Martin S. Kumar

Influence of nutrient loads, feeding frequency and inoculum source on growth of Chlorella vulgaris in digested piggery effluent culture medium

Large amount of waste produced in the livestock industry could be reused to produce valuable products such as microalgae, which are used predominantly in the primary treatment of wastewater for bioremediation. In this study digested piggery effluent was used as nutrient source to substitute mineral nutrients for culturing feed grade Chlorella vulgaris. Two experiments were conducted to investigate the effect of total ammonia nitrogen (TAN) levels, inoculum mediums and the feeding frequencies on the performance of C. vulgaris. The first experimental results showed that 20mg TAN/l in the culture media resulted in better algal SGR (0.345/day; P>0.05). The adding 200 ml effluent into 10 l culture medium at the start (20.6 mg TAN/l) in the second experiment resulted in a large increase of algal population from day 1 to 6 and reached 11.9 million algae/ml at day 6. This study indicated that high production of C. vulgaris could be achieved at short time by feeding digested effluent once.

Size grading did not enhance growth, survival and production of marron (Cherax tenuimanus) in experimental cages

Abstract The necessity for size grading prior to stocking in marron culture is not clear. In this study, production characteristics of marron of three size-graded groups (15.2, 78.3 and 157.6 g) and one mixed group were tested in 24 experimental cages (6×3×2 m) with six replicates for each treatment. After 258 days, mean weight of small marron in the graded group increased from 15.2 to 40.1 g, while small marron in the mixed group increased from 14.8 to 46.4 g. Mean weight of medium marron in the graded group increased from 78.3 to 129.5 g, while medium marron in the mixed group increased from 76.7 to 132.6 g. Mean weight of large marron in the graded group increased from 157.6 to 218.9 g, while the large marron in the mixed group increased from 165.3 to 223.7 g. Size grading of marron did not lead to improved growth. Marron survival rate was not improved by grading either. Instead, survival rate of medium and large individuals was significantly greater in the mixed group than in the graded group. Size specific growth rates were size-dependent and small marron grew faster than either medium or large individuals. The sequence of standing biomass of different sized groups at harvest was medium size (3080 kg/ha)>mixed size (2941 kg/ha)>mall size (2482 kg/ha)>large size (2037 kg/ha). The sequence of net production of different sized groups was small size (1374 kg/ha)>mixed size (1042 kg/ha)>medium size (756 kg/ha)>large size (−275kg/ha). Marron size grading during growout seems to be an unnecessary operation to improve the growth and survival.

Review of Nutrient Management in Freshwater Polyculture

Abstract One of the most important issues concerning fish-pond fertilization is the determination of the optimal amount of fertilizer to be applied to the pond system. Another important concern is the suitability of fish species for polyculture in order to optimize production. The dynamics of nutrients, phytoplankton, and fish is a complex subject and practitioners are often compelled to formulate solutions without detailed scientific and practical consideration. The primary objective of pond fertilization is to maintain an optimal nutrient concentration for sustained biological production. Current fertilization practices in the Asia-Pacific region include: a fixed rate of fertilization and fertilization based on water color. Individual pond ecology determines how fertilization affects pond productivity, not the ponds physical location in relation to international borders. There is no universal recipe of “maximal” fertilization rates due to pond-specific variability. There is also no clear guide in the literature with regard to many aspects of fish-food; the type of organisms consumed, mechanisms of food consumption, and the digestibility and nutritive value of plankton. The usual practice is to divide fish according to their foraging in natural habitats; feeding on phytoplankton, zooplankton, zoo benthos, or detritus. The distinction between different feeding habits is not always absolute as many species of fish may change food preference depending on the abundance of different food items. This paper reviews the nutrient (nitrogen, N and phosphorus, P) management in regard to pond fertilization; use of organic and inorganic fertilizer and the impacts on fish production; use of organic fertilizer from different organisms (pig, cow and buffalo) and their interactions with primary production and water quality; optimum N:P concentration in pond water; and individual pond factors and their influence on fish production. A significant interaction was evident with time between water quality variables such as pH and alkalinity, and other factors, including manure type and fish species composition. This was reflected in the difference between pig and cow manure treatments. A significant interaction between species composition and fish production has been demonstrated. Fish survival and biomass production was influenced by the stocking ratio of the: rohu, Labeo rohita; mrigal, Cirrhinus mrigala; and Nile tilapia, Oreochromis niloticus. The recommended nutrient level for pond fertilization based on the South Australian Research and Development Institute (SARDI) and Research Institute for Aquaculture No. 1 (RIA#1) study is 1 ppm N:0.5 ppm P. The required quantity of fertilizer varies significantly with time. However, regional research is highly recommended to optimize fish production focusing on significant climate variability, which affects both primary and secondary production.

