There is a lot here on the subject.

The simple answer , at least as to LMB and BG , is the further you get away from the genetics that naturally work in your area the larger the chance that the results will be unacceptable. Just because a fish survives does not mean that it will reach its potential. For example there are different results as to some common traits between the 2 reciprocal F-1 crosses mNLMB X fFLMB vs fNLMB X mFLMB .