What can be done when i live in calif and my Alaska employer not making bounced payroll check good?

My nephew worked on a salmon prossesing ship in out of washington that went to alaska. He got 2 checks while on the boat, then tried to cash them when the job was over. By the time he got back to California and was able to cash them, they bounced. He called his employer who told him they had told everyone they were changing banks and they needed to cash the checks soon he was not told this , his last payroll check cleared but not the two issued on boat. He called them and they said they would reissue the checks but, 2 months later the employer has yet to reissue the checks, now what? He also got hurt on boat and went to a dr, in alaska they gave him no paperwork for injury, he was unable to work and no workers comp payment was issued. Now what, tried calling do dhd, they keep giving me another and another number to call that won't answer phone.