Bio-conversion rate and optimum harvest intervals for Moina australiensis using digested piggery effluent and Chlorella vulgaris as a food source.

The bio-conversion rate of Moina australiensis fed with Chlorella vulgaris grown on digested piggery effluent at three different feeding rates was determined and a 2, 3 and 4-day harvest interval strategy was investigated. This study indicates that C. vulgaris is a suitable food source for M. australiensis. A significant difference (P < or = 0.001) in the feeding rate against mean total populations was found among treatments. The increase in the amount of algae fed accelerated the production rate, and the population density peaked faster in the high C. vulgaris fed treatment. The BCR calculated from this experiment indicates that for every 1000 mg of C. vulgaris fed there was an increase of 437.9 mg of M. australiensis biomass produced. A significant difference (P < or = 0.001) in biomass production among the different harvest interval treatments was observed. The 2-day harvest interval treatment produced 7.78 g of M. australiensis followed by 6.89 g in the 3 day and 5.01 g in the 4-day harvest interval treatment. This study provides strong evidence that M. australiensis can utilise the bacterial blooms and bio-films associated with digested piggery effluent as a food source.

Evaluation of Optimal Species Ratio to Maximize Fish Polyculture Production

Abstract There are questions remaining about many aspects relating to fish food, including, the type of organisms consumed, mechanisms of consumption, and the digestibility and nutritive value of plankton. Common practice has been to divide fish into different types according to foraging in natural habitats, that is, fish are described as feeding on phytoplankton, zooplankton, benthic animals, macrophytes, or detritus. The distinction between the different feeding habits is not always absolute. Although species such as rohu, Labeo rohita, mrigal, Cirrhinus mrigala(Indian major carp), and Nile tilapia, Oreochromis niloticus(African origin) are omnivorous, their adaptability in different climatic conditions varies. A study was carried out to determine the optimal stocking ratio of tilapia and Indian major carp (rohu and mrigal) and with common carp, Cyprinus carpio; silver carp, Hypophthalmichthys molitrix; and big head carp, Aristichthys nobilisin polyculture. Four ratios of Nile tilapia and Indian and Chinese carp (60%, 40%, 20% and 0%) were tested in pig and in cow manure fertilized ponds. Results of this study indicated that the fish ratio and manure type significantly influenced fish survival and biomass over time. The interaction between species ratio, pH, and alkalinity was found to be significant. The stocking density of rohu, mrigal, and tilapia influenced fish survival and biomass production. Ratio 1 with 60% Nile tilapia was the poorest performing treatment in both types of manure. Ratio 3 (20% Nile tilapia, 20% silver carp, 10% big head, 20% rohu and 20% mrigal) was the best performing ratio in pig treatments. Fish production in ratio 2 and ratio 4 with cow manure treatments were not significantly different. In general, fish production in pig manure fertilized ponds was significantly higher than in cow manure treatments.

The Nutrient Profile in Organic Fertilizers

Abstract In order to manage nitrogen (N) and phosphorous (P) through organic fertilization in aquaculture ponds, it is important to understand the nutrient profile of different animal manures at various concentrations and the respective biological response. The rate of nutrient released from animal manure over time is a key factor in deciding the frequency and quantity of manure required to fertilize ponds. This study was conducted to elucidate the nutrient profile, and its efficiency in terms of primary productivity, of pig, cow, and buffalo manure, at different N:P concentrations in tank. Appropriate concentrations were maintained by using the minimum amount of inorganic fertilizer supplement. This paper also investigated the impact of lime-treated manure, a traditional practice in Vietnam, on primary production (phytoplankton abundance). The average nitrogen (N) and phosphorus (P) content was higher in pig manure (0.54% N and 0.173% P) compared to cow (0.31% N and 0.028% P) and buffalo (0.34% N and 0.013% P). The ammonia release rate increased with increase in N concentration. The average ammonia release rate (all concentrations, 1-2 ppm N) in the pig manure treatment was significantly higher than cow and buffalo manure treatments. Cow and buffalo manures were found to be similar in terms of ammonia release rate. However, soluble phosphorus level was significantly lower in buffalo manure treatments compared with cow manure. The pig manure treatment produced maximum soluble phosphorus levels in the tanks. The primary productivity obtained at various concentrations (1-2 ppm N:0.5 ppm P) did not differ significantly (P > 0.05) in cow and buffalo manure treatments. The primary productivity performance of pig manure was highest amongst the manure types tested. The 1 ppm N:0.5 ppm P concentration from pig manure yielded the maximum average (1.64 mg C/L) net primary productivity. Based on the primary productivity pattern in the tank, which had a significant correlation with nutrient release rate for all manures tested, the frequency of fertilizer application appeared to be most suitable every 8-10 days. However, increasing the frequency of manure application based on the level of nutrient available in the water will provide more control on nutrient and water quality management for pond aquaculture systems. This level of monitoring may not be practical for regional farmers.

