Unnamed fish
The following is a list of unnamed fish.

Archer IV fish

Some eel-like fish were seen swimming in a lake on Archer IV. ()

Ba'ku fish

A blue fish was seen swimming past Data in the Ba'ku lake. ()

Cardassian fish

The skeleton of a huge Cardassian fish was displayed on Deep Space 9's promenade. ()

Cetacean Institute fish

Several different species of fish were seen in large aquariums in the Cetacean Institute in Sausalito. ()

Enterprise-D aquarium fish

Captain Jean-Luc Picard's quarters aboard the  contained an aquarium full of colorful tropical fish. () Similar aquariums were also present in the guest quarters of Doctor Paul Stubbs, () and the quarters of Counselor Deanna Troi. ()

Hima fish

A species of small fish swam in the lakes of the planet Hima. The fish had blue-and-black or orange-and-black stripes, with four appendages extending from the rear of the animal matching the blue or orange stripes. In 3188, a school of these fish were spooked when Cleveland Booker and Michael Burnham were transported into the water. ()

K'Tuevon Prime eel

A tank full of eels was present at Imperium Magistrate Clar's history stone etching party on K'Tuevon Prime in 2380. Guests who displeased him were put into the tank, which was known as the Tank of Contempt. ()

Qualor II fish

The Ferengi Omag had a very large fish for dinner in a bar on the planet Qualor II. ()

Trill fish

A species of flying fish swam in the ponds of the planet . The fish had orange skin. In 3189, several of these fish were swimming in and flying over a pond near the Caves of Mak'ala when Michael Burnham and Adira Tal visited the planet. ()

The Waters marine life 
 
This marine lifeform was encountered under the surface of "The Waters" at a depth near 600 kilometers. The creature, which was likened to the electric eel found on Earth, was significantly larger and more powerful that the Earth counterpart, as it emitted biothermic discharges that exceeded 500,000 volts. ()

Xyrillian fish

A large  on the Xyrillian starship had eel-like creatures swimming in a liquid within it. ()