Fish has Omega 3, which you can take in form of Flax seed oil.
There isn't anything else in fish that you can't also get in a balanced vegetarian diet.

okay that guy is so wrong!!!! see we vegetarian got to stick together. we have everything like they do just take a pill like the person said and then we're all through hmp.

You don't need to eat fish. Flax seed and walnuts are great sources of Omega-3s.

According to the US National Library of Medicine and the National Institutes of Health, a diet that is sufficient in protein and calcium is also sufficient in phosphorus.

Omega-3 fatty acids are found in flax seeds and flax oil, walnuts, hemp seeds, dark green vegetables, tofu, soybeans, canola oil and butternuts. The fish themselves get it from marine microalgae and you can get supplements made from purified algae.

If you have specific health concerns, you should see a registered dietitian to help you plan a vegetarian diet that meets your needs. Physicians, unfortunately, are not the most reliable source of nutritional advice. Most medical schools put very little emphasis on nutritional education and many MDs have as little as two or three lecture hours covering it.

Hi!

Congratulations!! I believe you are doing something good for your self and the whole world (although some of the world may nor know it); in order to do that, it seems you are making a good thing: Learning.

I'm no professional nor student, but I've just done a research, in the Internet, about issues related to your question, and I strongly believe that in a well balanced veg(etari)an diet, one should consume the following "ingredients", which are the source of "key" substances found in fishes (and in more):

http://en.wikipedia.org/wiki/Flax#Possible_medical_benefits
http://en.wikipedia.org/wiki/Chlorella#Nutrition
http://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)#Essential_fatty_acids
http://en.wikipedia.org/wiki/Salvia_hispanica#Chia_seed

I believe it's not necessary (maybe neither recommendable) one should consume all of them, and there are recommended levels of nutrients related to them: http://en.wikipedia.org/wiki/Omega-3_fatty_acid#Dietary_sources

When someone talks about the importance of consuming fish, that someone is very porbably talking about this: http://en.wikipedia.org/wiki/Omega-3_fatty_acid#Fish

Specifically, they are probably talking about EPA and DHA, which are omega-3 essential fatty acid.

Please, read it, because it seems there are potentially problems with consuming fish.

A quote from it: “Although fish is a dietary source of n?3 fatty acids, fish do not synthesize them; they obtain them from the algae in their diet. ”

About algae, because chlorella is green algae: http://en.wikipedia.org/wiki/Algae#Nutrition

This way, one will have got very good levels of EPA and DHA, which are omega-3 essential fatty acid.

Of course, after all this information, one can consult a good nutrition specialist, who knows about veg(etari)an nutrition, preferably, I believe, with a naturopathic approach.
( http://en.wikipedia.org/wiki/Naturopathic_medicine#Naturopathic_practitioners )

Well, try to get information from good sources, and I recommend you to widen your decision with philosophical, ethical and spiritual concerns. I could say more, but it is probably enough for now.

Thank you for doing a good thing to the world.

Be well!!

(Sorry about any errors and about my English, I'm a "ovo-lacto-vegetarian" from Argentina.)