The bio-economic analysis of a super-intensive closed shrimp farming in Japan showed various factors that decreased productivity, and suggested improv
Bio-economic analysis of super-intensive closed shrimp farming in Japan
Thursday, January 14, 2021, 07:00 (GMT + 9)
Evaluation reveals factors reducing productivity, proposes improvements for efficient management
Closed systems for shrimp culture have been developed in recent years to mitigate some environmental issues and to reduce the risk of shrimp disease. Super-intensive culture systems using minimal exchange of rearing water are evolving and promising new aquaculture technologies that can conserve land and water resources and reduce environmental impacts. Some recent studies have tried to evaluate the optimal conditions for increasing shrimp biomass production. However, few studies have examined the balance of costs and benefits of closed-system culture under commercial production. Ways of achieving optimal economic management and addressing unforeseen problems when these systems are adopted have not been sufficiently explored.
Simulations based on numerical models can provide insight into how to achieve better management strategies. Bio-economic modeling is one such adequate approach for studying the complex interactions among the different factors that affect aquaculture production. Along these lines, there are several examples of recent studies using bioeconomic approaches that have been useful in improving strategies for shrimp farming in intensive and semi-intensive systems.
SEM model evaluating the mechanisms causing daily mortality and changes in the health conditions of shrimp in pools at the study site. Solid squares indicate observable variables, and circles represent latent variables. Health conditions are expressed as scores. Gray arrows indicate positive effects, and white arrows indicate negative effects. The numbers in the boxes are the standardizing coefficients at each respective path. The terms of error are not shown in this figure for purposes of simplicity.
This article — adapted and summarized from the original publication (Shinji, J. et al. 2019. Bio-economic analysis of super-intensive closed shrimp farming and improvement of management plans: a case study in Japan. Fish Sci 85, 1055–1065) — describes a study that focused on the utility of such bio-economic approaches in improving management strategy for super-intensive closed culture shrimp production using the Indoor Shrimp Production System (ISPS) plant operating in Myoko City, Niigata Prefecture (Japan) as a case study.
We used the Indoor Shrimp Production System (ISPS) shrimp plant located in Myoko City, Niigata Prefecture (Japan), as the case study site (operated by IMT Engineering Inc., Tokyo, Japan). Rearing data for eight batches of Pacific white shrimp (Litopenaeus vannamei) were provided by the operator of the aquaculture system (IMT Engineering Inc.). The ISPS is a super-intensive closed culture system that recirculates the rearing water, with virtually no water inflow and outflow between the production lanes and the outside. Environmental factors can be easily maintained, as the control of this system is easier than that of conventional aquaculture systems that are not enclosed.
Harvesting patterns to maximize profits per batch (a) and annual profits (b). Dotted lines indicate the optimized harvesting patterns in the spring/autumn season when optimized harvesting patterns in the summer or winter season are shifted.
Moreover, the price of the shrimp product has already been defined by cross-trading and does not change with market supply and demand, and shrimp products are generally sold out at every production cycle. We considered that this system contains few uncertain factors in terms of both farming and market conditions, making it preferable for analyzing the mechanisms of both aquacultural and economic production.
To establish a model for the purpose of optimizing production plans at the study site, we performed path analysis using structural equation modeling (SEM). This process involves screening the critical factors that determine the dynamics of shrimp production at the chosen study site by holistically analyzing the relationships among daily changes in environmental factors, rearing conditions, growth rates and mortality rates. We focused on the grow-out stage of the production process (following the nursery phase), because shrimp biomass mostly increases during this phase, and is thus the most important part of the process to target in order to achieve overall improved production efficiency. Then we established models relating to population dynamics.
Actual harvesting quantities and harvesting patterns to maximize annual production, annual profits, profits per batch and production per batch. Each plot indicates actual harvesting.
Harvesting models were developed to estimate profits; harvesting is also a means of controlling the population dynamics in an aquaculture setting by reducing future dead biomass via the process of culling. Accordingly, the harvesting model includes culling as a means of circumventing risk due to mortality and improving overall yield, leading to economic gain. The economic yield can be directly calculated using the harvesting model independent of the influence of the shrimp market, because the price is fixed by cross-trading. The profit per single batch and the annual profit can be calculated based on the balance of the economic yield and the total cost required for production.(continued...)
For detailed information on the case study site; data sources; concept of analysis and model specification; and simulation methodology, refer to the original publication.
Authors: Junpei Shinji, Ph.D. Nobuyuki Yagi, Ph.D. Setsuo Nohara, Ph.D. Marcy Wilder, Ph.D. / Global Aquaculture Advocate | Read the full article by clicking the link here