Atlantic cod individual spatial behaviour and stable isotope associations in a no-take marine reserve

Foraging is a behavioural process and, therefore, individual behaviour and diet are theorized to covary. However, few comparisons of individual behaviour type and diet exist in the wild. We tested whether behaviour type and diet covary in a protected population of Atlantic cod, Gadus morhua. Working in a no-take marine reserve, we could collect data on natural behavioural variation and diet choice with minimal anthropogenic disturbance. We inferred behaviour using acoustic telemetry and diet from stable isotope compositions (expressed as δ13 C and δ15 N values). We further investigated whether behaviour and diet could have survival costs. We found cod with shorter diel vertical migration distances fed at higher trophic levels. Cod δ13 C and δ15 N values scaled positively with body size. Neither behaviour nor diet predicted survival, indicating phenotypic diversity is maintained without survival costs for cod in a protected ecosystem. The links between diet and diel vertical migration highlight that future work is needed to understand whether the shifts in this behaviour during environmental change (e.g. fishing or climate), could lead to trophic cascades.

Eco‐evolutionary dynamics of Atlantic cod spatial behavior maintained after the implementation of a marine reserve

The effects of marine reserves on the life history and demography of the protected populations are well‐established, typically increasing population density and body size. However, little is known about how marine reserves may alter the behavior of the populations that are the target of protection. In theory, marine reserves can relax selection on spatial behavioral phenotypes that were previously targeted by the fishery and also drive selection in favor of less mobile individuals. In this study, we used acoustic telemetry to monitor the individual spatial behavior of 566 Atlantic cod (Gadus morhua Linnaeus, 1758) moving within a marine reserve and a control site in southern Norway, starting 1 year before the implementation of the marine reserve and lasting up to 9 years after. Following a before‐after‐control‐impact approach, we investigated changes in (1) survival, (2) selection acting on behavioral traits, and (3) mean behavioral phenotypes, after the implementation of the marine reserve. We focused on three behavioral traits commonly used to describe the mobility of aquatic animals: home range size, depth position, and diel vertical migration range. Survival increased after reserve implementation, but contrary to our expectations, it subsequently decreased to preprotection levels after just 3 years. Further, we found no significance in selection patterns acting on any of the three behavioral traits after reserve implementation. Although some changes related to water column use (the tendency to occupy deeper waters) were observed in the marine reserve after 9 years, they cannot unequivocally be attributed to protection. Our results show that survival and behavioral responses to marine reserves in some cases may be more complex than previously anticipated and highlight the need for appropriately scaled management experiments and more integrated approaches to understand the effects of marine protected areas on harvested aquatic species.

Warming Accelerates the Onset of the Molecular Stress Response and Increases Mortality of Larval Atlantic Cod

Temperature profoundly affects ectotherm physiology. Although differential thermal responses influence fitness, thus driving population dynamics and species distributions, our understanding of the molecular architecture underlying these responses is limited, especially during the critical larval stage. Here, using RNA-sequencing of laboratory-reared Atlantic cod (Gadus morhua) larvae of wild origin, we find changes in gene expression in thousands of transcripts consistent with a severe cellular stress response at both ambient and projected (+2°C and +4°C) temperatures. In addition, specific responses to stress, heat, and hypoxia were commonly identified in gene ontology enrichment analyses and 33 of the 44 genes comprising the minimum stress proteome of all organisms were upregulated. Earlier onset of the stress response was evident at higher temperatures; concomitant increased growth and mortality suggests a reduction in fitness. Temporal differences in gene expression levels do not correspond to differences in growing degree days, suggesting negative physiological consequences of warming beyond accelerated development. Because gene expression is costly, we infer that the upregulation of thousands of transcripts in response to warming in larval cod might act as an energetic drain. We hypothesize that the energetically costly stress response, coupled with increased growth rate at warmer temperatures, leads to faster depletion of energy reserves and increased risk of mortality in larval cod. As sea surface temperatures continue to rise over the next century, reduced fitness of Atlantic cod larvae might lead to population declines in this ecologically and socioeconomically important species. Further, our findings expand our understanding of transcriptomic responses to temperature by ectothermic vertebrate larvae beyond the critical first-feeding stage, a time when organisms begin balancing the energetic demands of growth, foraging, development, and maintenance. Linking the molecular basis of a thermal response to key fitness-related traits is fundamentally important to predicting how global warming will affect ectotherms.

