Fishermen on Sierra Leone's Sherbo Island (a coastal community roughly 120km south of the capital, Freetown) say their catches have dropped by around 40% in recent years, blaming large foreign trawlers — overwhelmingly Chinese, according to campaigners — that allegedly enter a protected seven-mile exclusion zone at night, cutting local nets and damaging small vessels. West Africa is estimated to account for 40% of the world's unlicensed fish catch, costing the region some $10 billion annually in lost revenues and threatening the food security of millions. Sierra Leone's government insists the problem is improving through mandatory vessel tracking and financial penalties, but critics say enforcement is negligible and that Beijing must do far more to rein in its distant-water fleet.