Since his early teenage years in the 1990s, Yusuf Usman has drawn his livelihood from the waters of Lake Chad in his hometown of Baga, northeastern Nigeria. He recalls a time before the Boko Haram insurgency hit hard, when he would cast a net and return home with a heavy catch to feed his family and sell at the market. Today, the 41-year-old said that those bountiful days are long gone. But he refuses to abandon his net and continues to wade int…