Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Use of built barriers in New Zealand streams as a conservation management tool (#161)

Sjaan Bowie 1 , Daniel Jack 2 , Dean Nelson 3
  1. Department of Conservation, Christchurch, CANTERBURY, New Zealand
  2. Operations, Department of Conservation, Dunedin, New Zealand
  3. Operations, Department of Conservation, Twizel, New Zealand

New Zealand has 77 species of freshwater fish. Fifty-seven of them are native, most are endemic and 72% are threatened with, at risk of extinction or extinct; a higher proportion than almost any other country in the world. While providing fish passage is advantageous for most fish, some of New Zealand’s native freshwater fish, other instream species and habitats cannot cope and/or compete with some invasive species. In these situations, physical barriers, which impede or prevent upstream and/or downstream movement of unwanted fish species, can help protect key locations by keeping invasive species out and providing safe refuge areas. Prior to retaining or installing a new fish passage barrier, consideration should be given to what species and habitats are present, their distribution and extent, their conservation status, habitat preferences, timing of migration and spawning, life history and possible impacts of providing or impeding fish passage. Natural waterfalls do protect a few of these key native locations, however under changing climates and flows these key native fish hotspots are also being compromised and invasive species are impacting on a number of these populations. Fish removal and barrier installation has been successfully undertaken in a number of key locations in New Zealand to remove invasive species and prevent reinvasion and has resulted in good recovery of native fish species. An overview of the use of physical built barriers in small streams as a conservation management tool; focusing on lessons learnt from invasive species removal, important design criteria for structures to exclude invasive species, and monitoring and maintenance considerations will be presented.