Before settling in Metropolis, Clark Kent travels the world to figure out his place in it. That's been an aspect of the comics for a long time now and the movie is following suit.Why Clark is participating in Deadliest Catch I'm a bit curious.
If I had to guess, I'd say he's either (a) on assignment for a story( which I doubt) or (b) the fortress is still in the Artic and he's either working his passage there by working on the boat or he's working on the boat to escape Smallville and accidentally finds out that the Fortess is near and leaves the boat. Either way, he has to hide his powers while on the boat. The third option is he's just on the boat temporarily and then moves on to some other job.