Abstract
Techniques for maturation, spawning and larval rearing of Pacific yellowtail, Seriola mazatlana, were developed in Ecuador during the last five years. Using the methodology described in this paper, we were able to obtain continuous and sustainable year-round spawning of both wild and captive reared broodstock fish in maturation tanks. After collection from the wild and acclimation for about one year at the hatchery facilities, one group of twelve broodstock fish was producing about 400, 000 fertilized eggs twice a week over a 18-month period. Another group of ten wild broodstock fish spawned 4, 500, 000 fertilized eggs per month from February to October, 1997. Similar results were achieved with a third group of twelve wild caught broodstock fish in another commercial hatchery in Ecuador. During 1997, 50 months after hatching, we were able to get a hatchery grown group of brood fish (first generation in captivity) to spawn about 200, 000 fertilized eggs twice a week in captivity. Larval husbandry was conducted using three different techniques: intensive, semiintensive and extensive. Results have been highly variable. Depending upon the egg quality from the different batches, survival rates ranging from 0-70% were achieved throughout larval rearing of Seriola until metamorphosis. High mortalities of fingerlings and early juveniles after metamorphosis have been lowering the average survival rates through the juvenile stage to 0.5-2.0%. Epitheliocystis has been shown to be the most important disease to occur during early developmental stages. Epizootics of this disease have caused mass mortalities of fingerlings. Other factors directly or indirectly related to the high mortality rates observed are broodstock nutrition, variability in egg quality among different batches, larval nutrition, weaning from live feeds onto artificial diets, as well as high levels of cannibalism after metamorphosis. Commercial production of Pacific yellowtail in Ecuador and other Latin American countries has been hampered exclusively by high mortalities of fingerlings and early juveniles. All other technicalities related to their aquaculture are thought to be mastered. The technological feasibility of Pacific yellowtail aquaculture has been proven. The commercial, economical viability of the operation remains uncertain.