Fish belong to vertebrates like human, and small fish like zebrafish and medaka (Fig. 42.1) are often used as model organisms for basic biology such as developmental biology and genetics, as well as for medical sciences related to human diseases [1, 2]. The advantages of small fish reside in the ease of genetic manipulation and the availability of a wide range of strains, including wild, mutant, transgenic, target induced local lesion in genome (TILLING) strains, and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) strains. In Japan, the collection, preservation, and provision of small fish species are being carried out by the National BioResource Project. In the field of glycoscience, the importance of glycolipids and glycoproteins in fertilization, development, and neurogenesis is being well studied [3, 4]. On the other hand, the usefulness of small fish as model organisms for diseases such as muscular dystrophy is also recognized [5]. While zebrafish research is numerous worldwide, an increasing number of research using medaka which has been established as an experimental animal in Japan are also prominent. Thus, it is believed that the importance of both fish species as research targets in the field of basic biology and medical sciences of glycans will be more recognized in the future.