My wife and I are trying to go vegetarian for a month. We enjoy fish quite a bit. Is there any way to replicate the taste of say salmon, tuna, or cod with vegetarian, or better yet vegan, ingredients?
I have been around vegan meat/fish substitutes for a while being vegan myself, and often you can find (in specialized vegetarian stores - especially asian vegetarian stores or online) stuff labeled as "vegan fish" which most of the time refers to soy, seitan or some other protein pieces with a seaweed "skin". Sometimes recipes call for linseed oil ... presumably adding a fishy flavor. None of this really tastes like any fish I ever ate ... but I guess it comes quite close in texture and some components of the flavor, for people who really don't want to give those up.
I like japanese cuisine where a lot of seaweed is used ... which gives a "sea" taste to food, but again I wouldn't really call it fish flavor (whereas a longtime vegan friend of mine wouldn't eat seaweed cause it reminds her of fish too much, so I guess it depends on your taste).
I agree with what @SAJ14SAJ says in the comment above. And I believe it would be really hard to perfectly imitate the fish texture and flavor. And for me, being vegetarian means giving up eating animals, and to accept that this means not eating a couple of foods that might taste very delicious. However, if giving up fish is hard for you, I hope some of the "mock fish" products are close enough to make it easier for you to keep up the vegetarian path/cause!
Just as a fun side note: recently I watched a (otherwise horrifically annoying) TV show where a young chef using some fancy high-tech machinery pressed dashi (which is a kind of japanese seaweed or fish broth) into cubes of watermelon and the people who ate it (none of which seemed to be vegetarian) all thought the texture and flavor were like tuna (hard to test if you don't get catered to by someone owning the machine).
If you freeze a block of regular (non-silken) tofu, it will take on a flaky texture kind-of-sort-of like cooked white fish. If you combined this with the fishy flavor of kelp powder, you might be able approximate something cod-ish.
It might be easier to identify what aspects of fish you want to replicate and aim specifically for those. For instance, if you want something that's a little bit fatty and mildly fish tasting, you can make a "tuna salad" with mashed garbanzo beans or flaked frozen tofu and dulse flakes or kelp powder. If you want to approximate the whole texture, flavor, and mouthfeel of grilled salmon, you're going to have a much harder time.
I found this great recipe for mock fish http://spiceislandvegan.blogspot.com.au/2008/08/how-to-make-vegan-fish-or-mock-fish.html
They use it in a most vegetarian Asian restaurants. For me taste just like fish or the closest you will get to it. Have fun and all the best :)
you can make chickpea sandwiches: http://www.theppk.com/2013/07/chickpea-salad-sammiches/
there's lots of great recipes on the ppk site. (here's a great dessert recipe; that my friends (who are omnivores) love: http://www.theppk.com/2011/02/berry-creme-tart-with-cocoa-olive-oil-crust/)