Others believe that slavers had a vested interest in capturing rather than killing, and in keeping their captives alive; and that this coupled with the disproportionate removal of males and the introduction of new crops from the Americas (cassava, maize) would have limited general population decline to particular regions of western Africa around 1760–1810, and in Mozambique and neighbouring areas half a century later. There has also been speculation that within Africa, females were most often captured as brides, with their male protectors being a "bycatch" who would have been killed if there had not been an export market for them.