Fishes (pisces) are a very heterogeneous group of vertebrates that primarily live in water. The Ichthyological Collection comprises approximately 133,490 specimens, including approximately 50 % of more than 29,000 named species. The specimens include 1,100 fish skeletons, 1,750 dry specimens and fish skins and 130,640 fish preserved in ethanol.

It is a medium-sized collection, but the abundance of historic specimens from all over the world makes it a unique collection in Germany, and it is a major international reference for taxonomic and biogeographical research.

The oldest and historically most valuable parts of the collections are the collection by Marcus E. Bloch (1723–1799) and some preserved fish specimens from Peter S. Pallas (1741-1811). Both collections were compiled in the late 18th century.

The collection also houses specimens from the Friedrich W. Hemprich (1796-1825) and Christian G. Ehrenberg (1795-1876) North African expedition of 1820-1825, many preparations from Johannes Müller’s anatomy collection. Johannes Müller (1801-1858) is considered to be the founding father of modern zoological systematics. Many fishes were caught during the Valdivia German deep sea expedition. The Valdivia expedition was the first German marine research expedition driven by a zoological-scientific interest. It yielded a plethora of insights into deep sea organisms and habitats.

More recent, comprehensive additions to the collections come – among other places – from the Institut für Hochseefischerei in what was East Germany.