Varying Stocking Densities Research Articles

Growth Performance and Culture Economics of Mud Eel Semi-Intensively Cultured Under Varying Stocking Densities in Rain-fed Earthen Ponds

Growth Performance and Culture Economics of Mud Eel Semi-Intensively Cultured Under Varying Stocking Densities in Rain-fed Earthen Ponds

Heat balance, haematology and serum chemistry of layers under varying stocking density reared in locally fabricated metal-type cage system

One hundred and thirty five 18weeks old Bovans Nera Black strain pullets were used in a 10week study to determine their heat balance and blood profile under varying stocking density in locally fabricated metal-type cage system. The cages were stocked 2, 3 and 4birds/cell. Daily ambient temperature and relative humidity of the cage and rectal temperature of the birds were taken and heat balance calculated. Record of Packed cell volume (PCV), Haemoglobin concentration (Hb), Red blood cell (RBC), White blood count (WBC) and differential of the birds were taken at beginning and end of the study for the haematological indices while blood glucose, total protein, Albumin and blood urea were taken for the bio-chemical measurements. Ambient temperature, relative humidity, and heat balance showed no significant (P>0.05) difference with cage stocking density. Cage stocking density had significant (P<0.05) effect on rectal temperature of layers. Bird stocked 3/cell recorded the least (41.14oC) rectal temperature while those stocked 4/cell recorded the highest (41.27oC). All the haematological parameters of the birds were not significantly (P>0.05) influenced by stocking density of the cage type. Bio-chemical measurements were not significantly (P>0.05) different among layers under varying stocking density of the cage except total protein (P<0.05). Layers stocked 4/cell recorded highest (5.22g/dl) total protein while those stocked 3/cell had the least value (4.37g/dl). However, the values were within the normal range recommended for healthy chicken. The study concluded that locally fabricated metal-type battery cage could be used to rear layers and stocking density of 3birds/cell is ideal without compromising the welfare of the birds.

Growth and Economics of Silver Barb (Barbonymus gonionotus) in Rice-fish-vegetable Integrated Culture System at Different Stocking Densities in a Rainfed Arid Zone

Sustainable integrated farming involving the combination of rice-fish-vegetables requires advanced technology to be adopted in crop production in arid zones characterized by red or yellow soil. In the present study, we used suitable and varying stocking densities of Silver barb (Barbonemus gonionotus) and evaluated in a structured production and economic framework under four treatments (T1, T2, T3, and T4) assigned with a stocking density of 10, 20, 30 and 40 fish/decimal, respectively. We used standard methods of water, soil, and plankton monitoring of the rice field. The study showed that lower stocking density provided the fish with more spaces and less competition for food resulting in higher growth performance in T1 compared to other treatments. Although stocking density did not show any significant (P>0.05) effect in rice, straw and vegetable production in all the treatments, the highest rice and straw production at T4 could be ascribed to the improvement in soil fertility by the accumulation of fish excreta and subsequent release of nutrients from the soil by the higher number of fish in that treatment. The best fitted polynomial regression line obtained between gross yield and net yield with different stocking densities of Silver barb described an inevitable fluctuation in net yield of fish with increasing stocking density. Despite the stable growth performance of fish in T1, a combined effect of lower total input cost, higher yield of fish and rice, and economical vegetable production, T2 showed a significantly (P<0.05) higher total return. Furthermore, the benefit-cost ratio (BCR) for rice-fish-vegetables integrated culture system in the rain-fed rice field was also high. In conclusion, this study revealed that maintaining a stocking density of 20 fish/decimal was economically profitable for rice-fish-vegetables integrated culture systems in arid zones on a global scale.

