| 1. |
- Brännäs, Eva, et al.
(författare)
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Arctic charr farming : production of juveniles; a manual
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Arctic charr (Salvelinus alpinus L.) is a holarctic salmonid fish species with both landlocked and anadromous populations. In Scandinavia it is mainly found in the mountain area, but it also appears in deep and large lake further south, i.e. in the Alps. It is the northernmost freshwater fish and A. charr is generally regarded as the most cold-adapted freshwater fish. A. charr has been commercially farmed since the early 90ths and today, the total production is 3000, 2300 and 700 tonnes/year in Iceland, Sweden and Norway, respectively. Both in Sweden and Iceland, there are selective breeding programs in effect and the bulk of the farming production is conducted using offspring from the national breeding programs in each country. A. charr is renowned for its ability of high growth rate at low temperature and is therefore especially suitable for farming at high latitudes and altitudes. Moreover, due to the success of the breeding programs, the charr used in farms today grow faster and mature at a larger size and age than the original wild charr. Hence, although being a fairly small industry at present, A. charr farming is predicted to grow in all three countries. This booklet summarises up-to-date knowledge on A. charr farming production cycle, from brood stock to juvenile on-growing stage (Fig. 1). It is intended to be useful for people taking their first steps in A. charr culture but also to serve as a farming manual for more experienced farm staff. Therefore, the booklet is divided in to two chapters. The first chapter (Arctic charr farming in practice) provides a straight forward introduction to each production step from brood stock to juveniles. The second chapter (theory and background) presents some details and research data on the background of specific farming practices and procedures
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| 2. |
- Jeuthe, Henrik
(författare)
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Brood-stock management and early hatchery rearing of Arctic charr (Salvelinus alpinus(Linnaeus))
- 2020
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Ingår i: Reviews in Aquaculture. - : Wiley. - 1753-5123 .- 1753-5131. ; 12, s. 1595-1623
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Tidskriftsartikel (refereegranskat)abstract
- Arctic charr (Salvelinus alpinus(Linnaeus)) is a stenothermic cold-water fish, which has been cultured in Northern Europe and North America since the 1980s. The industry has remained relatively small with an annual production between 6000 and 10 000 tonnes, and is still challenged by an unreliable offspring production. This review focuses on offspring production in Arctic charr aquaculture including holding conditions for brood-stock, fertilisation and egg rearing until hatch. Brood-stock requires low temperatures during summer (<12 degrees C) with the optimum still unknown. The temperature maximum for egg incubation lies between 6 and 8 degrees C. The composition of an optimal brood-stock diet is debated regarding fatty acids. A demand for a freshwater-based diet rich in omega-6 fatty acids is indicated, but results remain inconclusive. Extensive knowledge has been gained on the timing of spawning and its manipulation through photoperiod, temperature and hormone treatments; spawning can be induced by short-day photoperiod; and temperature drops to 5 degrees C. Eggs are fertilised dry in ovarian fluid. Egg quality is highly variable and positively related to egg size and energy density. Contrary, little information is available on sperm quality and its impact on egg survival. There may also be profound differences between Arctic charr of stationary or anadromous origin regarding requirements for holding conditions of brood-stock and their diet. However, these differences have received little attention, and direct comparative studies are in demand.
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| 3. |
- Jeuthe, Henrik, et al.
(författare)
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DNA fragmentation and membrane integrity in sperm of farmed Arctic charr (Salvelinus alpinus)
- 2022
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 547
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Tidskriftsartikel (refereegranskat)abstract
- Despite the relatively long history of captive breeding, the Arctic charr still exhibits a generally low, but highly variable reproductive performance in aquaculture. A recent publication exposed potential paternal factors influencing the reproductive outcome of Arctic charr broodstock from the Swedish breeding program. Interestingly, the paternal factor appeared to be more closely connected to embryo survival than to fertilisation rates. This lead to speculations on whether e.g. chromatin related issues, potentially related to oxidative stress could be involved. In order to investigate this hypothesis the present study assessed the levels of DNA fragmentation, using the SCD-method, and membrane integrity, using flow cytometry, in sperm of farmed Arctic charr. Moreover, the existence of associations was tested between DNA fragmentation and membrane integrity in individual semen samples and viability of their resulting progeny. We found high levels of DNA fragmentation in sperm from the Arctic charr sires, ranging from 24% to 86% with a median of 67%. Membrane integrity values were high, with individual levels of 93.1% to 99.6% viable sperm cells, median 98.8%. DNA fragmentation and membrane integrity values were moderately correlated (r = 0.304, p < 0.05). Fertilisation rates and proportions of eyed eggs showed substantial individual variation and were correlated (r = 0.497, p < 0.05). However, large differences between proportion of eyed eggs and fertilisation rate, median 52% and 81.6% respectively, highlight that the main loss occurred due to embryo mortality rather than failed fertilisation. No correlation was found between either DNA fragmentation or membrane integrity and the resulting reproductive outcome (fertilisation rate and eyed eggs) of the individual Arctic charr sires. Overall, our study identified very high levels of DNA fragmentation, which could influence the fertility of the broodstock in question and thereby be a mitigating mechanism involved in the low reproductive success most often observed in farmed Arctic charr. Further exploration of this relationship would be needed, though.
