open access

https://hdl.handle.net/2115/97787

Mass Occurrence of Walleye Pollock Gadus chalcogrammus (Gadidae) in the Surface Layer of the Oyashio Basin (Western North Pacific) : Possible Benefit from Abundant Copepods

英語

Neocalanus

2025

Pleiades Publishing Inc

Journal of Ichthyology

65

488-494

A total of 2999 individuals of walleye pollock Gadus chalcogrammus was caught by a surface trawling net covering the 0-ca. 30 m depth layer during May 2022, at two sites, 36 and 172 km off the southern coast of Hokkaido Island. The fact that no fish was caught at a station further south suggested that the pollock originated from the coastal area of Hokkaido Island rather than Honshu Island. Although the body length of the fish from both sites was similar, ranging ca. 35-45 cm standard length, fish condition differed significantly with fish from the southern (offshore) station having stouter bodies. Stomach contents analysis revealed that the fish from the southern station ingested 2.1 times more prey (measured as stomach contents index) consisting mainly of copepods (86% in dry weight) than those from the northern station. Because the southern station was in a more advanced condition of phytoplankton blooming, it has been suggested that the walleye pollock migrated south to utilize the abundant copepods in the surface layer during the blooming.

学術雑誌論文

Accepted Manuscript

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1134/S0032945224602471

0032-9452

1555-6425

AA00699612