relaxed full text search?

Hello,

My first implementation of full text search is generally working -- but I'd
like to be able to relax the matching rules.

For example, searching for "salmon" does not find "salmonella" as
configured out of the box for postgresql 9.3.10.

Here's my, probably naive, query:
SELECT * FROM table WHERE tsv @@ plainto_tsquery('salmon');

I've read the docs and searched via google -- and learnt a lot.
But I don't understand how to bend the full text search feature to do what
I want?

Thanks for any help,
Steven

--
*Steven Marcus*
Software Development Manager

*P: *+61 2 9007 5600
*E: *steven(at)silvertrak(dot)com(dot)au
*A: *10 Addison Road Marrickville NSW 2204

www.silvertrak.com.au