H5 bird flu has been detected in a Southern elephant seal and a kelp gull on Macquarie Island.
The detection is the first recorded case of the virus in a marine mammal in Tasmania.
Island staff collected samples from the two animals and brought them back for testing, which came back positive, Environment Minister Guy Barnett said.
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As of Wednesday, Tasmania had recorded 50 bird flu events, with four new detections confirmed since October 7.
An event is one or more confirmed cases at the same location.
The latest positives were a Pacific gull at St Helens, a greater crested tern at Bridport, a little penguin at Cooee and a black currawong on Flinders Island.
There have been no detections in commercial poultry or backyard flocks and no mass bird deaths in Tasmania.
Barnett urged people to keep reporting sick or dead birds, saying these reports help authorities find and respond to cases.
People should avoid touching sick or dead birds.
Sightings can be reported by calling the emergency animal disease hotline on 1800 675 888.
