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Earthquake‐induced habitat migration in a riparian spawning fish has implications for conservation management
- Orchard, Shane, Hickford, Michael J.H., Schiel, David R.
- Aquatic conservation 2018 v.28 no.3 pp. 702-712
- Galaxias maculatus, deformation, earthquakes, fish, flood control, geographic information systems, habitats, land use, rivers, salinity, spawning, sport fishing, surveys, tectonics, waterways, New Zealand
- Galaxias maculatus is a riparian spawning fish that supports an important recreational fishery in New Zealand, with spawning habitat requirements strongly structured by salinity gradients at river mouths. This study reports changes to the spawning habitat following a series of large earthquakes that resulted in the widespread deformation of ground surfaces in the vicinity of waterways. Assessments of habitat recovery focused on two river systems, the Avon and Heathcote, with pre‐disturbance data available over a 20‐year period. Recovery dynamics were assessed by field survey and mapping of spawning habitat prior to and on seven occasions after the disturbance event. Riparian land‐use and management patterns were mapped and analysed using overlay methods in a geographical information system (GIS). Habitat migration of up to 2 km occurred in comparison with all previous records, and several anthropogenic land uses have become threats because of changed patterns of co‐occurrence. Incompatible activities now affect more than half of the spawning habitat in both rivers, particularly in areas managed for flood control purposes and recreational use. The results are an example of landscape‐scale responses to salinity and water‐level changes driven by tectonic dynamics. These dynamics are not the source of the stress per se; rather, they have increased the exposure of the species to pre‐existing stressors. The case illustrates important principles for managing subtle, yet widespread, change. Adaptive conservation methods and investments in information are priorities for avoiding management failure following environmental change.