Monsoonal wet season influences the migration tendency of a catadromous fish (barramundi Lates calcarifer)

Many animals exhibit partial migration, which occurs when populations contain coexisting contingents of migratory and resident individuals. This individual-level variation in migration behaviour may drive differences in growth, age at maturity, and survival. Therefore, partial migration is widely considered to play a key role in shaping population demography.
Otolith chemistry and microstructural analysis were used to identify the environmental and individual-specific factors that influence migratory behaviour in the facultatively catadromous barramundi (Lates calcarifer) at two distinct life history stages: firstly, as juveniles migrating upstream into fresh water; and secondly, as adults or sub-adults returning to the estuarine/marine spawning habitat.
Monsoonal climate played an important role in determining the migration propensity of juveniles: individuals born in the driest year examined (weak monsoon) were more than twice as likely to undergo migration to freshwater than those b...