The taxonomy and summer and fall vertical distribution of the Chaetognatha off Galveston, Texas.

Adelmann, H.C.
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Texas A&M University.

The chaetognaths off Galveston, Texas have been studied from specimens collected during June, July, September, and November, 1963. Two genera and six species were identified, described, and illustrated. One species, Sagitta serratodentata, present in the Galveston area has not been reported from the Texas coast previously. However, six species reported from Port Aransas were not found in the present study. No marked difference was found between the species of the west coast of Florida and the western Gulf. Occurrence and abundance were summarized in the form of a table. Vertical distribution and diel migration were also discussed and accompanied by numerous diameter and line graphs. Vertical distribution was evident for the combined chaetognath populations, with definite diel migration patterns exhibited by the two abundant species, Sagitta enflata and Sagitta tenuis. Temperatures and salinities were relatively constant during the periods of sampling and appeared to have no significant effect on the distribution of the species present. The combined effects of varied light intensity and turbidity appeared to affect vertical migration time. The organisms migrated downward later and upward earlier during the periods when the water was most turbid and the light intensity was lowest. Diel migration varied slightly between summer and fall. No marked difference was found between the migration patterns of adults and immature forms.

117 pages
Sagitta serratodentata, Sagitta enflata, Sagitta tenuis, Chaetognatha, vertical distribution, seasonal distribution, taxonomy, abundance, seasonal variations, diurnal variations