Abstract
In aquaculture systems, insufficient nutrients impede shrimp growth while excessive amounts of nutrient inputs lead to environmental degradation and unnecessary high investment. A study of in-out nutrient budgets in an intensive Litopenaeus vannamei farm was conducted in this work to measure the amount of nitrogen (N) and phosphorus (P) input and output from the system. The feed conversion ratio (FCR) was obtained to determine the level of nutrient input performance. Between September and December 2017, monthly water and sediment samples were taken within one crop cycle. Nutrient concentrations in sediment and water increased over 90 days. The total nitrogen concentration in the pond water and effluents were in accordance with wastewater quality control for aquaculture; however, the total phosphorus concentration failed to meet the water quality control from the water input through the end of the crop cycle. The nutrient budget model showed that the input/output contained 107.8 kg N and 178.4 kg P. Most of the N input came from shrimp diets (80%) while most of the P came from fertilizer (57%). Both N (46%) and P (54%) mainly deposited in the sediment as an output process. The FCR of this farm is 2.0. Based on the 1.8 FCR scenario, this farm could reduce 147 kg of feed in total, which accounts for 9.04 kg N and 2.21 kg P reduction. The farmer could save $1027 USD crop− 1 ($1 USD = 32.7 baht), as well as reducing uneaten food at the bottom of the pond. This study offers a simple and straightforward model that can practically reduce environmental impacts and increase the profitability of farms.
Highlights
Shrimp farming accounts for one of the fastest growing aquacultures in many countries
The direct impacts of overused feeds result in high feed conversion ratios (FCRs) – the simplest form of conversion feed used for animal meat
The water was suitable for shrimp farming, as recommended by the Department of Fisheries
Summary
Shrimp farming accounts for one of the fastest growing aquacultures in many countries. Intensive shrimp production has produced significant shortterm profits for small-scale entrepreneurs; many shrimp farming practices have driven towards substantial financial and environmental risks and long-term. This study is organized with three main objectives: 1) determine the nutrient balance in a small-scale intensive shrimp pond; 2) perform explicitly spatio-temporal aspects of nutrient concentrations across the shrimp pond; and 3) explore the current potential for improving economic efficiency. Such analysis can provide directions to farmers with similar framing practices, as well as supporting policy formulation on shrimp production efficiency management
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