Occurrence of the pelagic shrimp Pasiphaea japonica (Decapoda: Pasiphaeidae) in gut contents of demersal predators in a submarine canyon (Toyama Bay, Japan)

Abstract

The purpose of present study is to clarify the predation of P. japonica including larvae by investigating guts of predators caught as a by-catch in the P. japonica fishery. The by-catch, including fish, cephalopods and decapods, were caught once or twice a month between April and November 2008 in a submarine canyon adjacent to the mouth of the Jinzu River in Toyama Bay. Size of the potential predators was measured and the gut contents were identified to the lowest possible taxa. Ostracods, copepods, mysids, cumaceans, amphipods, euphausiids, and decapods were the most common prey in the gut contents of the predators. Pasiphaea japonica, including larvae before metamorphosis, were preyed upon by demersal fishes Crystallichthys matsushimae, Lycodes nakamurae, and Bothrocara hollandi. Occurrence of P. japonica in the guts of these predators may be due to the aggregation of larvae in the canyon head which is enclosed by the steeply sloping bottoms and the truncation of the vertical migration of P. japonica from the pelagic to the benthopelagic environment.