I'm not familiar with what all the symbols mean; I use a tileset.
You may want to consider looking at captnduck or tinypirate's tutorials if you haven't done so already (both are stickied). Also, if you download the package from tinypirate's tutorial, it comes with a tileset and dwarf manager (the first makes the game easier on the eyes and the second makes it much easier to manage your dwarf's labors).
Once you can irrigate something as small as a 6x6 plot, you will be set for years, and by then you can find several other sources of food or irrigate something larger. Examine the river with k and look around; if there are carp, longnose gar, pike, or tigerfish, you won't be able to come near the river with your limited resources and it will take someone more experienced than I to come up with a solution.
O right. I haven't done this, but you could try channeling a 6x6 plot near (but not too close to the river), and then connect it to the river by mining until you're one tile away from the river. Then dig fortifications so that the fish can't get through in the tile adjacent to the water. But remember; water can flow diagonally...This gets tricky, though. To get rid of the water it needs to evaporate, so you need to install a floodgate, to plug up the channel from the river connected to a lever, or else find some other way to reroute the water, which might not be easy with 7 unskilled dwarves and limited resources. Until this gets done, you can eat your pets -- and don't forget those other ways to gather food to supplement your stocks until this project is complete.
Or you could restart on an easier map.