Small scale distribution and transport of the Japanese anchovy, Engraulis japonica, larvae determined from a free-drifting buoy survey in Iyo-Nada, Seto inland sea [Japan]
1995
Fukuda, M. (Nansei National Fisheries Research Inst., Ono, Hiroshima (Japan)) | Hanamura, Y.
The small scale distribution and transport of the Japanese anchovy larvae was studied in Iyo-Nada, Seto Inland Sea, by tracking a free-drifting buoy attached with a radar reflector over a 48 hour period and the surface abundance of anchovy larvae monitored using a fish pump. The free-drifting buoy was released onto the surface water at midnight of 7 July 1993 and it moved counter-clockwise being transported westward along the edge of a cold water mass formed at the center of the research area. The traveling distance of he buoy over the 49 hour period totaled about 50 km. The anchovy larvae were collected by 5 minutes pumping at 12 positions at 6 hour intervals on a crossline which was established in relation to the position of the free-drifting buoy. The total number of larvae caught in the daytime was larger in number than at night throughout the two days. The mean standard length of larvae tended to decrease during the first 24 hours but then increased in the later 24 hours. The continuous samplings on the closslines revealed that the abundance of larval anchovy in the daytime were higher than at night, and noticeably high aggregations were encountered at two or more stations in the daytime, in contrast consistently low densities at all sampling points were found during the night series. This possibly resulted from the daytime aggregation and the night-time dispersion rather than any vertical migration
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