Reports of hypoxic conditions (oxygen <1.5 ml L−1) off the U.S. west coast over the last two decades led us to investigate hypoxia in the Southern California Bight (SCB) and its potential impacts on fisheries. The secular trend in hypoxia in the SCB over the last 57 years is not monotonic, and reversed trend in the mid-1980s, bringing oxygen concentrations back to levels measured in the late 1950s to early 1960s. Thirty-seven percent of the rockfish (Sebastes spp.) habitat in the Cowcod Conservation Area at 240–350 m depths suffers exposure to hypoxia in the summer of normal years. If current trends in shoaling of low oxygen water continue for another 20 years, rather than reversing as happened previously, we predict loss of 18% of the habitat with 55% of the total habitat exposed to hypoxia.