I don't know how "simple: you consider the method, but western blotting works: http://informahealthcare.com/doi/abs/10.3109/17435390.2014.982737

http://informahealthcare.com/doi/abs/10.3109/17435390.2014.982737

I did by qPCR, but of course is expression in one moment of stress, I don't know if you mean this, but I think the method is relatively simply if you have the material near. And the methos is very specific.

Transcriptome sequencing is a simple method to estimate the number of HSPs in fish.

Here are some good papers on HSA:

http://link.springer.com/article/10.1023/A:1008812500650

http://www.sciencedirect.com/science/article/pii/0306456594900701

http://onlinelibrary.wiley.com/doi/10.1046/j.1461-0248.2003.00528.x/full

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2761.2010.01183.x/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false

Wstern blotting is OK, on the other hand one does not determine protein with qPCR, only the template so one does not know anything about protein level without previous inormation about mRNA protein correspondence

Thank you Mr. Mikko Nikinmaa for your kind answer