THE CHAETOGNATHA OF THE WEST COAST OF FLORIDA

¹ Department of Biology, University of Florida, Gainesville, Florida

1. From November, 1948 through January, 1950 quantitative plankton collections were made at monthly intervals from nine stations along the west coast of Florida.

2. Surface water temperatures and salinities were taken at each station. The warmest water temperatures were similar at all stations but the coldest water by several degrees was found at the Cedar Key station (3A).

3. The inshore water at all stations showed reduced salinity. This was correlated with rainfall. The salinity increased from the inshore to the offshore stations.

4. Three maturity stages were described for the chaetognaths based on development of testes and ovaries.

5. The chaetognaths collected were: S. hispida, S. helenae, S. tenuis, S. enflata, K. pacifica. One of these, S. hispida, exists characteristically in dilute inshore water. S. helenae and S. enflata were normally absent at the inshore stations where S. hispida was abundant. They were most numerous at the C stations where the salinity of the water varied around 35°/_00. S. tenuis appeared to be rather tolerant of fluctuations in salinity although in the Cedar Key area, where the lowest salinities were encountered, it was noticeably scarce at the inshore stations. The catches of K. pacifica were too few and scattered to give a good picture of its local distribution. It was more abundant in waters of high salinity than elsewhere.

6. The data indicated that breeding was, with some fluctuations, continuous the year round.

7. S. hispida and S. helenae were found at all seasons. Increased numbers of Stage I forms appeared in the late spring and summer, resulting in an over-all increase in the population. S. tenuis and S. enflata were noticeably most abundant during the colder months.

8. A northward movement of the coastal water helps distribute the chaetognaths and apparently does not interfere seriously with the persistence of water of reduced salinity in the inshore areas.