Application of biofloc technology for Indian major carp culture (polyculture) along with water quality management

In this study, the efficacy of biofloc system was assessed for culturing Indian major carps, e.g., rohu (Labeo rohita), catla (Catla catla), and mrigal (Cirrihinus mrigala) at varied stocking densities (STD) from 4.28, 8.57, and 12.85 fish m−3 of tank volume. Biofloc system could efficiently remove inorganic nitrogen from culture water and substantially improved the growth parameters of fishes as compared to the control system without the application of biofloc. Among different STDs in biofloc system, water quality and floc formation were noted to be higher with a STD of 4.28 fish m−3 and the average concentration of NH4 – N, NO2 – N and NO3 – N of 0.61 mg L−1, 0.35 mg L−1 and 1.8 mg L−1, respectively was recorded lowest as compared to the other STD. As a result, catla and rohu could achieve a specific growth rate of 1.1 % day−1 and 0.98 % day−1, respectively. However, in the other two STDs, the respective concentrations were noted in the range of acceptable water quality, and the growth rates were satisfactory. It can be concluded that the biofloc system is efficient to culture IMC in polyculture mode amd therefore, can be directly applied in scaled-up culture modules.

Growth performance and yield of hybrid catfish Clarias gariepinus (♂) x Heterobranchus bidorsalis (♀) at various stocking densities

The study evaluated effects of varying stocking densities on growth, protein utilization, survival rates and yield of hybrid catfish reared in 1m x 1m x 1m collapsible tarpaulin trough. Fish fry (0.60± 0.01g) were randomly stocked at 25, 50, 75 and 100fish/m3 and fed commercial diet (45% protein) for twelve weeks. At harvest, growth responses and economic performances of fish under various densities were evaluated. Results showed that significant differences (p &lt; 0.05) existed in specific growth rates, gross profit, profit index and economic conversion ratio. Fish stocked at 75 fish/m3 produced the best growth {mean final weight (30.93±1.3g), specific growth rate (4.06±0.07%/day)}; the best protein utilization {food conversion ratio (0.11), protein productive value (1.20±0.02%), protein index (5.34±0.16g/day) and the highest yield {gross profit (₦2931±125/m3), profit index (6.23±0.10) and economic conversion ratio (3.73±0.23).Survival was generally high. The results concluded that hybrid catfish reared in collapsible trough gave the best yield at 75fish/m3.Keywords: Hybridization, catfish, growth, survival, yield, profit index, economic conversion ratio, nutrient utilization

Growth performance and survival of &lt;i&gt;Clarias gariepinus&lt;/i&gt; under varying stocking density

The experiment evaluated the growth performance and survival of Clarias gariepinus under varying stocking density. Three-day-old hatchlings (15,750 in number) were selected from the bred population after absorption of their yolk sac and were randomly stocked at three different densities of 40 fish/litre (T1), 20 fish/litre (T2) and 10 fish/litre (T3). The fish were sampled every 10 days for 60 days. The result showed that fish in T3 has the highest mean final weight which was not significantly different (p>0.05) from the value recorded in T2 but was significantly different (p 0.05) in the specific growth rate among the treatments, the highest was recorded in T3 while the least was recorded in T1. The highest performance index was recorded in T3 and was significantly different (p<0.05) compared to other treatments with higher stocking densities, the least was recorded in treatment with the highest stocking density (T1). The percentage survival (58.80±2.55) at the end of the experiment in T3 was significantly higher compared to T1 (16.72±1.72) and T2 (28.97±0.58). It could be concluded that lower stocking density will increase the survival as well as enhance the growth performance of C. gariepinus fingerlings.Keywords: Aquaculture, Fish fry, Hatchery, Stocking density