Evaluation of Fish Production Using Organic and Inorganic Fertilizer

Abstract Efficient usage of fertilizers in organic or inorganic forms show conflicting results in terms of net fish production under various climatic conditions. Manures applied to polyculture ponds as organic fertilizer, require a process of decomposition before the nutritional contents are released, assimilated, and utilized by plankton. On the other hand, inorganic (chemical) fertilizers are granular and concentrated with primary nutrients. Major nutrients such as nitrogen (N) and phosphorus (P) readily dissolve in water in ionic forms of nitrate, ammonium and orthophosphate. The differences in fertilizer solubility (nutrient release rate) and decomposition processes (organic fertilization) make the water quality and biological response distinctively different in inorganic fertilizer applied ponds. Previous research has indicated that one grass carp, Ctenopharyngodon idella, can support the growth of three silver carp. This means the excreta of herbivorous fish can be utilized to fertilize the water and produce plankton for filter-feeding fish to consume. Due to an inconsistent supply of grass foliage, farmers in North Vietnam found it difficult to include an adequate percentage of grass carp to support polyculture operation without supplementary fertilization to maintain adequate levels of natural foods in the pond. This supplementary fertilization, in particular manure application, often impacted water quality, which negatively affected health of grass carp. In the present study, an attempt was made to evaluate the production of grass carp polyculture when N:P were maintained through supplementary organic fertilization. An assessment of organic and inorganic fertilizer application on fish production was also undertaken and compared with grass carp polyculture performance. Fish biomass change and fertilizer treatments had significant interaction (P= 0.001). The fish production was found to be significantly different for organic fertilizer, grass carp + organic fertilizer and inorganic fertilizer treatments. The net fish production was highest (5.6±0.03 tonnes/ hectare) in grass carp + organic fertilizer treatment followed by organic fertilizer (4.0±0.06 tonnes/hectare). The inorganic fertilizer treatment yielded the least with 3.0±0.05 tonnes/hectare. The control ponds with no fertilizer was applied produced only 0.29±0.01 tonnes/hectare.

The Impact of Nutrient Concentration (N:P) and Manure Type on Fish Polyculture

Abstract Nutrient availability is considered to have a major role in controlling primary productivity. Therefore, an important aspect of successful aquaculture management in fish culture systems is making available basic nutrients, for example, phosphorous (P), nitrogen (N), and carbon (C) in optimal concentrations. The use of fertilizers in relation to pond productivity has been studied in order to develop better fertilization procedures under given environmental conditions. Many researchers from across the world have suggested different N:P ratios for optimizing fish production. The primary aim of this study was to understand the influence of nutrient quality and quantity on fish and primary productivity in terms of optimizing fish production. Two objectives of this study include evaluating the performance of pig and cow manures in terms of primary productivity and fish production; and understanding the influence of different N concentrations ranging from 1-2 ppm on fish production while P was maintained at 0.5 ppm. It was evident from this research that fish species nutrient-sensitivity to nitrogen concentrations ranging from 1-2 ppm was significantly different. The 1 ppm N:0.5 ppm P concentration was found to be the most suitable nutrient ratio for pond fertilization as significantly higher fish production and lower mortality were recorded in this treatment. In terms of plankton and fish production, pig manure was found to be significantly more effective than cow manure. Higher nutrient (>1 ppm N) concentrations negatively impacted zoo-plankton and zoo benthos development. Daily manure application would considerably reduce the organic load in the fish culture system, enabling more efficient use of nutrients for primary and secondary production.