Zonal variations in abundance and body length of chaetognaths in the 140°E seasonal ice zone during the austral summer of 2001/02

• Published in: Polar Science
• Main Authors: Terazaki Makoto, Takahashi Kunio T., Odate Tsuneo
• Format: Article in Journal/Newspaper
• Language: English
• Published: 国立極地研究所 2013
• Subjects: Eukrohnia hamata; Southern boundary; Multi-ship survey; Antarctic; Austral; The Antarctic; Antarc*; Polar Science
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=10124; http://id.nii.ac.jp/1291/00010122/

Time-series observations of chaetognaths were carried out during four cruises along the 140°E transect between 61°S and 66°28'S from November to March in the 2001/02 austral summer. Three species - Eukrohnia hamata, Sagitta gazellae and S. marri - occurred in the samples between 0 and 150 m. E. hamata was the most dominant species comprising between 89.6 and 100% of the chaetognath population, followed by S. gazellae (0-5.7%). There were large differences in the abundance and size frequency distribution of body length of E. hamata between the north and south of the Southern Boundary of the Antarctic Circumpolar Current (SB-ACC) which was located between 64°S and 65°S. For E. hamata, low abundance and large sized animals (22-24 mm) occurred south of the SB-ACC. A possible reason could be that the breeding season in waters north of the SB-ACC may be early spring and summer. On the other hand, low reproduction was recognized by low the abundance of E. hamata and few occurrences of juveniles south of the SB-ACC (65°S). The result of a general comparison suggests that the abundance of chaetognaths along the 140°E transect has decreased during the 20 years since 1983. 2001/02シーズンの夏季（11－3月）に南大洋インド洋区東経140度線の季節海氷域においてヤムシ類の現存量および体長を調査した。試料採集は同海域においてNORPACネットを用いた0－150mの鉛直曳きを11、1、2、3月の4回実施した。ヤムシ類はEukrohina hamata、Sagitta gazellae、S. marriの3種が出現した。E. hamataは最も優占して出現し（89.6－100％）、南緯64－65度付近に存在していた南極周極流のSouthern Boundary (SB-ACC) を境に、南北で現存量および体長は大きく異なっていた。SB-ACCの南では3月に現存量が低く小型サイズ（< 6 mm）の個体がほとんど見られなかった。そのためSB-ACCの南北で本種の再生産時期が異なっていることが示唆された。