Studies on Fishing Depth and Difference in Catch by Color of Jigs for Purpleback Flying Squid Symplectoteuthis oualaniensis and Luminous Flying Squid Eucleoteuthis luminosa

Abstract

Symplectoeuthis oualaniensis and Eucleoteuthis luminosa were caught with hand-lines under fish attracting light, and a study was made to investigate the depth of catching, water temperature and the relationship between the catch and the color of Jigs. The following results were obtained. 1. At each fishing area, a large number of S. oualaniensis was caught above the thermocline (high temperature zone), their catch zone was shallower than that for E. luminosa. On the other hand, E. luminosa appeared to be caught in a large number in the deeper zone, within the thermocline (low temperature zone). This fact seems to indicate that rather than the brightness in water, the vertical distribution of the water temperature, is greatly related to the difference of the swimming zone (catch zone) of the two species. 2. The chi-squares test was applied to the number of squids by jigs of various colors (red, white and green). The results supported a hypothesis that the catch of squids is independent of the color of a jig. The results are thought to indicate that squids do not have such a good sense of color. © 1988, The Japanese Society of Fisheries Science. All rights reserved.