For example, differences between ruffe from the Nadym and Ob' Rivers may be an adaptation to long spawning and overwintering migrations (Kolomin 1977).
(differences between ruffe from the Nadym and Ob' Rivers; may be; an adaptation to long spawning and overwintering migrations)
differences between ruffe from the Nadym and Ob' Rivers
may be
an adaptation to long spawning and overwintering migrations