Hydropower-induced selection of behavioural traits in Atlantic salmon (Salmo salar)

Renewable energy projects such as hydropower facilities contribute towards meeting the world`s growing energy demands and urgent need for mitigating climate change. However, such infrastructure has the potential to substantially alter the environment which, in turn, can induce new challenges related to for instance fish migration conditions. As a consequence, local adaptations related to pre-development migration conditions may be affected for influenced populations. To explore selection regimes operating at a river hydropower plant, we monitored Atlantic salmon smolt individuals during their seaward migration. When passing the hydropower plant, the smolts chose between a surface fish passage or a submerged turbine intake. Smolts were scored for behavioural type (basal locomotor activity, net restrain (a measure of escape responses) and willingness to leave a familiar environment) prior to their migration choice, and we found that smolts with high basal activity had higher probability of using the fish passage than the turbine intake. In addition, migration route choice was a partly consistent trait in that fish that had previously passed a hydroelectric facility by using a fish passage rather than the turbine intake were significantly more likely to use it again when faced with the same choice. Higher mortality among turbine migrants could potentially reduce or eliminate particular behaviour types within populations- and the corresponding population genetic diversity that is essential to cope with future environmental challenges.

Disentangling conditional effects of multiple regime shifts on Atlantic cod productivity

Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary and detection methods are still developing. Here, we employ a novel statistical algorithm based on the Bayesian online change-point detection framework to simultaneously identify shifts in the mean and (or) variance of time series data. We detected multiple regime shifts in long-term (59-154 years) patterns of coastal Norwegian Atlantic cod (>70% decline) and putative drivers of cod productivity: North Atlantic Oscillation (NAO); sea-surface temperature; zooplankton abundance; fishing mortality (F). The consequences of an environmental or climate-related regime shift on cod productivity are accentuated when regime shifts coincide, fishing mortality is high, and populations are small. The analyses suggest that increasing F increasingly sensitized cod in the mid 1970s and late 1990s to regime shifts in NAO, zooplankton abundance, and water temperature. Our work underscores the necessity of accounting for human-induced mortality in regime shift analyses of marine ecosystems.

Protected areas buffer against harvest selection and rebuild phenotypic complexity

Harvest mortality typically truncates the harvested species' size structure, thereby reducing phenotypic complexity, which can lead to reduced population productivity, increased population variability, and selection on an array of life history traits that can further alter these demographic processes. Marine protected areas (MPAs) are a potential tool to protect older, larger individuals and therefore mitigate such ecological and evolutionary effects of harvest, depending on the degree of connectivity among areas. Such MPA protection relies on a shift in size-dependent mortality, the measurement of which can therefore serve as an early indicator of whether MPAs might achieve the desired longer-term ecological and evolutionary responses. We directly measured MPA effects on size-selective mortality and associated size structure using mark-recapture data on European lobster (Homarus gammarus) collected at three MPA-control area pairs in southern Norway during one decade (n = 5,943). Mark-recapture modeling, accounting for variation in recapture probabilities, revealed (1) that annual mean survival was higher inside MPAs (0.592) vs. control areas (0.298) and (2) that significant negative relationships between survival and body size occurred at the control areas but not in the MPAs, where the effect of body size was predominantly positive. Additionally, we found (3) that mean and maximum body size increased over time inside MPAs but not in control areas. Overall, our results suggest that MPAs can rebuild phenotypic complexity (i.e., size structure) and provide protection from harvest selection.

Possible adverse impact of contaminants on Atlantic cod population dynamics in coastal ecosystems

While many in-laboratory ecotoxicological studies have shown the adverse impact of pollutants to the fitness of an individual, direct evidence from the field on the population dynamics of wildlife animals has been lacking. Here, we provide empirical support for a negative effect of pollution on Atlantic cod (Gadus morhua) population dynamics in coastal waters of Norway by combining unique time series of juvenile cod abundance, body size, environmental concentration of toxic contaminants and a spatially structured population dynamics model. The study shows that mercury concentration might have decreased the reproductive potential of cod in the region despite the general decline in the environmental concentration of mercury, cadmium and hexachlorobenzene since the implementation of national environmental laws. However, some cod populations appeared to be more resistant to mercury pollution than others, and the strength and shape of mercury effect on cod reproductive potential was fjord-specific. Additionally, cod growth rate changed at scales smaller than fjords with a gradient related to the exposure to the open ocean and offshore cod. These spatial differences in life-history traits emphasize the importance of local adaptation in shaping the dynamics of local wildlife populations. Finally, this study highlights the possibility to mitigate pollution effects on natural populations by reducing the overall pollution level, but also reveals that pollution reduction alone is not enough to rebuild local cod populations. Cod population recovery probably requires complementary efforts on fishing regulation and habitat restoration.

Disentangling structural genomic and behavioural barriers in a sea of connectivity

Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole‐genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord‐type cod. Continuous behavioural tracking over 4 year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord‐type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.

