No. I logged in 45 minutes late today and still had 129 fish by the end. If you just fish on Yojamba, and no one chases them up the coast by fishing out the ones down coast, they will stop coming around. You have to go down the coast and get those pools and chase them so they respawn on Yojamba. I think a large part of the reason they stop respawning so fast is that the high level toons leave and quit chasing them up the coast. But they also seem to let you pull less fish from them before they disappear after the tournament is over. So they might also spawn less frequently. But they do still spawn, and quite a lot.