All non-concentrated fish oils contain a myriad of other omega fatty acids besides the omega-3s EPA and DHA. The average fish oil contains 23 omega fatty acids. Any quality fish oil manufacturer should be able to provide a chromatogram listing the levels of all the omega fatty acids found in their fish oil.
Often, when fish oil is concentrated, some of these other fatty acids will be removed in order to increase the amounts of EPA and/or DHA. You often hear the most about the omega-3s EPA and DHA because those are the fatty acids that have been shown, by decades of scientific research, to yield important health benefits for every cell, organ, and system in the body, and are considered the most functional omega-3s. And they are also drastically deficient in the food supply of Western nations, making it very difficult for us to get adequate amounts from our diet.