Dietary amino acids impact sperm performance traits for a catadromous fish, Anguilla anguilla reared in captivity

Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited.[EN] Little is known about the role of dietary amino acids on male reproductive performance and gamete quality in fishes. Thus, the objective of this study was to investigate how "enhanced" feeds (EH-4, EH-5, EH-6), with modified amino acid composition, and the standard on-growing diet (DAN-EX) impact body composition, milt biochemistry, and sperm performance in male European eel, Anguilla anguilla. The fatty acid composition of EH4, EH-5, and EH-6 was similar but differed to that in DAN-EX, while amino acid composition varied between all four diets. Diet did not influence organ-somatic indices (e.g. HSI, GSI), while males fed EH-4 were heavier than other groups. Arginine, alanine, and lysine were the most abundant amino acids in milt (>11%), followed by glycine, aspartic acid, valine, glutamic acid, and leucine ( >5.66%). Diet impacted milt arginine, serine, proline, methionine, and histidine levels. Specifically, males fed DAN-EX, EH-4, and EH-5 had the highest percentages of arginine, while males fed EH-4 to EH-6 had higher percentages of serine. Proline was most abundant in males fed DAN-EX, EH-5, and EH-6. Both methionine and histidine were detected at low percentages ( 0.5 mL) for fertilization procedures. Spermatocrit (43.1 +/- 1.80%) did not differ between the diets (ranged from 37.57 to 47.21%). Dietary regime had an impact on sperm motility, such that eels fed EH-5 and EH-6 had the greatest percentage of motile cells. In addition, fish fed EH-5 and EH-6 (or DAN-EX) had the fastest swimming sperm. Spermatogenic maturity index of hormonally treated eels varied within groups but did not differ between dietary treatment groups after 9 weeks of injections (ranged from 0.54 to 0.80). The most interesting amino acids to scrutinize from PCA plots were proline, histidine, and valine as well as lysine and arginine. Here, eels with highly motile sperm had milt with high relative proportions of proline, histidine, and valine, but were particularly low in lysine and arginine. Together, our findings add evidence that certain amino acids regulate milt biochemistry, and that male ejaculate traits may be promoted by amino acid intake. Further studies to evaluate effects of supplemented amino acid diets on fertilization ability and inter-linked early developmental stages are required.This study was funded by the Innovation Fund Denmark under grant agreements no. 5184-00093B (EEL-HATCH) and 7076-00125B (ITSEEL). 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(2013). Evaluation of Methods to Determine Sperm Density for the European eel,Anguilla anguilla. Reproduction in Domestic Animals, 48(6), 936-944. doi:10.1111/rda.12189Støttrup, J. G., Jacobsen, C., Tomkiewicz, J., & Jarlbaek, H. (2012). Modification of essential fatty acid composition in broodstock of cultured European eelAnguilla anguillaL. Aquaculture Nutrition, 19(2), 172-185. doi:10.1111/j.1365-2095.2012.00967.xStøttrup, J. G., Tomkiewicz, J., Jacobsen, C., Butts, I. A. E., Holst, L. K., Krüger-Johnsen, M., … Kaushik, S. (2015). Development of a broodstock diet to improve developmental competence of embryos in European eel,Anguilla anguilla. Aquaculture Nutrition, 22(4), 725-737. doi:10.1111/anu.12299Dayal, J. S., Ahamad Ali, S., Thirunavukkarasu, A. R., Kailasam, M., & Subburaj, R. (2003). Nutrient an

Impact of dietary fatty acids on muscle composition, liver lipids, milt composition and sperm performance in European eel

