Nearly 30 transient orcas were spotted in the Salish Sea around British Columbia and Washington state over the Labor Day weekend, a positive sign for the species, according to local whale watchers and researchers.

The most common pod of southern resident killer whales who migrate to the Salish Sea during the summer have not been seen for than 100 days, marking a highly unusual absence from their historic summer hunting ground, according to researchers.

Southern resident killer whales which are often spotted in the Salish Sea near Vancouver throughout June haven't been seen this season, and scientists believe that could be because of the lack of chinook salmon.

Researchers say their absence is a stark reminder that the orcas are slowly starving to death because there is not enough Chinook salmon to sustain them.

The population of endangered killer whales has hit a 30-year-low, numbering only 75 this year.