Quality evaluation must focus on sensory standards and cold chain integrity. For fresh fish, ensure clear, bulging eyes, bright red gills, and firm flesh that springs back when pressed. For frozen products, check for the absence of freezer burn (white patches) and ensure the glazing percentage (ice coating) is within the agreed 5-10% range to prevent dehydration. Always request Third-Party Inspection (TPI) reports from agencies like SGS or BV to verify histamine levels, TVB-N (Total Volatile Basic Nitrogen) values, and the absence of heavy metals like mercury or lead.