PRIMARY PRODUCTION AND FISH YIELDS IN FISH PONDS UNDER DIFFERENT MANAGEMENT PRACTICES

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Primary Production and Fish Yields in Fish Ponds under Different Management Practices

J. OLÁH¹, V.R.P. SINHA, S. AYYAPPAN, C.S. PURUSHOTHAMAN and S. RADHEYSHYAM

ABSTRACT

The primary production and fish production patterns in temperate and tropical ponds under different management practices are described. An attempt is made to understand the relation between the two under the given conditions. With a more or less narrow range of primary production, varying fish production and conversion efficiencies were recorded, indicating the influence of a combination of environmental and management factors. The constraints involved in establishing the relationship are discussed.

INTRODUCTION

There have been a number of attempts at correlating fish yields with limnological factors influencing the productivity of lakes (Rawson, 1955; Northcote and Larkin, 1956; Ryder, 1965). The direct approach, which has received greater attention recently, is the correlation of fish yields with primary production (Smith and Swingle, 1938; McConnel, 1963; Hrbacek, 1969; Sreenivasan, 1972; Wolny and Grygievek, 1972; Melack, 1976; Oglesbby, 1977; McConnel et al., 1977; Noriega-Curtis, 1979; Liang et al., 1981). However, most of these studies pertain to natural waters and there are only a few on fish ponds.

Sufficient data on the primary production and fish yields of culture ponds at different management levels have been collected in recent years during work on their ecosystem structure and functioning, as a part of the investigations carried out at the Fisheries Research Institute, Hungary. Similar work on the basic production and yields of the tropical, undrainable, rural fish ponds of Orissa, India, had been initiated in 1982 and considerable information is available from 18 ponds. It should be pointed out that, in these ponds, the productive potential is often not utilized to the maximum due to understocking and it is the actual relation between the primary production and the fish yields as recorded by the farmers which is considered. The present paper evaluates the data from these systems with significantly varying management practices and compares the efficiencies of energy conversion from primary levels to that of fish production.

In Aquaculture, 58 (1986) pp. 111–122
Elsevier Science Publishers B.V., Amsterdam (Netherlands)

MANAGEMENT PRACTICES

Stocking only

Simple stocking was tested in two small Hungarian water bodies of 0.14 ha each, with an average depth of 1 m, in 1976. The ponds were drained during the previous autumn, dried thereafter, and filled and stocked at the end of March 1976. The stocking structure, given as mean weight (g) and density (ha^-1), was silver carp 180 and 370; bighead carp 190 and 450; common carp 210 and 200; and grass carp 200 and 150. With no feeding or organic or inorganic fertilization applied during the growing season, the fish were harvested in October (after 6 months).

Stocking and inorganic fertilization

This management practice was tested in two Hungarian fish ponds of 0.14 ha each with an average water depth of 1 m (in 1977). The ponds were drained during the previous autumn, dried thereafter, and filled and stocked at the beginning of April 1977. The stocking structure, given as mean weight (g) and density (ha^-1), was: silver carp 40 and 1900; bighead carp 50 and 1200; common carp 190 and 3800; and grass carp 50 and 600. The fish were harvested in October. During the growing season, a total amount of 20 kg P in the form of superphosphate and 150 kg N in the form of NH₄NO₃ was supplied in weekly rations.

Stocking and fertilization with domestic sewage

This experiment was carried out in Hungary applying a technology which had been elaborated earlier (1975). Sedimented raw domestic sewage was introduced daily through a rotary sprinkler into the fish ponds (with and area of 1.6 ha and an average depth of 1 m) at the rate of 100 m³ ha^-1. All the six ponds were drained and dried during the winter, and the fish were stocked at the beginning of April and harvested in October. The stocking structure, given as mean weight (g) and density (ha^-1), was: silver carp 190 and 1500; bighead carp 180 and 800; common carp 200 and 1400; and grass carp 170 and 300.

Stocking and fertilization with pig manure

In Hungary, liquid pig manure with a mean dry weight of 10% was introduced daily into fish ponds of a 0.14-ha area and an average depth of 1 m through a rotary sprinkler with flexible rubber openings at the rate of 2 m³ ha^-1. The ponds were drained and dried during the winter, and the fish were stocked at the end of March and harvested in October. The stocking structure, given as mean weight (g) and density (ha^-1), was: silver carp 190 and 3500; and common carp 150 and 1800.

