No, you can't; however you can "cheat" this mission by changing the composition of your convoy.
What you can do is to accept the mission while using "light" ships; i.e. 3 Bargues; as escort ships, while having some "heavy"; i.e. Warfrigate's; as cargoships in the same convoy.
As soon as you are blockading the port of a city, keep an eye out for the convoy of Genoa. When that one has left the port of Genoa, switch to the "heavy" ships as escort; making the fight a bit more balanced. Another thing you need to be sure of, is that you got plenty - think 40+ - barrels of oil aboard your convoy. You're going to need them in the fight.
Make sure you save the game before the fight, as you might repeat the fight a few times just to get the maximum profit of it.
When you're in the fight, use only ONE ship to fight. Order the other two to avoid the fight, as you'll most likely going to need them later. The advantage of doing so is that you got 3 ships at your disposal which are in a good condition; giving you an advantage in manoeuvrability later in the fight.
As soon as the game un-pauses, drop some oil barrels and sail away from the enemy convoy. Keep dropping oil and start sailing in an S-pattern in front of the ship(s) following the one you have under control. Don't bother with the ship(s) following your other two ships; right now it's important to tear the enemy convoy apart.
The oil will burn the sails of the enemy's ships, thus lowering their speed and manoeuvrability; giving you the opportunity to pound them with Chainshot to speed the process of destroying rigging even faster. When all rigging are destroyed, you can switch to your 2nd and 3rd ship to do the same, or you can switch your ammo to Grapeshot and start decimating the crew; followed by a boarding action.
After that it's rince and repeat, resulting in 5 captured ships.
Another trick you can use, is to accept the mission; use a convoy with "light" ships to do the blockade and have a convoy with "heavy" ships nearby to intercept the convoy from Genoa. The fight is just similar; however, you don't need to switch ships in your blockading convoy and while you're fighting, the blockade remains; which in turn might speed up the good result of the mission. Use the captured ships to increase your fleet or sell them off; but either way they'll help you to get a profit.
Another way - and probably better - is to dock a large convoy in that particular town and buy up all essential (read: food) goods up to the point they're depleted. When that's done, hire all workers and wait another day, before you buy all goods again and hire new workers. if you keep repeating this for a while, sooner or later the population will drop.
Then: as soon as the mission is completed; SELL all you've bought BACK to the city. That'll give you a reputation boost in that particular city and it gives you some money in return; which with the mission reward should give you a profit. Eventually you can even dump the workers back into the city; or you can simply unload them elsewhere where they're needed more.
Hack seinen Kopf ab. Ich brauche einen Aschenbecher!