Influence of photoperiod on the timing of reproductive maturation in pink salmon (Oncorhynchus gorbuscha) and its application to genetic transfers between odd- and even-year spawning populations

Abstract

Pink salmon (Oncorhynchus gorbuscha) embryos were obtained in April 1991 from the first generation of a 1989 brood line, which had been induced to spawn 6 months earlier than wild populations, which spawn in October. These embryos and subsequent juveniles were reared at a development temperature and under a photoperiod regime that induced some fish from this second generation to mature in October 1992, the correct time of year for spawning of wild populations. Other captive groups of pink salmon also matured in April 1993, permitting a comparison of fecundity, egg fertility, and egg size among female spawners in different photoperiods. Although the wild population spawns only in odd years, the captive population, originally derived from odd-year spawners, has been manipulated to spawn in even years. This shifting of the spawning time of the captive population may permit a transplant of odd-year genes into an even-year line, perhaps allowing the development of a run of even-year pink salmon in the Fraser River, British Columbia.