Relative influence of local and landscape‐scale features on the density and habitat preferences of longfin and shortfin eels

The relative structural influence of local‐scale versus landscape‐scale habitat features on size‐class matrices of both longfin ( Anguilla dieffenbachia ) and shortfin ( Anguilla australis ) eels collected along six different New Zealand rivers (10 river‐year combinations) are quantified using variance decomposition. The total explained variation of these species and size‐class matrices was related to both local‐scale and landscape‐scale variables, and some proportion was shared between these two scales. When compared with landscape‐scale variables, local‐scale physical habitat variables such as water velocity and fish cover explained more about patterns in the size‐distribution of longfin eels. The opposite situation was true for shortfin eels whose size‐distribution was more strongly related to landscape‐scale variables such as distance from sea and channel slope. These findings suggest that management of river flows is required to ensure flow regimes that maintain availability of suitable local‐scale hydraulic conditions, and that biodiversity conservation efforts need to be targeted at protecting a gradient of rivers across New Zealand's river landscape.