Detailed Explanation of Key Technical Points for Stocking Icefish in Reservoirs

For the selection of stocking sites, choose as far as possible reservoir bays that are at a certain distance from the shore, with a water depth of about 2 m, a hard mud-sand or gravel substrate, and relatively abundant small prey organisms such as insects, and select several stocking sites at the same time for multi-point stocking, so as to avoid failure caused by improper stocking at a single point.

Method for stocking fish eggs: when the fertilized eggs arrive at the destination, first place the nylon bag containing the fertilized eggs into the water, and when the water temperature inside the bag and the reservoir water temperature are basically the same (temperature difference less than 3°C), slowly and evenly scatter the fertilized eggs into the water; each release point should have a certain range. In northern regions, more ice holes should be drilled, and the fish eggs should be released directly into the water through the ice holes. The action of releasing eggs should be quick to avoid the fish eggs freezing. If the bottom soft mud is thick, several ice holes 1 m square should be opened in the ice surface; first sink the net cage below the water surface, then pour in the fertilized eggs, slowly lower the net cage to a depth of 2 m, and fix it with plastic floats.

Management after stocking fertilized eggs: in reservoirs that do not freeze, after the fish eggs are stocked, the egg release site should be watched over and protected for 1 month, mainly to prohibit seining, fishing, and other above-water and underwater activities in this area. In frozen reservoirs, especially those where fish eggs are stocked using net cages, for the first few days one should frequently patrol the egg release site to prevent the net cage from being lifted out of the water and the fish eggs from being damaged by freezing, causing losses. After half a month, break open the ice layer and lift the net cage to the water surface, use a brush to scrub off the attachments on the net cage, and at the same time siphon out a certain number of eggs, check the embryonic development and survival rate, and then slowly sink the net cage back into the water. Under the low-temperature environment beneath the ice at 1.5°C-5°C, the hatching time of fish eggs is 63-65 days, and the water temperature at hatching is 6°C-7°C. When the water temperature during the incubation period is 2°C-10°C, the incubation time is 30 days. When hatching at a water temperature of 11°C-16.5°C, the number of days is about 6 days (referring to Neosalanx taihuensis).

Transplant density and repeated transplantation: in large and medium-sized reservoirs (lakes), generally 150-800 fertilized eggs are transplanted per mu. Usually, after one transplantation, it should be repeated once the following year to strengthen the population size and enhance the population's viability. In addition, according to the biological characteristics and living habits of icefish, adult transplantation can also be carried out during the low-temperature period (relatively difficult), generally in November-December, at a water temperature of 10°C-15°C, with a male-to-female ratio of 3:1. During transport, oxygen-filled sealed plastic bags can be used, with 50 fish per bag, and the fish must not be touched by hand throughout the entire process.