This recipe differs from the others here due to the addition of the lightly sour, vinegary taste. I hardly ever add salt to foods; thus some things need an extra punch from a different source. Anyhow, for the fish, use vertebral bones/heads/tails from trout, striped bass and/or salmon. I also include lobster or shrimp shells in this amount. Other fish may also work. If using heads, remove the gills first, as they will add a bitterness to the stock. As for the clams, other hard shell clams substitute nicely, just make sure they lack sand or grit in their juices. And yes, other vinegars, such as red wine vinegar, will also work, although for appearance reasons I prefer to stick with the rice vinegar.