Aquaculture-agriculture Systems Research Articles

Optimizing growth and yield of striped catfish (Pangasianodon hypophthalmus) and quinoa (Chenopodium quinoa) in a biosaline integrated aquaculture–agriculture systems

Soil salinity and freshwater scarcity are among the major global threats to sustainable development owing to their adverse impacts on agricultural productivity especially in arid and semi-arid regions. There is a need to find sustainable alternatives such as salt-tolerant crops and fish to improve people’s livelihoods in marginal areas. This study aimed to maximize the growth and yield of striped catfish (Pangasianodon hypophthalmus) and quinoa (Chenopodium quinoa) cultivated under a biosaline integrated aquaculture–agriculture system. The study was laid in a randomized completely block design of three saline effluent treatments under three replicates: 5000 ppm (T1), 10,000 ppm (T2), 15,000 ppm (T3), and control (T0). Agro-morphological and physiological attributes of quinoa were measured. The crop yield in biomass and mineral element composition was also studied. Additionally, fish growth performance parameters such as feed intake and efficiency, growth, and survival rate were also calculated. Our results indicated that irrigating quinoa with saline aquaculture effluents above 10,000 ppm enhanced the plant growth, yield, and nutrient content of seeds. Furthermore, rearing striped catfish in saline water reaching up to 15,000 ppm did not have adverse impacts on the growth and survival of fish. Overall, integrating catfish and quinoa production under a salinity regime of 10,000 ppm could be a potential solution to ensuring alternative food sources in marginal areas.

Can Integrated Aquaculture-Agriculture Systems Contribute to Food Security in Egypt? – A Review Article

Can Integrated Aquaculture-Agriculture Systems Contribute to Food Security in Egypt? – A Review Article

Can Integrated Aquaculture-Agriculture Systems Contribute to Food Security in Egypt? – A Review

Can Integrated Aquaculture-Agriculture Systems Contribute to Food Security in Egypt? – A Review

Maximization of brackish water productivity for the sustainable production of striped catfish (Pangasianodon hypophthalmus) and grain sorghum (Sorghum bicolor (L.) Moench) cultivated under an integrated aquaculture–agriculture system

Freshwater scarcity, salinity, and poor soil fertility are the major challenges affecting both food and feed productions in arid and semi-arid regions of the world. Utilization of brackish water in the production of saline-tolerant fish and valuable field crops under an integrated system is promising in the maximization of yield per crop. The aim of this study, therefore, was to (1) assess the effect of saline aquaculture wastewater on the growth, yield, forage quality, and nutritive composition of sorghum seeds and (2) assess the effect of different water qualities on the survival, growth performance, and health status of Pangasianodon hypophthalmus. The experiment was conducted in a randomized completely block design of four salinity treatments with three replicates, i.e., control (freshwater mixed with inorganic fertilizers), 5000 ppm, 10,000 ppm, and 15,000 ppm. Our results indicated that although the control exhibited the highest growth (plant height, leaf number, internode number, leaf area, and soil–plant analysis development), grain, and forage yield, no significant differences were noted among the treatments. Likewise, no significant difference in the grain nutrient composition was noted among all the treatments. Assessment of the forage quality revealed improved crude protein content in the control compared to the saline treatments. However, no significant differences in the leaves and stalks fiber fractions were noted among all the treatments. Furthermore, rumen fermentation in terms of in vitro digestibility indicated no significant differences in the in vitro digestible dry matter, digestible organic matter, metabolic energy, net energy, microbial protein, short-chain fatty acids, and total dissolved nutrients among the treatments. However, rearing P. hypophthalmus in water salinities exceeding 10,000 ppm reduced the growth performance and health status of fish. Therefore, the integration of sorghum and P. hypophthalmus production in water salinities not exceeding 5000 ppm is a viable alternative to maximize brackish water productivity in freshwater-scarce regions.

