As a result the percentage of hatchery fish in the natural spawning population has decreased to an average of less than 7% in the last three years.
(the percentage of hatchery fish in the natural spawning population; has decreased; to an average of less than 7% in the last three years)
the percentage of hatchery fish in the natural spawning population
has decreased
to an average of less than 7% in the last three years