Natural spawning beds of herring [Clupea pallasii] in the Rumoi district [Japan] along the coast of northwestern Hokkaido from 1998 to 2001

• Published in: Scientific Reports of Hokkaido Fisheries Experimental Station (Japan) no. 62
• Main Authors: "Akaike, S. (Hokkaido. Wakkanai Fisheries Experiment Station (Japan)), Tada, M, Takiya, A, Imai, Y, Nabata, S, Yoshimura, K, Kiyokawa, S, Mizuno, K, Kawai, W.
• Format: Journal Article
• Language: Japanese
• Published: 01.03.2002
• Subjects: CLUPEA; JAPAN; SEA OF JAPAN; SEAWEEDS; SPAWNING GROUNDS
• ISSN: 0914-6830

"Natural spawning beds of herring (Clupea pallasii) were investigated along the Rumoi coast, Hokkaido, Japan from 1996 to 2001. Seven spawning beds were found at seaweed beds shallower than 2m deep from 1998 to 2001. Milky-white turbidity of the sea surface due to herring spawning was observed in three times (Reuke in 1999, 2001 and Onishika in 2001). Estimated total number of eggs ranged from 84.5*l0E6 to 263.1*l0E6 average egg density ranged from 10834 to 571000/square m, and maximum egg density ranged from 176*l0E3 to 2.5*l0E6/ square m Species of seaweeds attached with the large number of eggs were Phyllospadix iwatensis, Sargassum confusum, and Coccophora langsdorfif. Daily average of water temperature during spawning periods ranged from 2.8 to 4.71degC. Spawning bed salinity in these periods was diluted and fluctuated due to melting snow. On spawning days, it was calm with the character of low wave height, low wave velocity, easterly winds, and cloudy sky. Spawning herring schools were belived to approach spawning beds from offshore through sea-floor trenches."