Diversification strategies have a stabilizing effect for income and food availability during livelihood shocks: Evidence from small-scale aquaculture-agriculture systems in Myanmar during the COVID-19 pandemic

CONTEXTDiversification is an important strategy used by millions of small-scale food producers globally to improve yields, farm profitability, and food security. Diversification can also enable small-scale producers to cope better with livelihood shocks. However, it is not always clear through which pathways diversification practices can stabilize livelihoods and food security in small-scale production systems, especially in the context of the recent COVID-19 pandemic. OBJECTIVEIn this study we examined whether and how diversification practices stabilized income and food availability in small-scale food production systems during the COVID-19 pandemic. The diversification practices explored in this study included fish polyculture and integrated aquaculture-agriculture (IAA), and their combination. We compared small-scale systems employing different combinations of these diversification strategies, with systems that did not contain them. METHODSWe analyzed 300 surveys of small-scale aquaculture producers in Myanmar. Structural equation modeling was applied to examine the multivariate relationships between the adoption of diversification practices among the small-scale producers, and whether and how the adoption stabilized their livelihoods during the COVID-19 pandemic in Myanmar. RESULTS AND CONCLUSIONSWe find that the integration of diversification practices in different small-scale aquaculture-agriculture (SSAA) production systems had generally positive effects for the stabilization of income, food availability or both during the COVID-19 pandemic. The novelty of the study is the unraveling of the differentiated pathways between production models that enabled these stabilization processes emerge. We find major divergences in the stabilization potential between polyculture and IAA, both in terms of the magnitudes of the stabilization effects and the pathways. Polyculture generally offered more significant stabilizing effects than IAA. Surprisingly the highest and more significant positive effects for the stabilization of food availability came through the purchase of food items from extra fish/crop income, rather than their increased self-consumption. SIGNIFICANCEOverall, the SSAA production systems combining different diversification practices could form proactive strategies to help small-scale food producers cope with livelihood shocks.

Smallholder aquaculture diversifies livelihoods and diets thus improving food security status: evidence from northern Zambia

BackgroundMuch has been made of the potential for aquaculture to improve rural livelihoods and food and nutrition security in Africa, though little evidence exists to back such claims. This study, conducted in northern Zambia, assessed the benefits of adopting aquaculture by comparing a sample of households with (n = 177) and without fishponds (n = 174).ResultsOn-farm food production was assessed by summing all crop and livestock activities and calculating a production diversity score (PDS) of key food groups. Aquaculture households had greater crop diversification and were more associated with key nutritious foods grown on the farm, possibly due to additional water irrigation capabilities. A greater diversity of cultivated crops led to better household dietary diversity scores (HDDS). We further assessed the frequency of consumption of 53 food items (including 30 fish species) over a period of 4 weeks via a Food Frequency Questionnaire (FFQ). Using the Simpson’s Index, aquaculture households had greater diversity and evenness in the distribution of foods and fish species consumed, particularly for foods grown on the farm. Using livelihood and dietary factors in a multilevel probit regression on the Household Food Insecurity Access Scale (HFIAS), we found that adopting aquaculture gave households almost two times more likelihood of improving their food security status. Households could further improve their food security outcomes by growing and consuming certain vegetables, especially those that could be integrated along pond dykes.ConclusionsThe study suggests three clear pathways to food security. (1) Increasing wealth and income from the sale of fish and integrated vegetables and/or crops, which can be used to purchase a diversity of foods. (2) Increasing food and nutrition security via the direct consumption of fish and vegetables grown on the farm. (3) Improving irrigation capabilities in integrated aquaculture–agriculture systems that has direct impact on pathways 1 and 2. Aquaculture should be promoted in the region for its crop diversification and food security benefits, so long as it fits the local farming system and livelihood context. Moving away from productivist approaches to nutrition-sensitive aquaculture widens the scope of uncovering the many benefits of pond farming in smallholder systems.

