Studies In Affecting Factors On Spawning Rate Of Channel Catfish (Ictalurus Punctatus Rafinesgue)

This article focus on the impact of the channel catfish Ictalurus punctatus spawning rate caused by the stocking density, the spawner weight, the water depth of spawning pond, the sediment thickness and the artificial propagation.This experiment selects 4-5 years old, good shape, unwounded, good gonadal developed channel catfish spawner to make a comparing according to different stocking quantity, different weight and different pond conditions. The spawners are raised in 4 trial ponds of 2668m2 respectively. Each pond is surrounded by stone revetment film with oval shaped slope bottom. The sediment thickness is 10-15cm, convenient drainage and irrigation, good water conditions. Each pond is 2 meters deep and is equipped by a 3-kw aerator, the dissolved oxygen is kept over 5mg/L.Enhance the cultivation before winter, feed pellets of 37% crude protein content, feed living animal bait every 2 days, the feeding quantity and times will be fixed according to the weather, the water temperature and the water conditions. Generally, the daily feeding quantity is 2-3% of the spawner weight and the daily feeding times is 2 times. 30 days before spawning(water temperature is 16℃), feed chilled carp steaks, the feeding quantity is 5-8% of the fish weight.Spawning. On May 5th, the spawners are found grown up well in the above 4 trial ponds by dragnet inspection. On May 12th, the spawners begin to lay eggs when the water temperature reach 24℃383 egg masses are got. The average spawning rate is 45.3%, the average fertilization rate is over 92%, 6830 thousand fish fries are got.The artificial spawning. This step is taken after the channel catfish spawner got gonadal development while the water temperature reach 25℃. The spawning medicine is PG, HCG, LRH-A 3 ,D0M. The dosage may be PG1.0mg+DOM2.0mg+LRH-A310ug +HCG1000IU. And half volume of the male spawner. At last the general spawning rate is 62.5%, 535 thousand eggs are got, fertilization rate is over 94%, 453 thousand fish fries are got.The experiment result shows that:1.Under the same condition of pond square, water depth, sediment thickness, spawner weight and sex ratio, the spawner stocking density of 50/667m2 and 70/667m2, their average spawning rate are 92.17% and 67.38% respectively, the former is superior than the latter. Therefore we can see that the stocking density is a key factor to the channel catfish spawning, rational stocking density may lead to high spawning rate. And vice versa.2. Under the same condition of pond square, water depth, the sediment thickness, stocking density and sex ratio, the channel catfish weigh 2～2.5kg, the spawning rate is 92.17%; the channel catfish weigh 3～4.5kg, the spawning rate is 54.85%, they have obviously difference. The author consider that this phenomenon is related to the spawner's weight. Generally, the channel catfish of 3～5 years old and 2.0～3.0kg weight has good physique, rapid gonadal development, good fertility and high spawning rate. And vice versa.3.Under the same condition of pond ecology and spawner stocking, the pond that is 2m and 1.6m deep, the average spawning rate are 92.17% and 69.41% respectively, the former is superior than the latter. The author consider that the water depth of the pond will not over 2m, otherwise the dissolved oxygen is not enough. And the water depth will not less than 1.2m, otherwise the strong sunlight will affect the spawning rate.4. Under the same condition of pond ecology and spawner stocking, the sediment thickness that is 10～15cm and 25～35cm deep, the average spawning rate are 69.41% and 44.78% respectively, the former is superior than the latter. Too much and too thick sediment is full of organic, such as N and Nitrite, which will affect the spawning rate. The author consider that different sediment thickness will lead to different spawning result.5.Under the same condition of spawning, the average spawning rate by artificial cow or not are 80% and 90% respectively. The significantly T test shows that their difference is not significant (t=0.6000, p>0.5). The artificial cow method is not adopted during spawning, only when the weather changed, the pond water deteriorated and the dissolved oxygen descent, this method is available.