More than 20,000 dead fish and other marine life have washed up on a beach in Canada, in what experts described as a 'perplexing' occurrence.

Fisheries and Oceans Canada said it was investigating the incident, which occurred at Savory Park in southwest Nova Scotia, although it is not yet clear what caused the fish and other sea animals to die.

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DFO said at a press briefing reported by CBS News: "It's perplexing. We've gone through our 'usual suspects'. But we're not stumped yet. We're still actively investigating."

However, the department did clarify the dead fish, lobsters, starfish, crabs and other animals were not thought to be linked with the dead, decomposed whale that washed up at Digby in Nova Scotia, and said the Herring found by authorities had been dead for around 4-5 days prior to being discovered.

Environmental workers are currently carrying out tests to determine what was responsible for the fishes' deaths, with water pollution and oxygen levels considered as two possible causes, although thus far the investigations are believed to have suggested the cause is not environmental, the department tweeted.

While investigations are being carried out, consumers are being told to use only authorised vendors when purchasing fish and other seafood, CNN reported.

In a tweet, the Fisheries and Oceans department said: "Dead fish found on shore should not be collected by general public. Consumers should only purchase from licensed harvesters/sellers."

Numerous fish and seas creatures have been washing up dead on Nova Scotia beaches over the past month, with no clear explanation as to what is causing them to die.