Early game food problems

Fisherman are a great supplement for your food stores, but I wouldn't rely on them exclusively. I don't know how your setup looks, but you also have to make sure that their areas don't overlap at all. It will destroy your efficiency.

When you first start out, the best options for food are Gatherer Huts. Place them in the middle of a forest so the entire circle is completely filled with trees to maximize their output. Make sure that you get a Forester log next to them to plant more trees for them to gather from as well. This should hold you over for a pretty good amount of time before you need to start expanding into things like Fields, Orchards, etc.

Edit::Completely missed the second part of your question. Sorry

As for how Gatherers are supposed to be efficient, look into what is referred to as the "Forest(er) Cluster".

These are when you place a Forester(set to plant), Herbalist, Gatherer and Hunter all right against each other. The Forester will provide the trees necessary to reach maxium output of the other buildings. Make sure that you set this up in an area with as few hills, mountains, streams, rivers or anything else trees will not grow on as possible, agian to achieve maximum output from the Forester.

Once you have this set up you have a few options. I've seen many people place a couple houses directly in the forest cluster, but personally I like to set up a little living/storage area just outside of the tree line so I don't take up anymore growth space. This will provide the workers for each of these buildings a place to live, eat, stay warm and drop off goods so they don't have to walk too far anymore.

All of the production buildings in game benefit from short travel distances, but they do so differently. Fishing huts should include as much water in their radius as possible, their production is heavily dependent on that, so put them on a spot where they have less land in their radius (where rivers meet lakes etc). Put a storage barn overlapping its "road" with the one of the fishing hut, than place 2 houses right next to them. Same for crops/orchads, they get the same benefit from having this kind of setup. Gatherer huts, herbalists, and hunting lodges are not as dependent on closeness to storage and houses. Keep those just outside the radius of this food buildings, if you use a forester, keep its workers numbers low (one or two) and set it on plant mode only. Because this food buildings have huge working areas and food can "spawn" anywhere in that radius its best not to waste "tree space" by having houses and storage barns inside working areas. Hope it helps :),

I've found that fishermen work just fine for the first few years, and I rarely setup a gathering hut until year 2 or 3.

My strategy is to build 1-2 Fishing docks and 2 crop fields. I assign 2 farmers to the crop fields, and 2 fishermen. After the farmers finish gathering the crops for the winter, I re-assign them to be fishermen, and sometimes I'll even setup 6 total fishermen during the winter.

If you do this, remember to re-assign the 2 farmers when spring comes!