Dictionary of Ichthyology  

nest = a structure created for housing eggs and sometimes young, usually involving some cleaning or grouping of materials such as gravel or weeds, e.g. in Gasterosteidae and many Cichlidae.

Nest of Amia calva from Lydekker et al. "Reptiles, Amphibia, Fishes and Lower Chordata", 1912.  Photograph by Brian W. Coad.

Canadian Museum of Nature