This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.
Spatially dynamic maternal control of migratory fish recruitment pulses triggered by shifting seasonal cues
Environmental regimes set the timing and location of early life history events of migratory species with synchronized reproduction. Modified habitats over human-dominated landscapes, however, may amplify uncertainty in predicting recruitment pulses, impeding efforts to restore habitats invaluable to endemic species. This study assesses how environmental and spawner influences modulate recruitment variability and persistence of the Missouri River shovelnose sturgeon (Scaphirhynchus platorynchus) under modified seasonal spawning and nursery habitat conditions. Using a spatially explicit individual-based biophysical model, spawning cycle, early life history processes (dispersal, energetics, and survival), and prey production were simulated under incrementally perturbed flow (–10 to –30%) and temperature (+1 and +2°C) regimes over 50 years. Simulated flow reduction and warming synergistically contracted spring spawning habitats (by up to 51%) and periods (by 19%). Under these conditions, fewer mature females entered a reproductive cycle, and more females skipped spawning, reducing spawning biomass by 20–50%. Many spawners migrated farther to avoid increasingly unfavorable habitats, intensifying local density dependency in larval stages and in turn increasing size-dependent predation mortality. Diminished egg production (by 20–97%) and weakened recruitment pulses (by 46–95%) ultimately reduced population size by 21–74%. These simulations illustrate environmentally amplified maternal influences on early life histories can lower sturgeon population stability and resilience to ever-increasing perturbations.
MF17082 Accepted 21 December 2017
© CSIRO 2017