The complete dataset is in the 'all data 'sheet, , Column,Explanation Fish ID,individual fish identification Day,"Day (1, 4, 7) of consecutive measurements" Tank,"One group of fish was kept within individual tanks; ""Tank"" is a random factor" Lnegth,Standard length in m Mass,Mass in g Cstart,fastest c-start of four trials; in m/s Asprint,sprint speed determined in a continuous acceleration protocol; in m/s Av Realised speed,average speed attained while competing for food; abverage of 10 daily trials; in m/s Max Realised speed,maximum speed attained while competing for food; abverage of 10 daily trials; in m/s Aggression,number of aggressive behaviours directed towards another fish in the group (10 trials/day) Submission,number of aggressive behaviours received from other fish in the group (10 trials/day) Compsuccess,number of times food item was obtained in all 10 trials per day