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| 4. |
- Jeuthe, Henrik, et al.
(författare)
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Effects of egg size, maternal age and temperature on egg, viability of farmed Arctic charr
- 2013
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 408, s. 70-77
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Tidskriftsartikel (refereegranskat)abstract
- The present study aims to analyze several biological and environmental variables to explain the unpredictable reproductive success at the main aquaculture facility involved in the Swedish Arctic charr breeding program. Data from 540 egg batches, collected from the years 2000 to 2011, were analyzed for the effects of factors such as temperature conditions, female age and egg size on egg viability (% of eyed eggs). An exploratory factor analysis (EFA) reduced 12 variables into 4 factors. Factor 1 mainly explains the negative relationship between high temperature in summer and egg viability. Factor 2 mainly explains a significant relationship between increasing temperatures in autumn (September to November) and decreased egg viability. Factor 3 explains that an early stripping date and increased temperature during stripping and egg incubation together have a negative, although not statistically significant, relationship to egg viability. Factor 4 explains a significant positive relationship between female age and egg size on the proportion of eyed eggs. The most relevant factors in explaining egg viability identified by the EFA analysis were evaluated further, indicating how farming conditions need to be improved. The broodstocks have been subjected to critically high water temperatures during July and August, resulting in decreased egg viability. Access to sufficiently cool water during summer is crucial. Based on the negative correlations found between incubation temperature and egg survival we suggest that a more moderate water heating may be beneficial. Most females were used as broodfish for several years. By applying individual tagging, data on the individual reproductive performance of females for up to 5 consecutive years could be analyzed. In this analysis, both egg size and the proportion of eyed eggs increased with the mean female age. There was also a strong age-unrelated positive correlation between egg size and survival. (C) 2013 Elsevier B.V. All rights reserved.
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| 5. |
- Jeuthe, Henrik, et al.
(författare)
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Effects of variable egg incubation temperatures on the embryonic development in Arctic charr Salvelinus alpinus
- 2016
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Ingår i: Aquaculture Research. - : Hindawi Limited. - 1355-557X .- 1365-2109. ; 47, s. 3753-3764
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Tidskriftsartikel (refereegranskat)abstract
- An evaluation of different thermal regimes during incubation of Arctic charr Salvelinus alpinus L. egg was conducted with regard to embryo survival and development. The study consisted of two major parts: In experiment A, a range of commonly used thermal regimes, constant and variable ranging from 2.7 degrees C to 7 degrees C, were tested for differences in embryo survival and developmental status of newly hatched alevins. Experiment B assessed the timing of a shift from autumn (6 degrees C) to winter temperature (2.5 degrees C) and its effect on embryo survival and the occurrence of spinal deformities in newly hatched alevins. In general, incubations that were initiated at temperatures below 3 degrees C resulted in significantly higher mortality rates and spinal deformity frequencies than other treatments. Hence, Arctic charr eggs require an initial warmer period for unimpaired embryonic development. A general negative correlation was found between the duration of this warmer period (6 degrees C) and both mortality rates and frequency of spinal deformities. The total absence of the 6 degrees C period had the most detrimental effect, with deformity frequencies at least four times higher than all treatments with an initial warmer period. The upper incubation temperature threshold was not reached in the study. The highest temperature tested (7 degrees C) did not result in excess mortality or increased deformity frequency. Higher incubation temperature resulted in less developed alevins at hatching, i.e. alevins were smaller with more yolk remaining. However, measurements on alevins from incubations at variable temperatures revealed different temperature effects on growth and yolk consumption during different parts of embryonic development.
