Data from: Selection on offspring size and contemporary evolution under ocean acidification size number tradeoffs.csv file contains data on egg size and batch fecundity of California Grunion (Leuresthes tenuis). SL is standard length in cm; Wt is weight in grams; mean.egg.diameter is measured in mm; sd and n refer to standard deviation of mean diameter and number of eggs measured Larval size OA and mortality.csv file contains data on instantaneous mortality rates (d-1), larval volume (mm3; conical approximation), temperature (degrees C) and pCO2 levels (uatm). larval size_animal model.csv file contains data on variation in larval size measured by both standard length (SL.mm) and body depth (BD.mm). Both measurements are in units of mm. 'animal' is a unique id for each fish measured and the Sire and Dam column track parentage. the larval size_pedigree.csv file contains data on the parentage of each of the fish in the larval size_animal model.csv file. The separate file for the pedigree is formatted for analysis using the MCMCglmm package in R