Dietary preferences of the Japanese mitten crab Eriocheir japonica in a river and adjacent seacoast in north Kyushu, Japan

Abstract

Abstract:The diet of the Japanese mitten crab Eriocheir japonica was investigated by examining the stomach contents of middle-and large-sized crabs (carapace width Ͼ10 mm). Crabs were collected in the freshwater area (growth area), tidal river, and seacoast area (reproductive area) of the Saigo River, Fukuoka Prefecture, Japan. Analysis of the diet of E. japonica was carried out using the frequency of occurrence and percentage point methods. The stomach contents were classified into 4 large and 27 small categories. It was evident that E. japonica was an omnivore and a deposit feeder, mainly feeding on the detritus derived from vascular plants growing along the river channel. Filamentous algae Cladophora sp., aquatic insects (e.g., Chironomidae), sediments such as mud or sand, and artificial products such as plastic or yarn were often found, suggesting that E. japonica mainly feeds on detritus lying on the substrate without sorting well. Stomach contents of adult crabs in the tidal area exhibited higher frequency of animal materials (i.e., fish, gastropods, and crabs) than those of young and adult crabs in the freshwater area, suggesting that adult crabs in the tidal area eat more animal materials. Such an omnivorous feeding habit is similar to other related brachyuran crabs (grapsoidae) and may be one of the important factors which enables E. japonica's wide distribution along the river and seacoast.

Feeding behaviour, predatory functional responses and trophic interactions of the invasive Chinese mitten crab (Eriocheir sinensis) and signal crayfish (Pacifastacus leniusculus)

“…The importance of periphyton in the diet of mitten crabs has been reported previously (e.g. Czerniejewski et al ., for Chinese mitten crab, Kobayashi, for Japanese mitten crab), and although crayfish may graze directly on periphyton, they are inefficient consumers compared to gastropod grazers (Nyström, ). Gastropods in the sympatric treatment were reduced by an intermediate amount relative to the allopatric treatments; hence, the observed increase in periphyton may reflect reduced grazing pressure.…”

Dietary preference of the potamid crab Geothelphusa dehaani in a mountain stream in Fukuoka, northern Kyushu, Japan

“…The frequency of predation on live animals is very low, especially during the juvenile stage (river phase). Thus E. japonica is a detritus food web member functioning as a shredder that decomposes large detritus (CPOM, coarse particle organic matter) into small particles (FPOM, fine particle organic matter) (Kobayashi 2009). In the upper regions of rivers (mountain streams), large crabs with large chelipeds (CW>50 mm) are distributed in the deeper underwater areas of the main stream (Kobayashi & Matsuura 1991), and predation on this species by other animals is considered to be low.…”

“…A previous study of stomach content analysis investigated the feeding preference of Eriocheir japonica (de Haan), the Japanese mitten crab (Kobayashi 2009). This catadromous varunid crab is widely distributed along the course of rivers in Japan, and often coexists with G. dehaani in the upper regions of rivers (mountain streams).…”

A freshwater crab (Barytelphusa sp.) feeding on a catfish (Pterocryptis sp.)

“…This species is commonly collected as a food commodity and is also often reared in captivity for the same purpose (Padghane et al 2016). In captivity, these crabs seem to prefer animal-based food (Kobayashi 2009) and are generally fed about 10% of their total biomass in prawn and rice flakes daily (Padghane & Chavan 2018b). Observations of B. cunicularis feeding in nature are scant in the literature, and to the best of my knowledge there have not been any reports of the species feeding on fish.…”