Nondestructive method of estimating dry matter content in pereiopods of snow crab Chionoecetes opilio and red snow crab Chionoecetes japonicus (Decapoda: Oregoniidae) using a near-infrared spectrometer

The commercial value of snow crabs and red snow crabs is low immediately after molting due to low meat quantities and soft shells. As time passes, the meat content and shell hardness increase, making them more valuable. In Japanese market, male snow crabs are arbitrary divided into soft and hard shells. Previous studies also categorized crabs soft-shell and hard-shell arbitrarily and compared the quality between the two groups. A durometer and a penetrometer have been used to determine the shell hardness in the stock management of the snow crab and the red snow crab, but they destroy the crab shells. In the present study, we developed a new non-destructive technique using a portable near-infrared spectrometer to evaluate the dry matter content of pereiopods, which were correlated with the shell hardness. The cheliped was found to be sufficient for measurement in both species, providing a wider range of values and higher precision than the first walking leg. This non-destructive technique would be valuable for assessing both commercial value and the approximate time since the terminal molt of snow crabs and red snow crabs.