| 1. |
- 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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| 2. |
- Brännäs, Eva, 1951-
(författare)
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Effects of abiotic and biotic factors on hatching, emergence and survival in Baltic salmon (Salmo salar L.)
- 1988
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with important factors that affect the temporal organization of emergence and early survival of Baltic salmon (Salmo salar L.). The study population was obtained from the Norrfors hatchery (63°50'N,20°05'E), Umeälven (Ume river) in Northern Sweden. The main objectives of the thesis has been to study; a: the effect of female and egg characteristics on embryonic survival, b: the effect of egg size, temperature and photoperiod on the emergence pattern and c: the impact of early or late emergence on survival in relation to predation and limited territorial space.The main results are summarized as follows: (1) Fecundity and egg size increased with increasing weight of females. No effect of female size were found on egg colour. Longer impoundment and later stripping increase egg colour. Egg mortality was not correlated with egg colour. Stripping date was found to have the strongest effect on mortality. (2) Egg size had no effect on the timing of emergence but fry of different egg size emerged synchronously. Fry from large eggs left the gravel as heavier fry and with a larger proportion of yolk left compared to fry from small eggs. (3) The number of days and number of degree days from hatching to 50% emergence decreased exponentially with increasing temperature. Synchronization of emergence increased with increasing temperature. Fry emerged with more yolk at 12 °C compared to 6 °C. (4) Eggs kept in a LD 16:8 light regime hatched mainly during the light period, while eggs kept in constant darkness hatched continously over a 24 hour period. Alevins kept at different light regimes (light>4h) from hatching until emergence left the gravel during the dark period. Daylength had no effect on the annual onset of emergence. (5) In a laboratory stream channel, predator presence at emergence increased mortality especially in early emerging fry. If the predator was introduced after completed emergence high mortality was noted among late emerging fry. The presence of fish predators and a limited territorial space for fry seemed to make early and late emergence hazardous and to favour a "peak" emergence. In the presence of a predator the fry changed their behaviour by reducing their swimming activity.
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| 3. |
- Nilsson, Jan, et al.
(författare)
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Effects of age and rearing environment on genetic parameters of growth and body weight and heritability of skin pigmentation in Arctic charr (Salvelinus alpinus L.)
- 2016
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 453, s. 67-72
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish breeding programme for Arctic charr aims to improve traits that are important for farming. Selection has been ongoing since the 1980s, and the aim of this study was to re-estimate the genetic parameters in the selected population. In addition, the genetics of skin pigmentation was studied, as previous work indicated a relationship between pigmentation and the ability to cope with stress.One hundred twenty-five full sib families of Arctic charr were hatched and reared separately until they were individually tagged (n = 12,266). In connection with the tagging, three replicates were formed, which were subsequently reared at different sites. The genetic relationships were known from a seven-generation pedigree. Body weight and length were at one site measured at six occasions until 27 months old, and these measurements were used to estimate the DGC (daily growth coefficient) and condition factor. At a second site fish were measured at 21 and 27 months age and at a third site at 27 months age.Skin pigmentation was measured using image analysis. The final weight at 27 months of age varied widely between rearing sites, ranging from 529 g to 1443 g. Weight heritability differed among the sites, at 0.45, 0.11, and 0.07. At one of the sites, where growth was followed closely, weight heritability varied among growth periods, ranging from 0.01 to 0.25, and similar results were obtained for the DGC. In contrast, condition factor heritability did not show such pronounced variations within and among sites. The magnitude of the differences in heritability of weight and growth among different sites that was observed here was not observed previously with this charr population. In particular, the low heritability among the fastest growing fish is unprecedented. Skin pigmentation showed a high heritability of 0.76, indicating a strong additive genetic component. At most ages, pigmentation showed a weak positive genetic correlation with growth. The genotype environment interaction (GEI) was estimated using genetic correlations among sites. For the final weight, genetic correlations were high, indicating weak GEI, although the presence of GEI was suggested from the DGC data.Statement of relevance: The ms will impact charr breeding for commercial farming. (C) 2015 Elsevier B.V. All rights reserved.
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