What are the methods for collecting eel fry in eel farming?
Because artificial hatching of eel fry has still not been achieved to date, eel fry are mainly obtained by natural collection. From late December each year to March of the following year is the eel fry flood season, and fishermen in Zhongshan and other places set nets in the Pearl River Estuary to collect them day and night during the rising and falling tides.
Each year after winter begins, mature parent eels swim from the Pearl River Estuary to the deep sea about four to five hundred meters deep near the Xisha and Nansha Islands to spawn and reproduce into young eels; the seedlings are willow-leaf shaped, transparent, and 10 cm long. After hatching, the eels migrate back to the inland rivers of the Pearl River Estuary through a “long journey” to develop and grow. Because artificial hatching of eel fry has still not been achieved to date, eel fry are mainly obtained by natural collection. From late December each year to March of the following year is the eel fry flood season, and fishermen in Zhongshan, Foshan and other places set nets in the Pearl River Estuary to collect them day and night during the rising and falling tides. At present, the main methods for collecting eel fry along the coast are:
1. Fixed set nets
Large-scale catching of eel fry uses fixed set nets. Most often at night during the rising tide, the set net is placed in a relatively wide, deep river or by the sea, so that the eels enter the net with the water flow. Generally, the nighttime rising tide period is used to catch eels. Fixed set nets have high yields, but there are more dead fry, miscellaneous fish and debris; if a fry collection box that can float up and down with the water flow is connected at the tail end and the eel fry are scooped out promptly, the survival rate will increase.
2. Triangular hand dip net operation
The commonly used triangular hand dip nets are all relatively light and simple in structure; generally, 2 small bamboo poles each 1.5 m long are crossed and fitted with polyethylene net cloth, forming a triangular dustpan shape. Hand dip net operations are often carried out by a single person along small riverbanks or in shallow areas within a water depth of 1 m, using a flashlight for illumination and scooping back and forth in the water. Because eel fry caught with hand dip nets are of better quality and have a high survival rate, they are widely used.
3. Board lift net operation
The net is woven from polyethylene or nylon thread, square shaped (generally 3 m in both length and width), with a net bag in the center; the mesh gradually becomes denser from the edge to the center, and the smaller the mesh in the central area, the better. When in use, the elasticity of small bamboo poles is used to prop open the four corners of the net, and then it is placed in the water near a sluice; the person operates it from the shore and is equipped with a long-handled small cloth scoop net. When the net is about to leave the water surface, the eel fry in the net bag are scooped out with the small scoop net and placed into the fry container carried along. This net is operated by a single person, is simple and flexible to use, and although the yield is relatively low, the eel fry are of good quality and have a high survival rate. A flashlight, kerosene lamp or carbide lamp, etc. can be hung under the board lift net pole to attract and catch eel fry by light and increase the yield.
4. Trawl net operations
The net shape is similar to that of fixed set nets, but a towable rope is installed at the opening of the sleeve net, and catching is carried out farther from the shore. This kind of net can be attached to a steel wire rope and equipped with a 1-kilowatt electric motor to pull it back and forth in front of a sluice to catch eel fry.