Rusik the cat was recruited by police at a checkpoint in the Stavropol region, bordering the Caspian Sea, to uncover illegal cargoes of the endangered fish.

Police believe it was a contract killing, Russian Ren television reported.

The cat was hit by a car in which he had found smuggled sturgeon some time before, the station reported.

Sturgeon have been poached to the brink of extinction

The feline crime fighter walked into a police checkpoint a year ago as a stray kitten. The staff quickly adopted it, feeding it on scraps of fish confiscated from smugglers.

Rusik soon proved a formidable weapon. Staff said no matter how ingenious the smugglers were in their attempts to hide the fish, Rusik was always able to point his nose in the right direction and find it.

Areas bordering the Caspian Sea are plagued by poachers keen to cash in on stolen sturgeon, whose roe is the delicacy caviar, which sell for huge sums in Moscow and other cities.

An estimated 95% of the world's caviar comes from the Caspian Sea and this lucrative market has meant that the sturgeon has been hunted to the brink of extinction.