Egg size and density estimates for three gadoids in Icelandic waters and their implications for the vertical distribution of eggs along a stratified water column

Postponed access: the file will be accessible after 2021-12-20The vertical distribution of fish eggs can have important consequences for recruitment through its influence on dispersal trajectories and thus connectivity between spawning and nursery locations. Egg density and size are key parameters for the modelling of vertical egg distributions, both of which show variation at the species level, as well as between and within individuals (i.e., through ontogeny). We conducted laboratory experiments on the eggs of wild-spawning cod, haddock and saithe from Icelandic waters to estimate these parameters throughout ontogeny. Subsequently, this information was used in a 1-dimensional model to generate vertical distributions for each species along a stratified water column. Saithe eggs were significantly smaller and less dense than cod and haddock eggs. Cod eggs were slightly denser than haddock eggs in the first ontogenetic stage but statistically similar in the later stages. No significant differences were found between the egg diameters of cod and haddock. For each species, both parameters changed significantly through ontogeny. Yet despite these significant results, the 1-d model suggests that neither the interspecific nor ontogenetic differences would have a significant impact on the vertical egg distributions. Only under highly stratified conditions, when buoyancy is minimised due to the freshwater layer, do distributional differences become evident. In such situations, incorporating intraspecific variation in egg density into the model substantially reduced the distributional differences and this is highlighted as an important consideration for the modelling of pelagic vertical egg distributions.acceptedVersio

Evaluation of bioactivity of fucoidan from laminaria with in vitro human cell cultures (THP-1)

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked FilesBackground: Seaweeds represent one of the few remaining food sources available globally which are not being fully utilized or even over utilized. Kelps (Laminaria spp.) are one of the numerous species of brown seaweeds, a popular marine vegetable, which has been used as a source of iodine and minerals for centuries. Kelps contain anionic polysaccharides called fucoidans heteroglycans with L-fucose units. Their monosaccharide composition, physicochemical and bioactive properties vary between seaweed species. The objective of this work was to evaluate the bioactive properties of laminaria fucoidan (L. digitata and L. hyperborea) toward THP-1 macrophages, a human macrophage like cell line, and investigate its potential antioxidant and immunomodulatory characteristics. Methods: THP-1 macrophages were incubated with five fucoidan concentrations. The Oxygen Radical Absorbance Capacity (ORAC) assay was determined for cell lysates and for the fucoidan extract, in addition to Total Polyphenol Content (TPC). Cytotoxicity of fucoidan was assessed by light microscopy, followed by XTT proliferation assay. Enzyme-linked immunosorbant assays (ELISA) were performed to determine concentrations of the secreted tumor necrosis factor a (TNF-a), interleukin 6 (IL-6), and interleukin 10 (IL-10). Results: Fucoidan did not affect macrophage ability to scavenge oxygen radicals (ORAC) confirming its antioxidant properties toward activated macrophages. The laminaria fucoidan extract at 100 mu g/ml concentration lowered macrophage viability. Lower concentrations of laminaria fucoidan did not have impact on cell viability. Very low concentration of fucoidan at 0.1 mu g/ml triggered secretion of TNF-alpha. However, IL-6 and interleukin IL-10 were expressed when concentration of applied fucoidan was 10 mu g/ml indicating bioactivity of laminaria fucoidan through immunomodulatory actions. Conclusions: The study demonstrated how laminaria fucoidan may have bioactive properties towards THP-1 macrophages. Changes in cytokine secretion between pro-inflammatory (TNF-alpha, and IL-6) and anti-inflammatory (IL-10) cytokines confirmed bioactivity of the laminaria fucoidan extracts.University of Iceland Research Fun

Author correction : a global database for metacommunity ecology, integrating species, traits, environment and space

Correction to: Scientific Data https://doi.org/10.1038/s41597-019-0344-7, published online 08 January 202

Author correction : a global database for metacommunity ecology, integrating species, traits, environment and space

Correction to: Scientific Data https://doi.org/10.1038/s41597-019-0344-7, published online 08 January 202

Egg production of Baltic cod (Gadus morhua) in relation to variable sex ratio, maturity, and fecundity

Observed fluctuations in relative fecundity of Eastern Baltic cod (Gadus morhua L.) were related to food availability during the main feeding period and were used to develop a predictive model that explained 72% of the interannual variations in fecundity. Time series of sex ratios, maturity ogives, and relative fecundity were combined with mean weights-at-age and stock sizes from an analytical multispecies model to estimate the potential egg production (PEP). Relationships between PEP and independent estimates of realized daily and seasonal egg production from egg surveys were highly significant. The difference between estimates of potential and realized seasonal egg production was of a magnitude corresponding to the expected loss of eggs as a result of atresia, fertilization failure, and early egg mortality. The removal of interannual variability in sex ratio, maturity, and fecundity on estimates of PEP deteriorated the relationships in all three cases. PEP proved to be superior to spawning stock biomass as measure of the reproductive potential in a stock-recruitment relationship of Eastern Baltic cod. PEP in combination with the reproductive volume explained 61% of the variation in year-class strength at age 2

How variable is the fecundity within and between cod stocks?

Stock reproductive potential is determined by the number of fish at age, sex ratio, proportion of mature female at age and fecundity. Fecundity data, which are fundamental in estimating egg production are not collected routinely for most fish stocks. Thus, variability in fecundity is largely ignored in the estimations of reproductive potential. The objective of this study was to identify patterns of spatial and temporal variation in the fecundity within and between different stocks of Atlantic cod (Gadus morhua) in the North Atlantic and Baltic Sea. A review of fecundity data for cod of different stocks and years was made. The examination of fecundity at size indicated a very large variability in the fecundity of cod between stocks and years. The fecundity of a 60 cm cod varied from 210 000 eggs to 2 250 000 eggs. Baltic and North Sea cod stocks were very distinct from the others, highest fecundity-at-size notwithstanding years being observed for these stocks. A different pattern of variation was observed for the other stocks. Temporal variation in fecundity appeared as important as or even more important than differences associated with stocks. Without excluding genetic differences, variations in the environmental conditions and fishing pressure could possibly explain much of the variation in the fecundity of these stocks. At a smaller scale, it also appears that the increase in the reproductive investment with age/size can differ between stocks and years. Thus, routine measurement of fecundity should be essential in estimating reproductive potential of cod