Shag Island is a low island located at the mouth of Fisherman Bay in Spencer Gulf, South Australia.

[2] It is uninhabited by humans but is home to thousands of cormorants which roost and breed there.

[3] In April 2013, the discovery of several sick and dead cormorants near Fisherman Bay raised public concerns for the health of the Shag Island colony.

[4] The discovery coincided with significant fish and dolphin mortality events around the state, mostly concentrated in Spencer Gulf and Gulf St.

[5] The following birds have been recorded at Shag Island: great cormorant, little black cormorant, pied cormorant, little pied cormorant, red-necked stint, sharp-tailed sandpiper, red-capped plover, banded stilt, bar-tailed godwit, grey plover, common greenshank and masked lapwing.