This is a list of fish species found in different parts of the River Lagan. They do not necessarily appear at the same time of year or share the same habitat. There are likely more species than those listed below. In the brackish water near the river’s mouth, several species of saltwater fish can also be found.
- Salmon – Salmo salar
- Sea trout – Salmo trutta
- Perch – Perca fluviatilis
- Bream – Abramis brama
- Chub – Blicca bjoerkna
- Pike – Esox lucius
- Zander – Sander lucioperca
- Rainbow trout – Oncorhynchus mykiss
- European flounder – Pleuronectes platessa
- Eel* – Anguilla anguilla
*Note: Eels are endangered and fishing for them is prohibited in the Lagan FVO (Fishing Conservation Area).