Prospects of rice-fish farming system for low lying areas in Bihar, India

An attempt has been made to explore the potentiality of organic integrated rice-fish farming from seasonally waterlogged areas for overall improvement of water productivity of the system. Two separate experiments were conducted. In experiment 1, five paddy fields (0.1 ha) of uniform topography were selected where center 10% area has been used as a fish refuge (1.2 m depth). MTU 7029 rice variety were transplanted in the already prepared field and a total of 50 numbers (25 each) of stunted Rohu (Labeo rohita) (104.7 ± 2.65 g) and Catla (Catla catla) yearling (95.1 ± 3.22 g) were stocked in the refuge area. Rice was harvested after 120 days and net fish production was recorded after the culture period of 180 days. At the end of 5 months, Rohu attained growth of 545.1 ± 24 g and Catla 589.5 ± 42.6 g. Average productivity of five fish refuges was 1.70 t ha−1 of fish and recovery was around 78%. In the experiment 2, using the same plot with a varying stocking density and size of fish and with MTU 7029 rice variety, average production of paddy straw and grain from 1-ha area were 6.73 and 4.36%, higher than controls (without fish stocking), respectively. Overall income from this integration was 72.21 thousand rupees which are around 26% higher than the income from control (57.28 thousand rupees). From the study, it can be summarized that organic rice-fish integration can be a viable technique, especially for low lying areas compared to rice monoculture.

Farmer participatory pond based cage aquaculture for raising fish seed in South Garo Hills, Meghalaya, India

Fingerling sized fish seeds are always in great demand for any type of aquaculture operations. The paper highlights the results of a maiden study undertaken to popularise pond based cage culture for raising fingerling sized fish seed aimed at stocking quality fish fingerlings for augmenting fish production in the Garo Hills of Meghalaya. A farmer participatory study was undertaken for raising fry to fingerling sized fish seeds of 3 fish species viz., silver carp (Hypophthalmichthys molitrix), gonius (Labeo gonius) and common carp (Cyprinus carpio) in pond based cages during September-November 2011. Fry sized fishes of these species were reared in locally made bamboo-net cages (2 x 1.5 x 2 m) at different stocking densities. The primary objective was to increase the survival rate and observe the comparative growth rate of different species under varied stocking densities. A total of 18 cages were grouped under 3 stocking densities viz., 150, 250 and 300 fry m-3. Highest survival rate was observed at a stocking density of 150 fry m-3 for all the three species. Among the three species, silver carp demonstrated the highest survival rate at all the stocking densities. In terms of growth, better performance was observed with stocking density of 250 fry m-3 for all species.

Consequences of High-Density Fish Culture as Monitored By Growth, Behavior and Immune Responses of Nile Tilapia (Oreochromis niloticus)

An experiment was performed in a twelve weeks period at three varied stocking densities: low density (LD, 100 fish m-3), medium density (MD, 200 fish m-3) and high density (HD, 400 fish m-3) to analyze the biological performances and ingestive behaviour, of Nile tilapia (Oreochromis niloticus) and Lately, fish were challenged with Aeromonas hydrophila to evaluate the cumulative mortality (%). Stocking density had no effect on survival rate, the final weight markedly reduced with increased density, ingestive behaviour was higher in fish reared in MD than fish reared in LD, however, fish at HD have a higher feed intake (%) and feed conversion ratio. Fish at LD showed marked higher levels of total protein, albumin and globulin compared with those reared at HD. plasma glucose and cortisol levels were high in HD contrast to LD and MD groups. LD fish had higher RBCs and WBCs parallel to MD and HD. similarly, lymphocytes, neutrophils, and monocytes (%) decreased with increasing density. In addition, Serum antioxidant and lysozyme enzymes were considerably (P

Multi-species farming of major and minor carps for enhancing fish production in freshwater aquaculture

An year long experimental multi-species farming of Indian major carps (IMC) and minor carps was conducted with varied stocking densities in 15 earthen ponds (0.08 ha) to develop a suitable farming model. The IMC group included Catla catla, Labeo rohita and Cirrhinus mrigala at 35:40:25 ratio while minor carp and barb (MCB) group included Puntius gonionotus, Labeo fimbriatus and Puntius sarana at 40:35:25 ratio. Fingerlings were stocked in five density combinations (treatments) as: T1 - IMC at 8000 ha-1, T2 - IMC at 8000 ha-1 + MCB at 4000 ha-1, T3 - IMC at 4000 ha-1 + MCB at 4000 ha-1, T4 - IMC at 4000 ha-1 + MCB at 8000 ha-1 and T5 - MCB at 16000 ha-1. Survival of all species in both groups showed inverse relation with their stocked densities. T4 with IMC and MCB at 4,000 and 8,000 fingerlings ha-1, respectively, formed the ideal density with 28.8 and 76.0% higher yield realisation compared to T1 with only IMC and T5 with only MCB group, respectively. All multispecies treatments having MCB group as major component yielded higher fish biomass than those with IMC group. Such results indicated potential of multispecies farming system to increase production in seasonal ponds and water bodies retaining lower water level.

