In early November the fish died at the Tropical House (Tropenhaus) tourist attraction after pumps and air tanks broke down due to overheating, the ATS news agency reported on Wednesday.
The Tier im Recht foundation, a legal group based in Zurich, said the case may involve a possible breach of Switzerland’s law for the protection of animals.
It has called for the incident to be investigated.
The Tropical House, which raises Siberian sturgeon to produce caviar, said the technical problems have been fixed.
The institution, opened to the public in 2009, is billed as an award-winning showcase for renewable energy in the Alps.
It uses warm (20-degree) water that naturally flows from the mountain near the Lötschberg base tunnel to not only breed fish but to grow tropical fruit in greenhouses.
The production facilities to breed the sturgeon were developed in collaboration with the Centre for Fish and Wildlife Health at the University of Bern, the company says on its website.
With two restaurants, the Tropical House is advertised as an attraction for visitors by Switzerland Tourism.