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| 6. |
- Jeuthe, Henrik, et al.
(författare)
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Evaluation of gamete quality indicators for Arctic charr Salvelinus alpinus
- 2019
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 504, s. 446-453
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Tidskriftsartikel (refereegranskat)abstract
- The reproductive performance of farmed Arctic charr exhibits substantial individual variation. The causes behind this variation have not yet been properly explained, despite the species relatively long history in aqua-culture. The aim of the present study was to provide better understanding of the issue by evaluating parent and gamete traits in relation to fertility and offspring viability under routine hatchery conditions. Are losses mainly due to failed fertilisation or mortality? Are maternal or paternal factor more predominant? The study covered sex hormone status of the broodstock, egg traits (egg size and wateriness of egg batches), milt traits (volume, density, and sperm motility characteristics), and symmetry of early cell division.We found that the majority of offspring loss occurred as embryo mortality, although a significant additional loss could be assigned fertilisation failure. Fertilisation and mortality rates were not inter-correlated. Neither of the evaluated egg traits, egg size and wateriness of newly stripped egg batches, proved to be useful indicators of egg quality. With regard to sperm traits, milt density as well as several computer assisted sperm analysis (CASA) parameters, i.e. swimming speed (VAP, VSL, and VCL) and beat cross frequency (BCF), were correlated with reproductive performance and could potentially be used as quality indicators for Arctic charr. Together, male 17,20β-P levels and BCF explained 69.5% of the between male variation in proportion of successfully eyed eggs.The results support previous indications that post-ovulatory aging of oocytes is contributing to the impairment of reproductive performance in farmed Arctic charr. In addition, a significant paternal factor to this impairment has been exposed. However, the cause and mechanism involved are still far from clear.
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| 7. |
- Jeuthe, Henrik, et al.
(författare)
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Mal i Båven 2017 – Inventeringsstudier i lekområden
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fram till 1800-talets mitt var malen (Silurus glanis) allmänt förekom-mande i Sverige, men idag är utbredningen begränsad till ett fåtal vat-ten i sydöstra delarna av landet. Malen är rödlistad som sårbar, och 21 november 2017 fastställdes ett nytt åtgärdsprogram för arten. Ett av de huvudsakliga hoten som listas är brist på reproduktionsområden. För att kunna åtgärda detta måste kunskap finnas kring malens exakta preferenser för lekplatser, d.v.s. vilka typer av miljöer som måste skyddas och utvecklas. Det är även så att dagens inventerings-metodik och därmed beståndsuppskattningar är bristfälliga.Den föreliggande rapporten presenterar arbetet som utförts av SLU Aqua inom två projekt riktat mot mal i nordvästra Båven. Fokus låg på att öka förståelsen kring malens reproduktionsbiologi men omfat-tade även tester av nya inventeringsmetoder. Vuxna malars rörelse-mönster och beteende kartlades med hjälp av radiotelemetri och sonarkamera (ARIS). Försök gjordes även att fånga in malyngel med elfiskebåt för att ta reda på var och i vilken omfattning lek och yngel-produktion skett under den gångna säsongen (2017).Projekten omfattar även två studentarbeten som i skrivande stund ännu är under arbete. Denna rapport innehåller därför endast utdrag ur resultaten från fältstudien. För detaljerade resultat hänvisas till respektive stu-dentarbete som ska finnas tillgängliga januari 2018.Radiopejling av märkta individer visade att huvuddelen av tiden spenderades under eller i närheten av gungflyn. En del aktivitet regi-strerades även ute på öppet vatten. Ett stort antal malar (ett hundratal) i storleksordningen 0,5–2 meter kunde lokaliseras och studeras i Kvarnsjön, Lillsjön och Hornsundssjön med hjälp av ARIS. ARIS vi-sade därmed stor potential för att användas som ett nytt verktyg för inventering av vuxna malar. Den absoluta majoriteten av malarna hit-tades under gungflyn. Ofta fanns många malar samlade på samma ställe. Som mest kunde ett 20-tal malar observeras längs en gungfly-sträcka på ca 30 meter.Ingen lek eller yngelproduktion kunde påvisas under reproduktions-säsongen år 2017, vare sig genom direkt observation av lek eller fynd av årsyngel. Malarnas beteende under gungflyn kunde framgångsrikt studeras med ARIS, men inget beteende som direkt kan kopplas tilllek observerades. Ingen mal, oavsett storlek, fångades vid båtelfisket. Anledningen till malynglens frånvaro är ännu oklar. Det kan vara så att reproduktionen misslyckades detta år. Det kan också handla om bris-ter i inventeringsmetodiken. Klart är att det kvarstår många fråge-tecken kring malens reproduktion och arbetet med att räta ut dessa fortsätter.
