Developing welfare advice in light intensities and incidence of sexual maturation
The objective of this trial is to test the hypothesis that there is no single, universal light intensity threshold which triggers maturation in Atlantic salmon, but rather that it is the difference between intensities experienced within a 24 hour period which alters perceived photoperiod, and thus modulates sexual development.
Artificial lights are widely used in salmon aquaculture to inhibit maturation in spring (Leclercq et al. 2011), but if used in the autumn can have the opposite effect and actually stimulate sexual development (Fjelldal et al. 2011). However, recent research suggesting that behavioral modification using submerged lights is an effective lice prevention strategy has spawned a desire to use lights in marine cages year-round (Frenzl et al. 2014). This research aims to increase the feasibility of light use as a parasite prevention technique by exploring which light conditions instigate maturation, and which do not.
To do this we will expose ~120 g male Atlantic salmon smolts to eight different light regimes in full salinity seawater at 16 °C for 10 weeks, and at the end of the trial evaluate frequency of maturation. The trial will be conducted at the Matre Research Station operated by Havforskningsinstituttet. Each treatment will be replicated four times, with 60 fish per tank (Ntotal = 8 treatments x 4 replicates x 60 salmon/tank = 1920 salmon).
The experiment is expected to cause only mild distress to the animals as a result of pit tagging for individual identification and brief handling for transfer into the experimental tank systems. All fish will be maintained in gray 1 x 1 x 0.43 m3 tanks using best known salmon husbandry practices with no stressors of any kind. After 10 weeks the trial will be terminated and all fish will be euthanized via anaesthetic overdose. Length, body weight and gonad weight of every individual will be measured.
There are no alternatives which we can use to evaluate the impacts of light regime on maturation, however every effort has been made to reduce the number of animals used in this trial. We have chosen to use 120 g all-male salmon maintained in warm temperatures (16 °C) because previous work by Fjelldal et al. (2011) showed that such are the most likely conditions to induce sexual maturation, and thus provide a conservative baseline. The minimum number of replicates and individuals to minimize the risk of type I and type II statistical errors were determined by power analysis, and final fish numbers per tank were then calculated to achieve an optimal stocking density in each system for social cohesion.
Artificial lights are widely used in salmon aquaculture to inhibit maturation in spring (Leclercq et al. 2011), but if used in the autumn can have the opposite effect and actually stimulate sexual development (Fjelldal et al. 2011). However, recent research suggesting that behavioral modification using submerged lights is an effective lice prevention strategy has spawned a desire to use lights in marine cages year-round (Frenzl et al. 2014). This research aims to increase the feasibility of light use as a parasite prevention technique by exploring which light conditions instigate maturation, and which do not.
To do this we will expose ~120 g male Atlantic salmon smolts to eight different light regimes in full salinity seawater at 16 °C for 10 weeks, and at the end of the trial evaluate frequency of maturation. The trial will be conducted at the Matre Research Station operated by Havforskningsinstituttet. Each treatment will be replicated four times, with 60 fish per tank (Ntotal = 8 treatments x 4 replicates x 60 salmon/tank = 1920 salmon).
The experiment is expected to cause only mild distress to the animals as a result of pit tagging for individual identification and brief handling for transfer into the experimental tank systems. All fish will be maintained in gray 1 x 1 x 0.43 m3 tanks using best known salmon husbandry practices with no stressors of any kind. After 10 weeks the trial will be terminated and all fish will be euthanized via anaesthetic overdose. Length, body weight and gonad weight of every individual will be measured.
There are no alternatives which we can use to evaluate the impacts of light regime on maturation, however every effort has been made to reduce the number of animals used in this trial. We have chosen to use 120 g all-male salmon maintained in warm temperatures (16 °C) because previous work by Fjelldal et al. (2011) showed that such are the most likely conditions to induce sexual maturation, and thus provide a conservative baseline. The minimum number of replicates and individuals to minimize the risk of type I and type II statistical errors were determined by power analysis, and final fish numbers per tank were then calculated to achieve an optimal stocking density in each system for social cohesion.