Jim Atchison, chief executive officer for SeaWorld Entertainment, is to step down from his role, effective from 15 January 2015.

Atchison and SeaWorld have been under immense pressure in recent months, with the anti-SeaWorld documentary Blackfish causing a raft of problems including lagging attendance, tumbling share value and loss of corporate sponsors.

Atchison had operated as CEO since 2009. David D’Alessandro will take over as interim chair in January, until a permanent replacement is found.

In the wake of Atchison’s announced departure, 311 more workers have been released across SeaWorld’s 11 parks and its headquarters, according to a company spokesperson. Following Atchison’s departure, SeaWorld is expected to make US$50m (€40.2m, £32m) worth of cuts in total, with more job losses expected to its 25,000-strong workforce.

Atchison is to become vice chair for SeaWorld and will continue to consult on the company’s international expansion.