Multi-species farming of major and minor carps for enhancing fish production in freshwater aquaculture

An year long experimental multi-species farming of Indian major carps (IMC) and minor carps was conducted with varied stocking densities in 15 earthen ponds (0.08 ha) to develop a suitable farming model. The IMC group included Catla catla, Labeo rohita and Cirrhinus mrigala at 35:40:25 ratio while minor carp and barb (MCB) group included Puntius gonionotus , Labeo fimbriatus and Puntius sarana at 40:35:25 ratio. Fingerlings were stocked in five density combinations (treatments) as: T1 - IMC at 8000 ha-1, T2 - IMC at 8000 ha-1 + MCB at 4000 ha-1, T3 - IMC at 4000 ha-1 + MCB at 4000 ha-1, T4 - IMC at 4000 ha-1 + MCB at 8000 ha-1 and T5 - MCB at 16000 ha-1. Survival of all species in both groups showed inverse relation with their stocked densities. T4 with IMC and MCB at 4,000 and 8,000 fingerlings ha-1, respectively, formed the ideal density with 28.8 and 76.0% higher yield realisation compared to T1 with only IMC and T5 with only MCB group, respectively. All multispecies treatments having MCB group as major component yielded higher fish biomass than those with IMC group. Such results indicated potential of multispecies farming system to increase production in seasonal ponds and water bodies retaining lower water level.

Lake-Based Nursery Rearing of Nile Tilapia (&amp;lt;i&amp;gt;Oreochromis niloticus&amp;lt;/i&amp;gt;) Fingerlings in Nylon Hapas: Effects of Stocking Density on Growth, Survival and Profitability

The inadequate supply of tilapia fingerling is a major limitation to cage culture development in Ghana. Lake-based hapa systems are very efficient in nursing fingerlings although the process can be tricky due to inherent effects of stocking densities and environmental factors. This study aimed at assessing the growth, survival and profitability of Nile tilapia (Oreochromis niloticus) fingerlings of the Akosombo strain reared in nine 1 m3 Lake-based hapas at different densities. Each hapa was stocked with 2.12 ± 0.14 g sex-reversed tilapia fingerlings at varying stocking densities of 400 fish/m3, 800 fish/m3 and 1200 fish/m3 serving as treatments T1, T2 and T3 respectively. Each treatment was replicated thrice. Bi-weekly samplings were done and water quality parameters were measured. After the experiment, analysis of variance showed significant differences (p < 0.05) in the weight gained, specific growth rate, profit index and feed conversion ratio among treatments. The T1 fingerlings exhibited the highest specific growth rate (3.28 ± 0.10%/day) and FCR (1.42 ± 0.09) than others. Overall, profit index was affected by stocking density and varied significantly between treatments. Treatment T3 was found to be better for commercial fingerling production because survival rate (91.14 ± 3.23%) and profit index (3.96 ± 0.24) were the highest while treatment T1 recorded the least index of 1.31 ± 0.10. Survival rates ranged between 89% and 91% but no statistical differences were observed among treatments. It is concluded that the stocking densities used had significant effects on the specific growth rate, gain in weight and feed conversion ratio of fingerlings reared in Lake-based hapas. However, in fingerling production, not only profit but also rapid growth needs consideration, hence, T2 is highly recommended for nursery rearing of tilapia fingerlings in this system due to the relatively high profit index, growth rate and survival.

