Effects of short‐day treatment on long‐term growth performance and maturation of farmed Arctic charr Salvelinus alpinus reared in brackish water

Abstract

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.

Impact of environmental factors on the growth and maturation of farmed Arctic charr

“…They identified variation in body weight QTL across multiple families of Arctic charr and this, combined with moderate heritability and genetic correlations between full-sibs reared in fresh and brackish water environments, indicates there is potential for genetic improvement of growth in both environments. In another study, Gunnarsson et al (2014) found that Arctic charr maintain high NKA activity and relatively stable levels of plasma Na + at 27 ppt, although growth rate was lower at 27 ppt than at 17 ppt. Similarly, Arnason et al (2014) reported lower long-term growth at 29 ppt than at 25 ppt.…”

“…The juvenile production is all Figure 1 Map showing the global distribution of Arctic charr inclusive of all nominate subspecies and closely related "species" considered to belong to this group in the narrow sense (http://www.grida.no/resources/7758). in freshwater, but in Iceland, the fish are commonly transferred to brackish water at a size of 50-150 g Gunnarsson et al 2014). The land-based farms offer varying degrees of possibilities of controlling environmental factors such as rearing temperature, salinity and photoperiod.…”

“…Due to the limited and seasonal seawater tolerance (Finstad et al 1989;Arnesen et al 1993a, b), most of the production of Arctic charr (on-growing) takes place either in freshwater or in brackish water. In Iceland, the bulk of the Arctic charr farming takes place in brackish water (15-27 ppt) during on-growing Gunnarsson et al 2014).…”

Preference for nearshore and estuarine habitats in anadromous Arctic char (Salvelinus alpinus) from the Canadian high Arctic (Victoria Island, Nunavut) revealed by acoustic telemetry

“…While anadromous Arctic char would no longer be transitioning between freshwater and saltwater physiological states midsummer (Bystriansky et al 2007), there may still be growth benefits to residing in brackish water. Indeed, salinity in estuaries might be closer to blood osmolarity, leading to lower energy expenditures to maintain ion homeostasis and could thus result in higher growth (Wootton 2011;Gunnarsson et al 2014). In short, estuaries seem to provide critical habitats for Arctic char during their summer migrations, and future studies should focus on the factors that make these environments favorable.…”

Controlling preharvest maturity in farmed Arctic char: A review from the Canadian perspective

“…Because of the high value of Arctic char products, there is a growing interest in improving hatchery techniques to increase farming of this species in Canada, and several research groups across North America and Northern Europe are focusing on this subject. Several studies have shown the benefit of reduced water temperature during vitellogenesis, ovulation (Gillet, 1991;Gillet & Breton, 2009;Jeuthe, Brännäs, & Nilsson, 2015;Jeuthe, Brännäs, & Nilsson, 2016;Jobling, Johnsen, Pettersen, & Henderson, 1995), and embryonic development (Huuskonen, Penttinen, & Piironen, 2003;Jeuthe et al, 2016); the effect of photoperiod on the timing of sexual maturation (Frantzen, Arnesen, Damsgård, Tveiten, & Johnsen, 2004;Gunnarsson et al, 2012;Gunnarsson et al, 2014;Liu & Duston, 2016;Liu & Duston, 2018); the role of egg size and related energy density on embryonic survival and individual performance (Leblanc, Kristjánsson, & Skúlason, 2016); the importance of female age on egg mass and fecundity (Jeuthe et al, 2013;Lasne, Leblanc, & Gillet, 2018); and the relevance of broodstock nutrition on Arctic char embryonic development and survival (Izquierdo, Fernández-Palacios, & Tacon, 2001;Pickova, Brännäs, & Andersson, 2007).…”