Several walkers spotted the sea creatures at the high tide mark from Christmas eve, as well as what are believed to be orange jellyfish.
Regional co-ordinator for the Sea Watch Foundation Stephen Savage said it was hard to be sure exactly why they had been washed up, but that the recent stormy weather was probably partly to blame.
He said starfish gathered on the seabed and rough seas often brought a lot of material up to the surface.
“It could have been incidental,” he said. “We do tend to get larger creatures washed up at this time of year because we get the storms.
“But nobody has come up with any conclusive evidence for why it’s happening.
“Certainly after any big storm we find whelks and crabs washed up, and we have had quite a succession of stormy weather, which is obviously playing a part in it.”
Similar scenes were witnessed in December 2008, when a porpoise was washed ashore just East of Lancing Sailing Club, along with hundreds of starfish, crabs, a stingray and a dogfish.
Bad weather was blamed for the animals’ deaths, although trawler fishing was not ruled out.
WADARS’ senior animal rescue officer Billy Elliott said there was a large colony of starfish living near Shoreham Harbour, and that he suspected the weather was to blame.