Abstract The species composition, distribution and generations of the thaliacea in relation to the sea surface temperature, salinity and chlorophyll a were studied in the Koaping coastal waters, southwestern Taiwan, from June 2001 to October 2002. In all, 16 species of the thaliacea belonging to 3 families and 11 genera were identified. Among these, Doliolum denticulatum was the most dominant species and comprised 62.2% of the numerical total of thaliacea, other common species including: Thalia orientalis (22.8%), Thalia democratica (7.5%), Thalia rhomboids (2.4%) and Dolioliletta gegenbauri (2.3%). The mean numerical abundance of thaliacea was 690.6 1601.4 ind./100m3. Most species showed apparently seasonal changes, with the highest abundance in March 2002 and the lowest was in November 2001. Higher abundances of thaliacea were generally found in the 100m oblique tows when compared with the surface tows, except in March and October 2002 that bulk abundances were found in the surface waters. The variation of thaliacean species composition and abundance among stations and mouths was larger in 2002 than in 2001. Higher similarity in community structure of thaliacea was found between August and November 2001, while larger variations among stations were found in March and July 2002. In general, the abundance of thaliacea species showed significantly negative correlation with water temperature but significantly positive correlations with salinity and chlorophyll a. Blastozooid(phorozooids and gonozooids) of the Doliolum denticulatum and Dolioletta gegenburia dominated in the study area and comprised 99.2% of total doliolids. Blastozooid(gonozooids) was also dominated in Salpida species and comprised 84.3% of total Salpida, except Thalia rhomboids that blastozooid occupied only 40.1%.

Abstract The species composition, abundance, body lengths and stages of chaetognaths in relation to environmental factors at nine stations in Kaoping coastal waters were investigated during June 2001 to March 2002. In the surface tows, 20 species of chaetognaths, belonging to 10 families and 4 orders, were found, with the mean abundance of 17753 ¡Ó14593 ind./ 100m3. The 4 most dominant species, Flaccisagitta enflata, Aidanosagitta crassa, Sagitta bipuncata and Ferosagitta ferox, comprised > 80% of total chaetognaths. Flaccisagitta enflata was the most common and abundant species and occupied 53% of total chaetognaths. In 100m oblique tows, 21 species of chaetognaths, belonging to 11 families and 4 orders were found, with the mean abundance of 23535 ¡Ó 18696 ind./ 100m3. The 4 most dominant species were Flaccisagitta enflata, Aidanosagitta regularis, Serratosagitta pacifica and Aidanosagitta crassa, and comprised 77% of total chaetognths. Pseudosagitta lyra was the species found only in the 100m oblique tows. The abundance of chaetognaths changed with seasons and had the highest abundance in summer and the lowest in late autumn. The relation between abundance of chaetognaths showed significantly negative relationship with salinity but not for temperature, and had larger variation when salinity > 32 o/oo. Multi-Dimensional Scaling (MDS) method was used to elucidate the variation of chaetognaths community among seasons and stations. The community structure of chaetognaths had somewhat difference among seasons, with higher similarity between August and November, but these two months showed apparently different from June and March. The variation of chaetognaths community among stations was different seasonally, with higher in August and lower in March and June. Furthermore, three species groups were distinguished and their distribution patterns were herein disscussed. The Stage¢¹of chaetognaths dominated in this study area and occupied > 70 % of total count, and the number decreased rapidly following the developmental stages. The most dominant species, Flaccisagitta enflata, was also dominated by stage¢¹throughout the year, implied it might breed in the whole year. The body length of chaetognaths increased apparently with increasing of developmental stages, but overlapped among stages due to the wider variation in each stage.