"At this point we are in very early stages of our inquiries and are appealing to the public to report any activity that could have contributed to the dead snapper," MPI said in a statement.
"We are very thankful to members of the public for contacting MPI."
Anyone with information about this incident - or any other suspicious fishing activity - is urged to call 0800 4 POACHER line (0800 47 62 24) or email ncc@mpi.govt.nz to report it.
The incident follows the death of thousands of mackerel last month, with the dead fish found washed up across the shores of Kawau Island.