Earthen pond-based floating beds for rice-fish co-culture as a novel concept for climate adaptation, water efficiency improvement, nitrogen and phosphorus management

The current study was carried out to evaluate and investigate a unique rice/fish-polyculture as Integrated Aquaculture-Agriculture Systems (IAAS) model established in Egypt, using Earthen Pond-based Floating Bed (EPFB). This novel idea is intended to improve Water, Nitrogen, and Phosphorus Use Efficiency (WUE, NUE, and PUE, respectively). Three experiments were carried out in this investigation. The first and second experiments investigated the effects of rice planting density (20, 25, and 30 plant m2) and rice seed germination methods (Styrofoam Trays Technique, SFT; Directly Outside Germination method, DOG, and Outside Germination for 24 h, 24 h-OG) on rice characteristics, N-contents, P-contents, N-retention, and P-retention of different rice parts. While the third trial, which lasted 90 days, assessed the impact of the EPFB on rice production characteristics, fish growth performances, and nutrient utilization efficiency (N-, P-contents, and retentions) in comparison to Traditional Rice Cultivation (TRC). In terms of rice production characteristics, 30 plants m−2 had the highest significant (p ˂ 0.05) yield values. A density of 20 plants m−2 produced the highest N-contents and total dietary P-content values in rice stem and leaf, whereas a density of 30 plant m−2 produced the highest total dietary N-retention and P-content values. The SFT approach produced the most significant results in terms of rice production variables and total yield, with the EPFB surpassing the TRC in terms of rice production characteristics. TRC produced slightly more (4412.32 kg Fadden −1, 2.5%) than EPFB (4295.58 kg Fadden −1). The EPFB system demonstrated a cumulative improvement in apparent FCR values (1.15) when compared to the apparent average FCR (1.80) of the polyculture system (catfish and tilapia). In terms of nutrient utilization efficiency (N-content and retention), the EPFB exceeded the TRC with values of 41.49%, 61.16%, 32.39%, and 28.01%, respectively, in root N-content and retention, kernel N-retention, and total N-retention. TRC achieved higher P-contents and P-retentions contents (%) in all rice parts than the EPFB system. EPFB had a total N-retention gain of 70.22% (15.83% in Nile tilapia, 12.15% in catfish, and 42.23% in rice), and a total P-retention gain of 30.68% (7.48% in Nile tilapia, 7.38% in catfish, and 15.82% in rice). FBPS's net income, on the other hand, was 5.45 times that of TCR. In conclusion, fish culture coupled with rice has a low environmental impact since it avoids contaminated streams and recycles wastewater ponds after biological treatment with rice. By producing rice without the use of agrochemical fertilizers, the present unique EPFB idea as an integrated system model can positively boost biomass production, improve WUE, NUE, and PUE, and decrease climate impact.

Influence of salinity on the biometric traits of striped catfish (Pangasianodon hypophthalmus) and barley (Hordeum vulgare) cultivated under an integrated aquaculture-agriculture system

BackgroundSoil salinity, soil infertility, and freshwater scarcity are among the major constraints affecting agricultural ecosystems in arid and semi-arid regions of the world. Hence, there is a need to look for salt-tolerant crops and fish that can be successfully cultivated and reared respectively in such harsh environments. The implementation of biosaline integrated aquaculture-agriculture systems (IAAS) utilizing both salt-tolerant crops and fish could improve food and feed production in arid and semi-arid regions. This study, therefore, investigated the influence of salinity on the biometric traits of striped catfish (Pangasianodon hypophthalmus) and barley (Hordeum vulgare) under an IAAS.MethodThe experiment followed a randomized completely block design of three salinity treatments with three replicates namely, T0: Control (freshwater mixed with chemical fertilizers), T1: 5,000 ppm, T2: 10,000 ppm, and T3: 15,000 ppm.ResultsIrrigating barley with saline aquaculture wastewater at different salinities (5,000 ppm, 10,000 ppm, and 15,000 ppm) did not significantly affect the agro-morphological parameters (internode number per plant, stalk diameter, leaf number per plant, leaf area index, and leaf chlorophyll content (SPAD)) of the plants at 90 days after sowing. Moreover, the forage yield and forage quality in terms of fiber fraction, nutrient composition, and in vitro digestibility of the forage biomass were not severely affected by high salinity compared to the control (freshwater and inorganic fertilizers). Our results also showed that rearing striped catfish in saline water not exceeding 10,000 ppm did not negatively impact the growth performance (final weight, body weight gain, feed conversion ratio, specific growth rate, condition factor, and survival) and the health status of the fish.ConclusionsThe integration of striped catfish and barley production in water salinities below 15,000 ppm could be a feasible alternative in safeguarding food and feed security in regions affected by soil salinity, soil infertility, and freshwater scarcity. Moreover, the salinity regime of 5,000 ppm could bring higher economic gains to farmers regarding higher crop yields (fish and forage yield).

