He said he was astonished when the judge called his name out.
"I was really surprised to hear I'd won."
Matthew was awarded a cup, a trophy for his school and a cash prize of $740 for his efforts.
The Year 7 student had a keen interest in science and hoped to be a marine biologist when he was older.
He said it felt really good to know his experiment had placed ahead of those of high school students.
Matthew based his experiment at the Te Wairoa Stream, which led into Lake Tarawera, and predicted that water temperature was the predictor for trout to swim upstream to spawn.
During his investigation he looked at the effects moon phase, water temperature, rainfall, flow of water and water condition had on spawning.
After two months of collecting data every morning before school, Matthew discovered the trout headed upstream the day before a large amount of rainfall.
He said he found the study really interesting and had decided to conduct it after taking up fly-fishing with his dad.
"I like investigating and coming up with conclusions."
Matthew had also placed first in the school's own science fair this year.
Mrs Hyde said the school was incredibly proud of Matthew.
Normally, the regional winner of the Niwa science fair would proceed to Realise the Dream - the National School Science and Technology awards. But Matthew does not meet the age limit which is Year 9. However the school is hoping to negotiate his entry under special circumstances.
