Sperm competition trials were conducted, each trial using a single female and two male chinook salmon from a two-stage social manipulation experiment. Trials were also conducted using two seminal fluid treatments, (1) milt was unmanipulated, (2) seminal fluid was switched between the males in each trial. This data file contains sperm velocity measurements and paternity share data for each male. The paternity share of each male was determined using mircosatellite loci. Social dominance was determined within each pair using video recordings of aggressive behavior. Sperm concentration was measured using a haemocytometer. Sperm velocity was measured using Computer Assisted Sperm Analysis
