Species diversity and abundance of rhizoatome scyphozoans (Phylum cnidaria) along the coasts of Chon Buri and Phetchaburi Provinces

Abstract

This study focuses mainly on the species diversity, as well as the abundance, of rhizomedusae along the coasts of Chon Buri and Phetchaburi Provinces, Where jellyfish fisheries are carried out annually. Samplings were conducted from December 1999 to December 2000 in the Inner Gulf of Thailand consequently, 6 species of rhizomedusae were obtained. They are Cassiopea Andromeda (Forskal, 1775), Acromitus flagellates (Maas, 1903), Acromitus hardenbergi, Catostylus townsendi mayer, 1915 and two well-know commercial species, which are Lobonema smithii Mayer, 1910 and Rhopilema hispidum (Vanhoffen, 1888). R. hispidum was predominantly found along the coast of Chonburi Province while L. smithii was found exclusively along the coast of Phetchaburi Province. The results revealed the highest abundance of rhizomedusae in March 2000 (>23 individuals. 10⁴ m⁻³ ) (>302 individuals. 10⁴ m⁻³ ) for Chon Buri and Petchaburi, respectively. Among the 6 species obtained, A. flagellates, a relatively small noncommercial species, was the most common species found in both provinces and yielded the highest abundance in term of density (> 300 individuals. 10⁴ m⁻³ in November 2000). The environmental factors, which affected the abundance and size structure of rhizomedusae at both provinces, were salinity, water current, and zooplankton concerntration in addition to the life history of themselves.