English

This study was carried out to evaluate the growth performance and some haematological functions of Clarias gariepinus fed different levels of crude protein under varying stocking densities. Fish of even sizes were randomly selected and stocked in plastic circular tanks (0.05 x 0.03 x 0.03 m) at three stocking densities of 10 fish/m3 (control), 15 fish/m3 and 20 fish/m3. The fish of each stocking density were fed either a diet containing 40% Crude protein (CP) or 45% CP with a feeding rate of 3% body weight twice daily. The experiment was replicated thrice and it lasted for 12 weeks during which haematological parameters and plasma biochemistry were measured. From this study, haemoglobin (Hb) and Red Blood Cell (RBC) slightly increased in all treatments but the variation was not significant in relation to protein level in the diets. Plasma glucose increased significantly (P<0.05) in relation to the stocking densities. The plasma protein showed insignificant variation in relation to the stocking density but the variation was more pronounced (P<0.05) at the lowest stocking density as the protein level in the diets varied. It can be concluded that enhancing feed quality especially protein level in the fish diet may ensure faster growth, stress reduction and improve health status of the fish. Key words: Crowding stress, haematological functions, Clarias gariepinus, diet quality.

Effect of varying stocking density of bottom feeder fish Cirrhinus mrigala and Cyprinus carpio on growth performance and fish yield in polyculture system

The present project was planned to study gradual replacement of Cirrhinus mrigala with Cyprinus carpio and its impact on pond ecosystem. A total of 900 fishes belonging to six species viz. Catla catla, Labeo rohita, Cirrhinus mrigala, Ctenopharyngodon idella, Hypophythylmichthys molitrix and Cyprinus carpio were stocked in four earthen ponds. The dimensions of each pond were 220 × 198 × 7 feet length, breadth and depth. The stocking density in pond 1 (T1) was C. catla 150, L. rohita 200, C. mrigala 200, C. idella 150, H. molitrix 150 and C. carpio 50. The stocking density of C. mrigala and C. carpio in pond 2 (T2) was 150 and 100, in pond 3 (T3), 100 and 150 and in pond 4 (T4) it was 50 and 200, respectively while the stocking density of all the other four fish species remained constant in all the four ponds. All the fish were fed with a diet of 25.16% crude protein at 2% body weight. C. idella and C. mrigala showed maximum growth in T1, C. catla and H. molitrix in T2, L. rohita and C. carpio in T3. Maximum growth was observed in T3 followed by T4, T1 and T2. Among fish species C. idella and C. carpio showed higher growth rates than the rest of fish species. Our results reveal that in polyculture system stocking density of C. mrigala and C. carpio in a ratio of 1: 1.5 gives better results. Key words: Aquaculture, freshwater, phytoplankton, zooplankton, exotic fish.

Effect of different stocking densities on growth performance and profitability of Oreochromis niloticus fry reared in hapa-in-pond system

A one month trial of sex reversal treatment of O. niloticus fry of varying stocking densities was performed in hapas-in-pond to determine the growth performance characteristics and profitability. Larvae were selected, collected, weighed and stocked inside a 10.0 m2 hapas in a 0.2 ha pond with stocking densities of 10000 (A), 15000 (B) and 20000 (C). Each stocking were made in triplicate. Fry were fed with a 36% crude protein plus hormone incorporated feed five times a day. Weekly samplings of fry were done including water quality parameters. Final average body weights of treated fry were 0.226 ± 0.02, 0.125 ± 0.02 and 0.080 ± 0.01 g for treatments ‘A’, ‘B’, and ‘C’ stocks respectively. The fry growth in treatment ‘A’ was significant (at p < 0.05) among all other stocks. It also exhibited high specific growth rate and a lower feed conversion rate than others; however, high survival was achieved with fry in treatment ‘B’. High value of fry crop was achieved in treatment ‘C’ with a value of GH¢ 638.96. Although profit index did not vary significantly from each other, the treatment ‘B’ reached the highest value of 23.13 ± 9.01. The increasing fry stocking density of fry significantly affected the growth and feeding conversion rate, however, it did not affect the survival data. Due to the high profit index, relatively high growth rate and high survival, treatment ‘B’ is recommended for fry rearing in a 10.0 m2 hapa-in-pond system. Key words: Nile tilapia, hormonal feed, specific growth rate, profit index, feed conversion rate.

