Vertical Distribution of Chaetognatha in the Central Northwest Atlantic Near Bermuda

AbstractIn March 1973 the vertical distribution of chaetognaths near Bermuda showed faunal changes at about 300 m, 500 m, 800 m, 1,250 m, and possibly 2,500 m. These changes sometimes coincided with different water masses; sometimes they occurred within one water mass. Chaetognaths were most abundant from 50 to 100 m by day and from 0 to 10 m at night. Chaetognath species show a more limited vertical distribution than ostracod and euphausiid species from the same set of samples. Limits of distribution and levels of maximum density are greatly influenced by the stage of maturity, as most species show ontogenetic vertical distribution. Diurnal vertical migration is present in all species living mainly or exclusively above 500 m, except for S. sibogae. Closely related taxa live in different vertical layers. Taxa with identical vertical distribution limits either have different levels of maximum density or show different sexual cycles.