紀伊水道におけるエビ類の水深別分布

Abstract

The vertical distribution and seasonal change of abundance of benthic shrimps and prawns were studied at six different depths between 10m and 60m in the Kii Channel around Tokushima Prefecture, Japan. Twenty-six species belonging to 16 genera of 11 families of shrimps and prawns were collected in 109 operations with small otter trawls from April 1988 to June 1991. Number of species for which more than 10, 000 individuals in total were collected was seven: Plesionika izumiae, Crangon consobrinus, Atypopenaeus stenodactylus, Parapenaeopsis tenella, Alpheus japonicus, Metapenaeopsis barbata and Trachypenaeus curvirostris. The total number of catches increased with depth from 10m to 60m. Numerically, P. izumiae ocurred most abundantly at 50-60m in depth which contained warm water mass from the Kuroshio while C. consobrinus at 10-30m was influenced by coastal water. P. izumiae increased owing to new recruitment from January to April and then decreased rapidly from April to July because of high fishing pressure. Cluster analysis based on the species similarity index indicated that the study area was divided into three zones: a nearshore zone (10-20m), a transition zone (30-40m) and an offshore zone (50-60m). Species diversity was high in the transition zone followed by the nearshore zone and low in the offshore zone.