Fish larvae performance during the mesocosm experiment in the Peruvian upwelling system near Lima from February-April 2020. Light (ambient = high vs. reduced = low) was manipulated from the beginning (day 0) and upwelling (0 to 60% deep water addition) two weeks into the experiment (day 13). Larvae Peruvian anchovy (Engraulis ringens, 24 days-post-hatch) and chita (Anisotremus scapularis, 44 days-post-hatch) reared in the laboratory were introduced shortly after (day 19). Fish mortality was monitored continuously via carcasses sinking to the sediment trap. This 'Sediment' category of samples is only reliable for counts, while many length and weight measures will be inaccurate due to degradation. While live fish were subsampled during the experiment, not enough individuals could be caught for a proper analysis. Instead, the main sampling of live fish was at the end of the experiment (day 36). Most fish had reached the late larvae or early juvenile stage by that time. Fish length and wet mass were assessed for all these individuals. A subsample of both species was used to establish wet to dry to C to N mass relationships. These were applied to convert wet mass into dry, C and N mass for all other fish. Methodological details in Goldenberg et al. and Thielecke et al. (manuscripts in progress).