Fine-scale population differences in Atlantic cod reproductive success: A potential mechanism for ecological speciation in a marine fish

Successful resource-management and conservation outcomes ideally depend on matching the spatial scales of population demography, local adaptation, and threat mitigation. For marine fish with high dispersal capabilities, this remains a fundamental challenge. Based on daily parentage assignments of more than 4,000 offspring, we document fine-scaled temporal differences in individual reproductive success for two spatially adjacent (<10 km) populations of a broadcast-spawning marine fish. Distinguished by differences in genetics and life history, Atlantic cod (Gadus morhua) from inner- and outer-fjord populations were allowed to compete for mating and reproductive opportunities. After accounting for phenotypic variability in several traits, reproductive success of outer-fjord cod was significantly lower than that of inner-fjord cod. This finding, given that genomically different cod ecotypes inhabit inner- and outer-fjord waters, raises the intriguing hypothesis that the populations might be diverging because of ecological speciation. Individual reproductive success, skewed within both sexes (more so among males), was positively affected by body size, which also influenced the timing of reproduction, larger individuals spawning later among females but earlier among males. Our work suggests that spatial mismatches between management and biological units exist in marine fishes and that studies of reproductive interactions between putative populations or ecotypes can provide an informative basis on which determination of the scale of local adaptation can be ascertained.

Stable coexistence of genetically divergent Atlantic cod ecotypes at multiple spatial scales

Coexistence in the same habitat of closely related yet genetically different populations is a phenomenon that challenges our understanding of local population structure and adaptation. Identifying the underlying mechanisms for such coexistence can yield new insight into adaptive evolution, diversification and the potential for organisms to adapt and persist in response to a changing environment. Recent studies have documented cryptic, sympatric populations of Atlantic cod (Gadus morhua) in coastal areas. We analysed genetic origin of 6,483 individual cod sampled annually over 14 years from 125 locations along the Norwegian Skagerrak coast and document stable coexistence of two genetically divergent Atlantic cod ecotypes throughout the study area and study period. A "fjord" ecotype dominated in numbers deep inside fjords while a "North Sea" ecotype was the only type found in offshore North Sea. Both ecotypes coexisted in similar proportions throughout coastal habitats at all spatial scales. The size-at-age of the North Sea ecotype on average exceeded that of the fjord ecotype by 20% in length and 80% in weight across all habitats. Different growth and size among individuals of the two types might be one of several ecologically significant variables that allow for stable coexistence of closely related populations within the same habitat. Management plans, biodiversity initiatives and other mitigation strategies that do not account for the mixture of species ecotypes are unlikely to meet objectives related to the sustainability of fish and fisheries.

Personalities influence spatial responses to environmental fluctuations in wild fish

Although growing evidence supports the idea that animal personality can explain plasticity in response to changes in the social environment, it remains to be tested whether it can explain spatial responses of individuals in the face of natural environmental fluctuations. This is a major challenge in ecology and evolution as spatial dynamics link individual- and population-level processes. In this study, we investigated the potential of individual personalities to predict differences in fish behaviour in the wild. Specifically, our goal was to answer if individual differences in plasticity of space use to sea surface temperature could be explained by differences in personality along the reactive-proactive axis. To address this question, we first conducted repeated standard laboratory assays (i.e., open-field test, novel object test and mirror stimulation test) to assess the personality type of 76 wild-caught Atlantic cod (Gadus morhua). Next, we released the fish back into the sea and monitored their spatial behaviour over large temporal (16 months) and spatial (a whole fjord) scales, using high-resolution acoustic tracking. We demonstrate that (a) cod personality traits are structured into a proactive-reactive syndrome (proactive fish being more bold, exploratory and aggressive), (b) mean depth use of individuals is mainly driven by sea temperature and (c) personality is a significant predictor of home range changes in the wild, where reactive, but not proactive, individuals reduced their home range as sea temperature increased. These findings expand our understanding of the ecological consequences of animal personality and the mechanisms shaping spatial dynamics of animals in nature.

Harvesting changes mating behaviour in European lobster

Removing individuals from a wild population can affect the availability of prospective mates and the outcome of competitive interactions, with subsequent effects on mating patterns and sexual selection. Consequently, the rate of harvest-induced evolution is predicted to be strongly dependent on the strength and dynamics of sexual selection, yet there is limited empirical knowledge on the interplay between selective harvesting and the mating systems of exploited species. In this study, we used genetic parentage assignment to compare mating patterns of the highly valued and overexploited European lobster (Homarus gammarus) in a designated lobster reserve and nearby fished area in southern Norway. In the area open to fishing, the fishery is regulated by a closed season, a minimum legal size and a ban on the harvest of egg-bearing females. Due to the differences in size and sex-specific fishing mortality between the two areas, males and females are of approximately equal average size in the fished area, whereas males tend to be larger in the reserve. Our results show that females would mate with males larger than their own body size, but the relative size difference was significantly larger in the reserve. Sexual selection acted positively on both body size and claw size in males in the reserve, while it was nonsignificant in fished areas. This strongly suggests that size truncation of males by fishing reduces the variability of traits that sexual selection acts upon. If fisheries continue to target large individuals (particularly males) with higher relative reproductive success, the weakening of sexual selection will likely accelerate fisheries-induced evolution towards smaller body size.