[EN] In order for European eel aquaculture to be sustainable, the life cycle should be completed in captivity. Development of broodstock diets may improve the species' reproductive success in captivity, through the production of high-quality gametes. Here, our aim was to evaluate the influence of dietary regime on muscle composition, and liver lipids prior to induced maturation, and the resulting sperm composition and performance. To accomplish this fish were reared on three "enhanced" diets and one commercial diet, each with different levels of fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Neutral lipids from the muscle and liver incorporated the majority of the fatty acid profile, while phospholipids incorporated only certain fatty acids. Diet had an effect on the majority of sperm fatty acids, on the total volume of extractable milt, and on the percentage of motile sperm. Here, our results suggest that the total volume of extractable milt is a DHA-dependent process, as we found the diets with the highest DHA levels induced the most milt while the diet with the lowest DHA level induced the least amount of milt The diet with the highest level of ARA induced medium milt volumes but had the highest sperm motility. EPA also seems important for sperm quality parameters since diets with higher EPA percentages had a higher volume of milt and higher sperm motility. In conclusion, dietary fatty acids had an influence on fatty acids in the tissues of male eel and this impacted sperm performance. (C) 2015 Elsevier Inc All rights reserved.This study relates to the project: Reproduction of European Eel: Towards a Self-sustained Aquaculture (PRO-EEL) funded by the European Commission 7th Framework Programme under the Theme 2 "Food, Agriculture and Fisheries, and Biotechnology" (Grant Agreement no. 245257). JFA and LP had a grant to stay in Denmark from the Universitat Politecnica de Valencia (PAID-00-11). Special thanks to P. Lauesen (Billund Aquaculture Service), and C. Graver (Danish Aquaculture Organisation) for help during experimentation, and Lars Holst, BioMar A/S, who took part in sourcing and feed production. IAEB, RB, LP, JFA and JT received travel grants from COST Office (Food and Agriculture COST Action FA1205: AQUAGAMETE).Butts, IAE.; Baeza Ariño, R.; Stottrup, JG.; Kruger-Johnsen, M.; Jacobsen, C.; Pérez Igualada, LM.; Asturiano Nemesio, JF.... (2015). Impact of dietary fatty acids on muscle composition, liver lipids, milt composition and sperm performance in European eel. Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology. 183:87-96. https://doi.org/10.1016/j.cbpa.2015.01.015S879618

The potential importance of the paternal contribution to the ‘Stock Reproductive Potential’ of North-East Arctic cod (Gadus morhua)

Over the years there has been a growing interest in determining the real stock reproductive potential (SRP) as a means of understanding the dynamics of a fish population. For the purposes of assessment the spawning stock biomass (SSB) is generally used, however, this is not a good descriptor for processes types of population modelling. In general, the focus in SRP studies has, with a few notable exceptions, been on female fecundity and realised egg production. In North-east Arctic cod, potential egg production for the stock, over the years 1946 to 2002 has been estimated. In this paper we present preliminary data on the total viable sperm production, estimated for the same years. There have been large changes in the total sperm production, which to a certain extent reflects changes in the mature biomass of the stock. Since 1946 there have also been changes in mean length of mature males and females with a tendency toward smaller fish in the most recent time period. With the relatively large decline in mean size of mature females and the tendency to mature at a smaller size in the latter years the mature fish of both sexes are now of a similar mean size. The relationship between mean size of mature males and females is substantially different than when the stock was large in the early part of the time series. This could have implications for fertilisation success, a factor that is dependent on the dynamics of both sexes

Management of mixed cod stocks in the transition zone between the North Sea and the Baltic Sea: How can this be achieved efficiently? (FABBIO)

