赤道周辺海域におけるDOの航走連続記録-I

Abstract

As mentioned in the previous report, several types of oxygen decline belts were recorded by cruising in the Equatorial Current and adjacent seas. In this paper, the ecological significance of the belts to suspended particles and fishing rates of tunas were investigated. The observations were carried out in the same areas as in the previous survey, and the data of DO records obtained from it are cited in this paper. During the cruise, the water was sampled by a mini-pump at the rate of 15ml every 30minutes and preserved automatically in 2 or 3% formalin by modified HIRATA'S automatic solution adder. Then, the amount of suspended particles was determined using a Coulter Counter. Tunas were caught by longline gears in the Equatorial Current and Solomon Sea. High density of suspended particles was observed in areas where oxygen decline belts were recorded, 30times out of 34 recordings. It is interesting to note that a high correlation (γ=+0.84) was obtained between the frequency of sharp oxygen con caved curve and fishing rate of tunas. It might be suggested that the oxygen decline belt in the surface waters could be an important indicator for ecological studies of tuna fishing grounds.