BioTIME: A database of biodiversity time series for the Anthropocene

MOTIVATION

The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.

MAIN TYPES OF VARIABLES INCLUDED

The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.

SPATIAL LOCATION AND GRAIN

BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).

TIME PERIOD AND GRAIN

BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.

MAJOR TAXA AND LEVEL OF MEASUREMENT

BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

SOFTWARE FORMAT

.csv and .SQL.

Fine-scale population dynamics in a marine fish species inferred from dynamic state-space models

Identifying the spatial scale of population structuring is critical for the conservation of natural populations and for drawing accurate ecological inferences. However, population studies often use spatially aggregated data to draw inferences about population trends and drivers, potentially masking ecologically relevant population sub-structure and dynamics. The goals of this study were to investigate how population dynamics models with and without spatial structure affect inferences on population trends and the identification of intrinsic drivers of population dynamics (e.g. density dependence). Specifically, we developed dynamic, age-structured, state-space models to test different hypotheses regarding the spatial structure of a population complex of coastal Atlantic cod (Gadus morhua). Data were from a 93-year survey of juvenile (age 0 and 1) cod sampled along >200 km of the Norwegian Skagerrak coast. We compared two models: one which assumes all sampled cod belong to one larger population, and a second which assumes that each fjord contains a unique population with locally determined dynamics. Using the best supported model, we then reconstructed the historical spatial and temporal dynamics of Skagerrak coastal cod. Cross-validation showed that the spatially structured model with local dynamics had better predictive ability. Furthermore, posterior predictive checks showed that a model which assumes one homogeneous population failed to capture the spatial correlation pattern present in the survey data. The spatially structured model indicated that population trends differed markedly among fjords, as did estimates of population parameters including density-dependent survival. Recent biomass was estimated to be at a near-record low all along the coast, but the finer scale model indicated that the decline occurred at different times in different regions. Warm temperatures were associated with poor recruitment, but local changes in habitat and fishing pressure may have played a role in driving local dynamics. More generally, we demonstrated how state-space models can be used to test evidence for population spatial structure based on survey time-series data. Our study shows the importance of considering spatially structured dynamics, as the inferences from such an approach can lead to a different ecological understanding of the drivers of population declines, and fundamentally different management actions to restore populations.

Eight decades of sampling reveal a contemporary novel fish assemblage in coastal nursery habitats

In order to adequately monitor biodiversity trends through time and their responses to natural or anthropogenic impacts, researchers require long time series that are often unavailable. This general lack of datasets that are several decades or longer makes establishing a background or baseline of diversity metrics difficult - especially when attempting to understand species composition changes against a backdrop of climate and ecological variability. Here, we present an analysis of a community of juvenile nearshore fishes based on nearly 8 decades of highly standardized Norwegian survey records. Using multivariate statistical techniques, we: (i) characterize the change in taxonomic community composition through time, (ii) determine whether there has been an increase in warm-water affinity species relative to their cold water affinity counterparts, and (iii) characterize the temporal change in the species' functional trait assemblage. Our results strongly indicate a shift toward a novel fish assemblage between the late 1990s and 2000s. The context of changes within the most recent two decades is in stark contrast to those during the 1960s and 1970s, but similar to those during the previous warm period during the 1930s and 1940s. This novel assemblage is tightly linked to the warming temperatures in the region portrayed by the increased presence of warm-water species and a higher incidence of pelagic, planktivorous species. The results indicate a clear influence of ocean temperature on the region's juvenile fish community that points to climate-mediated effects on the species assemblages of an important fish nursery area.

Spatial ecology of coastal Atlantic cod Gadus morhua associated with parasite load

Acoustic tags and receivers were used to investigate the spatial ecology of coastal Atlantic cod Gadus morhua (n = 32, mean fork length: 50 cm, range: 33-80 cm) on the Norwegian Skagerrak coast in 2012. Monthly home ranges (HR), swimming activity and depth use varied considerably among individuals and through the months of June, July and August. HR sizes for the period ranged from 0.25 to 5.20 km2 (mean = 2.30 km2. Two thirds of the tagged G. morhua were infected with black spot disease Cryptocotyle lingua parasites; these fish had larger HRs and occupied deeper water compared with non-infected fish. The infected fish also tended to be more active in terms of horizontal swimming. From an ecological and evolutionary perspective, any environmental change that modifies G. morhua behaviour may therefore also alter the parasite load of the population, and its conservation and fishery status.

