Spawn quality and GnRHa induction efficiency in longfin yellowtail (Seriola rivoliana) broodstock kept in captivity

The longfin yellowtail (Seriola rivoliana) is a preferred species for aquaculture diversification in the Canary Islands. The aim of the present study was obtain a large number of spawns whit hormonal induction, which would provide reliable numbers of juveniles for the sustainable development of longfin yellowtail culture. Two females with oocytes bigger than 500 μ, and four males, previously captured from the wild were used for this study. Females and males of 10.7 ± 1.4 and 8.5 ± 0.9 kg body weight and 86.2 ± 5.3 and 78.9 ± 1.9 cm total length, respectively, were acclimated in 10 m3 tanks. Fish were injected three times per month between June and November with 20 μg kg− 1 of GnRHa. During the experimental period, temperature ranged from 21.9 ± 0.2 °C in June to 23.5 ± 0.4 °C in November. Broodstock feeding consisted in Atlantic mackerel (Scomber scombrus) at 2% BW, three times per week. A total of 20,189,700 eggs (944,326 eggs female kg− 1) were obtained with fifteen injections and 33 spawns (2.2 ± 0.7 spawns per injection). A significant positive was found, between the numbers of eggs obtained each month and the average monthly temperature. Latency period was approximately of 28 h and 30 min. A highly significant negative statistical relation (P < 0.01) was found between latency period and the water temperature at the induction time. Percentages of fertilization, viable eggs, hatching and three day-old larvae were 99.1 ± 1.2, 77.2 ± 9.8, 96.2 ± 5.6 and 82.5 ± 11.0, respectively. The results showed that intramuscular injections of 20 μg kg− 1 of GnRHa every 10 days in fluent males and 500 μm oocytes bearing females of longfin yellowtail broodstock were successful to obtain a high induction efficiency and excellent spawn quality.