Gudgeon and Percoid fish

Gudgeon noun - Small spiny-finned fish of coastal or brackish waters having a large head and elongated tapering body having the ventral fins modified as a sucker.

Percoid fish and gudgeon are semantically related. In some cases you can use "Percoid fish" instead a noun "Gudgeon".

Percoid fish noun - Any of numerous spiny-finned fishes of the order Perciformes.

Gudgeon and percoid fish are semantically related. Sometimes you can replace term "Gudgeon" with "Percoid fish", this terms are similar.