Matti Janhunen

Appropriate fertilization practices play a crucial role in the maintenance of genetic diversity within captive fish broodstocks. We assessed the influence of in vitro storage of gametes (0-, 7- and 14-days post-stripping) at 1 °C on ovarian fluid pH, sperm motility, and embryo viability in the critically endangered Finnish landlocked salmon (Salmo salar m. sebago) population. A repeated full-factorial design used in both sperm-ovarian fluid activation analyses and fertilizations allowed us to separate the effects of female, male and their interaction on gamete quality and embryo survival across storage times. The ovarian fluid pH decreased most significantly during the first week of storage and showed considerable variation among females. The decrease of sperm motility varied across males, females and male–female (sperm-ovarian fluid) combinations. The mean proportion of viable embryos was initially 96.4%, but dropped to 45.5% after 7 days, and to 13.1% after 14 days of gamete stora...

The modern theories of sexual selection predict that male sexual ornaments may have evolved as reliable signals of male fertilization efficiency. However, among the studies of fishes with external fertilization, the results have yielded ambiguous evidence. In the present study, we present data on the phenotypic relationships between red spawning coloration and ejaculate quality (spermatocrit, sperm motility) from Arctic charr, Salvelinus alpinus. We studied two generations (F1 and F2) of males from a large lake population, reared in a standardized hatchery environment, to determine whether differential hatchery history, or duration of hatchery selection, affected the variation in ejaculate characteristics or abdominal coloration. After controlling for body length, there was no difference between the hatchery generations in these traits. However, the degree of redness increased with fish size. We found a positive correlation between sperm velocity and sperm longevity, indicating a fu...

24 The modern theories of sexual selection predict that male sexual ornaments may have evolved 25 as reliable signals of male fertilization efficiency. However, among the studies of fishes with 26 external fertilisation, the results have yielded ambiguous evidence. Here, we present data on 27 the phenotypic relationships between red spawning coloration and ejaculate quality 28 (spermatocrit, sperm motility) from Arctic charr, Salvelinus alpinus. We studied two 29 generations (F1 and F2) of males from a large lake population, reared in a standardized 30 hatchery environment, to see whether differential hatchery history, or duration of hatchery 31 selection, affected the variation in ejaculate characteristics or abdominal coloration. After 32 controlling for body length, there was no difference between the hatchery generations in these 33 traits. However, the degree of redness increased with fish size. We found a positive 34 correlation between sperm velocity and sperm longevity, indi...

Enrichment of rearing environment with natural elements has been suggested to improve the welfare and post-release survival of cultured fish. We studied the combined effects of shelter structures, periodical water flow and water level changes on pre- and post-release performance of critically endangered landlocked Atlantic salmon (Salmo salar m. sebago). Relative to standard (plain) rearing tanks, provision of enrichment improved fish condition factor and survival during the first year of rearing when most mortality was attributable to parasitic and bacterial infections. The consequent higher density in enriched tanks probably induced greater growth variation and more dorsal fin damages than found in fish of standard tanks. Possibly this was partly due to the applied changes in water level. Experimentally determined smolt migration tendency at age 3 did not differ, on average, between the rearing groups, but enriched-reared fish showed clearly less variation in total movement activi...

Sperm pre-fertilization environment has recently been suggested to mediate remarkable transgenerational consequences for offspring phenotype (transgenerational plasticity, TGB), but the adaptive significance of the process has remained unclear. Here, we studied the transgenerational effects of sperm pre-fertilization thermal environment in a cold-adapted salmonid, the European whitefish (Coregonus lavaretus L.). We used a full-factorial breeding design where the eggs of five females were fertilized with the milt of 10 males that had been pre-incubated at two different temperatures (3.5°C and 6.5°C) for 15 hours prior to fertilization. Thermal manipulation did not affect sperm motility, cell size, fertilization success or embryo mortality. However, offspring that were fertilized with warm-treated milt were smaller and had poorer swimming performance than their full-siblings that had been fertilized with cold-treated milt. Furthermore, the effect of milt treatment on embryo mortality ...

When a rainbow trout stock from a single breeding program is reared in diverse production environments, genotype-by-environment interaction (GxE) may present itself. Growth and its uniformity are considered as two of the most important traits by trout producers worldwide. However, GxE for uniformity of growth has not been studied. Using a double hierarchical generalized linear model and data from the Finnish breeding program, we quantified the genetic variance and correlation of body weight (BW) and its uniformity, as well as the degree of GxE for uniformity of BW in a breeding (BE) and a production (PE) environment. To investigate whether scaling effects (high variance related to high mean) affect the estimated parameter, the data were also log-transformed. Although heritability for uniformity (ℎ í µí±£ 2) in the BE (0.014) and in the PE (0.012) was low and of similar magnitude, the genetic coefficient of variation for uniformity was 19 and 21%, respectively, revealing high potenti...

