How does photoperiod affect growth?

In many cultured animals, increasing the day length has been associated with increased feed intake and therefore, increased growth rate. The reverse seems to be true for the arctic charr, at least in the juvenile phase.http://www.thefishvet.com.au

Aquaculture
Volume 353, Number 11 (June 2012)
	Enhanced growth of farmed Arctic charr (Salvelinus alpinus) following a short-day photoperiod
	Authors:	Snorri Gunnarsson, Albert K. Imsland, Sten I. Siikavuopio, Jón Árnason, Arnþór Gústavsson, Helgi Thorarensen
	Author Affiliations:	no affiliations available
	Source:	Aquaculture, Volume 353, Number 11 (June 2012)
	Page Numbers:	75 – 81
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: Unknown Location: Publisher’s Site Authentication: Publisher’s Site
	Abstract:	The short and long term effects of short photoperiods on growth and maturity were investigated in 240 individually tagged juvenile Arctic charr (Salvelinus alpinus). The Arctic charr were reared at constant temperature (12°C) and on four different light regimes; one group on continuous light (LD24:0) as control and three groups experienced a period of short day (LD8:16) on a three subsequent 6week periods i.e. 24th September–6thNovember (LD8:16Sep–Nov), 6th November–19th December (LD8:16Nov–Dec), 19th December-29th January (LD8:16Dec–Jan). Before and after the short photoperiod treatment the groups were reared at continuous light. The growth of the fish was monitored over a period of 11months. At the termination of the experiment in September 2009, the body mass of the three groups receiving a short day period (LD8:16 Sep–Nov, LD8:16 Nov–Dec and LD8:16 Dec–Jan) was significantly higher (13.9%, 12.9% and 10.7% respectively) than that of the group reared at continuous light (LD24:0). The three groups receiving the short photoperiod did not differ in weight at the end of the trial so the time of the year at which the short photoperiod was applied did not seem to be of importance regarding the growth enhancement. The maturation rate did not appear to be affected by the photoperiod treatments. The improved growth was mainly a result of a higher feed intake and improved feed conversion efficiency for the period following transfer of the charr from a short photoperiod to the continuous light. Application of such a winter photoperiod during the juvenile phase can, therefore, be used as a tool to increase the biomass and growth rate in Arctic charr farming.
	Citation:	Snorri Gunnarsson, Albert K. Imsland, Sten I. Siikavuopio, Jón Árnason, Arnþór Gústavsson, Helgi Thorarensen . Enhanced growth of farmed Arctic charr (Salvelinus alpinus) following a short-day photoperiod. Aquaculture, Volume 353, Number 11 (June 2012), pp. 75-81, ;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=4242A8AA50DD97827D52

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