Data from ongoing age 2 male maturation assessments of yearling Chinook and Sockeye salmon at hatchery facilities located in the interior Columbia basin

Pacific salmon have diverse life histories including phenotypic plasticity
in the age at which males initiate maturation (range 1-6
years).  Both genotype and rearing practices (feed type
and rate, rearing temperatures) influence age of
maturation.  We have been monitoring age 2 (minijack)
precocious male maturation rates at various Columbia River basin hatchery
facilities from 1997 to the present. Thus, it is a compilation of over two
decades of monitoring minijack rates at hatcheries primarily focused on
yearling reared spring, summer and fall-run Chinook salmon but also
includes yearling Snake River Sockeye salmon as well. The dataset includes
the size (both length and weight) of individual fish at the time of
maturation assessment, just prior to hatchery release in the spring as
yearling smolts. It was compiled from several studies that examine effects
of feed treatments within a hatchery population (lipid content of feed and
feed ration) and effects of rearing site (example: Hood River stock fish
reared at three different hatcheries) on fish growth and maturation.
Overall, we have found that the prevalence of minijack maturation is
variable among hatchery populations (ranging from 0-72% of males) and is
significantly influenced by species, stock, life-history type and hatchery
rearing practices.