Abstract Text: Minimal variation in fish growth increases profit of fish farming and improves fish welfare. Uniformity can be increased by reducing additive genetic and residual variation. We first present a mating strategy to create a production stock that has only 38% of the original genetic variance, and assuming heritability of 0.26 for body weight of rainbow trout, 84% of the original phenotypic variance. An experimental test confirmed that phenotypic variance can be indeed reduced to 80% of the variation in the original breeding programme. Secondly, genetic CV for residual variation in body weight was notable (37%). Hence, one generation of sib selection for reduced residual variation is expected to reduce phenotypic variance to 87-89% of the original phenotypic variance. Both methods aid to produce more uniform populations for on-growing, while simultaneously maintaining genetic variation in the nucleus. Keywords: additive genetic variance heterogeneity of residual variance r...

Abstract Text: Rainbow trout breeding scheme was simulated to estimate how within-family pre-selection of fingerlings and information on culled fish affect genetic evaluation of grow-out weight traits in two environments. Fish for different datasets were randomly sampled (R) or pre-selected and information on culled fish were either individually measured (S+IND), replicated with their family-specific averages (S+AVER), or missing (S-MIS). Variance estimates in R and S+IND did not diverge from simulated values, whereas S+AVER decreased residual variances. Accuracies of EBVs were equally high for R, S+IND and S+AVER. For S-MIS, convergence problems occurred, variance components were distorted, and EBV accuracies were low. Selection bias was consistently expressed by overestimated genetic and common environment variances, and underestimated residual variances. Data adjustment by S+AVER is concluded to sufficiently control for selection bias in genetic evaluation of growth, but for esti...

ABSTRACT Genetic improvement programs for some fish species apply a two-stage selection scheme in which phenotypic selection is first practiced within families based on early body size. Pre-selection improves genetic gain in the breeding objective traits correlated with the pre-selection criteria, and it can also reduce management costs of a program. In this study, stochastic simulation of a rainbow trout, Oncorhynchus mykiss, breeding scheme with 150 full-sib families (2:2 mating design) was utilized to explore how within-family pre-selection and different information on the culled fish affect variance estimates and accuracy of genetic evaluation in grow-out body weights. The bias in genetic parameters and breeding values (EBVs) was quantified for fingerling weight at id-tagging (BW1), used as the criterion for pre-selection, and for two harvest weights recorded at the freshwater nucleus (BW2) and sea test station (BW2sea) in a split-family design. At tagging, fish from each full-sib family were either randomly sampled (R) or pre-selected, and the BW1 records of the culled fish were either individually measured (S + IND), augmented with the replicated family-specific averages of the culled fish (S + AVER), or were treated as missing (S–MIS). These four alternative data treatments were compared using a fixed initial family size of 100 individuals before tagging and two different pre-selection intensities (40% or 21% of fish per family selected). Variance estimates in R and S + IND did not diverge from the simulated a priori values in either of the selection intensities studied. The strategy S + AVER resulted in unbiased genetic variance estimates but decreased the residual variance, especially for BW1 and BW2. The accuracy of EBVs was, nevertheless, equally high for R, S + IND and S + AVER, and these values did not essentially differ between the two selection intensities. For S–MIS, the variance estimates were strongly biased in each trait, and the EBV accuracies were, on average, lower than in the other three treatments. Common environment variances were consistently overestimated and residual variances underestimated, whereas genetic variances were biased in both directions depending on the trait and pre-selection intensity. Further, for S–MIS, frequent convergence problems occurred in the estimation of variance components. For fish breeding schemes applying within-family pre-selection, data augmentation for culled fish by their average values of BW1 will sufficiently control for selection bias in genetic evaluation of growth. For accurate estimation of variance components either random samples from families or individual records from all culled fish are preferable.

The parental influences on three progeny traits (survival to eyed-embryo stage, post-hatching body length and yolk-sac volume) of Arctic charr Salvelinus alpinus were studied under two thermal conditions (2 and 7 degrees C) using a factorial mating design. The higher temperature resulted in elevated mortality rates and less advanced development at hatching. Survival was mostly attributable to maternal effects at both temperatures, but the variation among families was dependent on egg size only at the low temperature. No additive genetic variation (or pure sire effect) could be observed, whereas the non-additive genetic effects (parental combination) contributed to offspring viability at 2 degrees C. In contrast, any observable genetic variance in survival was lost at 7 degrees C, most likely due to the increased environmental variance. Irrespective of temperature, dam and sire-dam interaction contributed significantly to the phenotypic variation in both larval length and yolk size. A significant proportion of the variation in larval length was also due to the sire effect at 2 degrees C. Maternal effects were mediated partly through egg size, but as a whole, they decreased in importance at the high temperature, enabling a concomitant increase in non-additive genetic effects. For larval length, however, the additive component, like maternal effects, decreased at 7 degrees C. The present results suggest that an exposure to thermal stress during incubation can modify the genetic architecture of early developmental traits in S. alpinus and presumably constrain their short-term adaptive potential and evolvability by increasing the amount of environmentally induced variation.