Environmental Sustainability and Food Security of Traditional Agricultural Practices in India: A Review

This synthesis consolidates current research on sustainable agriculture and its pivotal role in enhancing food security, conserving biodiversity, and mitigating climate change. Sourced from a wide array of references, it accentuates exercises such as organic farming, agroforestry, and diversified farming systems as cornerstone approaches, sustainable agriculture. The potential of these practices is also explored, highlighting the carbon sequestration capacity of agroforestry systems, the environmental advantages of organic farming over conventional methods, and the implications of diversified farming systems on food security. However, sustainable agriculture still confronts numerous challenges, especially regarding the environmental repercussions of pesticide use and the barriers hindering the adoption of sustainable farming practices. The substantial role of traditional agricultural practices, which often reflect fundamentals of sustainability and resource preservation, is also underscored. The transformative impact of integrated aquaculture-agriculture systems on small-scale farms in Southern and Southeastern Asia is with Farmer Field School experiences worldwide. Critically, the synthesis acknowledges the daunting task of feeding a burgeoning global population and the environmental ramifications of land utilization. Synthesis concludes by asserting that future research and policy must perpetually focus on these issues, aiming to generate innovative strategies for sustainable agriculture and to bolster the resilience of farming systems in the face of climate change.

Aquaponics for Improved Food Security in Africa: A Review

Increasing demand on water resources, reduced land water availability, and concerns over food security have spurred the evolution of many innovative and complex food production. An aquaponic system is a productive, innovative, and sustainable fish and vegetable production system that is revolutionizing agriculture in the face of drought, soil fertility losses, and climate change. Aquaponics, as an advanced aquaculture-agriculture system, is expected to improve food security in developing countries. However, as an emerging technology, there is very limited information on the system in Africa. Questions about the ecological and socio-economic sustainability of aquaponics are answered in this comprehensive review. This review considers aquaponics projects in Africa, categorizes the technology by evidences of their effectiveness, fish and plant yields, and juxtaposes the technology within best-use practices to make recommendations that will inform evidence-based policymaking. It also maps the present spatial adoption of the technology in sub-Saharan Africa and highlights the system's contribution to improving food security on the continent. Egypt and South Africa are countries where aquaponics is emerging and being adopted at faster rates and contributing to food security. In West Africa, significantly lower net-discounted benefit-cost ratios were realized when aquaponics systems were constructed using imported materials compared to using locally available materials. Despite aquaponics systems generally having higher start-up costs currently, its potential to be economically viable when undertaken with local materials is very high.

Environmental Tradeoffs between Nutrient Recycling and Greenhouse Gases Emissions in an Integrated Aquaculture-Agriculture System.

The unlimited nitrogen (N) availability that has characterized crop production in the last few decades is accompanied by environmental burdens, including the greenhouse gas (GHG) emissions associated with fertilizer production, post-application nitrate (NO3–) pollution of water bodies, and emissions of reactive gaseous N forms into the atmosphere. Here, we quantified the environmental tradeoffs of replacing mineral N fertilizer with NO3– and ammonium (NH4+) originating from effluent water of aquaculture in a cucumber (Cucumis sativus) cultivation system. While the yield, nitrogen use efficiency (NUE), and NO3– leaching were similar between the cucumbers fertilized and irrigated (fertigated) by aquaculture effluent water containing 100 mg of NO3–-N L–1 (AN), by aquaculture effluent water supplemented with NH4+ (AN+), or by tap water with NO3– and NH4+ added (FN+), there were significant differences in the nitrous oxide (N2O) emissions between the systems. The N2O emissions peaked after each irrigation event followed by an exponential decline. The cumulative N2O emissions were between 60 and 600 g N2O-N ha–1, smaller than predicted based on a fertilizer application rate of 600 kg N ha–1 and were in the order AN+ ≫ FN+ > AN.

