CULTIVATION CAPACITY OF A CULTIVATION FACILITY-INTEGRATED STRUCTURE BASED ON DISSOLVED OXYGEN BALANCE

Abstract

In Hokkaido, cultivation (underwater farming) for shipment control of seafood or intermediate breeding of fries is conducted in some waters behind breakwaters with the seawater exchange function.This study discusses the cultivation capacity of a cultivation facility-integrated structure with the seawater exchange function, using the optimum dissolved oxygen content for the sea urchin, which is the species being cultivated, as the basis. As a result, the following matters were clarified(1) Temporal changes in the dissolved oxygen content in the preserve, in which 4, 000 sea urchins were continuously cultivated for a month, were observed using the wave data of January 1991. Changes in wave height and dissolved oxygen corresponded mostly with each other, and the dissolved oxygencontent in the preserve, which was 5.4mg/l 120 hours later, recovered to 8.0mg/l, the same level as the open sea water, by the effect of waves approximately 40cm in wave height. The lowest value of dissolvedoxygen in one month was 5.4mg/l, and the lower limit of optimum dissolved oxygen (2.7mg/l) was satisfied.(2) The dissolved oxygen content in the preserve decreased almost linearly in relation to the number of sea urchins cultured.(3) When sea urchins were cultivated for one month in a preserve using the wave data of 36 months from 1989 to 1991, the cultivation capacity in winter (February and March) was 5, 000 sea urchins, greater than the capacity of 4, 000 in summer