Oval oysters? Marine cage culture technology

Oval oysters? Marine cage culture technology

Abstract: Oviform oysters are an important species in seawater aquaculture, particularly in South China. They are highly valued for their nutritional content and commercial potential. This article outlines the primary methods of egg culture and disease prevention in sea cage farming. The successful breeding techniques described here provide a useful reference for aquaculturists. Keywords: Oviform oysters; cage culture; disease control Oviform oysters, also known as golden pheasants or yellow laminar, are prized for their tender meat, rich flavor, and high nutritional value, making them popular in Southeast Asian markets. These fish grow quickly, adapt well to different environments, and have a high survival rate. When farmed in the same year, they can reach marketable sizes and offer significant economic returns, which has made them a favorite among farmers. With advances in artificial breeding and aquaculture technology, oviform oysters are now widely cultivated along the southern coast of China. Common cultivation methods include cage culture, pond culture, and fish farming. In recent years, cage culture has become increasingly popular, especially in Hainan and Guangdong provinces. This paper focuses on the key aspects of cage culture for oviform oysters. 1. Selection of Sea Area and Cage Preparation Cage sites should be located in areas with minimal wave action, good water flow, and stable water quality. The depth should ideally range from 10 to 15 meters during low tide, with deeper cages suitable for areas over 20 meters deep. It is essential that the distance between the cage bottom and the seabed is at least 2 meters during low tide. Water quality parameters must meet certain standards, including salinity between 20–30, temperature between 18–32°C, pH between 7–9, transparency of 8–15 meters, and dissolved oxygen levels above 5 mg/L. Cages are typically made of polyethylene mesh with a size of 2.5–3.0 cm. Their dimensions vary depending on the size of the fry and local conditions, ranging from 3m x 3m x 4m to 4m x 4m x 4m. Deep-sea cages, up to 20 meters in diameter, are also used. Cages can be fixed individually or arranged in grids, with spacing of at least 3 meters to ensure water circulation. 2. Stocking of Fish Species Stocking is usually done from April to May when water temperatures rise above 18°C. The stocking density depends on factors such as water quality, feeding practices, and market goals. For early harvest, fry around 10 cm in length can be stocked at 40–50 per cubic meter. If delayed harvesting is preferred, density can be increased slightly. 3. Feeding and Management 3.1 Feeding Oviform oysters are carnivorous. Traditionally, they were fed minced fresh fish, but modern aquaculture often uses high-quality marine fish pellets. Under optimal conditions, daily feeding amounts can be more than 20% of the fish’s body weight, especially during warmer months. Some farmers increase feed to 40% of body weight during peak seasons to accelerate growth. 3.2 Daily Management Regular monitoring is essential. Farmers should observe fish behavior, water color, and quality. Water temperature and pH should be measured daily and weekly, respectively. Every 15–20 days, fish body length and weight are sampled to track growth and adjust feeding accordingly. Cage cleaning and net replacement are critical to maintain water flow and prevent fouling. Nets are typically replaced every 3–6 months, and care must be taken to avoid injuring the fish during this process. 3.3 Harvesting Fish raised in the same year typically reach 10 cm in length within 4–5 months and can reach marketable sizes of over 400 grams. Harvesting is recommended when fish weigh over 600 grams, as this fetches better prices. Farmers should also consider market trends and growth rates when deciding the best time to harvest. 4. Disease Control Diseases in oviform oysters are rare, but prevention is key. Seedlings should be disinfected before stocking using freshwater or a 0.1 mg/L potassium permanganate solution for 10–15 minutes. Regular inspections help detect issues early. Dead fish should be disposed of safely to prevent disease spread. Common diseases include white spot disease and skin fungus. White spot disease causes white spots on the body, mucus buildup, and respiratory distress. Treatment includes freshwater baths or formaldehyde solutions. Skin fungus leads to dull appearance, loss of appetite, and eye swelling. Freshwater dips for 5–10 minutes daily for 2–3 days are effective. 5. Safety Measures Cage safety must be regularly checked. Inspections should focus on net attachment, cable wear, and anchor stability. Before bad weather, nets should be covered, anchors tightened, and personnel moved to safe locations. These measures help prevent accidents and protect both the fish and the operation.

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