A preliminary evaluation of an integrated aquaculture-agriculture systems (tilapia and peppers) at mesocosm scale

A preliminary assay was conducted to evaluate the feasibility of an integrated aquaculture-agriculture production system. Tilapia (Oreochromis niloticus) was farmed in plastic tanks (500L), with and without bioflocs incorporated. The effluents were passed to PVC tubes for a hydroponic culture of jalapeño pepper (Capsicum annum). The final effluent was used to a fertigation culture of mini bell pepper (Capsicum annum). The production response of tilapia was little better in tanks with bioflocs. The jalapeño pepper had not a good performance in the hydroponics system. Contrarily, mini bell pepper showed a good performance. We concluded that this aquaculture-agriculture system could be efficient, but some adjustments need to be done.

Seeing from Above: Observation of Contemporary Dike-Pond Landsca pe

A dike-pond landscape is characterized by asymbiotic and interacted relationship between water and land and considered an integration of human settlements with an aquacultureagriculture system. The Pearl River Delta has historically enjoyed a rich river network and been shaped by the mosaic-like constructed ponds with the meandering natural river systems, where the boundary of the constructed and the natural blurred and a resilient dike-pond landscape prevailed. However, the increasing demand for land resource during urbanization and industrial development has made such a landscape shrunk and surrounded by urban sprawl. The expansion of human settlements has not only changed the water-land symbiosis but also reshaped the pattern of the dike-pond landscape. This article, as an ongoing work, intends to observe and document the changes of such water-related landscapes from a different perspective, “seeing from above,” with historical satellite photos, Google Map images, and contemporary aerial drone photography. It discovered three important transformations: the settlement sprawl and transformation, the shrinking dike surfaces and imbalanced ratio of dike to pond, and the disappearance of the organic pond pattern. These findings can evoke critical studies on the dialectical relation between urbanization and ecology, and offer possibilities of re-creating a sustainable landscape in the Pearl River Delta.

Optimization of nitrogen use efficiency by means of fertigation management in an integrated aquaculture-agriculture system

Recirculating aquaculture system (RAS) effluent has a high concentration of nitrogen, which can be a valuable asset as fertilizer for agricultural use in the vicinity of the RAS. A novel fully-automated experimental set-up of 24 lysimeter-plots was used to determine the optimal irrigation rate for cucumber plants fertigated with RAS effluents of three different nitrogen concentrations. Three RASs were stocked with 7, 14 and 21 kg of barramundi (Lates Calcarifer), which were fed 1.75% of their body mass daily. Then, 10% of the water in each RAS was exchanged daily, resulting in three nitrate–N concentrations of approximately 30, 60 and 90 mg/L. A synthetically fertilized control treatment was kept at 60 mg/L nitrate–N, and the other essential plant nutrients were kept at the same concentration for all treatments. The water from these four sources was then used to irrigate six plots per nitrate–N concentration treatment, at a rate of 1–6 times the amount transpired, which was measured in an automated fashion by the experimental set-up.Two yield response to nitrogen fertigation models fit well to the measured data, and although they led to different conclusions in terms of optimal fertigation can be a useful tool for decision support. The nitrogen use efficiency dropped with increased fertigation, from about 80% to 55%, and more fertigation led to an exponential increase in drainage and gaseous emissions of nitrogen. The observed data can be used to optimize irrigation for each nitrogen concentration, but the values are highly dependent on climate, plant type, and root zone characteristics, demonstrating the need for more inclusive modelling. Determination of how to optimally make use of RAS effluent water and the comparison with synthetic fertilizer can lead to the development of simplified protocols concerning integrated aquaculture agriculture systems, making it accessible to a wider range of growers.

