Thousands of dead fish floating in Marina del Rey harbour in Los Angeles

The dead stingrays, anchovies, and octopi caused a stench in the harbour

Thousands of dead fish wash up along boat slips at the Marina Del Rey (AP Photo/Nick Ut)

Clean-up crews began scooping dead fish from a marina in Southern California on Monday, after tens of thousands of the creatures appeared in the water.

The piles of dead anchovies, stingrays and octopi caused a pungent smell and a feeding frenzy among the seals, pelicans and seagulls local to the harbour.

State officials believe the fish died due to a lack of oxygen.

Six tons of dead fish, filling 300 bags, have already been removed by wildlife workers from Marina del Rey, Sky News reported.

It is most likely that the animals had fled into the harbour to escape a predator when they became starved of oxygen in the water, marine biologists told the broadcaster.

A recent heat wave was considered as possible reason for the deaths, but this idea was later rejected.

Dead fish at Marina Del Rey (AP)

Similar scenes were last seen in the area in 2011, at Ventura Harbor and at Redondo Beach, according to the broadcaster.