Migratory animals often achieve superior growth relative to resident individuals. In a partially migratory population, growth disparity arises from differences in life-history choices. Natural movement of aquatic migratory species is constrained by the modified riverine landscapes. Whether the growth benefit of migration persists in these fragmented habitats remains inconclusive.
To quantify the impact of life-histories and habitat-use choices of migratory species in modified habitats, we used otolith Sr:Ca ratio and increment widths of facultatively catadromous barramundi (Lates calcarifer) as proxies for individual habitat-use history and growth trajectory.
We found that catadromous individuals were initially smaller than resident conspecifics. The predictive growth models indicated that catadromous individuals exhibited significantly faster growth, particularly in their early years (at age 2 to 6), compensating for earlier depressed growth rates. We found a positive correlation between growth rates and freshwater residency duration, with the greatest benefits achieved by a prolonged stay. However, the overall growth advantage was lower than that reported in other studies, likely due to the difference in habitat modification levels.
Our findings underscore the role of freshwater habitats for L. calcarifer development and demonstrate that maintaining habitat connectivity is essential for maximising growth potential and population productivity in altered riverine-estuarine systems.