The primary technical measures for fish farming in reservoirs include several key steps to ensure efficient and sustainable aquaculture. First, it is essential to install fish barriers at all inflows and outflows of the reservoir before stocking with commercial fish species. These barriers are crucial for preventing fish from escaping and maintaining a controlled fish population. There are three common types of fish-blocking facilities: net barriers, electric barriers, and bamboo or wooden fences.
Net barriers are widely used due to their effectiveness, low cost, and ease of installation and maintenance. The length and height of the net should be increased by 10-15% compared to the actual width and depth of the area being blocked. The mesh size is determined based on the size of the fish being stocked, with a horizontal shrinkage coefficient typically ranging between 0.6 and 0.7. These nets are usually installed using a pile system and anchored securely to remain stable.
Electric barriers operate on the principle that fish avoid electric fields. When fish encounter an electric grid, they are stimulated and change direction, effectively preventing them from passing through. This method is especially useful in areas where physical barriers may not be practical.
Bamboo and wooden fences are also used but are less common today due to their vulnerability to strong currents and floods. While they are inexpensive and easy to build, their safety and durability are limited, making them unsuitable for large-scale applications.
Second, the selection and stocking of fish species play a critical role in the success of reservoir fish farming. In China, many reservoirs have high levels of plankton, making salmon a popular choice. However, other species such as grass carp, silver carp, and omnivorous fish can also be stocked to utilize various food sources more efficiently.
The quality and size of fingerlings are equally important. Small fingerlings often struggle to adapt to the reservoir environment, leading to poor growth rates and higher mortality. Larger fingerlings, on the other hand, grow faster and have better survival rates. However, larger fish come with higher production costs, so local conditions, reservoir size, and the presence of predatory fish must be considered when determining the ideal size.
Stocking density and species mix ratios vary depending on the reservoir's nutrient levels. Eutrophic reservoirs, which are rich in nutrients, can support higher densities, while oligotrophic reservoirs require lower stocking rates. For example, eutrophic reservoirs may hold 110–140 fish per mu, with specific percentages allocated to different species. In smaller reservoirs, more flexible approaches like "extensive" or "intensive" culture methods can be applied, depending on management capabilities and available resources.
In summary, effective reservoir fish farming requires careful planning, proper infrastructure, and thoughtful species selection to maximize productivity and sustainability.
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