I believe I can answer my question. After some Google search I found this:
It is my understanding that it is difficult to fish on a sailing ship. Many fish won't bite a worm or other bait swimming 12-15 knots through the ocean - this isn't a natural mealtime option for them - the bigger fish may (marlins, tuna), but these are very large fish requiring a fishing operation, not a simple sailor fishing for his afternoon cup of chowder. The option then would be to take down the sails, stopping the vessel for a few hours to allow the men to fish (and fish populations tend to be much more plentiful near the coasts, rather than in the shipping lanes of the deep sea), which could take a lot of time and resources and leave the men on the high seas (where weather was their worst enemy) for a longer period of time. Conversely, they could travel nonstop to the nearest port of safety simply by storing food in some of their holds. Read more
So maybe this picture for the Phoenician trade route explains that they tried to stay on the coast so they can either take food from nearby villages or hunt fish on the shore. On the long trips, they probably had to count on corn because such food lasts longer (but a trip to Sicily, for example, seems like it took more than a month, how they were able to survive such trip).
Perhaps the picture I included in my question means they hunt fish on the shores because there is a crab included on the stone. I guess most of the fishing for the sailor was on the coast. However in the sea, they had to count on hard tack and corn meal because it could last longer