The project ”Management of mixed cod stocks in the transition zone between the North Sea and the Baltic Sea: How can this be achieved most efficiently?” focused on one of the key challenges for assessment and management of fish stocks: Movement of individuals and stocks mixing. The project focused on resolving issues of stock mixing in cod stocks between the North Sea (Subarea 4), Skagerrak (SD 20), Kattegat (SD 20), the western Baltic (Belt Sea (SD 22), and Sound (SD 23)), and the eastern Baltic Sea (SDs 24 – 32). The project was funded by European Maritime and Fisheries Fund and the Danish Fisheries Agency. The activities in the project involved providing new biological knowledge on genetic and ecological connectivity, advancing methods, and providing a tool to evaluate the impact of stock mixing on stock assessment.Genetic identification of populationsFull genome resequencing data revealed marked genetic differences between samples of fish at spawning time collected in the North Sea, eastern Baltic Sea and the transition zone between the two areas (i.e. SD 21-SD 24). In contrast, we found limited divergence between spawning fish collected in the southern Kattegat, Belt Sea, Sound and Arkona Sea (SD 24, spring), suggesting that these fish belong to the same biological population, identifying a total of three major biological units for management in this system. Weaker gradient signals within the transition zone may be related to introgression in the hybrid zone from parental populations in the North Sea and eastern Baltic Sea, and they are much weaker than any difference observed between the three populations. Future sampling may refine these analyses, in particular regarding the relationship between spawning fish in the transition zone. However, they are not expected to change the overall relationship and magnitude of differentiation between the three populations presented in the currentreport.Genetic identification of population mixingThrough the use of a panel of genetic markers specifically designed to identify population of origin in a scenario with three baselines (North Sea, transition zone, eastern Baltic Sea, as supported by the genomic analyses above) we analyzed samples collected across the full transition zone to estimate proportions from the three baseline populations. The results confirmed previous findings of substantial mixing in the Kattegat and Arkona Sea, with North Sea fish and transition zone fish mixing in Kattegat and eastern Baltic Sea fish and transition zone fish mixing in the Arkona Sea. We also confirmed the gradient of mixing in the Kattegat, with higher proportions of North Sea fish in the northern parts of the area. In contrast, we found limited mixing in the Belt Sea and the Sound where fish appeared to be primarily of transition zone origin. While data for older age classes were limited, we also found evidence for higher proportions of North Sea fish among younger age classes, as also reported in previous studies.Natal origin and movements of adultsThis project investigated the natal origin and adult movements of cod in the transition zone, focusing on spatial differences in the chemical composition (the chemical “fingerprint”) recorded in the cod’s otoliths. Examining the elements analyzed in this study, it becomes apparent that they reflect gradients in environmental conditions and physiological processes, aligning with known mechanisms of otolith biomineralization. Therefore, otolith chemistry proves to be a suitable method for assessing the movement patterns of fish in the transition zone.The analyses of the otolith cores, representing the natal origin of cod, revealed spatial variations in their chemical fingerprint, indicating at least three different clusters (= spawning areas). Without baseline samples from cod larvae, it is not possible to identify where these spawning areas are, but combined with knowledge of known spawning areas, the results suggested that the cod originated primarily from the North Sea (concentrated in the Skagerrak and northern Kattegat), the Southern Kattegat (spread throughout Kattegat and partly in the Sound and Belt Sea), and the Belt Sea (predominantly found in the Belt Sea and the Sound). The contribution of the spawning area clusters varies significantly among different year classes of cod, indicating fluctuations in the relative contribution of cod originating from each spawning area.Cod inhabiting the Skagerrak and northern Kattegat regions either exhibit a similar chemical fingerprint throughout their lives or exhibit extensive mixing. Generally, these cod populations do not migrate south into the western Baltic Sea. However, some cod in the southernmost Kattegat display a Belt Sea/Sound signal throughout their lives, which is likely not due to movements but rather due to the incomplete alignment of environmental gradients with the boundaries of management areas. In contrast, the Belt Sea region predominantly hosts cod that remain resident throughout their lives, with minimal movements observed. In contrast, cod in the Sound region show a connection with the Belt Sea. The majority of cod immigrate from the Belt Sea to the Sound before the age of 3 and tend to remain resident there. However, occasional Belt Sea signals detected at irregular intervals suggest some movement in and out of the Sound.The combined analysis of natal origin and adult movements provided valuable insights into the dynamics of the cod population in the transition zone. While cod in this zone may originate from different