Answer:
The answer is no, high biological fitness in one environment doesn't have to be high in another environment. Biological fitness is a term used in evolutionary biology and it is the quantitative representation of how a genotype (or phenotype) is successful (reproductively) in a certain environment. The biological fitness of an organism is dependent on its ability to survive and reproduce in a given environment. If different traits or alleles increase the fitness of an organism, those alleles will consequently increase in the gene pool, and that trait will increase in the population.
I hope this helped you out some~ <3
-Dream