What visual cue in pre-packaged fish trays indicates deterioration or inconsistent chilling?

Significant amounts of milky liquid or 'weeping' collecting beneath the fish

When examining fish sold in supermarket packaging, the fluid visible within the tray offers vital clues about its handling history. If there is a substantial collection of milky liquid, often referred to as 'weeping,' pooling beneath the fillet, this is a strong indicator of quality degradation. This liquid is a mixture of natural moisture and cellular fluid leaking out, which occurs when the required consistent chilling process has been interrupted or when the fish itself is beginning to break down. The superior visual indicator for proper packaging is the presence of a thick layer of clean ice placed directly underneath the product.