Causal factors of interannual decrease in stomach content index (SCI) of juvenile western sand lance <i>Ammodytes japonicus</i> in Harima-Nada, eastern Seto Inland Sea, Japan

Hashiguchi Seiho, Nishikawa Tetsuya, Uozumi Kaori, Furusawa Kazushi, Mori Atsushi, Imao Kazumasa, Tanda Minoru

doi:10.34423/jsfo.85.1_24

Bibliographic Information

Other Title

播磨灘におけるイカナゴ当歳魚の胃内容物重量指数の経年的低下とその要因

Abstract

<p>It has been pointed out that the decline of western sand lance (Ammodytes japonicus) catch in Harima-Nada is mainly caused by food shortage. In this study, the stomach content index (SCI), condition factor, and prey composition of juvenile western sand lance collected in Harima-Nada in March were investigated from 1987 to 2018. The SCI decreased significantly from 1987 to 1997 and remained less than 1% after 2001. The condition factor also decreased significantly from 2001 to 2018. Main prey items of the juvenile western sand lance were the copepods Calanus sinicus and Paracalanus sp. throughout the investigation period, and the frequency of their occurrences did not change significantly before or after 2001. On the other hand, the dissolved inorganic nitrogen concentration in January and the chlorophyll a concentration from February to March showed a significant positive correlation, and the chlorophyll a concentration and SCI also showed a positive relationship. These results suggest that poor nutrient levels were responsible for low primary production, which was in turn a potential cause of low zooplankton production. As a result, the juvenile western sand lance possibly suffered from chronic food shortage in recent years.</p>

Journal

Bulletin of the Japanese Society of Fisheries Oceanography

Bulletin of the Japanese Society of Fisheries Oceanography 85 (1), 24-32, 2021-02-25

The Japanese Society of Fisheries Oceanography

Keywords

Details 詳細情報について

CRID: 1390293865789286144

DOI: 10.34423/jsfo.85.1_24

ISSN: 24352888; 09161562

Text Lang: ja

Data Source

JaLC

Abstract License Flag: Disallowed

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