The quality changes during frozen storage of two underutilized species of fish: mackerel (Scomber scombrus), a fatty species, and white hake (Urophycis ten&), a nonfatty, gadoid species, with or without a bag, vacuum, and/or erythorbic acid, were measured using the dimethylamine (DMA) test for hake and the thiobarbituric acid (TBA) test for mackerel, and by Instron deformation, expressible moisture, thaw drip, cook loss, and sensory evaluation for both species. Texture deterioration and lipid oxidation limited the shelf-life of hake and mackerel, respectively. Air (oxygen) prolonged the shelf-life of hake but lessened that of mackerel. Erythorbic acid accelerated the rate of texture deterioration in hake but inhibited the rate of lipid oxidation in mackerel.