In one lake live perch, ruff, crucian carp, pike, roach. In the neighboring, isolated from the first lake – perch, pike, pikeperch, bream, roach. How many species of fish and how many of their populations inhabit both reservoirs?
The total number of species in two reservoirs: 7. Number of populations: 10. Since roaches living in one and the other reservoir belong to different populations, but to one species.
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