Question about creating unique content

Hi

I've been googling and come across a few articles on the Internet which is related to my niche. So I copyed some sections from that article and some from another article (on a different site)...

In addition I rewrote parts of the article to make it fit more into my niche etc...

So now I have a 530 words article.

Now I wonder if I can create a new article based on the article I already gave. Created by replacing the keyword. Lets say niche is about fishing and I've written an article about fishing... Now I want to create an article about fishing salmon, so I replace the keyword "fishing" with "fishing salmon". Thus that create another unique article or will google give me duplicate content penalty?

You may want to check this link below:
The last time i've checked it there was a video tutorial about changing a keyword from dog to cat, and so on. You might wanna check it out yourself for review.

thanx for shrng link. much apprctd.