Seasonal dynamics of Atlantic herring (Clupea harengus L.) populations spawning in the vicinity of marginal habitats

Gillnet sampling and analyses of otolith shape, vertebral count and growth indicated the presence of three putative Atlantic herring (Clupea harengus L.) populations mixing together over the spawning season February–June inside and outside an inland brackish water lake (Landvikvannet) in southern Norway. Peak spawning of oceanic Norwegian spring spawners and coastal Skagerrak spring spawners occurred in March–April with small proportions of spawners entering the lake. In comparison, spawning of Landvik herring peaked in May–June with high proportions found inside the lake, which could be explained by local adaptations to the environmental conditions and seasonal changes of this marginal habitat. The 1.85 km² lake was characterized by oxygen depletion occurring between 2.5 and 5 m depth between March and June. This was followed by changes in salinity from 1–7‰ in the 0–1 m surface layer to levels of 20–25‰ deeper than 10 m. In comparison, outside the 3 km long narrow channel connecting the lake with the neighboring fjord, no anoxic conditions were found. Here salinity in the surface layer increased over the season from 10 to 25‰, whereas deeper than 5 m it was stable at around 35‰. Temperature at 0–5 m depth increased significantly over the season in both habitats, from 7 to 14°C outside and 5 to 17°C inside the lake. Despite differences in peak spawning and utilization of the lake habitat between the three putative populations, there was an apparent temporal and spatial overlap in spawning stages suggesting potential interbreeding in accordance with the metapopulation concept.

Contrasting evolutionary demography induced by fishing: the role of adaptive phenotypic plasticity

Mounting evidence now shows that fishing activity modifies both heritable life-history traits and ecological processes in harvested populations. However, ecological and evolutionary changes are intimately linked and can occur on the same time scale, and few studies have investigated their combined effect on fish population dynamics. Here, we contrast two population subunits of a harvested fish species in the Northeast Atlantic, the European hake (Merluccius merluccius), in the light of the emerging field of evolutionary demography, which considers the interacting processes between ecology and evolution. The two subunits experienced similar age/size truncation due to size-selective fishing, but displayed differences in key ecological processes (recruitment success) and phenotypic characteristics (maturation schedule). We investigate how temporal variation in maturation and recruitment success interactively shape the population dynamics of the two subunits. We document that the two subunits of European hake displayed different responses to fishing in maturation schedules, possibly because of the different level of adaptive phenotypic plasticity. Our results also suggest that high phenotypic plasticity can dampen the effects of fisheries-induced demographic truncation on population dynamics, whereas a population subunit characterized by low phenotypic plasticity may suffer from additive effects of ecological and life-history responses. Similar fishing pressure may thus trigger contrasting interactions between life history variation and ecological processes within the same population. The presented findings improve our understanding of how fishing impacts eco-evolutionary dynamics, which is a keystone for a more comprehensive management of harvested species.

Probabilistic maturation reaction norms assessed from mark-recaptures of wild fish in their natural habitat

Reaction norms are a valuable tool in evolutionary biology. Lately, the probabilistic maturation reaction norm approach, describing probabilities of maturing at combinations of age and body size, has been much applied for testing whether phenotypic changes in exploited populations of fish are mainly plastic or involving an evolutionary component. However, due to typical field data limitations, with imperfect knowledge about individual life histories, this demographic method still needs to be assessed. Using 13 years of direct mark-recapture observations on individual growth and maturation in an intensively sampled population of brown trout (Salmo trutta), we show that the probabilistic maturation reaction norm approach may perform well even if the assumption of equal survival of juvenile and maturing fish does not hold. Earlier studies have pointed out that growth effects may confound the interpretation of shifts in maturation reaction norms, because this method in its basic form deals with body size rather than growth. In our case, however, we found that juvenile body size, rather than annual growth, was more strongly associated with maturation. Viewed against earlier studies, our results also underscore the challenges of generalizing life-history patterns among species and populations.

Small-scale genetic structure in a marine population in relation to water circulation and egg characteristics

Until the last decade it was assumed that most marine species have pronounced gene flow over vast areas, largely because of their potential for dispersal during early life stages. However, recent genetic, modeling, and field studies have shown that marine populations may be structured at scales that are inconsistent with extensive dispersal of eggs and larvae. Such findings have stimulated the birth of new studies explaining the mechanisms that promote population structure and isolation in the oceans, in the face of high potential for dispersal. Here we study the vertical and horizontal distribution of cod (Gadus morhua) eggs in relation to small-scale circulation and water column hydrography in a coastal location of southern Norway. Previous studies conducted in this region have shown that cod populations inhabiting fjord locations, which are on average 30 km apart, are genetically differentiated, a remarkable outcome considering that Atlantic cod have pelagic egg stages and long pelagic larval duration. We document that cod eggs are found in greater abundance in shallow water layers, which on average are flowing up the fjord (away from the open ocean), and in the inner portion of the fjord, which is subject to lower current speeds compared to the outer or mouth of the fjord. Eggs were found to be neutrally buoyant at shallow depths, a trait that also favors local retention, given the local circulation. The same patterns held during two environmentally contrasting years. These results strongly suggest that population structure of Atlantic cod is favored and maintained by a balance between water circulation and egg characteristics.

