Effect of photoperiod and feeding frequency on growth and feed utilization of fingerlings Persian sturgeon (Acipenser persicus) Mehdi Zolfaghari, Mohammad Reza Imanpour & Esfandyar Naja¢ Fishery Faculty, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Correspondence: M Zolfaghari, Fishery Faculty, Gorgan University of Agricultural Sciences and Natural Resources, Beheshti St., Gorgan, Iran. E-mail: zolfaghari.mz@gmail.com Abstract The e¡ects of photoperiod (12L:12D and18L:6D) and feeding frequency (three, four and ¢ve evenly spaced daily feedings) of 10% biomass per day during light hours on growth and stress response of Persian stur- geon ( Acipenser persicus ) ¢ngerlings were evaluated. The interaction between photoperiod and feeding frequency was not signi¢cant ( P40.05). Faster growth was observed in ¢sh exposed to an 18L:6D photoperiod ( Po0.01). The feed conversion e⁄ciency (FCE) was also better with an 18L:6D photoperiod ( Po0.05). Fish fed four and ¢ve meals per day grew similarly ( P40.05) and faster than when fed only three meals ( Po0.01). The FCE with four or ¢ve meals per day was better than with three meals ( Po0.05). At harvest, the proximate composition was similar in all treatments ( P40.05). Stress indicators (cortisol, glucose and haematocrit) did not di¡er between photoperiods ( Po0.05). The results showed that 0.9^ 8.0 g Persian sturgeon ¢ngerlings should be reared with an 18L:6D photoperiod and fed four times per day to obtain good growth and FCE. Keywords: Acipenser persicus , feeding frequency, growth, photoperiod Introduction The Persian sturgeon ( Acipenser persicus ) is an ana- dromous species belonging to the Acipenseridae family and is widely distributed along the Caspian Sea coast of Iran (Birstein, Hanner & DeSalle 1997). It is a critically endangered species due to over¢shing and pollution (Jackson, Hurvitz, Din, Goldberg, Pearl- son, Degani & Levavi-Sivan 2006). Arti¢cial propaga- tion and culture of Persian sturgeon could enlarge the supply and help to reduce ¢shing pressure. A long photoperiod has been applied successfully to improve the growth of numerous ¢sh species (Bis- was & Takeuchi 2003; Biswas, Seoka,Tanaka,Takii & Kumai 2006; Tucker, Booth, Allan, Booth & Fielder 2006; Ruchin 2007; Biswas, Seoka, Ueno, Yong, Biswas, Kim,Takii & Kumai 2008; Askarian & Kuosha 2009), including for larval stages (Fielder & Barsdley 2002). However, varying photoperiod lengths showed no e¡ect on the growth of beluga ¢ngerlings (Bani,Ta- barsa, Falahatkar & Banan 2009). Purchase, Boyce and Brown (2000) observed a decreased growth in yellowtail £ounder with the increasing photoperiod. Optimal feeding strategies can enhance growth and feed conversion e⁄ciency (FCE) (Dwyer, Brown, Par- rish & Lall 2002). Feeding frequency during the day should target optimal feed intake and growth (Dwyer et al . 2002; Mohseni, Pourkazemi, Bahmani, Falahat- kar, Pourali & Salehpour 2008). The feeding frequency maximizing ¢sh growth depends on various factors including species and life stage (Wang, Kong, Li & Bu- reau 2007). In general, available information relates to white sturgeon ( Acipenser transmontanus ) (Hung, Her- old, Gawlicka & Noue 1998; Deng, Koshio, Yokyama, Shao & Hung 2003) and Siberian sturgeon (Koksal, Rad & Kindir 2000), not to Persian sturgeon. Stress negatively in£uences growth and disease resistance (Askarian & Kuosha 2009). Biswas et al . (2006) demonstrated that photoperiod manipulation did not cause signi¢cant acute or chronic stress response in red sea bream ( Pagrus major ) reared from 20 to 100g. There is no information regarding the e¡ect of photoperiod manipulation on the stress Aquaculture Research, 2011, 42 , 1594^1599 doi: 10.1111/j.1365-2109.2010.02749.x 1594 r 2010 Blackwell Publishing Ltd