CONSERVATION OF AN ENDANGERED CARNIVOROUS FISH RITA RITA THROUGH INDUCED BREEDING

In present study the Effects of different doses of ovaprim on induced spawning activities of Rita rita were observed with an aim to standardize the dose of ovaprim for successful breeding. In the trial experiment, the females of Rita rita were treated with ovaprim at the rate of 0.5, 0.8 and 1.0ml/kg body weight and males of Rita rita in all the cases were treated at the rate of 0.4ml/kg. The doses of ovaprim at the rates of 0.5, 0.8, 1.0 ml/kg body weight resulted in 0%, 100% and 100% ovulation respectively. In case of injection of ovaprim at the rate of 0.8ml/kg, the fertilization rate was observed to be about 70% and hatching rate was 58%, which occurred within 20-25 hours after fertilization at water temperature of 270C-290C. In case of injection of ovaprim at the rate of 1.0ml/kg, 18% fertilization rate and 5% hatching rate was observed. The doses of ovaprim at the rates of 0.8ml/kg and 0.4ml/kg body weight for female and male Rita rita respectively was found to be satisfactory for overall breeding performance and the commercially successful production of this fish. Hatchlings from over all experiment were reared up to fingerlings size to about 2 month and were finally stocked into the Chashma lake.

Advancement in spawning period of Labeo dyocheilus (McClelland, 1839) in the mid Himalayan regions by hormonal manipulation using Ovatide

An attempt was made to advance the spawning period of Labeo dyocheilus (McClelland, 1839) by pretreatment with the synthetic gonadotropin releasing hormone analogue, Ovatide. Total 12 females and 24 males (1: 2 ratio) were used for breeding operations conducted during 30th May to 30th June 2016 comprising six sets. Female fishes of set I to IV were pretreated with intramuscular injection of the ovatide at the rate 0.3 ml kg-1 body weight twice at an interval of two weeks while males were injected @ 0.1 ml kg-1 body weight once before 15 days of induced breeding trial for achieving advance maturity and spawning during pre-spawning phase. Fishes of set V and VI were not subjected to any pretreatment with ovatide. On 30th of June all the six breeding sets were were treated with ovatide for induced spawning. Female and males were injected at 0.7 ml kg-1 and 0.3 ml kg-1 of body weight, respectively and left overnight in FRP tanks for spawning. Results indicated that in sets I to IV, fishes successfully spawned and fertilised eggs were collected in morning hours whereas fishes of set V and VI failed to spawn. Fertilisation and survival rates recorded were 79-82% and 67-71%, respectively. Results indicated that treatment of ovatide during prespawning phase is beneficial for advancing the gonadal maturity, successful induced spawning and prolonging the breeding period which may play a key role in production of substantial quantity of seed of L. dyocheilus.

Breeding and Larval Rearing of Asian Moon Scallop Amusium pleuronectes in Eastern Samar, Philippines

Asian moon scallop, Amusium pleuronectes, is among the most common commercially harvested scallop in the Philippines. This study investigated suitable conditioning methods, induced spawning, and documented scallop larval development at the Marine Fisheries Research and Development Center (MFRDC) Guiuan, Eastern Samar. Scallops held in tanks with flow-through water system without substrate yielded high survival rate of 48.06 ± 5.95%. Optimum water temperature was 28-29°C for maintaining scallops. Isochrysis galbana and Chaetoceros calcitrans were suitable microalgal feed for A. pleuronectes consumed at 7,388,888 cells min-1 per scallop. These significant results were applied in maintaining scallops at the hatchery. As a result, scallops with an average 19.8 mm shell length (SL) reached 37.5 mm SL within four months with a survival rate of 96.57 ± 2.04%, average daily growth rate (ADGR) of 0.13 ± 0.04 mm.day-1, and specific growth rate (SGR) of 3.92 ± 1.31%.d-1. Natural spawning was successful under controlled conditions while induced spawning trial through thermal stimulation, food shock, sexual stimulation, and serotonin injection resulted unsuccessful release of sperm and eggs. The estimated number of fertilized eggs per spawning ranged from 0.22-1.4 million. Fertilized eggs appeared spherical and dark in color with 54.2-62.57 µm in diameter. After nine hours, the larvae developed into trochophore stage with 59.08-84.4 µm in length. D-veliger with 120.37-157.07µm shell length developed after 24 hours. Development of the early umbone stage was reached on day 5; and on day 7, the umbo larvae become well-developed with shell length of 135.45-173.36 µm. On day 9, pedi-veligers were observed in the culture. Spat grew 312.41-509.48 µm on day 16 and survived until four months with final shell length of 4-10 mm. For the larval rearing, stocking density of A. pleuronectes larvae observed highest survival rate of 0.04 ± 0.03% at 200 larvae/L, while no larvae survived at 800 larvae/L due to contamination of protozoans in the culture medium.