Pearling in Western Australia includes the harvesting and farming of both pearls and pearl shells (for mother of pearl) along the north-western coast of Western Australia. The practice of collecting pearl shells existed well before European settlement. Coastal dwelling Aboriginal people had collected and traded pearl shell as well as trepang and tortoise with fisherman from Sulawesi for possibly hundreds of years. After settlement, Aboriginal people were used as slave labour in the emerging commercial industry in a practice known as blackbirding. Pearling centred first around Nickol Bay and Exmouth Gulf and then around Broome, to become the largest in the world by 1910. The farming of cultured pearls remains an important part of the Kimberley economy, worth million in 2014 and is the second largest fisheries industry in Western Australia after rock lobster. Pearls were first gathered in Western Australia by Aboriginal Australians. The European pearling industry began in the 1850s at Shark Bay where pearls (called the 'Oriental, or Golden' Pearl) were found in the Pinctada albina oyster in relatively large numbers. The industry soon folded however. At Nickol Bay, decorative pearl shells (Riji) made by local Aboriginal people from Pinctada maxima, were noted by Europeans. The industry began in the mid-1860s with pastoral workers who collected shell in shallow waters, either from shore or in small boats. During the late 1860s many more boats left Fremantle and the pearling industry at Torres Strait, Queensland for the new fishery at Nickol Bay with its port of Tien Tsin Harbour (later known as Cossack). While Broadhurst and a few other proprietors experimented, during the 1860s, with the use of breathing apparatus by professional divers, it proved at the time to be expensive, unreliable and dangerous. While local Aboriginal people were excellent swimmers, known to have covered great distances over water, sometimes to escape imprisonment, unlike their counterparts in some other parts of Australia they had no cause to dive in conditions where the tidal range provided all they needed.