Occurrence of Predation of Juvenile Chum Salmon (Oncorhynchus keta) by Chub Mackerel (Scomber japonicus) and Spotted Mackerel (Scomber australasicus) in Miyako Bay, Iwate Prefecture, Japan

Authors

Kei Sasaki, Miyako Field Station, Fisheries Technology Institute, Japan Fisheries Research and Education Agency (FRA), Miyako, Iwate 027-0097, JAPANFollow
Miwa Yatsuya, Miyako Field Station, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Miyako, Iwate 027-0097, JAPAN
Daisuke Shimizu, Yokohama Field Station, Fisheries Technology Institute, Japan Fisheries Research and Education Agency, Yokohama, Kanagawa 236-8648, JAPAN
Daisuke Ojima, Miyako Field Station, Fisheries Technology Institute, Japan Fisheries Research and Education Agency (FRA), Miyako, Iwate 027-0097, JAPAN
Shinji Komatsu, Nemuro Salmon Hatchery Station, Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Shibetsu, Hokkaido 086-1109, JAPAN

Abstract

In recent years, chub mackerel (Scomber japonicus) and spotted mackerel (Scomber australasicus) have started migrating to the coastal areas off Iwate Prefecture earlier than they did previously, resulting in a geographic overlap between hatchery-bred juvenile chum salmon (Oncorhynchus keta) released at sea and the occurrence of predatory mackerel. To clarify whether the mackerels prey on the juvenile chum salmon, we captured adult mackerels by angling during the period when these species overlap in Miyako Bay, Iwate Prefecture. After capture, the stomach contents of the mackerel were examined using a combination of visual examinations and DNA metabarcoding analysis. As a result, chum salmon were identified in the stomachs of 4 of 97 chub mackerel (May 19), 5 of 30 chub mackerel, and 1 of 7 spotted mackerel (May 26), providing the first evidence of chum salmon predation by mackerels. When the fork length of chum salmon prey was inferred based on otolith measurements, the results showed that the prey items ranged in size from 54.3 mm to 86.9 mm. These findings indicate that the body-size range of the chum salmon that were targeted by mackerels spans that of hatchery-released chum salmon.

Recommended Citation

Sasaki, Kei; Yatsuya, Miwa; Shimizu, Daisuke; Ojima, Daisuke; and Komatsu, Shinji (2023) "Occurrence of Predation of Juvenile Chum Salmon (Oncorhynchus keta) by Chub Mackerel (Scomber japonicus) and Spotted Mackerel (Scomber australasicus) in Miyako Bay, Iwate Prefecture, Japan," Journal of Marine Science and Technology: Vol. 31: Iss. 4, Article 15.
DOI: 10.51400/2709-6998.2722
Available at: https://jmstt.ntou.edu.tw/journal/vol31/iss4/15