Thermal stress in Arctic charr Salvelinus alpinus broodstock: a 28 year case study

Seasonal and age-related changes in sperm quality of farmed arctic charr (Salvelinus alpinus)

BACKGROUND

Substantial variation in male fertility is regularly observed in farmed Arctic charr. However, detailed investigations of its fluctuation during a reproductive season and across years are lacking. Furthermore, information about the effect of underlying genetic factors influencing sperm quality is scarce. The current study focused on seasonal and age-related factors that may affect sperm quality characteristics in males reared in natural and delayed photoperiods. Animals were sampled three times for two consecutive years, and sperm quality parameters were recorded using a computer-assisted sperm analysis (CASA) system. Thereafter, high-throughput sequencing technologies were applied, aiming to identify genomic regions related to the variation of sperm quality throughout the reproductive season.

RESULTS

An across-season variation in the recorded sperm quality parameters was evident. Overall, 29% and 42% of males from the natural and delayed spawning groups had a highly variable total progressive motility. Males at four years of age showed significantly higher sperm motility and velocities during the early October and November recordings compared to the following year when the same animals were five years of age. On the other hand, the opposite was observed regarding sperm concentration during the last sampling. A genome-wide FST scan detected SNP differentiation among males with high and low variability in total progressive motility (PM) on eight chromosomes (FST > 0.17), Genome wide windows with the highest FST contained SNPs in proximity (within 250 kb up- and downstream distance) to 16 genes with sperm quality biological functions in mammalian species.

CONCLUSION

Our findings provide a detailed view of seasonal, age-related, and genetic effects on sperm quality and can be used to guide decisions on broodstock selection and hatchery management.

Wild and Farmed Arctic Charr as a Tourism Product in an Era of Climate Change

The topic investigated is the social-ecological system of Arctic charr (Salvelinus alpinus) fishing and aquaculture as a tourism product in an era of climate change. Arctic charr is a resilient salmonid species that was traditionally an important part of the sustenance economy in Arctic and Subarctic communities as a source of fresh food throughout the year. Arctic charr populations have declined in recent years, in part due to climate change. These changes in the freshwater ecosystems in turn affect the cultural and economic traditions of freshwater fishing and consumption. This development has consequences for the tourism industry as hunting, fishing and consuming local and traditional food is important in branding tourism destinations. Fisheries are no longer the source of this important ingredient in the Nordic culinary tradition, instead aquaculture production supplies nearly all the Arctic charr consumed. In this paper, we pool the resources of an interdisciplinary team of scholars researching climate change, freshwater ecology, aquaculture and tourism. We integrate knowledge from these fields to discuss likely future scenarios for Arctic charr, their implications for transdisciplinary social ecosystem approaches to sustainable production, marketing and management, particularly how this relates to the growing industry of tourism in the Nordic Arctic and Subarctic region. We pose the questions whether Arctic Charr will be on the menu in 20 years and if so, where will it come from, and what consequences does that have for local food in tourism of the region? Our discussion starts with climate change and the question of how warm it is likely to get in the Nordic Arctic, particularly focusing on Iceland and Norway. To address the implications of the warming of lakes and rivers of the global north for Arctic charr we move on to a discussion of physiological and ecological factors that are important for the distribution of the species. We present the state of the art of Arctic charr aquaculture before articulating the importance of the species for marketing of local and regional food, particularly in the tourism market. Finally, we discuss the need for further elaboration of future scenarios for the interaction of the Arctic charr ecosystem and the economic trade in the species and draw conclusions about sustainable future development.

Assessing the potential of improving growth and survival to the eyed stage in selectively bred Arctic charr (Salvelinus alpinus)

The Arctic charr breeding programme has been a main driving force for developing the aquaculture industry in Sweden. Selection has been performed for almost 40 years using animals from a closed breeding nucleus. The aim of the current study was to evaluate the potential of further improving growth-related traits taking into account the existence of genotype-by-environment interaction. Furthermore, we investigated the magnitude of the genetic component associated with survival to the eyed stage and potential associations with inbreeding coefficients. A preliminary heritability estimate of 0.23 (SE 0.20) was obtained for survival to the eyed stage using records spanning from 2000 to 2017 (n = 230). Moreover, moderate-to-high heritability estimates (0.27-0.49) were obtained for growth-related traits (body weight and length), using animals from the latest generation of selection (year class 2017). Those animals (n = 2,776), originating from 55 full-sib families, were split into two groups and reared in separate land-based facilities of commercial fish farms in Sweden. The growth-related traits were recorded twice in both sites when animals were of >1 and >2 years of age. Existence of sexual growth dimorphism was indicated with the males having on average 6%-8% higher total length and 22%-34% higher body weight. Furthermore, high genetic correlations regarding growth traits were obtained amongst animals reared at the two different sites (0.82-0.95). In addition, we assessed the accuracy of best linear unbiased prediction (BLUP)-derived estimated breeding values (EBVs) when phenotypes from each rearing site were subsequently masked and used as a validation set. A mean prediction accuracy of 0.60 (length) and 0.64 (weight) were derived for both rearing sites. Overall, our results suggest that further growth improvements should be possible in the subsequent generations of selection. Finally, even though indications for the existence of an underlying genetic component(s) involved in survival to the eyed stage were obtained additional data will be required for elucidating its magnitude.

Cold temperature represses daily rhythms in the liver transcriptome of a stenothermal teleost under decreasing day length

The climate-change-driven increase in temperature is occurring rapidly and decreasing the predictability of seasonal rhythms at high latitudes. It is therefore urgent to understand how a change in the relationship between photoperiod and temperature can affect ectotherms in these environments. We tested whether temperature affects daily rhythms of transcription in a cold-adapted salmonid using high-throughput RNA sequencing. Arctic char (Salvelinus alpinus) from a subarctic population were reared at a high and a low temperature (15 and 8°C) for 1 month under natural, decreasing day length during late summer. Liver transcriptomes were compared between samples collected in the middle and towards the end of the light period and in the middle of the dark period. Daily variation in transcription was lower in fish from the low temperature compared with strong daily variation in warm-acclimated fish, suggesting that cold temperatures dampen the cycling of transcriptional rhythms under a simultaneously decreasing day length. Different circadian clock genes had divergent expression patterns, responding either by decreased expression or by increased rhythmicity at 15°C compared with 8°C. The results point out mechanisms that can affect the ability of fish to adapt to increasing temperatures caused by climate change.