It is only known from the Monte Bolca deposits in Italy, and was likely restricted to shallow, tropical waters of the Tethys Ocean.

[1][2] The existence of Blochius was known as early as 1709, where it is mentioned in a written account by Johann Jakob Scheuchzer, who identified a fragment of a Blochius skeleton and identified it as being either related to the Xiphias (swordfish) or Siluro (catfish).

[3] It is one of two known definite genera in the family Blochiidae, alongside Loancorhynchus from earlier in the Eocene of Chile.

[4] The indeterminate remains of a Blochius-like fish are known from the Late Paleocene of Peru.

[2][8][3] Some authorities have found the Blochiidae to be basal billfish not closely related to any extant groups, whereas others find them to be more closely related to swordfish (Xiphiidae) than to marlins & sailfish (Istiophoridae).