spawning areas, they are largely resident within the respective management areas as adults. Consequently, the project results suggested the presence of an ecological stock separation into two distinct stocks: The Skagerrak/Kattegat and the Belt Sea/Sound.Stock mixing: Combining genetics and otolith chemistryCollectively, the compilation of knowledge gained from historical data and new samples, from genome sequencing and otolith chemistry, indicate that there is considerable genetic and ecological structuring of cod between the North Sea and the Baltic Sea, with three genetically distinct populations: 1. North Sea, 2. eastern Baltic Sea and 3. transition zone (Kattegat, Belt Sea, Sound and Arkona Sea). The geographic distribution of these populations overlap in the Kattegat and Arkona Sea, respectively. While it was not possible to detect genetic differentiation in the transition zone, otolith chemistry revealed considerable ecological stock structuring. This scenario is consistent with considerable exchange of individuals between areas, presumably as a result of drift of early life stages. While cod in the transition zone may originate from different spawning areas (two apparently distinct areas were identified), they are largely resident within the geographical areas they settle into as adults. This leads to stock structuring in the transition zone with an ecological separation into two distinct components: 1. the (eastern) Skagerrak and the Kattegat, 2. the Belt Sea and the Sound.For cod in Belt Sea, the Sound and the spring-spawners in the Arkona Sea, the combined genetic and otolith chemistry results thus indicate that the current management area for western Baltic is appropriate. In the Kattegat, the spatially and temporally variable mixing dynamics with the North Sea need to be considered for a sustainable management of the stock, similarly to the mixing scenario with the eastern Baltic cod in the Arkona Sea. Recommendations as to what type of stock assessment approach is most suitable for this complex system of genetic and ecological stock structuring is not within the scope of this project.Impact of fish movements and stock mixing on stock assessmentThis project implemented the prototype of a simulation tool to evaluate migration impacts on stock assessment and propose mitigation strategies. While functional, the tool can be improved with documentation, user-friendly implementations, and inclusion of additional factors. Simulations highlighted challenges in specifying complex scenarios and limited data availability. Migration patterns affected assessment data. Closing parts of the norther Kattegat, for example, showed potential for stock recovery. A cost-benefit analysis compared genetic samples and otolith shape analysis for stock composition estimation. Precision and cost influenced the choice between methods. Note that the analysis did not consider sample collection or baseline costs. Given the new biological knowledge on genetic and ecological stock structure, movement patterns in the transition zone from the North Sea to the eastern Baltic, this will be the next focus area for the application of this tool.Potential management scenariosBased on the collective genetics, otolith chemistry and modelling simulation results from this project, we have identified three different scenarios for how stock mixing could be implemented in stock assessment and management for cod stocks in the transition zone:• Area-based assessment and management – current scenario. This is a status quo scenario, where current practices are continued with two distinct stocks in the transition zone: Kattegat and the western Baltic Sea (Belt Sea, Sound and Arkona Sea), with separate stock assessments and TACs, irrespective of genetic population. Stock mixing of eastern/wester Baltic cod in the Arkona Sea is already implemented in stock assessment. By not addressing stock mixing of North Sea/Kattegat populations, the severely declined Kattegat population is at risk of local depletion.• Area-based assessment and management – updated scenario. This scenario implies continuing with current practices of separate stock assessments for the current management areas Kattegat and western Baltic Sea (Belt Sea, Sound and Arkona Sea). In addition to the stock mixing of eastern/wester Baltic cod in the Arkona Sea the mixing of North Sea and Kattegat cod in the Kattegat should be addressed in a similar approach. This scenario disregards the fact that cod in the transition zone are genetically the same population, but would on the other hand reflect the ecological stock structuring, and thereby minimize the risk of local depletion of population components.• Population-based stock assessment and management. A population-based approach to stock assessment would require cod from the Kattegat, Belt Sea, Sound and Arkona Sea to be combined into a single stock representing the genetic “transitions zone population”. Stock mixing proportions in the transition zone population would need to be estimated for these areas, based on a genetic split of commercial and survey data. Subsequently, TACs can be allocated to exiting management areas, but should be informed by genetic estimates of mixing proportions in the different management areas to link estimated harvest rates in geographical areas to the stock assessments/advice for the underlying biological populations. components not accounted for with genetic split data, ii) how to allocate area-specific TACs, and iii) how to deal with social and political considerations

Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS; outputs from 2022 meeting)

The Working Group on Mackerel and Horse Mackerel Egg Surveys (WGMEGS) is responsible for the planning, data collection, and data analysis of the ICES triennial mackerel and horse mackerel egg surveys. This report focuses on the execution of the mackerel and horse mackerel egg survey (MEGS) in 2022.The results of the two 2021 online Workshops on Mackerel, Horse Mackerel and Hake Eggs Identification and Staging (WKMACHIS) and on Adult Egg Production Methods Parameters estimation in Mackerel and Horse Mackerel (WKAEPM) were discussed, with the subsequent enhancements and recommendations proposed during these workshops outlined in the workshop reports (ICES, 2022 a,b) and also incorporated into both of the WGMEGS manuals (ICES 2019a, b). Although the broad planning of the 2022 survey was undertaken during the 2021 planning meeting and detailed in the WGMEGS 2021 report, the provisionally agreed plan required additional intersessional refinements. The settled plan for the 2022 survey has been included as an annex in the latest version of the WGMEGS Manual for the Mackerel and Horse Mackerel Egg Surveys (ICES SISP 6, 2019a).In 2022, the survey once again faced significant challenges with regards to its ability to provide adequate geographical and temporal coverage given the limited vessel resources at our disposal. In 2022, Portugal, Spain (IEO and AZTI), Ireland, UK/Scotland, the Netherlands, Germany, the Faroe Islands, and Norway participated in the egg survey in the western and southern areas. Denmark and UK/England, with some additional assistance from Norway surveyed the North Sea as a single-pass DEPM survey. This is the first time in many years that all surveys have been completed in the same year.In 2022, the survey was split into six sampling periods. The final period ended in late July. Waters west and southwest of Portugal were surveyed in period 2 only. The Cantabrian Sea was sampled in periods 3–5 while Biscay was sampled in periods 3 to 6. The Celtic Sea and waters west of the British Isles were sampled in periods 3 to 7, and the waters north and northwest of Britain towards Iceland and into the Norwegian Sea were sampled in periods 5 and 6.Mackerel daily egg production was highest in period 5, (May), for the western component, while for the southern component the maximum spawning intensity was observed in period 3. Total mackerel egg production (provisional, southern and western component combined) was 1.64 * 1015. Provisional fecundity estimate was 1178 egg per gram female, resulting in an SSB index of 3.88 * 106 tonnes.For the Western stock of horse mackerel, highest mean daily egg production was estimated during June, period 6. Spawning was very low throughout all survey periods, with an obvious peak occurring in period 6. Total annual egg production for western Horse mackerel was 5.15 * 1014, almost a 300% increase on 2019

Thermal dynamics of ovarian maturation in Atlantic cod (Gadus Morhua)

The timing and success of spawning in marine fish are of fundamental importance to population persistence and distribution and, for commercial species, sustainability. Their physiological processes of reproduction are regulated, in part, by water temperature, and therefore changes in marine climate may have dramatic effects on spawning performance. Using adult Atlantic cod (Gadus morhua) as a case study, we examined the links between water temperature, body size, vitellogenesis, and spawning time by conducting extensive laboratory and field studies. Our experiments documented that vitellogenesis generally starts at autumnal equinox and that oocyte growth and investment are greater in cod held at warmer temperatures. Furthermore, spawning occurred earlier when oocyte growth was more rapid. Large females spawned earlier than smaller females at warmer temperatures, but this effect vanished at colder temperatures. The experimental results were confirmed by measurements of oocyte growth collected from wild-caught cod in northern (Barents Sea) and southern (Irish Sea and North Sea) populations. The established, general model of oocyte maturation was consistent with published egg production curves of cod from these waters, considering relevant in situ temperatures recorded by individual data-storage tags on cod. These findings have considerable relevance for future studies of fish recruitment in relation to climate change