suzhou, China (Pond $5 in 1984). Flows are in GJ.ha-2"year -1.

Based on the data presented in Tables 3 and 4, the energy of NPP was 30-48, 50, and 51-60% of the sum of energy of NPP and input of foodstuff in the ponds of stocking patterns I-III. This result shows that primary productivity plays an important role as an energy source for cultured fish production, and fulfills a key function in the effective cycling of substances in the integrated fish culture ponds. Fig. 2 shows the main pathways of energy flow in the food web of the integrated fish culture pond ($6) in Suzhou, China. The data for this figure were measured in 1984 and calculated using the turnover rate and food coefficient of each species (J0rgensen, 1980; Yan et al., 1987) and the energy equivalent coefficient (Table 2). This energy flow diagram shows the importance of phytoplankton primary productivity and its link to fish production. The transformation rate of NPP to fish is 6.34%, which is higher than that of the sum of NPP and input of foodstuff to fish output in this pond but lower than that in the ponds of stocking pattern II (5.9-8.4%) and III (7.9-13.7%; Table 3). This is because the density of filtering fish in the ponds of stocking pattern I was less than in stocking patterns II and III.

228

H. YAO

CONCLUSION

Although all integrated fish culture ponds of different stocking patterns belong to the model of multi-step and multi-layer use of substance and space for aquaculture and may be similar in energy flow, the amount of energy influx and storage may be different in ponds of different stocking patterns with similar fish output, or in ponds of similar stocking patterns with different fish output. The importance of primary productivity and its relationship to fish production depends on the stocking pattern and fish output. In general, this importance increases with increasing filter-feeding fish density. The importance of primary productivity usually disappears in ponds of intensive culture with a single species of non-filtering fish, because, in these ponds, algae is not used directly as the food for cultured fish. In integrated fish culture ponds, fish directly or indirectly use phytoplankton and this promotes the substance cycling, high output, low consumption, and water quality improvements. ACKNOWLEDGMENTS

Yan Jingsong, professor of the Nanjing Institute of Geography & Limnology, Academia Sinica, advised me on revisions of this manuscript. Special thanks are due to Julie Cronk, William Mitsch, and Ruthmarie Mitsch who revised and edited this manuscript, especially in English. Pat Patterson of the School of Natural Resources at the Ohio State University redrew the figures and typed the tables for this manuscript. I also wish to thank the Jiangsu Provincial Committee of Science & Technology and the Jiangsu Provincial Bureau of Fisheries for supporting this project. REFERENCES Bian, W., N. Wu and H. Yao, 1991. Energy values of culturing fishes and feeds. Fish. Sci. Technol. Inform., 18(5): 157-158 (in Chinese). Boyd, C.E., 1973. Summer algal communities and primary productivity in fish ponds. Hydrobiologia, 41: 357-390. Boyd, C.E., 1982. Water Quality Management for Pond Fish Culture. Elsevier, Amsterdam, pp. 78-83; pp. 159-162. Gao, L and H. Wang, 1988. The Integrated Technique of Net-enclosures Fishculture in Lakes. Jiangsu Science & Technology Publ. House, Nanjing, pp. 120-127 (in Chinese). He, Z. and Y. Li, 1983. Studies on the water quality in high-output fishponds in Helie, Wuxi. J. Fish. China, 7(4): 287-299 (in Chinese). Hepher, B., 1962. Primary production in fish ponds and its application to fertilization experiments. Limnol. Oceanogr., 7: 131-135. J~rgensen, S.E., 1980. Handbook of Environmental Data and Ecological Parameters. Elsevier, Amsterdam.

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