[H-TT16] Development and application of environmental traceability methods

[HTT16-P08] Stomach Contents and Stable Isotopes Reveal Dietary Shifts in Red Snow Crabs Across Body Sizes in Toyama Bay

*Takashige Mikami¹, JING ZHANG¹, Masahiro Sanga², Osamu Inamura³ (1.University of Toyama, 2.Toyama Prefectural Fisheries Research Center, 3.Uozu Aquarium)

Keywords:red snow crab, Toyama Bay, stomach contents, carbon and nitrogen stable isotopes

This study investigates the feeding habits of Chionoecetes japonicus (red snow crab), a key fishery resource in Toyama Bay, by analyzing stomach contents and stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N). In July 2024, a total of 136 crabs were collected from depths of 1,100 m in central Toyama Bay. Of these, 81 crabs were examined for stomach contents, and 59 crabs were subjected to isotope analysis. The stomach contents analysis revealed that crabs with a carapace width (CW) of ≦20 mm predominantly consumed gastropods, while those with CW >60 mm exhibited a shift towards a fish-based diet. Isotopes analysis supported this finding, showing a gradual increase in δ¹³C and δ¹⁵N with growth, indicating a progressive change in diet. Furthermore, surface fish were identified as the primary food source for red snow crabs, with minimal contribution from deep-sea fish. These findings highlight the importance of understanding the dietary shifts in red snow crabs for effective resource management and recovery, especially following environmental disturbances such as The 2024 Noto Peninsula Earthquake.