Are low but statistically significant levels of genetic differentiation in marine fishes 'biologically meaningful'? A case study of coastal Atlantic cod

A key question in many genetic studies on marine organisms is how to interpret a low but statistically significant level of genetic differentiation. Do such observations reflect a real phenomenon, or are they caused by confounding factors such as unrepresentative sampling or selective forces acting on the marker loci? Further, are low levels of differentiation biologically trivial, or can they represent a meaningful and perhaps important finding? We explored these issues in an empirical study on coastal Atlantic cod, combining temporally replicated genetic samples over a 10-year period with an extensive capture-mark-recapture study of individual mobility and population size. The genetic analyses revealed a pattern of differentiation between the inner part of the fjord and the open skerries area at the fjord entrance. Overall, genetic differentiation was weak (average F(ST)  = 0.0037), but nevertheless highly statistical significant and did not depend on particular loci that could be subject to selection. This spatial component dominated over temporal change, and temporal replicates clustered together throughout the 10-year period. Consistent with genetic results, the majority of the recaptured fish were found close to the point of release, with <1% of recaptured individuals dispersing between the inner fjord and outer skerries. We conclude that low levels of genetic differentiation in this marine fish can indeed be biologically meaningful, corresponding to separate, temporally persistent, local populations. We estimated the genetically effective sizes (N(e) ) of the two coastal cod populations to 198 and 542 and found a N(e) /N (spawner) ratio of 0.14.

Mating patterns and determinants of individual reproductive success in brown trout (Salmo trutta) revealed by parentage analysis of an entire stream living population

Reproductive success and its determinants are difficult to infer for wild populations of species with no parental care where behavioural observations are difficult or impossible. In this study, we characterized the breeding system and provide estimates of individual reproductive success under natural conditions for an exhaustively sampled stream-resident brown trout (Salmo trutta) population. We inferred parentage using a full probability Bayesian model that combines genetic (microsatellite) with phenotypic data. By augmenting the potential parents file with inferred parental genotypes from sib-ship analysis in cases where large families had unsampled parents, we could make more precise inference on variance of family size. We observed both polygamous and monogamous matings and large reproductive skew for both sexes, particularly in males. Correspondingly, we found evidence for sexual selection on body size for both sexes. We show that the mating system of brown trout has the potential to be very flexible and we conjecture that environmental uncertainty could be driving the evolution and perhaps select for the maintenance of plasticity of the mating system in this species.

Quantitative genetic parameters for wild stream-living brown trout: heritability and parental effects

Adaptability depends on the presence of additive genetic variance for important traits. Yet few estimates of additive genetic variance and heritability are available for wild populations, particularly so for fishes. Here, we estimate heritability of length-at-age for wild-living brown trout (Salmo trutta), based on long-term mark-recapture data and pedigree reconstruction based on large-scale genotyping at 15 microsatellite loci. We also tested for the presence of maternal and paternal effects using a Bayesian version of the Animal model. Heritability varied between 0.16 and 0.31, with reasonable narrow confidence bands, and the total phenotypic variance increased with age. When introducing dam as an additional random effect (accounting for c. 7% of total phenotypic variance), the level of additive genetic variance and heritability decreased (0.12-0.21). Parental size (both for sires and for dams) positively influenced length-at-age for juvenile trout--either through direct parental effects or through genotype-environment correlations. Length-at-age is a complex trait reflecting the effects of a number of physiological, behavioural and ecological processes. Our data show that fitness-related traits such as length-at-age can retain high levels of additive genetic variance even when total phenotypic variance is high.

New Danish reference values for height, weight and body mass index of children aged 0-5 years

AIM

To derive new reference values for height, weight and body mass index (BMI) of children aged 0-5 years in Denmark and to compare them with the national reference from the 1970s and the 2006 WHO standard.

METHODS

The height and weight of 4105 healthy singleton children born in 1995 were obtained from a cohort study. Children were measured at birth and at seven regular health examinations by a general practitioner up to 5 years of age. Generalized additive models for location, scale and shape were used to construct percentile curves.

