As in the case of trout, much of the earlier efforts at salmon culture were directed towards transplantation and hatchery production of young ones for stock enhancement or ranching. It was only in the latter part of the 1960s that the possibility of growing salmon received commercial attention. The decreasing price of trout and the high market value of salmon served as major incentives. Pioneering efforts in Scotland and Norway led to a modern cage culture industry of the Atlantic salmon, with specialization in egg and smolt production, grow-out for market fish, processing and marketing of smoked and frozen fish, feed and equipment manufacture, sales organizations, risk insurance arrangements, etc. Cage farming has spread to a number of other areas including Sweden, Iceland, Ireland, North America, Japan, New Zealand and Chile. The types of cages used for salmon farming have been described, and are very similar to those used for trout in sea water.
Another system of salmon culture is to grow them in impoundments of the type described (see fig. 6.32). Because of the high capital involved in such large-scale operations and the scarcity of suitable sites, this system is not commonly used. However, floating pen culture is not uncommon in Norway. Pens are built to enclose about 300–700m2 of the seashore. The management procedures for these pens are very similar to those for floating cages, except that for harvesting fish, repeated seining is necessary. Each enclosure can hold about 20 tons of fish, and if at any time the oxygen levels in the enclosure fall too low, a floating aerator is used to increase oxygen concentration.
Land-based pond or tank systems with supplies of pumped sea and fresh water are used only for growing smolts of salmon.
Copyright © 2018-2020 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.