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| 8. |
- Jeuthe, Henrik
(författare)
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Reproductive performance of farmed Arctic charr
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The production of farmed Arctic charr (Salvelinus alpinus) has increased rapidly over the last decade, and the industry is predicted to continue to grow in the coming years. One major bottleneck for this future expansion concerns the supply of viable eggs and juveniles. Hatching rates of Arctic charr eggs in aquaculture are generally much lower than for other farmed salmonids, and exhibit a large variation between individuals and years. The aim of this thesis is to evaluate current hatchery conditions and to deepen the understanding on how environmental and biological factors affect the reproductive performance of Arctic charr in routine farming. The thesis comprises four separate studies. In paper I, records of biological and environmental variables and individual egg survival data from an Arctic charr hatchery, covering a period of 12 years, were analysed in an attempt to find single and combined factors that can explain some of the variation in egg survival. Rearing temperature during summer was identified as the most critical factor for reproductive success of the current broodstock. The study also revealed strong positive relationships between female age, egg size, and egg viability, most likely enhanced by the thermal stress experienced by the broodstock. Paper II assessed broodstock rearing temperature and egg viability over a period of 28 years with focus on thermal stress in a changing climate. Mean summer water temperatures in the hatchery increased by approximately 2°C from 1986 to 2010. The temperature increase was most evident in July but was also apparent in May, August, and September. Egg survival was most closely linked to September temperatures, which indicates that it is not necessarily the warmest days that are the most detrimental. Paper III is a study on egg incubation temperature, and the first, to my knowledge, to show that the initial stages of embryogenesis in Arctic charr are much more cold-sensitive than later in the incubation period. Incubations initiated at low temperature (2.3°C to 2.8°C) resulted in significantly higher mortality and deformity rates. Paper IV is a case study which assessed hormonal status and gamete quality of male and female Arctic charr during routine artificial fertilisation. Female plasma levels of maturation inducing hormone during stripping indicated that post-ovulation aging of oocytes can explain part of the egg loss. The results also suggest that the paternal effect on reproductive performance of the current broodstock is considerable.
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| 9. |
- Jeuthe, Henrik
(författare)
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Reproductive success of farmed Arctic charr (Salvelinus alpinus)
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Swedish Arctic charr breeding programme was established in the early 1980's. Over 25 years of selective breeding has resulted in a fast-growing, late-maturing strain of charr called the Arctic Superior. However, the reproductive success of this strain is far from satisfactory. Egg hatching rates are erratic and often very low compared to other salmonid species in Scandinavian aquaculture. Securing a reliable supply of eggs and stocking fish is imperative to a continued expansion of the Swedish Arctic charr farming industry. The aim of this essay is to look into the biological and physical factors affecting gamete quality and offspring survival in fish and elucidate the most crucial of these factors concerning the Arctic Superior. I believe that physical factors regarding the holding conditions are the cause of the problem, rather than biological traits attained as by-products of the breeding process. I suggest high temperature to be the main factor behind the problems of poor reproductive success. However, it is unlikely the only explanation to the problem. Timing of spawning is an important part of the problem. Spawning period is often prolonged and poorly synchronised between sires and dams. This leads to increased handling and stress of the fish, over-ripening of eggs and difficulties with fertilisation, all contributing to lower reproductive success. Spawning period can be manipulated through altered photoperiod or hormonal treatment. Hormone implants can efficiently induce ovulation and spermiation, but may have detrimental effects on gamete quality. If the environmental holding conditions are right synchronised spawning and improved gamete quality should be achieved and the use of hormones should not be needed
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| 10. |
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