The Lake Taupo fishery declined substantially during 2010—2012
This had a major bearing on the local Taupo economy & some reports indicated an economic decline of up to 30% - largely due to the poor quality & quantity of trout harvested in the Taupo fishery. Advocates for the Tongariro approached freshwater fisheries scientist Professor David Hamilton of Waikato University for his opinion regarding the decline. Prof Hamilton suggested a study be made of the Taupo food web and offered to arrange for a graduate student from the University to carry out a 3 year food web study towards a PhD qualification. Prof Hamilton advised that the study would cost approximately $108,000.00. This amount was duly raised by the Advocates during 2012 & was provided by:
Dept.of Conservation ----$36,000.00
Taupo District Council ---$36,000.00
Pharazyn Trust -----------$36,000.00

Simon Stewart (who held a masters degree in freshwater ecosystems) was duly appointed to carry out the study which was completed in 2015
The major outcome of the study was that the annual mixing of the lake’s thermoclines has a big influence on the lake food web as the mixing process stimulates the growth of plant plankton—a major part of the food web. During El Nino conditions (as experienced in 2010) the mixing process can be severely affected. Largely as a result of Simon Stewart’s study a more proactive fisheries management approach has now been implemented by D.O.C. & Fisheries NZ to determine year by year trout catch & size limits.