Breeding and reproduction of grey mullet (Mugil cephalus L.)

Mazandaran and Gorgan provinces have temperate climate, thus they have more potential for aquatic animal culture. There are thousands hectare of salt and useless lands in adjacent to Caspian Sea. As these areas have provided a favorable back ground for aquatic animal culture. As a result, the successful results obtained from imported gray mullet (Mugil cephalus) culture project in north climate, it has demonstrated that the gray mullet has a good biocharacteristic for culturing in pond enclosure environment and in different aquatic conditions (fresh water, brackish water and salt water). From 1998 until 2001, the broodstock yield and gray mullet artificial propagation projects were performed by fisheries research center of Mazandaran in Ghomishan prawn culture station in adjacent to Caspian Sea (East north of Mazandaran Province). This investigation executed during two stages (phases). At first stage, the goal of this project included the survey of possibility available about matured fish as well as induction of final maturation and artificial propagation for producing of broodstock and larva. In addition, in this way, we will obtain new information about gray mullet propagation and culture as marine species. We introduce mass production in aquaculture. At present research, the possibility of broodstock yield and artificial propagation of gray mullet have investigated by gray mullet fingerlings imported from Hong kong and then they have cultured in earth ponds of Ghomishan areas during five years (1994-1998). In order to broodstock production in spring 1998, two earth ponds (0.5 hectare) were prepared. 100 specimens of fish stock (1-2.5 kg weight average and 5 years of age) placed in each pond. For providing of suitable water and nutrition, fish were fed by food containing rich protein (40%) with 3-5% body weight and maintained in water with 30-35 ppt salinity. The survey of sexual maturation was performed by sampling of sexual glands through year. There were four stages in dominant female broodstocks. This survey indicated that oocytes have emerged stage 1 (immature) from March to June, stage 2 (yolk vesicle) in September and stage 4 (yolk globule) in October. Three stages (first, second and third) of yolk formation in oocytes will occur but these stages take place in October, December and January respectively. It's obvious that oocytes will progress into the end of third stage (yolk formation) and then their growth was arrested. Ovum with 600 m diameter was observed when the water temperature declined less than 18 c and day time was short (from middle autumn to middle winter), on that time, fish were induced by hormone because lack of final maturation and ovulation, therefore, natural spawning was not occurred in pond condition. Furthermore, artificial propagation of mugil cephalus was occurred by hormonal induction. Hormonal induction was utilized by inject of many hormones (LHRH, Cph, HCG). Using different components of hormones and also their different doses obtained the best results from broodstock that the average ovum diameter was about 600 m. Several types hormones which were injected into gray mullet with two or several intermittent (24 h intervals) along with 20-25 c temperature and 30-35 ppt salinity. This condition can provide stage 4 maturity for fertilization. Totally (as whole), three intermittent fertilization was necessary for exiting of larva, larva production in first, second and third intermittents that were 2000, 2500 and 300 specimens respectively. Larva fed on chlorella algae and rotifera and they have maintained for 14-15 days. The results of obtainable research indicated the possibility of gray mullet broodstock production in cultural condition, artificial propagation and larva production. This research took place for the first time in north climate of Iran.