Chengchi Lake, home to the Changjiang Fisheries Research Laboratory, was originally a large-scale soft-shelled turtle farm. However, due to a decline in turtle market prices and lower breeding efficiency, monoculture of turtles became unsustainable. The key challenge was how to maximize production potential and improve economic returns within the existing pond conditions. In recent years, stingray farming has gained popularity, with a thriving market. Considering that stingrays require similar water quality as soft-shelled turtles and have non-conflicting feeding habits, an experiment was conducted to integrate stingrays into the turtle ponds. The results were promising, leading to the following technical strategies:
First, the pond setup involved selecting eight adult fish breeding pools (labeled 1-8), each covering about one mu (approximately 667 square meters) with a depth of 1.5 meters. These ponds were well-structured, with good sunlight exposure, ventilation, drainage, and a quiet environment, making them ideal for mixed culture.
Second, the fingerlings used included soft-shelled turtles, grass carp, silver carp, and white sturgeon—species produced on-site. Stingrays, however, were wild specimens from large lakes near Jingzhou City.
Third, stocking densities were carefully managed. Soft-shelled turtles were stocked at 800 per acre (150-200 grams each), grass carp at 10 per acre (250 grams each), silver carp at 40 per acre (150-200 grams each), and white sturgeon at 100 per acre (250 grams each). Stingrays were introduced at four different densities: 4 kg, 8 kg, 10 kg, and 15 kg per acre. Any dead seedlings within the first month were immediately replaced, and any data loss due to human error or early mortality led to the rejection of the entire pool's data.
Fourth, pond management focused on water quality. Ponds were disinfected with lime before stocking, and wild fish and frogs were removed. Water transparency was maintained between 30-40 cm, with monthly water changes of 30-50 cm. Lime or bleach was used every 10-15 days to maintain water balance.
Fifth, feeding practices were based on the needs of soft-shelled turtles, following the "four definite" feeding method. Feeding amounts were adjusted according to growth and health, and medicated feed was added when necessary. Stingrays, however, did not require additional feeding.
Sixth, disease prevention involved regular liming to keep the water slightly alkaline and monthly disinfection with bleach. This helped control common aquatic diseases.
Seventh, after approximately 150 days of cultivation, a total of 347.5 tons of stingrays were harvested without affecting the production of other species. On average, each mu yielded 46.8 kilograms of stingrays.
The study also found that the presence of stingrays did not negatively impact the growth of other fish species. No significant differences were observed in turtle, grass carp, or silver carp yields between the test ponds and those without stingrays.
In terms of yield and size, stingrays stocked at lower densities (4-8 kg per acre) grew larger compared to those at higher densities (10-15 kg per acre). This suggests that higher stocking density leads to smaller individual sizes.
Economically, stingrays with larger sizes (over 80 grams) commanded higher prices and were more popular among consumers. At 4-8 kg per acre, the economic return ranged from 370 to 395 yuan per mu, while at 15 kg per acre, it was only 113-130 yuan, highlighting the importance of optimal stocking density.
Finally, the study recommends that raising stingrays in existing ponds is a viable and efficient strategy. It does not interfere with other species, requires no additional investment, and makes full use of available resources. Based on market trends, the recommended stocking density for stingrays is 4-8 kg per mu, with individual weights of 12.5 grams per tail.
Lower Limb Locking plate is a kind of implant fracture orthopedics with locking thread holes.
The lower limb locking plate allows the bone to bind to the plate more firmly, so that the reduced limb is more stable. Locking plates were first used in spine and maxillofacial surgery 20 years ago to stabilize fractures while reducing extensive dissection and damage to soft tissues. When the threaded hole in the locking plate is screwed in by a screw with a threaded head, the plate becomes an Angle fixing device. It can have both locking and non-locking holes for different screws to be screwed in. Any plate that can be screwed into an Angle fixed (stable) screw or bolt is essentially a locking plate.
Locking plate system does not rely on bone friction to achieve connection, but completely depends on the interlocking structure of the plate itself. A certain gap between the plate and the bone surface can be left, which can eliminate the adverse effect of heavy pressure contact between the plate and bone, and greatly improve the blood supply and the growth and recovery of the periosteum. The main biomechanical difference from conventional plates is that the latter relies on friction at the bone-plate interface to accomplish plate compression on bone. Stability is maintained by an angularly stable interface between the screw and the plate. Because the locking internal fixator has a stable integrity, the pull-out force of the locking screw is much higher than that of the ordinary screw. It is difficult for a single screw to be pulled out or broken unless all the surrounding screws are pulled out or broken.