Gunnarsson S, Johansson M, Gústavsson A, Arnason T, Arnason J, Smáradóttir H, Björnsson B Th, Thorarensen H, Imsland A K
Akvaplan-niva Iceland Office, Akralind 4, 201 Kópavogur, Iceland; Department of Biology, University of Bergen, High Technology Centre, 5020 Bergen, Norway.
J Fish Biol. 2014 Oct;85(4):1211-26. doi: 10.1111/jfb.12524.
The effects of a 6 week short-day photoperiod followed by continuous light, applied during the juvenile phase of Arctic charr Salvelinus alpinus in fresh water on smoltification and on the long-term growth and maturity following transfer to brackish water (BW) (constant salinity of either 17 and 27 or increasing salinity in steps from 17 to 27) were investigated. Prior to salinity transfer, the juveniles were either reared at continuous light (C group) or reared for 6 weeks on a short day (8L:16D, S group) followed by continuous light (24L:0D). Increased salinity had negative effect on growth, with female fish reared at 17 salinity weighing 19 and 27% more than the salinity-step group (17-27) and the 27 salinity group, respectively. The stepwise acclimation to salinity had limited advantage in terms of growth rate. Short photoperiod for 6 weeks (November to January) followed by continuous light improved growth, but not seawater (SW) tolerance. Gill Na(+) , K(+) -ATPase activity and plasma Na(+) levels changed with time, indicating some variation in osmoregulatory capacity during the experimental period. Overall, there appear to be interactive effects on maturation from applying short-day photoperiod followed by rearing at higher salinities. Plasma leptin varied with time and may be linked to stress caused by the observed variations in osmoregulatory ability. It is concluded that changes in growth rates observed in this study are mainly related to rearing salinity with higher growth rates at lower salinities. Short-day photoperiod has some growth-inducing effects but did not improve SW tolerance. Farmers of S. alpinus using BW for land-based rearing should keep salinity at moderate and stable levels according to these results to obtain best growth.
研究了在淡水环境中，对北极红点鲑（Salvelinus alpinus）幼鱼期施加为期6周的短日照光周期后再持续光照，对其洄游驯化以及转移至半咸水（BW）（盐度恒定为17或27，或从17逐步增加至27）后的长期生长和成熟的影响。在盐度转移之前，幼鱼要么在持续光照下饲养（C组），要么先在短日照（8小时光照：16小时黑暗，S组）下饲养6周，然后再持续光照（24小时光照：0小时黑暗）。盐度增加对生长有负面影响，饲养在盐度为17的雌性鱼体重分别比盐度逐步升高组（17 - 27）和盐度为27的组重19%和27%。逐步适应盐度在生长速率方面优势有限。6周的短日照（11月至1月）后再持续光照可促进生长，但不能提高海水（SW）耐受性。鳃Na(+)、K(+) - ATP酶活性和血浆Na(+)水平随时间变化，表明实验期间渗透调节能力存在一些变化。总体而言，短日照光周期后在较高盐度下饲养对成熟似乎有交互作用。血浆瘦素随时间变化，可能与观察到的渗透调节能力变化所引起的应激有关。得出的结论是，本研究中观察到的生长速率变化主要与饲养盐度有关，较低盐度下生长速率更高。短日照光周期有一些促生长作用，但未提高海水耐受性。根据这些结果，使用半咸水进行陆基养殖的北极红点鲑养殖户应将盐度保持在适度且稳定的水平以获得最佳生长。
