# Sex- and Regio-Specific Lipid Profiling of Shishamo and Capelin Fish by Nontargeted Liquid Chromatography/Mass Spectrometry

## TL;DR

This study uses advanced lipid analysis to compare the lipid profiles of two fish species, focusing on sex and regional differences to help identify authenticity and nutritional value.

## Contribution

The study introduces nontargeted lipid profiling to reveal sex- and region-specific lipid markers in shishamo and capelin fish.

## Key findings

- Female S. lanceolatus heads have high triacylglycerol content similar to roe composition.
- Docosahexaenoic acid and eicosapentaenoic acid are enriched in female S. lanceolatus viscera.
- Monounsaturated fatty acids like FA 22:1 and FA 20:1 serve as markers to distinguish between the two fish species.

## Abstract

Shishamo smelt (Spirinchus lanceolatus), which is endemic to Hokkaido, Japan, is frequently substituted in markets with morphologically similar capelin (Mallotus villosus) imported from abroad. Lipids are essential nutrients that play important roles in fish authenticity, validation, and nutritional assessment. Although shishamo has long been consumed in Japan, its region-specific lipid distribution and composition are different from those of capelin and have not been well explored. To overcome these gaps, we used untargeted liquid chromatography–mass spectrometry to profile sex- and region-specific lipids in the Japanese S. lanceolatus and Nordic M. villosus. The results revealed that female S. lanceolatus heads exhibited high triacylglycerol (TAG) content, closely resembling roe composition. Docosahexaenoic acid and eicosapentaenoic acid were enriched in the female S. lanceolatus viscera. Multivariate analysis identified monounsaturated fatty acids, such as fatty acid (FA) 22:1 and FA 20:1, as robust discriminatory markers between S. lanceolatus and M. villosus. Overall, sex- and regiospecific differences in lipid composition between the two species were correlated and compared. These lipidomic signatures provide a basis for verifying species authenticity and geographic origin, while highlighting the nutritional lipid potential of S. lanceolatus, particularly from the female viscera.