RESULTS

Mean length, weight and BMI at birth and during the first months of life increased significantly, but the differences diminished thereafter, and at 1 year BMI had decreased. In boys, weight and BMI had decreased by 2 years of age but had increased, together with height, at 5 years. Children were taller, heavier and had a higher BMI than that referred to in the WHO standard.

CONCLUSION

New references for length or height, weight and BMI by age were constructed for children in Denmark. Since the 1970s, weight, length and BMI at birth increased, and growth during the first year of life appears to be healthier.

Sibling-size variation in brown trout Salmo trutta in relation to egg size and stream size

Sibling-size variation (SSV), estimated as the coefficient of variation of egg size, was investigated for 13 populations of brown trout Salmo trutta. SSV was negatively correlated with mean egg size both at the population and individual levels. After correction for the effect of mean egg size, SSV was also negatively correlated with stream size. These results provide new information about how salmonid SSV can vary at different ecological scales (individual, population and region). The results are discussed in light of competing theories for explaining SSV: (1) the passive effect hypothesis, stating that egg size variation follows passively from selection on egg size and (2) the bet-hedging hypothesis, stating that high SSV is adaptive in unpredictable environments.

Predictors (0-10 months) of psychopathology at age 11/2 years - a general population study in The Copenhagen Child Cohort CCC 2000

BACKGROUND

Epidemiological studies of mental health problems in the first years of life are few. This study aims to investigate infancy predictors of psychopathology in the second year of life.

METHODS

A random general population sample of 210 children from the Copenhagen Child Birth Cohort CCC 2000 was investigated by data from National Danish registers and data collected prospectively from birth in a general child health surveillance programme. Mental health outcome at 1(1/2) years was assessed by clinical and standardised measures including the Child Behavior Check List 1(1/2)-5 (CBCL 1(1/2)-5), Infant Toddler Symptom Check List (ITSCL), Checklist for Autism in Toddlers (CHAT), Bayley Scales of Infant Development (BSID II), Mannheim Eltern Interview (MEI), Parent Child Early Relational Assessment (PC ERA) and Parent Infant Relationship Global Assessment Scale (PIR-GAS), and disordered children were diagnosed according to the International Classification of Diseases (ICD-10) and Diagnostic Classification Zero to Three (DC: 0-3).

RESULTS

Deviant language development in the first 10 months of life predicted the child having any disorder at 1(1/2) years, OR 3.3 (1.4-8.0). Neuro-developmental disorders were predicted by deviant neuro-cognitive functioning, OR 6.8 (2.2-21.4), deviant language development, OR 5.9 (1.9-18.7) and impaired social interaction and communication, OR 3.8 (1.3-11.4). Unwanted pregnancy and parents' negative expectations of the child recorded in the first months of the child's life were significant predictors of relationship disturbances at 1(1/2) years.

CONCLUSIONS

Predictors of neuro-developmental disorders and parent-child relationship disturbances can be identified in the first 10 months of life in children from the general population.

Failure to thrive: the prevalence and concurrence of anthropometric criteria in a general infant population

BACKGROUND

Failure to thrive (FTT) in early childhood is associated with subsequent developmental delay and is recognised to reflect relative undernutrition. Although the concept of FTT is widely used, no consensus exists regarding a specific definition, and it is unclear to what extent different anthropometric definitions concur.

OBJECTIVE

To compare the prevalence and concurrence of different anthropometric criteria for FTT and test the sensitivity and positive predictive values of these in detecting children with "significant undernutrition", defined as the combination of slow conditional weight gain and low body mass index (BMI).

METHODS

Seven criteria of FTT, including low weight for age, low BMI, low conditional weight gain and Waterlow's criterion for wasting, were applied to a birth cohort of 6090 Danish infants. The criteria were compared in two age groups: 2-6 and 6-11 months of life.

RESULTS

27% of infants met one or more criteria in at least one of the two age groups. The concurrence among the criteria was generally poor, with most children identified by only one criterion. Positive predictive values of different criteria ranged from 1% to 58%. Most single criteria identified either less than half the cases of significant undernutrition (found in 3%) or included far too many, thus having a low positive predictive value. Children with low weight for height tended to be relatively tall.

CONCLUSIONS

No single measurement on its own seems to be adequate for identifying nutritional growth delay. Further longitudinal population studies are needed to investigate the discriminating power of different criteria in detecting significant undernutrition and subsequent outcomes.

The prevalence of mental health problems in children 1(1/2) years of age - the Copenhagen Child Cohort 2000

BACKGROUND

The Copenhagen Child Cohort, CCC 2000, was established to investigate developmental psychopathology prospectively from birth in a general population.

