It is important to keep fat in the winter, improve health before the propagation and restore vitality after the propagation. Before the winter, brood stocks must accumulate enough nutrition to make the sexual gland matured. The water should keep clean and contain ample oxygen in this period. The fishes were fed about 4-5% of their weight every day. In the spring before spawning, brood stocks were stocked more carefully for 30-40 days in order to improve the spawning ability. About 30% of the feeds in one year were fed in this period. Malnutrition could result in sterility. Small fish, entrails of animals and poultry were fed as a supplemementary, which will do good for the spawning rate,the insemination rate and the breeding rate .After insemination, attentions were paid to help the brood stock restore.Brood stocks were fed about 3-4% of their weight every day.
The fishpond was fed at 7:00 Pm for Danubian Wels like feeding under faint light. During the daytime, the fishpond was fed on the area where is shielded from light by shelters.
5.Management of Fishpond.
Danubian Wels has the same demand for oxygen as that of common carp. During the summer and autumn, we turned on "Oxygen Generator"installed in the pond between 5:00-6:00 Pm every day in order to increase dissolved oxygen.
River water was refilled to the pond every 15 days. About 1/8-1/6 of the fishpond was planted with some lotus as a shelter for brood stocks.
Results and Discussions
1. Identification of sexs.
The skin of the male Wels is generally darkish and has manble-like stripes. The head of an adult male Wels is angular, The pectoral fin is serrate and sharp. The male Wels has a flat papilla.
The skin of the female Wels is less darkish and has no stripe. The pectoral fin is generally smooth the papilla of the female is big, broad and protrusive and its tip is often red.
The matured female Wels has soft and large abdomen. The contour of the ovary is seen easilyon both sides of the abdomen. The anus is reddish. The matured male Wels looked narrow. Its anus is rice-shaped. The sperm is difficultly distinguished from the water. In the same fishpond, both the female and the male can grew up to sexual maturity concurrently.
2. Inducing and Insemination
(1). Spawn-inducing agents and injection: HCG, PG, LRH-A could be all used as spawn -nducingagents. The HCG was 4-6 mg/kg for the female and 2-3mg/kg for the male. LRH-A was generally used with HCG and PG.For the male, a single Injection was Enough. For the female, two injections were required. It was about 8-12 hours between two injections. The interval would adjust according to the temperature of the water and the kinds of spawn-inducing agents. It was long when the temperature was low, short when the temperature was high. When HCG was used, the interval would longer than that of PG.The first injection was carried out in the


Morning while the second injection, in the evening. For the male, the injection was carried out in the morning, The optimum temperature for spawning ranges 23-24oC.
(2). Insemination:
The egg could be gotten easily from the female after injected spawn-inducing agent. The sperm from the male was difficult to get because its sperm is grove-shaped and the sperm was watery. Moveover, the urine affected the insemination. So excluded out the wring first, inhaled out the sperm by a sucker, pressed out the eggs into a basin and mixed with the sperm immediately. Be careful to get rid of the water. The fertilized eggs are sticks and milk can be added as a diluting solution to remove the protein layer adhered to the egg surface. After that, the eggs can be placed into an incubation jar for hatching.
(3) Hatching
The incubator was made of galvanize sheet. The above of the incubator was made like a barred and the below was like a funnel. The barrel was 25cm in height and 15cm in diameter. The length of the funnel was 30cm to accomadate eggs.
A cocacola bottle can replace the incubator if eggs are few .One bottles can accommodate 60-80 thousand of eggs.
The water in the incubator kept flowing with 1L/min in speed in order to make all fertilized eggs even-turned. When the first group of larvae were observed, 0.1-0.2L/min to accelerate the separation of infertilized eggs should gradually reduce the speed of water flow. Infertilized eggs lose shells since they are heavier than the fertilized ones. Most of the fertilized eggs hatched after a few minutes and the larvae must be transferred with a plastic tube. The hatched and inhatched (but fertilized) eggs should be separated from the infertilized eggs. During this operation, no water flow is requried, as the hatching enzymes will start accumulating and speed hatching.
The optimum hatching temperature ranges 22-24oC. Fluctuation of the water temperaturewithin 1-2 per hour should be kept during incubating. The hatching takes about 40 hours when temperature is 22-24oC.
During hatching, fertilized eggs have chanced to be infected. So, disinfecting the incubator twice a day is necessary.
The newly hatched fry is extremly delicate and crowded under faint light. A trough or box made of nylon cloth can be used for further nursing. The size of box is 30′40′60cm3 and the mesh of nylon cloth is 0.5mm. About 10000-20000 yolk sac Frys Can be nursed in one box. Dead eggs and Frys should be cleared .The Frys are grey and swim actively the next day after hatched. "Oxygen Generator" should increase the water speed and dissoved oxygenafter 4-5 days. The Frys begin to look for feeds and swim around the box.