Rural fish ponds in India

A total of 18 undrainable rural fish ponds (Table 1) were stocked with the three major Indian carp species, catla (Catla catla), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala), as well as with common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix). The initial stocking weight was around 2–3 g in the smaller ponds and ranged between 20 and 60 g in the larger ponds. The stocking density varied between 2800 and 7000 ha^-1. Supplementary feed is rarely applied in these ponds and, when given, it has a low nutritive value and functions more as an organic fertilizer. These small ponds serve many purposes in the life of the villages and organic enrichment is also realized through these activities. Thus the magnitude of the organic fertilization relates to the sizes of the human population and animal livestock associated with the particular pond.

Stocking, fertilization and supplementary feeding

In all, 23 fish ponds were tested under a project designed to optimize inorganic fertilization technology in Hungarian polyculture. Using different dosages of nitrogen and phosphorus fertilizers, it was possible to regulate the primary production levels and establish a gradient from 1.3 to 5.0 g C m^-2 day^-1. Ponds of 0.14 ha with an average depth of 1 m were drained and dried during the winter, stocked at the beginning of April and harvested by the end of October. The stocking structure, given as mean weight (g) and density (ha^-1), was: silver carp (Hypophthalmichthys molitrix) 200 and 1500; bighead carp (Aristichthys nobilis) 180 and 1000; common carp (Cyprinus carpio) 210 and 4000; and grass carp (Ctenopharyngodon idella) 220 and 500. The dosages of fertilizers were a combination of 0,20,50 and 120 kg P ha^-1 year^-1 in the form of superphosphate and 0, 50, 150 and 300 kg N as NH₄NO₃, applied weekly in equal portions during the growing season. A total amount of 5–6 t ha^-1 wheat was applied to each pond as supplementary feed according to the increasing biomass of the fish.

METHODS

A major drawback in trials attempting to relate primary production to fish production is the diverse methodology used to measure plant photosynthesis in water. It is usually measured with ¹⁴C or oxygen changes inside dark and light bottles (Melack, 1976; Noriega-Curtis, 1979; Liang et al., 1981). Another approach is the direct measurement of diel changes of oxygen concentration in the whole water column (McConnel et al., 1977). In the present study, this in situ method was used applying our own calculating model with seven measuring points (Oláh et al., 1978), except in the 18 undrainable rural fish ponds, where diurnal oxygen was monitored with three measuring points and the McConnel (1962) equation was used to calculate the primary production. The oxygen concentration was measured using a Beckman Monitor II oxygen meter. Primary production was quantified in g C m^-2 day^-1. Here an average value of each pond is presented based on weekly measurements during the whole growing season.

Table 1. Main characteristics of undrainable rural fish ponds in Orissa, India.

Most of the earlier studies obtained their data on fish production from commercial estimates (Melack, 1976; Oglesby, 1977). In the present work, all the fish ponds were completely harvested and the yield was measured. A unit of g C m^-2 day^-1 has been chosen instead of per year considering the differences in the duration of the growing season in temperate areas and the tropics. The conversion efficiencies from primary production to fish production in terms of carbon were calculated as ratios and are presented as percentages.

RESULTS

With a mere stocking manipulation and no fertilization, a rather good conversion efficiency of 2–3% was achieved at the relatively low average primary production values of 1–1.7 g C m^-2 day^-1 (Table 2). The average primary production in ponds with stocking and inorganic fertilization was as high as 5.3 g C m^-2 day ^-1. The fish production was more than double that of the previous management practice but the percentage utilization was low (Table 2).

The wide range of fluctuations in the mean primary production values among the six experimental ponds fertilized with domestic sewage may be a result of the residual effects of the experiment with different organic loadings carried out in the preceding years (Table 3). Fish production, however, was more uniform and the variations did not follow the trend of primary production. Thus a definite relation between primary production and fish production was not observed.

In the ponds with liquid pig manure, a permanently high level of primary production was maintained (Table 4). The daily fish production ranged between 14 and 21 kg ha^-1 or 0.14 and 0.21 g C m^-2. The average conversion efficiency was around 3%.

