It´s fairly easy to spot the difference between wild and farmed salmon. I´d say the guidelines would be the following:
1. Wild Salmon´s meat color is more red or has a deeper pink, while farmed is fairly light pink/orange.
2. Wild salmon is much leaner, u can see nearly no white fat lines compared to farmed ones where it´s all over.
3. Wild salmon is less oily. Farmed salmon meat is usually very oily.
4. Wild salmon meat is usually more tough. Whereas farmed is very softish.
5. Wild salmon taste is much more intense, which farmed one is not.