Introduction:
It’s known that there are environmental factors as photoperiod and temperature that influence the onset of puberty in critical seasonal periods, however at commercial scale it is not so clear how this factors works to explain the high rates of early maturity observed. According to gonadal ultrasound monitoring performed frequently in Chilean salmon production, it has been identified a series of hatcheries with a high prevalence of minijacks before the seawater transfer. In the present study, we examine if manipulation of light intensity and temperature variations can trigger sexual maturation in male Atlantic salmon during freshwater phase and the specific weight of each of those factors in the stimulation of sexual maturity in pre-smolt Atlantic salmon
Materials and methods:
The study was carried out in flow trough commercial facility in La Araucanía region, Chile. 2 experimental groups were formed, each group in duplicate, with different regimes of light as described in the scheme of Fig 1.
Fig. N° 2. Ultrasound index performed in monthly sampling,. of male of male salmon from 50 to 200 g. during the progression of the spermatogenesis in the different sampling points. Were 6 represent an advanced degree of gonadal development or maturation.
Results:
There was a significant reduction of maturation observed in the results of regime 2 at high temperatures Fig 2.
The L allele and the homozygous LL genotype are fixed in all samples in the 2 groups, which should not predispose to greater maturity any treatments. LL genotype represent a low genetic disposition to early maturation. Table 1.
Conclusions:
In this field trial we observe how is possible reduced the maturation effect of temperature using an adapted photoperiod regime. Gonad ultrasound is a very useful tool to predict and control the maturation risk particularly as in this study with high temperature water. This may be of particular importance for FW salmon producers in flow through systems in warm regions such as northern salmon producing regions in Chile and Tasmania, also for production in RAS closed-containment where high temperatures are frequently observed.