METHODS

A random sample of 211 children from the CCC 2000 was investigated when the children were 1(1/2) years of age. The prevalence and associates of mental health problems and psychopathology were studied by clinical and standardised strategies, including videotape recordings, parent interviews and the following instruments: The Child Behavior Check List 1(1/2)-5 (CBCL 1(1/2)-5), The Infant Toddler Symptom Check List (ITSCL), Checklist for Autism in Toddlers (CHAT), Bayley Scales of Infant Development II (BSID II), The Parent Child Early Relationship Assessment (PC ERA) and Parent Infant Relationship Global Assessment Scale (PIR-GAS).

RESULTS

Mental health problems according to International Classification of Diseases (ICD-10) and Diagnostic Classification Zero to Three (DC 0-3) diagnoses were found in 16-18% of 1(1/2)-year-old children. Most common were disturbances of emotion, behaviour and eating and the DC 0-3 diagnosis of regulatory disorder. Parent-child relationship disturbances were found in 8%. High psychosocial risk was significantly associated with emotional and behavioural disorders (OR 3.1 95% (1.2-8.1)) and disturbed parent-child relationship (OR 5.0 95% (1.6-16.0)). The strongest association of risk was found between relationship disorders and emotional and behavioural disorders (OR 11.6 95% (3.8-37.5)).

CONCLUSIONS

The prevalence and distribution of psychopathology in 1(1/2)-year-old children seem to correspond to the distributions among older children. Disturbances in parent-child relationship have a key position in the risk mechanisms in early child psychopathology.

Maturation trends indicative of rapid evolution preceded the collapse of northern cod

Northern cod, comprising populations of Atlantic cod (Gadus morhua) off southern Labrador and eastern Newfoundland, supported major fisheries for hundreds of years. But in the late 1980s and early 1990s, northern cod underwent one of the worst collapses in the history of fisheries. The Canadian government closed the directed fishing for northern cod in July 1992, but even after a decade-long offshore moratorium, population sizes remain historically low. Here we show that, up until the moratorium, the life history of northern cod continually shifted towards maturation at earlier ages and smaller sizes. Because confounding effects of mortality changes and growth-mediated phenotypic plasticity are accounted for in our analyses, this finding strongly suggests fisheries-induced evolution of maturation patterns in the direction predicted by theory. We propose that fisheries managers could use the method described here as a tool to provide warning signals about changes in life history before more overt evidence of population decline becomes manifest.

[Cataract--an initial symptom of diabetes mellitus in a 14-year old girl]

A 14-year-old girl presented with cataract as an initial sign of IDDM. Before the diagnosis of DM, she showed no acute symptoms, including ketoacidosis. Retrospectively, there had been faint signs of polyuria, polydipsia, and nycturia. Diabetic cataract is a rare complication in young diabetics and is usually associated with long-standing DM and poor metabolic control. Previous cases have a striking resemblance to our patient, thus suggesting that a small group of young diabetics have weak symptoms, but are nevertheless at great risk of developing diabetic complications.

Endotoxinemia and thrombocytopenia during neonatal necrotizing enterocolitis

Thrombocytopenia frequently complicates neonatal necrotizing enterocolitis (NEC) and has been postulated to result from absorption of bacterial endotoxins from the injured gut. The authors tested blood obtained during 47 episodes of NEC for endotoxin-like activity (ELA), using a Limulus amoebocyte lysate assay and found 23 patients (49%) had positive results. Concentrations of ELA in plasma ranged from 0.26 to 300 ng/mL of Escherichia coli equivalent activity, with a geometric mean of 1.1 ng/mL. Serial platelet measurements were available from 40 infants, 11 (28%) of whom had nadir counts below 100,000/mm3 following NEC onset. Nine of 19 infants (47%) with ELA in plasma and only 2 of 21 without (9.5%, P less than 0.05) developed thrombocytopenia, suggesting that endotoxinemia may indeed contribute to platelet depletion during NEC.

Effect of heat treatment on the quality and utilization by the rat of protein in wheat germ meal

Five samples of wheat germ meal (WGM): raw, toasted 45 min, autoclaved 20, 45, or 90 min were analyzed for amino acids. Arginine and lysine were decreased by all treatments; the greatest loss was of lysine in 45- and 90-min autoclaved samples. Digestibility of protein and absorption of amino acids, determined with rats, was decreased by autoclaving. Decreased amino acid content and protein digestibility was reflected in lower weight gain and protein efficiency ratio (PER). Experimentally determined protein digestibilities of mixtures of raw and 90-min autoclaved WGM showed that the digestibility values of the two components were additive. Supplementation of raw WGM with amino acids showed that only methionine improved growth and PER. By these criteria, methionine-supplemented raw WGM was superior to methionine-supplemented soybean meal. Raw WGM exhibited no toxicity for the rat. The results confirm the excellent quality of protein in WGM. It is suggested that heat treatments applied during processing should be kept at a minimum.