Radial variation of wood cell features under different stocking densities management of two new clones of rubberwood (Hevea brasiliensis)

Wood characteristics vary from pith to bark and this can influence the final use. These variations can be related to the effects of plantation management. The radial variation in fiber cells, vessel elements, and ray cells was investigated for a commercial and fast-grown species, the rubberwood (Hevea brasiliensis), at varying stocking densities. Nine-year-old trees of two new clones (RRIM 2020 and RRIM 2025) were categorized into four stocking densities of 500, 1000, 1500, and 2000 trees ha−1. The sample blocks were anatomically analyzed to determine the changes in wood cells from pith to bark. The results generally showed a centrifugal increase in fiber features, vessel diameter, ray height, and ray area. Vessel density and ray density showed a decreasing trend. Vessel areas revealed a radial irregular variation. The ray area showed a striking relationship with ray density and ray height. Ray cell pattern indicated enough variation for visual approval to ensure within and between stocking density changes. Most radial variation was explained by the effect of cambial age. Owing to different stem width and growth rates, the mean cell features were not at the same radial distances from the pith.

Growth and Survival of Fingerlings of a Threatened Snakehead, Channa striatus (Bloch) in Earthen Nursery Ponds

Nursery rearing of a high-valued threatened snakehead fish, Channa striatus was studied in relation to varying stocking densities in earthen ponds. The experiment was conducted for eight weeks in nine earthen nursery ponds having an area of 0.012 ha with an average depth of 0.8 m. Fry produced from natural propagation was first reared in indoor cemented cisterns with hatched Artemia cyst as live food for 10 days and then stocked at 150,000, 200,000 and 250,000 ha-1 in treatment-1 (T1), treatment-2 (T2) and treatment-3 (T3), respectively. At stocking, mean length and weight of fry was 1.17±0.18 cm and 0.15±0.03 g, respectively. Fry in all the experimental ponds were fed with a supplementary feed comprising of fish meal (50%) and mustard oil cake (50%) at the rate of 5-8% of the estimated body weight. In addition, chopped trash fishes were supplied at the rate of 5% of the estimated biomass daily, till harvest. The physicochemical parameters of water and plankton were monitored simultaneously and were within the acceptable range for fish culture. Growth parameters (final weight, final length, weight gain, length gain and specific growth rate) and survival of fingerlings were significantly higher in T1 than those in T2 and T3, respectively. Feed Conversion Ratio (FCR) was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher survival of fingerlings was obtained in T1 than those in T2 and T3. Overall, highest growth and survival were obtained from T1 where stocking density of fry was 150,000 ha-1. Hence, of the treatments evaluated, stocking density of 150,000 fry ha-1 appears to be the most efficient stocking density for rearing of C. striatus fingerlings in earthen nursery ponds. This study represents the first successful attempt to produce fingerlings of the threatened C. striatus in nursery ponds, the findings of which might immensely be helpful towards the protection of snakehead from extinction as well as for its conservation, stock enhancement and rehabilitation.

