|Sea urchins production by inland farming (Abstract)|
Le Gall, P.; Bucaille, D. (1989). Sea urchins production by inland farming (Abstract), in: De Pauw, N. et al. (Ed.) Aquaculture: a biotechnology in progress: volume 1. pp. 53-59
In: De Pauw, N. et al. (Ed.) (1989). Aquaculture: a biotechnology in progress: volume 1. European Aquaculture Society: Bredene, Belgium. ISBN 90-71625-03-6. 1-592 pp., more
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Since 1982, we have been carrying out experimental research on intensive inland sea farming. Among marine species which present physiological potential and behaviour compatible with the necessities of such a technique, we have selected sea urchins. In many countries, sea urchins are considered as a good fisheries resource, and they are one of the highest-priced commodities sold in fish markets (Green Mottet, 1976). Recently, owing to a reduction in their population density, drastic problems have arisen in many fishing grounds. Urchins usually occur in high densities on rocky coasts, where trawling is difficult, so that only a few animals can be caught. Moreover, they have a high market value and an increasingly scarce. One of the main factors which led us to sea urchin farming was their ability to live on almost any type of food. In our rearing systems, we only need a small amount of new seawater every day. This allows good control and regulation of the water quality, without a real increase in cost. The three sea urchin species which have value or potential commercial value in France were tested in our experimental farming system. The first point which needed to be proved for each of them, was that the growth rate was sufficient for a rapid production and sale. We have demonstrated that commercial size can be reached in only 2 years. As sea urchin gonads are the only parts which is eaten, it seems important to compare the size of the gonads of urchins from different origins, especially from our farming systems and from natural populations. For this purpose, various formulas have been used as gonadal indices. The mean values of gonadal indices are always much higher for farmed sea urchins than for any natural population. This fact allows a better quality, and a much longer marketing period during the year than for natural sea urchin populations. In our systems, animals produce gametes throughout the year. The natural spawning period is extended so larvae can be obtained easily in any season. A high production of juveniles is readily obtained in special structures, such as our small experimental hatchery. When juveniles attain 3-4mm in diameter, the young urchins of each species are removed and settled in other systems. Our methods are already being applied in two places in order to confirm their viability in semi-industrial conditions, and to estimate the real cost of this type of farming production.