Bay of Plenty Regional Council staff, on behalf of the seven Ohiwa Harbour Strategy partner organisations, are trialing two methods of collecting environmental DNA (eDNA) from streams feeding into Ōhiwa Harbour. Why? To discover which fish species call these streams home and to plan remediation work according to their needs.
The first method being trialled is a syringe method. Water is pushed through a filter at the end of a large syringe which collects genetic material from the water. The second method simply sees filters placed in the stream for 24 hours which then passively collect genetic material as water passes through. The genetic material is then sent to a New Zealand company for the eDNA results.
The eDNA testing is extremely sensitive and less stressful on fish than other sampling methods. Plant and animal species in and around the waterbody are picked up too, providing a clearer picture of the health of the waterbody as a whole. If a rare species is found living in a particular stream, that stream can be prioritised for remediation work, including retrofitting culverts.
The work feeds into the fish passage project which has seen a survey of all culverts in the catchment. Many provide major barriers to migratory fish such as tuna (eel). Unlike with other human made environmental problems there is actually an easy fix to this one. Over the years Wainui local and nationally renowned expert on fish migration Kelly Hughes of ATS Environmental has worked on simple, low-cost solutions that assist native fish in overcoming these barriers. Floating ramps for swimming fish and mussel ropes for eels and banded kōkopu and the like enable these fish to negotiate the lip of a culvert and baffles through the structure to create depth and rest pools.
Check out Kelly Hughes' webinar on fish passage here.
