Answer:
set your sonar level to 5 and set a meat lure . wait and soon a gaust will find u and catch it , it will be big wave if u have red version and flame joe if u have blue version. after catching big wave or flame joe , exchange it with gameru , he will give u TR lure which u can keep on using it without losing it . then now u can catch all 7 great gausts , the go to 'buy' in gameru and u will find STR lure and u can now catch the boss gaust . Ultimo north dragon if red version and Hell sothzerk if blue version . hope this helped !!