There was no close relation between primary production and fish production in the rural fish ponds of Orissa, India (r=0.15). The highest daily fish production of 15.8 kg ha^-1 was observed in pond 11 which had a low primary production while pond 1 with an extremely high primary production produced a moderate fish yield of 8 kg ha ^-1 (Table 5).

A close correlation between primary production and fish production was observed in the 23 experimental ponds with supplementary feeding (r=0.87). The primary production fluctuated over a wide range according to the doses of inorganic fertilizers applied. Although the supplementary feed was applied in a nearly equal amount in all of the ponds, the fish production varied according to the fluctuating pattern of the primary production. This is due to the incomplete dietary composition of wheat for normal fish growth and their further dependence on natural food. Fish ponds with moderate primary production ranges of 1.3–2.1 g C m ^-2 day ^-1 maintained an average daily fish production in the range of 16.4–27.1 kg ha^-1, with high fish production efficiencies of 10.9–14.3. In the fish ponds with a high primary production in the range of 3.8–5.0 g C m^-2 day^-1, the average daily fish production was also high and ranged between 27.3 and 40.8 kg ha ^-1. The fish production efficiency was lower than in the previous ponds but remained in the range of 6.0–10.0 (Table 6).

Table 2. Gross primary production (GP), net fish production (FP), and conversion efficiency (FP/GP×100) in stocked ponds without fertilization and with inorganic fertilization.

Table 3. Gross primary production (GP), net fish production (FP) and conversion efficiency (FP/GP×100) in fish ponds fertilized with domestic sewage.

Table 4. Gross primary production (GP), net fish production (FP) and conversion efficiency in fish ponds fertilized with liquid pig manure.

Table 5. Gross primary production (GP), net fish production (FP) and conversion efficiency (FP/GP×100) in undrainable rural fish ponds in Orissa India.

DISCUSSION

The ranges of primary production, fish production and conversion efficiencies generated in the present study and also collected from published papers are summarized in Table 7. Among the 54 fish ponds tested in the present survey, those with stocking and inorganic fertilization or stocking with oxidized liquid pig manure fertilization exhibited stable primary production levels in the high range of 5.3–6.5 g C m^-2 day ^-1. The average primary production in the tropical undrainable rural ponds was low but similar to the published results for lakes and reservoirs both in temperate and tropical zones; the range of the values was wide being 1.8–12.3 g C m^-2 day^-1.

The fish production in 27 natural water bodies of the temperate zone ranged between three orders of magnitude from a few grams to a few kilograms per hectare per day. The low value of 2.8 g ha^-1 day^-1 was determined for both Lake Superior and Lake Huron (Oglesby, 1977) and the largest value of 3.9 kg ha^-1 day^-1 for Lake Dalneye (Oláh, in prep.). The range of variations in the tropical water bodies was smaller. In the ponds under management in this study, the average fish production remained rather constant: 3.5 kg ha^-1 day^-1 in the ponds with stocking only; 10.4 in the stocked and inorganic fertilized ponds; 11.0 in the stocked and domestic sewage fertilized ponds; 18.0 in the ponds with liquid pig manure and 28.1 in the stocked, inorganic fertilized and supplementary fed ponds. The fish production in rural fish ponds ranged between 2.8 and 15.8 kg ha^-1 day^-1.

The fish production efficiency varied over a wide range in both the temperate and tropical lakes and reservoirs. However, the average conversion was more efficient in the temperate zone. By applying the simple management practice of stocking only, we produced a tenfold increase compared with the natural situation. With the management practice of stocking with inorganic fertilization, the primary and fish productions were high but the efficiency decreased. High rates of efficiency were obtained for both types of organic fertilized fish ponds. This high efficiency was, however, the result of the bacterial food chain which has great importance in these organic loaded systems. The highest efficiency was observed in fish ponds with supplementary feeding. However, at this management level, the efficiency is greatly influenced by the supplementary feed.

Table 6. Gross primary production (GP), net fish production (FP) and conversion efficiency (FP/GP×100) in stocked fish ponds with fertilization and supplementary feeding.

