| Yakiboshi |
| Yale University Peabody Museum of Natural History, Connecticut |
| yard seine |
| yawling |
| year brood |
| year class |
| year mark |
| year-class |
| yearling |
| yellow cure |
| yellow fish |
| Yellow Sea (Hwang Hai) |
| yield |
| yield-per-recruit |
| yield-per-recruit analysis |
| Yokosuka City Museum |
| yolk |
| yolk ball |
| yolk cell |
| yolk diameter |
| yolk extension |
| yolk granule |
| yolk plug |
| yolk sac |
| yolk sac larva |
| yolk stalk |
| yolk stripe |
| yolk-sac |
| yolk-sac larva |
| yolk-sac placenta |
| yolk-sac viviparity |
| York College , Pennsylvania |
| young |
| young-of-the-year |
