Trout And Salmon Numbers Should Be Able To Be Maintained Under Project Aqua
Meridian Energy believes that the number of salmon and trout in the Lower Waitaki River should be able to be maintained
if Project Aqua is built.
Project Aqua is a proposed hydro-electric scheme that would run along the south side of the lower Waitaki Valley. It
would generate enough low-cost, renewable electricity to power the equivalent of about 375,000 households in an average
year and about 250,000 households in a very dry year. A very dry year is a 1-in-20 year event.
Meridian is giving the assurances because of findings in seven independent reports commissioned by Meridian Energy as
part of its consent applications for Project Aqua. The reports, which were compiled by NIWA, Meritec and the Cawthron
Institute, were prepared on the effects Project Aqua would have on fish populations (both native and introduced species)
in the Waitaki River.
In addition, separate independent reports have been prepared on the river’s in-stream habitat and how the proposed flow
regime would affect it.
The reports predict that there will be reductions in potential available physical habitat for most life stages of salmon
and trout, but these reductions will be offset to varying extents by improved flow stability and food supplies. The
reports predict that existing densities of aquatic insects should be similar, and could possibly be enhanced under Aqua,
primarily as a result of a higher proportion of the riverbed becoming stable and more optimal water velocities. Aquatic
insects are the primary food source for salmon and trout in the river.
Rainbow trout spawning is only known to occur in the three main tributaries, the Awakino, Hakataramea, and Maerewhenua
Rivers. The Awakino River is the most important location for rainbow trout spawning in the lower Waitaki River and the
section of river above Kurow is a prime rainbow trout fishing area. The salmon and trout report predicts this section of
the river will be unchanged by Project Aqua and therefore the rainbow trout population there is predicted to be
unaffected, provided adequate numbers of juveniles can gain access to the residual river.
“In summary, the research indicates that the number of brown trout in the Lower Waitaki should be at least sustained and
may increase. The number of salmon should also be able to be maintained but there is less certainty about numbers of
rainbow trout. The balance between numbers of brown and rainbow trout may change in the residual river depending on the
hydrology of floods and the extent of competition between the two species ” says Alan Seay. For rainbow trout and
possibly salmon numbers to be sustained it might be necessary to undertake some form of enhancement. In addition,
Meridian Energy would take several measures to limit the effect Project Aqua would have on fish stocks, including:
Screening the canal intake and outlet to keep migrating fish in the river Maintaining the braiding pattern of the river
through enhanced fairway vegetation control Adjusting historical flood management practice by using the upper Waitaki
storage lakes to meet the residual river requirements for maintaining the present stocks of salmon and trout The reports
also acknowledged that predictions about fish numbers in a big river such as the Waitaki are complex and also depend on
factors other than Aqua such as climate and ocean conditions. There is always some uncertainty with such predictions,
even when the most up to date scientific information is used. In response to this Meridian Energy would undertake
detailed monitoring of trout and salmon populations before, during and after construction, and would undertake
additional enhancement measures such as tributary habitat improvement and creation of spawning channels if required.
“We understand the environmental importance of the Waitaki River and we will take every precaution to retain that,” says
Alan Seay.
BACKGROUND
Some of the independent reports relating to how Project Aqua would affect fish life are:
Environmental study - aquatic ecosystems: native fish (NIWA). Appendix G to the Assessment of Effects on the Environment
Environmental study – aquatic ecosystems: salmon and trout (NIWA). Appendix H to the Assessment of Effects on the
Environment. Migrant Fish Protection Measures: Concept Report (NIWA). Appendix J to the Assessment of Effects on the
Environment. Summary of Screening Mitigation Considerations for Protection of Migrant Fish of the Lower Waitaki River.
Appendix J1 to the Assessment of Effects on the Environment. Canal Intake Fish Screen Concept Development Study
(Meritec). Appendix J2 to the Assessment of Effects on the Environment. Environmental study – Aquatic Ecosystems: Salmon
Angling Flow Requirements (Cawthron Institute). Appendix I to the Assessment of Effects on the Environment. Project Aqua
assessment of the effects: fish stranding in the lower Waitaki River. Appendix K to the Assessment of Effects on the
Environment.
Copies of these, and all the other independent reports carried out relating to Project Aqua are available. They can be
downloaded from the Project Aqua website: www.meridianenergy.co.nz/projectaqua or by calling 0800 AQUA INFO (0800
278-246)