Thousands more dead or dying shellfish have washed up on a beach on the same stretch of coast that saw a number of crustacean die-offs in autumn 2021 and last year. Visitors to Saltburn-by-the-Sea, a few miles south-east of the River Tees, were met by the sight of hundreds of thousands of dead mussels on the shoreline, as well as starfish, crabs and razor clams. Stuart Marshall, 58, who owns beach huts on the promenade, was mounting a clean-up on the sands. He said: “It’s devastating. There’s starfish dead, clams, oysters and crabs.” He questioned one possible official explanation that rough seas had killed the creatures, as he said the waters had recently been calm. Helen Whitworth, from Northallerton, North Yorkshire, was walking her border collie Drako on the beach. She said: “There’s all sorts of debris here. I’ve come down for a lovely walk with the dog and it’s such a shame to see all of this today.” There was confusion over a large deposit of black debris, which some said was sea coal, a type of coal that periodically washes up on the beach. Marshall, who has run the huts for almost seven years, said he did not believe the particles were coal, adding: “We do get bits of coal from time to time but not anything like this.” The Environment Agency said its experts concluded the wash-up was “a natural event” and “normal for this time of year”. A spokesperson said: “We can confirm the black substance washed up on the beach is coal deposit, which is not unusual for this stretch of coastline. This is likely to be in the intertidal system for a while given recent weather conditions, so may continue to happen in the coming weeks and months. “Creatures like starfish, razor clams and mussels occupy similar rocky habitat and are easily dislodged during storm events. And the physiology of juvenile flounder makes them vulnerable to being stranded on shallow gradient beaches such as Saltburn. “While we know people are concerned, the combination of recent heavy swell, spring tides and onshore winds means natural wash-ups will occur more often.” The mass die-off on the north-east coast in late 2021 prompted a series of investigations. In January this year, a panel of independent experts convened by the Department for Environment, Food and Rural Affairs concluded: “A novel pathogen is considered the most likely cause of mortality.” However, the panel was “unable to identify a clear and convincing single cause for the unusual crustacean mortality”. Some campaigners have feared that dredging for a new freeport on the Tees was linked to the die-off, but the Tees Valley mayor, Ben Houchen, has strongly disputed those claims.