Data from: Increased population size of fish in a lowland river following restoration of structural habitat

Most assessments of the effectiveness of river restoration are done at
small spatial scales (< 10 km) over short time frames (< 3
yr), potentially failing to capture large-scale mechanisms such as
completion of life-history processes, changes to system productivity, or
time lags of ecosystem responses. To test the hypothesis that populations
of two species of large-bodied, piscivorous native fishes would increase
in response to large-scale structural habitat restoration (re-introduction
of 4450 coarse woody habitat into a 110-km reach of the Murray River,
south-eastern Australia), we collected annual catch, effort, length, and
tagging data over seven years for Murray cod (Maccullochella peelii) and
golden perch (Macquaria ambigua) in a restored ‘intervention’ reach and
three neighbouring ‘control’ reaches. We supplemented mark-recapture data
with telemetry and angler phone-in data to assess the potentially
confounding influences of movement among sampled populations,
heterogeneous detection rates, and population vital rates. We applied a
Bayesian hierarchical model to estimate changes in population parameters
including immigration, emigration, and mortality rates. For Murray cod we
observed a three-fold increase in abundance in the population within the
intervention reach, while populations declined or fluctuated within the
control reaches. Golden perch densities also increased two-fold in the
intervention reach. Our results indicate that restoring habitat
heterogeneity by adding coarse woody habitats can increase the abundance
of fish at a population scale in a large, lowland river. Successful
restoration of poor-quality ‘sink’ habitats for target species relies on
connectivity with high-quality ‘source’ habitats. We recommend that the
analysis of restoration success across appropriately large spatial and
temporal scales can help identify mechanisms and success rates of other
restoration strategies such as restoring fish passage or delivering water
for environmental outcomes.