Horizontal distribution of Thetys vagina Tilesius (Tunicata, Thaliacea) in the Japan Sea during spring 2004

• Published in: Journal of Plankton Research
• Main Authors: Iguchi, Naoki, Kidokoro, Hideaki
• Format: Text
• Language: English
• Published: Oxford University Press 2006
• Subjects: Article; Subarctic
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/fbi138v1; https://doi.org/10.1093/plankt/fbi138

The occurrence of the salp Thetys vagina was observed in the Japan Sea during spring 2004. Catches up to 187 kg wet weight per 2.18 x 105 m3 (equal to ca. 0.9 g WW m-3) were collected with 10-m diameter surface-water otter trawl nets. The horizontal distribution indicated that the high biomass was related to the area with high chlorophyll a (Chl a ) concentration, which was located around the subarctic front with the warm Tsushima Current. Five prey taxa were identified from the gut contents of individuals from the high Chl a area. The diatom Coscinodiscus spp. (13-55 µm in diameter) dominated numerically. Another significant prey was the large diatom Coscinodiscus wailesii (219-313 µm), which is an indicator of the spring bloom in this area. The mass occurrence of Thetys vagina thus appears related to phytoplankton availability though the mechanisms remain uncertain.