Jacking in Chinook salmon (Oncorhynchus tshawytscha), is defined as precocious sexual maturation of males after at least 1 year in sea water, and occurring 1 year prior to females of the same cohort. Substantial evidence supports genetic, environmental, and genetic by environmental effects on precocious maturation in Chinook salmon, however the underlying mechanisms remain unclear.
Passive integrated transponder tagged fish were followed through fresh and salt water growth to the sexual maturation of the jacks. Growth data was recorded to examine the relationship between size/growth effects in freshwater rearing on subsequent precocious sexual maturation of the jacks. No effect of size/growth in freshwater was detected. Reanalysis of data from a previous study showed an effect of developmental rate on jacking.
Sequencing tested the possibility of a relationship between jacking and Major Histocompatibility (MH) genes at the MH class II β 1 locus. One genotype positively affected the likelihood of jacking