The Danubian Wels (Silurus glarus) has long been an important economic fish in the Danubian area. It has bigger size, tender flesh and is easy to be caught .In early 1940s, the Danubian fishermen cultured Wels in fishponds. The domestication of Wels for pond culture began after 1950. From 1970, with the development of compound pellet feed, the intensive operation and mass-culture of Danubian Wels began in developed countried such as Hungary and Germany. Compound feeds containing 36%-38% of protein are ideal feeds for Wels. The yield per hectare is 4500-8000kg. During 1992-1993 the test on mass-culture and the high yield of Danubian Wels conducted and the results are listed as follows.
Materials and Methods
1. Experimental fishpond.
The test on mass-culture and the high yield of Danubian Wels was conducted in three earthen fishponds (0.07-0.28 hectare in areas). Before culturing, the fishponds were disinfected by sodium pentachlorophenate to kill bacterium, wild fishes and parasites ,etc.In order to provide a quiet and shady circumstance for the wels,water hyacinth and lotus were planted,covering 1/8-1/6 of the pool area.
2.Stock density.
Danubian Wels grows fast. Stocked with 50-60g in weight it can grow up to1.5kg in one year. This is the foundation on which we based to determine the stock density. 370-930 fingerlings of Danubian Wels were stocked in mass-culture fishpond. At the same time, 230-335 fingerlings of silver carp and bighead carp, 60-70 fingerlings of grass carp and common carp were stocked per 0.07 hectare to utilize the feces of Danubian Wels and control the growth of wild grass in fishponds.
Before winter, brood stocks were stocked after disinfected. It is important to stock in the nest firstly and disinfects twice if brood stocks were carried for a long time.

3.Stocking methods
The feeds supplied for mass-culture fishpond were compound pellet feeds (containing 36-38% of protein) which were composed of fish meal, beancake, peanut cake, clam, shrimp, vitamin and additive .The amount of feeds changed according to seasons, weather and the temperature of water .It was 1-4% of the weight of Danubian Wels. Feeds were put in a terrace, 4m2 in area and made by cloth .The terrace was under the water about 1 m in depth. Around the terrace, water hyacinty was planted to provide
a shady and cool environment. Feeds were put at 8 Am and 8 Pm every day, the amount was 30% and 70% of tatal amount, respectively.
4.Analysis of the water.
Every month, a routine examination of the water was made . The items of the examination were the temperature, PH, dissolved oxygen, organic oxygen consumption and inorgantic salts etc. The results are listed in Table 1.
Results
1.Mass-culturing in 1992.
In October 1991, we conducted the mass-culture test of Danubian Wels in an earthen pond of 0.13 hectare. About 1071 fingerlings (55g/ind, with 19.5cm in body length) were stocked and fed with compound pellet feed. In order to culture these fingerlings as to be a batch of brood Wels and to accelerate growth rate, tubfex and clam were also given twice a week as supplementary feed. River water was refilled to the pond once a week. The amount was 1/5 of total pond water. During the warm days, we turned on "Oxygen Generator" installed in the pond in order to increase dissolved oxygen.
On November 1st of 1992, the test ended and the results are listed in Table 2.The total output was 1619.52kg. The Wels grew up to 1.68kg (1.52-1.95kg) and the survival rate was 90%, The net output per 0.07 hectare was 750.85kg. 252.22kg of silver carp, bighead carp and common carp were gained at the same time.
2.Mass-culturing in 1993.
To increase the output, a test of polyculture was initiated in two fishponds in 1993. The areas of the two fishponds were 0.13 hectare and 0.27 hectare, respectively (the former was mumbered as pond 1, the latter Pond 1). The results are listed in Table 3 and Table 4.


About 1860 fingerlings of Wels, 670 fingerlings of silver carp and 140 fingerlings of Wuchang fish were stocked in Pond 1. The output was 2089.84kg in total, 1394.4kg of Danubian Wels and
545.24kg of silver carp, respectively. The net output was 1920.9kg in total and 633.96kg of Wels. Food conversion rate was 0.95 in total and 1.44 of Wels.
About 1480 fingerlings of Wels, 1020 figerlings of silver carp and 240 fingerlings of Wuchang fish were stocked in Pond 2. The test lasted for 12 months. The output was 1840kg of Wels, 749.36kg of silver carp, and 89.38kg of Wuchang fish respectively. Food conversion rate was 1.44 in total and 1.72 of Wels.
3.Catching Efficiency
We evaluated the catching efficieny individually in three fishponds in Hubei,
Sichuan and Guangdong in 1992 and 1993. The areas of the fishponds were 667m2, 1334m2 and 867m2. The fish was caught by a "big-pull-net" equipped with a machine. The mesh size is about 5cm.The catching efficiencies of three harvests were 54% (33-75%), 38% (11-65%) and 7% (2-12%), respectively . The results showed that Wels has a high catching efficiency in fishponds.
Discussion and summary
1.Danubian Wels is one of economic fishes. In the central and south of China, as well as Shandong and Liaoning etc, it can be stocked once a year. Stocked with75g (5080g) inaverage, welscanrow up to 1.28kg (0.51-1.95kg).
2.Stock size and Survival Rate. The results showed that both ideal market size and high survival rate could be ouained when the stock sizes were above 50g. The survival rate was 90% of 55-68g in stock size and 93% of 87g in stock size.the same stock size is better.
3.Stock Density and Polyculture The suitable stock density is good to make the best use of water, yet not to inhibite the growth of fishes and affect the output and market size. It is better to stock 350-900 fingerlings of Wels per 667m2 and 60-70 fingerlings of silver carp grass carp and Wuchang fish.
4.Catching Efficiency Danubian Wels likes feeding and playing in-group. So the catching efficiency is up to 98%. It is easy to be caught and carried for long distance.
5.Adaptability To Environment Dissolved oxygen for Danubian Wels are the same as that of common carp. It can be stocked both in clean water and fertile water polycultured with silver carp and bighead carp.
6.Feeding habits. Compund feed containing 38.5% of portein is ideal feed for Wels, Theis kind of feed can meet the demand for nutrition and promote wels growth. Wels also feeds on zooplankton, tubfex, brine shrimp and eetritus besides compound feed.
Table 1. The analysis of the water

Table 3. Test on Mass-culture of Danubian Wels in pord 1

Tabel 4. Test on Mass-culture of Danubian wels in Pond 2.

Note: Common carp and crucian carp were not stocked on purpose.They rushed in with the river water.