Fish Out of Water (and Copyright)

Dear Rich: I am currently in the process of making a logo for trout nets I sell. My graphic design artist did a great job but used a trout silhouette off of a stock photo site. The site says it is prohibited to use their material as part of a logo, but it is just a silhouette of a trout jumping and I feel like that is more public domain than not. I talked to my graphic design artist who is willing to sketch one up from scratch, I just feel it is kind of silly as there are only so many ways to depict a silhouette of a trout jumping out of the water. 
Your argument -- that there are a limited number of ways to portray a jumping trout silhouette -- is a reasonable defense to copyright infringement and may possibly qualify under the merger doctrine or as "scenes a faire." However, if you obtained the image from a stock photo site and entered into a license agreement, copyright would take a back seat to the contract. If the stock company notices (and cares), they can hassle you over breach of license and your copyright arguments would have little value. Have you considered public domain or Creative Commons imagery? There's a lot of other fish in the sea.*
* and yes, there are saltwater trout!