Photoperiodic effects on precocious maturation, growth and smoltification in Atlantic salmon, Salmo salar

Abstract

Current Atlantic salmon farming practice induces early smoltification with artificial photoperiod regimes, however the importance of these photoperiods on parr maturation and interactions with smoltification are poorly understood. These questions were addressed in the present investigation, which examined the effects of photoperiod manipulation on the development, maturation and smoltification of individually tagged parr.

A decrease in photoperiod shortly after first feeding influences the development of Atlantic salmon (Salmo salar)

“…Furthermore, Thorpe (1994) has suggested that the initiation of maturation could be influenced prior to first feeding. Similarly, Berrill et al (2003) found that an 8 week period of short days (LD10:14) applied in May, shortly after first feeding in March, increased maturation rates compared to similar regimes applied later in the summer, highlighting a specific period of sensitivity in early development.…”

“…Consequently, the current study leads on from that of Berrill et al (2003) and aims to investigate the importance of the timing and duration of short day photoperiod regimes during a proposed sensitive period in early development. In order to achieve this 8 and 12 week periods of short days were applied at two times from shortly after first feeding.…”

“…In order to achieve this 8 and 12 week periods of short days were applied at two times from shortly after first feeding. The timing of the photoperiods was determined in order to compliment the study of Berrill et al (2003); in the current experiment the May treatments replicated the yearly timing of the May photoperiod group of Berrill et al (2003) regardless of age from first feeding. Then, due to a difference in the time of first feeding between the two experiments, the fish from the June photoperiods of the current experiment were of a similar chronological age as the May photoperiod fish from Berrill et al (2003 -ATPase activity were compared using a General Linear Model (GLM).…”

Chronobiology: implications for marine resource exploitation and management

“…With freshwater trout, experimental modification of the seasonally-varying cycle of day length has been used for the production of year-round supplies of eggs for commercial fish farms (Dustan and Bromage, 1986). Also, similar photoperiod manipulation is the tool most used by farms to control growth, reproduction and smoltification of Atlantic salmon (Berrill et al, 2003), though the physiological mechanisms underlying such commercial manipulations are still poorly understood. Increasing awareness of the likely occurrence of endogenous rhythms in cultured fish has, however, prompted studies, for example, of flexibility in rhythms of feeding (Boujard et al, 1995).…”

“…The fish exhibited free-running circa-annual rhythms of gonadal maturation and ovulation which were self-sustaining for three circa-annual cycles. The role of photoperiodic manipulation, against the background of circa-annual and circadian periodicity, needs to be more fully evaluated as a basis for increased aquaculture yields (Berrill et al, 2003).…”