Discussion on Water Quality Control Technology of Japanese Shrimp Breeding

Since the large-scale shrimp disease outbreak in the 1990s, Japanese shrimp has become a key species in aquaculture across various regions due to its fast growth rate, high-quality meat, strong resistance to diseases, and excellent survival during transportation. However, during the early stages of seedling cultivation, larvae often face developmental issues, leading to high mortality rates and ultimately failing the nursery process. The zoea stage is particularly vulnerable. To address this challenge, the author, drawing from years of practical experience in shrimp farming, conducted field studies between 2003 and 2005 at a second aquaculture testing site in Weifang City, Shandong Province. Focusing on water management and environmental optimization, the research aimed to improve water quality, create a better development environment for larvae, strengthen their physical condition, and reduce abnormalities, resulting in significant improvements. In the trial, the nursery facility covered 500 cubic meters with 20 ponds, each 1.3 meters deep. Essential infrastructure such as seawater, lighting, electricity, gas, heating, and storage tanks were all available. Water used for seedling rearing was sourced from the Baike River and underground freshwater. Nauplii were purchased from Qingdao, Rizhao, and Weifang, with quantities reaching 36 million, 36 million, and 47 million over the three years. Before stocking, fertilization was applied 20–30 days in advance, using diammonium phosphate or urea. The first application was 1.5 ppm, followed by 1 ppm every two weeks. Algae growth was monitored, and fertilization ceased when water clarity reached about 50 cm. During the seedling phase, minimal fertilizer was used if needed, generally not exceeding 0.5 ppm. Disinfection procedures included filtering seawater through a 300-mesh bag and disinfecting the pond before introducing nauplii. EDTA (2–10 ppm) was added, followed by sodium dichloroisocyanurate (1 ppm) for disinfection, then sodium thiosulfate to neutralize excess chlorine. Water changes began once larvae entered the next stage, starting with 5 cm increases daily, up to 30% per day. Preheated, disinfected seawater was used for each change. Aeration levels were carefully controlled, varying depending on the larval stage to maintain stable oxygen supply without disturbing the pond bottom. Feeding strategies involved compound feed, rotifers, Artemia nauplii, and adult brine shrimp. Feed types and quantities varied by larval stage, with careful monitoring to ensure full stomachs without overfeeding. Water quality was continuously monitored, maintaining temperature fluctuations below 0.5°C, pH between 7.8 and 8.6, dissolved oxygen above 5 mg/L, and stable salinity. These measures significantly improved survival rates and overall success in Japanese shrimp seedling cultivation.

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