Iwahara is a type of fish that resembles a maggot in shape and belongs to the subfamily Asteraceae. It is mainly found in the tributaries of the upper reaches of the Yangtze River, with larger populations in the middle and lower sections of the Jialing River. From February to April, Iwahara swim upstream to spawn in tributaries. Due to its slow growth rate, the average fourth-instar fish only weighs about 0.5 kilograms. However, the construction of dams along the upper reaches of the Yangtze River has blocked their migration routes to spawning grounds, leading to a gradual decline in wild populations. As a result, Iwahara is now classified as a vulnerable species in our country.
Through years of research and field trials, the author has developed a comprehensive artificial breeding technique for Iwahara. The following report outlines the methods and results of this study.
**Materials and Methods**
**Broodstock Prenatal Cultivation**
The experiment was conducted at a farm located in the Tongdian reservoir area of the Jialing River between 2002 and 2004, with the best results achieved in 2003. The broodstock were wild-caught fish from the Jialing River and were raised intensively in ponds. Each individual weighed between 1 to 2 kilograms. Two months before the breeding season, they were fed fresh snail meat and exposed to increased water flow to stimulate gonadal development.
**Preparation of Oxytocin Solutions**
Three types of hormones were used: human chorionic gonadotropin (HCG), luteinizing hormone-releasing hormone analogue (LRH-A), and domoxone (DOM). These were used as anabolic agents to induce spawning.
**Facilities for Artificial Insemination and Hatching**
Basic tools such as white basins, towels, feathers, physiological saline, troughs, needles, and cylinders were used for the process.
**Identification of Male and Female Fish**
Males can be identified by the distinct bead on their mouth, dark-black fins, and protruding gonopores. Females have gray fins and invaginated gonopores.
**Artificial Oxytocin Administration**
Females were injected with a mixture of HCG (800 IU/kg), LRH-A (5 µg/kg), and DOM (50 mg/kg). Males received a dose of 1 ml of physiological saline per kg of body weight, based on their maturity level. The injection was administered into the pectoral fin.
After oxytocin administration, the fish were placed in a circular spawning pond filled with large gravel to simulate natural conditions.
**Post-Induction Artificial Insemination**
Approximately 30 hours after induction, when the fish became calm after chasing each other, dry artificial insemination was performed. Fish eggs and semen were collected, mixed with physiological saline, gently stirred with feathers, allowed to settle for 2 minutes, and then washed with normal saline two or three times before being transferred for hatching.
**Artificial Hatching Process**
Fertilized eggs were placed in flat troughs at a density of about 10,000 eggs per square meter. They were treated with 1 ppm copper sulfate for sterilization and incubated with microfluidic water. The water flow rate was maintained at 1.5 cm/s.
**Test Results**
In this trial, there were 10 groups of broodstock. The average weight of females was 1.1 kg per fish, yielding approximately 12,000 fertilized eggs, of which over 7,000 successfully hatched.
**Discussion**
The study revealed that Iwahara is a batch-spawning species, resulting in relatively low egg production per individual—between 0.2 to 0.4 million eggs per kilogram. Additionally, male semen volume is very low, typically around 1 ml per kilogram. Therefore, during the collection of males and females, it is important to check their maturity without squeezing the semen unnecessarily.
Eas anti-theft antenna is mainly suitable for large supermarkets, shopping malls, bookstores, audio stores with Security hard tags, rf soft label, AM lable,Pin and Lanyard, eas detacher, Hook Lock,EAS Self Alarm Tag, EAS Safer Box,etc.
Am Label ,Am Label,Am Soft Label,Am Security Labels
Wenzhou Boshine Electronic Security Co. Ltd , https://www.boshine.com