The comparison of the relation between primary production and fish production in various fish pond ecosystems seems to corroborate the conclusion drawn by McConnel et al. (1977). There are real principal differences between different types of fish rearing ecosystems and a uniform equation cannot be elaborated and applied for all of the water bodies. Even the logistic curve describing the whole range of primary production and fish production relations proposed by Liang et al. (1981) seems to be inadequate to provide a satisfactory explanation of the relation at different management levels. Also our data on the management level with organic fertilization confirmed the conclusion of Noriega-Curtis (1979) that primary productivity alone is not sufficient to account for the high yields attained in organic fertilized systems. The significance of the bacterial food chain has high priority in these allochthonous systems. The non-significant correlation between primary production and fish production in the domestic sewage fertilized, the liquid pig manure fertilized and the undrainable rural fish ponds is thus explained. Hence, water bodies receiving substantial organic inputs compared with those which are autochthonous should be excluded from models describing the relation between primary production and fish production as was stated by Oglesby (1977).

There are many constraints in evolving a model describing the relation between primary production and fish yields. Several attempts at this have been inadequate to explain the mode of energy flow or to predict the fish production from different waters (McConnel et al., 1977; Liang et al., 1981). The methodology employed in studying this aspect has been far from perfect, as has already been explained earlier. A variety of factors influence the relation, viz., species composition, stocking density, nature of fertilization and feeding intensity. Significant differences in efficiency have been demonstrated in the case of Tilapia feeding on phytoplankton and Gambusia feeding on the next trophic level of zooplankters (McConnel, 1965; Goodyear et al., 1972), the former giving higher production levels within a narrow range of primary production. The stocking density influences the utilization of the natural food resources available and the basic production is under-utilized in the case of low stocking densities. Organic fertilization introduces a complex food web into the fish ponds, with a higher intensity of bacterial activity via the detrital food chain (Noriega-Curtis, 1979).

CONCLUSION

In an attempt to understand the relation between primary production and fish production, data were collected from 54 fish ponds of different trophic levels under various management practices, from simple stocking to fertilization and supplementary feeding, in Hungary and India. While primary production was determined by the diurnal oxygen curve method, fish production was measured from the actual harvests.

The gross primary production ranges in g C m^-2 day^-1 in the different systems were: 1.0–1.8 in the ponds which were only stocked; 5.3 in the stocked and inorganic fertilized ponds; 2.0–6.3 in the domestic sewage fertilized ponds; 5.4–6.5 in the liquid pig manure fertilized ponds; 1.8–4.8 in the undrainable rural fish ponds except for one high value of 12.3 in pond 1; and 1.3–5.0 in the stocked, fertilized and supplementary fed ponds.

The average fish production values were: 3.5 kg ha^-1 day^-1 in the simply stocked ponds; 10.4 in the stocked and inorganic fertilized ponds; 11.0 in the domestic sewage fertilized ponds; 18.0 in the liquid pig manure fertilized ponds; 2.8–15.8 in the undrainable rural ponds; and 28.1 in the stocked, inorganic fertilized and supplementary fed ponds.

The fish production efficiency, i.e., the fish yield expressed as a percentage of the primary production, varied widely: 2.3–3.0 in the simply stocked ponds; 1.9–2.0 in the stocked and inorganic fertilized ponds; 1.6–5.0 in the domestic sewage fertilized ponds; 2.6–3.2 in the liquid pig manure fertilized ponds; 0.7–6.8 in the undrainable rural ponds; and 6.0–14.3 in the stocked, fertilized and supplementary fed ponds. Even simple fish stocking without any fertilization treatment increased the efficiency levels tenfold and the high values obtained in the organic systems were largely due to the bacterial activity adding to the higher energy conversion.

With the higher levels of management practices, fish production seemed to depend to a lesser degree on the magnitude of the primary production. The latter, however, sustained the higher trophic levels to the requirement and regulated the utilization of the inputs. A universal relation between primary production and fish production could not be established.

There are many constraints in evolving a model describing the relation between primary production and fish production, including the methodologies employed and a variety of factors influencing the correlation such as fish species, stocking density, nature of fertilization and feeding intensity.

Table 7. Ranges and mean values of gross primary production (GP), net fish production (FP) and conversion efficiency (FP/GP×100) in lakes and fish ponds under varying management practices.

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