A Field Study of Predation of the Hyperiid Amphipod Parathemisto japonica on Larvae of the Japanese Sand Eel Ammodytes personatus

Abstract

A field study was carried out from January to April in 1981 and 1982 to estimate the effects of predation of the hyperiid amphipod Parathemisto japonica on larvae of the Japanese sand eel Ammodytes personatus in waters off the northeastern coast of the main island of Japan. The degree of vertical co-occurrence was similar during the day and at night and P. japonica fed on the larvae throughout the day. Overlap of the horizontal distributions of the two species increased from January to April. The proportion of sand eel larvae in the total stomach contents of P. japonica varied monthly in the range of 0-8.2% on a dry weight basis. The density of sand eel larvae decreased more markedly in the area where P. japonica occurred in greater abundance. Preliminary estimates of the rate of daily loss of sand eel larvae caused by the predation yielded figures of 0.1% for January, 3.3% for February, 2.8% for March, and 45.2% for April, closely associated with changes in the size and degree of overlap of distribution of the two organisms.