Location of demographic sources affects the distributions of a vulnerable native fish in invaded river networks

摘要: Summary 1. Invasive predators negatively affect native prey to varying degrees across landscapes, and spatial configuration of invader-free refugia may distributions invaded river networks. In New Zealand, introduced trout (Salmo trutta Oncorhynchus mykiss) create source-sink dynamics in Galaxias vulgaris populations, their co-occurrence with be enhanced by immigration from trout-free reaches. 2. We investigated how network demographic sources affected the distribution G. vulgaris trout-invaded riverscapes. Using quantitative biomass surveys spatially extensive presence–absence surveys, interaction between habitat variability location relative limiting reaches was assessed. 3. Galaxias at sink sites decreased increasing distance nearest barrier. The maximum barriers which occurred riverscape limited, so that galaxiids were excluded small stable streams far sources. 4. Large predatory (i.e. >150 mm fork length) high densities all year round seasonally disturbed flooding. Large probably provide increased for avoid predation trout, but narrowness stability act synergistically extirpate are too receive regular immigrants. 5. The mediating effects on indicates dependency predator–prey interactions networks. 6. These results indicate creating new source should enhance nearby invader-occupied reaches. Moreover, adding existing sources, ensuring prevent future invasion, will also allow fish dispersal sinks maximise conservation gains management