Remarks on Fixing and Preservation of Stomach Contents

Contents of the first stomach of sperm whale caught off Hokkaido. (Photo by T. Tamura, Research Institute of Cetacea)

The mantel in the center is identical to Moroteuthis robusta.

Click on the image to get a lager view.

　 Samples for stomach contents analysis are brought into the laboratory as a whole body of predators or only predator stomachs . from the body. They are under deeply frozen or preserved in formalin.

For frozen samples, biological measurements (body length, body weight etc.) should be achieved after thawing and the stomach is cut out from the body pinching both ends tightly and measured weight with contents. Then, contents are removed from the stomach rinsing stomach wall carefully, and empty stomach is measured again. Stomach contents weight (SCW) is deduced subtracting the empty stomach weight from the whole stomach weight.
Stomach contents are sorted into possible groups, i.e. fresh fish, fresh cephalopods, fresh zooplankton, digested fish tissue, digested cephalopod tissue including buccal mass, fish otolith, and cephalopod beaks and statoliths. Fresh and half digested tissues are preserved in formalin (about 10%). Fish otolith and cephalopod statolith must be stored in alcohol (70% of ethyl alcohol, 40% of isopropyl alcohol). Beaks are also recommended to store in alcohol.

Samples which were preserved in formalin in the fields, it is better sorted otolith and statolith as soon as possible and transfer them into alcohol due to decarboxylation of formalin solution.

Do not forget putting a water-proof label which records predator, size, weight, sex, sampling date, sampling methods, locality, etc in each of storing bottles.

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