Strontium:calcium ratios in statoliths of Japanese common squid Todarodes pacificus (Cephalopoda: Ommastrephidae) as indicators of migratory behavior

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 251:169-179 (2003) - doi:10.3354/meps251169 Strontium:calcium ratios in statoliths of Japanese common squid Todarodes pacificus (Cephalopoda: Ommastrephidae) as indicators of migratory behavior Yuzuru Ikeda1,*, Nobuaki Arai2, Hideaki Kidokoro3, Wataru Sakamoto4,5 1Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan 2Graduate School of Informatics, Kyoto University, Kyoto 606-8501, Japan 3Japan Sea National Fisheries Research Institute, Niigata 951-8121, Japan 4Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan 5Present address: Fisheries Laboratory of Kinki University, Shirahama, Wakayama 649-2211, Japan *Email: ikeda@brain.riken.go.jp ABSTRACT: Ontogenetic variation in the strontium:calcium (Sr:Ca) ratios was measured in statoliths of the Japanese common squid Todarodes pacificus. Two different geographical groups of T. pacificus inhabit the Sea of Japan; these groups are separated by the Subarctic Front during the summer. Element ratios were measured with a wavelength-dispersive spectrometer for 11 individuals from a cold-water subarctic region, which harbors large squid (Subarctic Group), for 12 individuals from a warm-water region, which harbors smaller squid (Tsushima Group), and for 2 individuals from the Subarctic Front. The squid ranged from 190 to 218 mm in mantle length (ML) and were 191 to 262 d old. Similar measurements were obtained for 12 tagged T. pacificus (187 to 259 mm ML; 214 to 312 d old) that were released and recovered in the Subarctic and the Tsushima Current between June and August 1997 (tagging duration 5 to >40 d). Ontogenetic variation in Sr:Ca ratios from hatchlings to sub-adults differed between the 2 geographical groups. Sr:Ca ratios were high at hatching followed by a drastic decrease up to 10 d of age for both groups. These ratios increased until 40 d of age, continuing at high levels until around 150 d, when they decreased in all specimens of the Tsushima Group. In the Subarctic Group, however, the variations in Sr:Ca ratios differed between individuals. Sr:Ca ratios at the age when squid recruited to either the Subarctic or the Tsushima Current were similar. These differences reflect the different spawning grounds and transport routes of the 2 groups. Thermal history was recorded from the statoliths of tagged individuals, and small fluctuations and seasonal variations in the Sr:Ca ratios were observed. These correspond to diel vertical movements and endogenous rhythms of the squid, and the formation and movements of the cold-water layer in their habitat. KEY WORDS: Japanese common squid · Statoliths · Sr:Ca ratios · Migration · Sea of Japan Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 251. Online publication date: April 11, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.