Integration of blue mussel (Mytilus edulis Linnaeus, 1758) with western king prawn (Penaeus latisulcatus Kishinouye, 1896) in a closed recirculating aquaculture system under laboratory conditions

Integrated farming methods, where filter feeders are used to absorb suspended particles have been used for treating nutrients and particulate wastes from prawn culture system. This study investigated the effects of integrating varying stocking densities of blue mussels (Mytilus edulis) with western king prawns (Penaeus latisulcatus) on the water quality and animals growth rates under a closed recirculating aquaculture system. The experiment was conducted using fifteen indoor recirculating systems which tested four different mussel and prawn stocking ratios (replicates of three) with a control of having prawns only. The four mussel densities and prawn biomass ratios were 0.25, 0.50, 1.00 and 2.00. Mussels in the system removed significant (P<0.05) amounts of the total nitrogen, total suspended solids and total bacteria but did not alter the ammonia nitrogen. The dissolved inorganic nitrogen, orthophosphate and total phosphorus concentrations increased with the increasing mussel stocking densities. Integrating mussels and prawns did not affect the prawn growth and survival but mussel growth rate was positively correlated with the increasing stocking mussel densities. Nitrogen and phosphate contents in dried mussel meat in integrated environment were lower in those were integrated with prawns than in the initial mussel stocks. The study showed that mussels can grow and survive in the closed integrated culture system and effectively remove total suspended solids, total nitrogen and the total bacteria from the cultured environment. The research recommends mussel stocking density to prawn biomass ratio of 2.00 for the closed integrated recirculating aquaculture system.

Aquatic environment and yield of sea bass (Lates calcarifer, Bloch) in ponds

This study was conducted for three years to investigate the aquatic parameters and growth of sea bass at varying stocking densities and sizes and requirement of quantity of forage fish for its culture in ponds. Two separate experiments were conducted: one for determining growth and seed stocking density and the other for ascertaining of quantity of forage fish. Under experiment 1, two trials namely, A and B were conducted with three stocking densities viz. 1000, 1500 and 2000 nos./ha of sea bass in each trial. In trial A, the specific growth rate (3.68%/day) was significantly better (P < 0.05) in T2 (1500 nos./ha stocking density), while in trial B, it was higher (2.06 and 2.00%/day) in T1 (1000 nos./ha) and T2 (1500 nos./ha), respectively, and significantly superior from T3. The survival was 100% in trial B, where advance fingerlings were used, as compared with 34.32% in trial A with fry size. The water parameters like temperature pH, salinity, dissolved oxygen, alkalinity nitrate-N2 nitrite-N2 and phosphate were recorded in all the experiments.

Integration of western king prawn ( Penaeus latisulcatus Kishinouye, 1896) and green seaweed ( Ulva lactuca Linnaeus, 1753) in a closed recirculating aquaculture system

Integrating recirculating aquaculture systems with seaweeds is one of the strategies that can minimise wastes and risk of disease outbreaks. This study investigated the effect of integrating green seaweed ( Ulva lactuca) with western king prawns ( Penaeus latisulcatus) at varying stocking densities on the water quality, nutrient conversion rates and nutrient budget under closed recirculating culture system. The experiment was conducted using fifteen indoor tank recirculating systems and tested four different stocking ratios of prawns and seaweed with a control having prawns only. The four stocking ratios of seaweed and prawn biomass were 2, 4, 8 and 16 per tank. The mean concentrations of total ammonia nitrogen (TAN), NO 3 −–N and PO 4 3−–P in the prawn and seaweed tanks were significantly lower (P < 0.05) in the integrated culture systems than in the prawn monoculture. U. lactuca was highly efficient in removing the inorganic nutrients from the culture systems with TAN removal rate of 59–81% and PO 4 3−–P removal rate of 50–55%. Integrating seaweed with prawns did not significantly alter the specific growth rate (SGR) and survival rate of the prawns (P > 0.05). Ratio of C:P in seaweed tissues decreased with increasing seaweed stocking densities while C:N ratio showed an adverse trend. The nutrient conversion rate into total biomass (prawns plus seaweed) in the integrated systems was significantly higher at the highest seaweed stocking density (2.00 kg m − 2 ). Nutrient budget revealed that seaweed retained about 6.5–29.7% nitrogen and 1.6–13.5% phosphorus inputs while values for prawns were 28.0–31.9% and 13.5–14.6%, respectively. Seaweed also removed dissolved inorganic nitrogen effectively in the closed recirculating aquaculture system.