The use of additional lighting and artificial photoperiods to recondition early maturing Atlantic salmon (Salmo salar) in Tasmania

Salmonid culture in Tasmania experiences high rates of early maturation due to the rapid growth rates achieved under favorable environmental conditions. The present study investigates the use of artificial photoperiod to recondition previously mature Atlantic salmon to provide a larger fish with higher market value. Individual groups of previously mature female Atlantic salmon (Salmo salar) were put under 24 hour artificial light from either May, June, July or maintained under ambient conditions during the austral winter. Fish maintained under lights attained a reversion from dark skin pigmentation, typical of mature individuals, to a silver sea-going coloration more rapidly than the control group. In addition flesh pigmentation, ovarian absorption and body wall thickness was significantly greater than that of the control fish resulting in a higher market price. The study demonstrates that artificial lights can facilitate the reconditioning of previously mature Atlantic salmon under southern hemisphere conditions.