Expert based model building to quantify risk factors in a combined aquaculture-agriculture system

In recent years, across tropical regions of the world, there has been an expansion of integrated farming systems that combine rice and shrimp production. While these systems were developed as a form of crop-rotation – growing rice in the wet season and shrimp in the dry season – some farmers grow both rice and brackish-water shrimp simultaneously during the wet season. Climatic variability has resulted in considerable crop losses in this system across many regions. Research has yet to identify the complete array of key risk factors, and their potential interactions, for integrated rice-shrimp farming. Consequently, different farming practices and environmental factors that may affect crop production need to be clarified to guide research efforts. We applied a staged, iterative process to develop a probabilistic Bayesian belief network based on expert knowledge that describes the relationships that contribute to the risk of failure of both crops in integrated rice-shrimp farming systems during the wet season. We applied the approach in the Southern Mekong Delta, Vietnam, in the context of a broader research program into the sustainability of the rice-shrimp farming system. The resulting network represents the experts' perceptions of the key risk factors to production and the interactions among them. While both farmers and extension officers contributed to the identification of the processes included in the network, the farmers alone provided estimates of the probability of the relationships among them. The network identified the challenges to minimise the risk of failure for both crops, and the steps farmers can take to mitigate some of them. Overall, farmers perceived they have a better chance to minimise risk of failure for shrimp rather than rice crops, and limited opportunities appear to exist for successful production of both. By engaging the farmers in this process of model development, we were able to identify additional research questions for the broader research team and to identify simple steps the farmers could take to reduce the risk of crop failure. Integrating additional empirical data into this network, as it becomes available, will help identify clear opportunities for improvements in farming practices which should reduce the risk of crop failure into the future.

From researcher to farmer: partnerships in integrated aquaculture—agriculture systems in Malawi and Cameroon

The potential for integrating aquaculture with agriculture has been widely recognized as a means of improving the use of inputs, diversifying output and economic opportunity, and enabling smallholder producers to maintain and strengthen livelihoods. This paper describes the outcomes of this approach and explains the extent to which it has been taken up and has led to sustained and self-generated capacity. Based in particular on experience in Malawi, Ghana and Cameroon, it also considers implications more widely in the region. The overall picture is that this is a partial and still emerging success story, linked as much with the social and economic drivers surrounding smallholder farmers as with the development support approach adopted.

Enhancing the fish production potential of Lake Victoria papyrus wetlands, Kenya, using seasonal flood-dependent ponds

We present the findings of a participatory experiment on integrated aquaculture-agriculture systems (Fingerponds) at the Lake Victoria wetlands, Kenya. Fingerponds are flood-based lacustrine or floodplain wetland fishponds. The aim of the study was to explore, within a wetland/floodplain interface environment, the potential of semi-intensive fish production to enhance the wetland fishery and protect the natural ecosystem from wide-scale, destructive encroachment. The ponds were stocked naturally by flood water. After flood recession, livestock manure was added to the ponds and the effects of manuring on water and sediment quality and fish yields were studied. Manuring had positive effects on the nitrogen, phosphorous and chlorophyll a concentrations of the pond water. Regression analysis results indicated that site, manuring and environmental and climatic variables explained 58–70% of the variation in dissolved nitrogen and phosphorous, and 71% of the variation in chorophyll a. Manuring enhanced the total phosphorus concentration in the sediment but it only had marginal effects on total nitrogen. Although the net fish yields were highly variable between sites and seasons, ranging from 402 to 1069 kg ha−1, the data showed that manuring was advantageous. The duration of the culture period, site variability and manuring explained 82% of the variation in fish yields. We conclude that Fingerponds fertilized with livestock manure from abutting riparian subsistence agriculture can improve fish production, enhance food diversity and security and contribute to more efficient use of papyrus wetlands for food production. This in turn may reduce large-scale conversion of wetlands to agriculture.

