DSC_9458 Most culverts are built with little concern for fish passage. The worst type is a ‘perched’ culvert such as this one – where water drops freely from a pipe into the waterway. Some of the native fishes are impressive climbers but they cannot climb upside down or jump to get into these pipes. Many of our fish are highly migratory – with lifecycles involving movements between the sea and freshwater, or between rivers and lakes. However, artificial barriers to migration such as this, frequently halt their journeys. Shenandoah Saddle *
DSC_9449 During major earthworks such as this, eroded soil settles out of the water as sediment between the stones of the substrate. Native fishes spend their inactive periods hiding amongst these stones, many lay their eggs under them and some burrow down deep amongst them to seek refuge from floods or droughts. Once these gaps become clogged with sediment there is less habitat for native fish. Maruia *
DSC_9477 Removal of forest cover dramatically alters drainage patterns and the properties of waterways. Forest clearance usually includes removal of riparian vegetation which in turn reduces the volume of food (terrestrial insects) falling into the stream. Removal of the forest canopy over streams removes shading and increases the temperature of the water. This increased temperature reduces the amount of dissolved oxygen in the water, and in turn the number of fish a stream can support. Shenandoah Saddle *
