Eonomics and larviculture: issues.
Larviculture plays a pivotal role in the survival of many aquaculture operations. In most aquaculture systems, dietary requirements, growth rates, mortality rates, and optimal rearing conditions for larvae are not well known. This increases the economic uncertainty faced by growers. In cases where larviculture is poorly developed or excessively costly, wild harvests play an important role. For example, much Ecuadorian shrimp aquaculture is primarily dependent upon the wild harvest of postlarval shrimp. Therefore, the shrimp aquaculture industry is potentially at risk from the uncertainties of wild production of postlarvae. In addition, aquaculture development may negatively influence wild harvest of both postlarval shrimp and market shrimp.
Greater attention from an economic perspective would be valuable to help guide research, spending, and investment. However, the economics of larviculture systems, or larviculture as part of a vertically integrated aquaculture operation have received little attention. The objective of this presentation is to illustrate the range of topics related to the economics of larviculture and their significance to the viability of the aquaculture sector.
Economic issues which will be discussed, include the evaluation of:
Present status of seed production of marine species in Japan.
In recent years, mass seed production techniques of about 80 marine species have been developed in Japan for stocking enhancement and aquaculture. For more than 30 years, the Japan Sea-Farming Association (JASFA), a semi-governmental organization, has played a leading role in this field. In this presentation we describe the present status of seed production of marine species in Japan, focusing on the results obtained by the JASFA.
The JASFA has 16 stations all over the country, and in 1993 for example produced 94 million seeds of kuruma prawn Penaeus japonicus, 12.8 million of swimming crab Portunus trituberculatus, 1.1 million of herring Clupea pallasii, 5.4 million of the Japanese flounder Paralichthys olivaceus, and 800 000 of yellowtail Seriola quinqueradiata. Yellowtail is an important species targeted for large-scale production because it is a major finfish species cultured in net cages in Japan. Although cultured female yellowtail have ovaries that contain oocytes at the tertiary yolk stage during the spawning season, they do not ovulate and spawn naturally. The most commonly used method for spontaneous spawning is with a single injection of HCG, however, this method resulted in eggs with low fertilization rates. Recently in our station, female yellowtail were kept under an extended day-length by artificial illumination in addition to HCG injection. As a result, the fertilization rate of the eggs spawned by this combination was twice as high as that of eggs released after HCG injection only.
(Goto Station of the Japan Sea-Farming Association, Tamanoura, Nagasaki 853-05, Japan)
Spawning and larval rearing of marine finfish (Bothidae, Carangidae, Centropomidae, Sciaenidae) in Ecuador.
This paper reports recent advances in spawning and larval rearing of marine fish accomplished during the research and development stage of a project to diversify the shrimp and fisheries industries in Ecuador into finfish aquaculture. The project has focused on commercially important species such as flounder (Paralichthys adspersus, P. woolmani), Pacific yellowtail (Seriola mazatlana), snook (Centropomus nigrescens), pompano (Trachinotus paitensis) and red drum (Sciaenops ocellatus). Experimental production of flounder, yellowtail, snook and red drum fingerlings has been successfully conducted from eggs. Broodstock flounder and yellowtail have been conditioned to spawn naturally in maturation rooms, while snook have been induced to spawn by the utilization of hormones (HCG and LHRH-a). Attempts to condition or induce red drum and pompano to spawn have failed thus far. The results of larval husbandry have been highly variable. The production of flounder fingerlings has been steady but survival rates remain low (3-8%). Survivals of over 50% are achieved throughout the larval rearing of Seriola, however, high mortalities after metamorphosis have been lowering the average survival rates through the juvenile stage to less than 1%. Larval rearing of red drum from eggs donated by the University of Miami was conducted with over 80% survival through metamorphosis. In addition, large numbers of wild-caught larval and postlarval pompano and flounder are being raised in hatcheries for growout trials in cages, ponds and tanks. Efforts are now concentrated on reducing mortalities during and after metamorphosis, due to cannibalism, weaning onto artificial diets and diseases. Epizootics of Epitheliocystis, Vibrio alginolyticus and Amyloodinium ocellatum have repeatedly occurred during the early developmental stages and remain the bottleneck to sustainable mass production of fingerlings. The future and viability of commercial marine fish operations in Ecuador and other Latin American countries will depend upon the outcome of current and future attempts on the prevention and control of disease outbreaks.
(Mariculture Project, Cinco S.A., P.O. Box 10229, Guayaquil, Ecuador)