Integration of smallholder wetland aquaculture–agriculture systems (fingerponds) into riparian farming systems on the shores of Lake Victoria, Kenya: socio‐economics and livelihoods

This paper presents the results of experimental fingerponds: an integrated flood recession aquaculture–agriculture production system in the Lake Victoria wetlands in Kenya. The overall aim of the study is to assess the potential of fingerponds as a sustainable wetland farming system for improving food security at the subsistence level and within the context of the existing livelihood activities. The contribution of this new activity to rural household livelihoods is evaluated. Since it is a sustainable technology, based on natural events, the production level is intermediate and the benefits may not be high in the short term. Economic analysis shows that the gross margin and net income of fingerponds is about 752 and 197 Euros per hectare per year, respectively. This is about an 11% increase in the annual gross margin of an average rural household around Lake Victoria. The additional per capita fish supply is 3 kg per season or more from a 192 m2 pond. The potential fish protein supply of 200 kg/ha is high compared with most existing terrestrial protein production systems. Fingerponds have the potential to contribute to household food security and to improve livelihoods. Sensitivity analysis indicates that biophysical variations, which may occur from one wetland to another, have implications for the functioning, and consequently the economic performance, of fingerponds. This reinforces the need for the integration of these systems into other household activities to buffer the household against potential risk.

Hydrology and the functioning of seasonal wetland aquaculture–agriculture systems (Fingerponds) at the shores of Lake Victoria, Kenya

Experimental seasonal wetland-based integrated aquaculture–agriculture systems called ‘Fingerponds’ were established at two sites (Nyangera and Kusa villages) at the shores of Lake Victoria in Kenya to enhance the wetland fishery potential. This paper examines the hydrological characteristics of Fingerponds. In Fingerponds’ design, the water supply is un-regulated and the water balance is maintained by natural losses and gains. At the beginning of the season, flood events are critically important for the initial water supply to the ponds. During their functional period (which lasted for about 6 months into the dry season after flood recession), precipitation accounted for nearly 90% of the total water gains while seepage and evaporation contributed an average of 30–70% of the losses, respectively. Seasonal pond water budgets indicated that the losses outweighed the gains leading to a progressive decline of water depth during the dry season. A prediction of the effect of pond volume and weather conditions on the functional period for fish production was carried out using a dynamic simulation model. The results indicated that the culture period can be extended by 2.5 months by deepening the ponds to an average depth of 1.5m: this would increase the overall fish harvest. Drier weather accelerated losses and shortened the culture period by 1–2 months.

A comparison of the yield and yield economics of three types of semi-intensive grow out systems, in the production of Heterobranchus longifilis (Teleostei: Clariidae) (Val. 1840), in Southeast Nigeria

The yield and yield economics of three types of semi-intensive catfish grow out systems in southeast Nigeria were compared. These were: an integrated aquaculture–agriculture system, a commercial feed based system using locally produced pellets, and traditional grow out techniques. They were designated treatments 1, 2, and 3 respectively. Replicate new ponds were stocked with 160 Heterobranchus longifilis fingerlings and 10 adult Oreochromis niloticus (5 male and 5 female), per treatment. Soybeans were planted at the beginning of grow out to produce grains used as feed supplement in treatment 1. This was done in two consecutive 1-year grow out periods. The feed was prepared by partially substituting the feed ingredients used in treatment 3 with the soy grains. The soy plant matter was used as additional fertilizer. Pond age significantly influenced soy grain and plant matter yield, soy proportion of feed, and its soy-derived protein content ( p < 0.01). H. longifilis yield was significantly affected by treatment ( p < 0.001). In treatment 1, first year cost:benefit was 1:0.48 over variable cost and 1:0.41 over total cost. Second year values were 1:1.39 and 1:1.18 respectively. Cost:benefit in treatment 2 was 1:1.11 over variable cost in both years. Over total cost it was 1:1.03 and 1:1.05 in the first and second years respectively. In treatment 3 first year cost:benefit was 1:0.45 and 1:0.17 over variable and total costs respectively. Second year values were respectively 1:0.92 and 1:0.68, with pelleted feed accounting for 66% and 62% of variable and total costs respectively. Treatment 1 is recommended for adoption as an intermediate step in H. longifilis grow out in southeast Nigeria, until the pelleted feed-driven system becomes profitable.