A total of 15 commonly occurring fish species have been recorded by the Trust whilst carrying out surveys across the Ness and Beauly catchments.
| Rivers and Lochs | Atlantic Salmon (Salmo salar) | Brown Trout (Salmo trutta) |
| Arctic Charr (Salvelinus alpinus) | Sea Lamprey (Petromyzon marinus) | |
| River Lamprey (Lampetra fluviatilis) | Brook Lamprey (Lampetra planeri) | |
| European Eel (Anguilla anguilla) | Pike (Esox lucius) | |
| European Perch (Perca fluviatilis) | Common Minnow (Phoxinus phoxinus) | |
| Transitional | Three-Spined Stickleback(Gasterostreus aculeatus) | Flounder (Platichthys flesus) |
| Coastal | Fifteen-Spined Stickleback (Spinachia spinachia) | Sprat (Sprattus sprattus) |
| Saithe (Pollachius virens) |
This list is by no means exhaustive, with other non-native salmonid species such as rainbow trout (Oncorhynchus mykiss) and American brook trout (Salvelinus fontinalis) having been introduced into a number of local lochs for fishery purposes. In addition to this, there are reports of coarse fish species such as roach (Rutilus rutilus) and carp (Cyprinus carpio) being present in Loch Ness and the Caledonian Canal system, although this is as yet unconfirmed. Other smaller lochs are also thought to contain carp and rudd (Scardinius erythropthalmus). These coarse fish species are outwith their natural range.