Maturation Schedules Research Articles

Applying a flexible spline model to estimate functional maturity and spatio-temporal variability in aurora rockfish (Sebastes aurora)

We outline a new flexible method for estimating maturity that incorporates skip spawning, which can lead to non-asymptotic behavior in the population maturity schedule. This new approach aids fisheries managers who seek to understand marine species’ responses to changing oceans. In an effort to assess shifts in maturity and spawning behavior of west coast groundfish, we used this new method to evaluate spatio-temporal trends in length at maturity, the annual reproductive cycle, and spawning behavior of aurora rockfish (Sebastes aurora). We estimated biological (presence of physiological maturity markers) and functional (potential spawners in a given year) maturity using a standard logistic and the new flexible spline model. The range in lengths at 50% maturity (biological and functional) slightly varied between the two methods (23.66–23.93 and 25.34–25.57 cm). We also investigated spatial trends in maturity and found ~ 2 cm difference in functional maturity between fish sampled north and south of Cape Mendocino, CA (26.22–26.48 and 24.38–24.74 cm). We demonstrate model sensitivity by updating the maturity estimates in the 2013 aurora rockfish stock assessment. Absolute, but not relative, spawning output, was sensitive to model choice, spatial resolution, and the updated data. This new flexible spline model can account for skip spawning, capturing potential spawners in a given year, and thus provides accurate measurements for spawning output models.

Estimating maturity from size-at-age data: Are real-world fisheries datasets up to the task?

The size and age at which individuals mature is rapidly changing due to plastic and evolved responses to fisheries harvest and global warming. Understanding the nature of these changes is essential because maturity schedules are critical in determining population demography and ultimately, the economic value and viability of fisheries. Detecting maturity changes is, however, practically difficult and costly. A recently proposed biphasic growth modelling likelihood profiling method offers great potential as it can statistically estimate age-at-maturity from population-level size-at-age data, using the change-point in growth that occurs at maturity. Yet, the performance of the method on typical marine fisheries datasets remains untested. Here, we assessed the suitability of 12 North Sea and Australian species’ datasets for the likelihood profiling approach. The majority of the fisheries datasets were unsuitable as they had too small sample sizes or too large size-at-age variation. Further, datasets that did satisfy data requirements generally showed no correlation between empirical and model-derived maturity estimates. To understand why the biphasic approach had low performance we explored its sensitivity using simulated datasets. We found that method performance for marine fisheries datasets is likely to be low because of: (1) truncated age structures due to intensive fishing, (2) an under-representation of young individuals in datasets due to common fisheries-sampling protocols, and (3) large intrapopulation variability in growth curves. To improve our ability to detect maturation changes from population level size-at-age data we need to improve data collection protocols for fisheries monitoring.

Characterization of CiWRI1 from Carya illinoinensis in Seed Oil Biosynthesis

Pecan (Carya illinoinensis) is a widely consumed edible woody oil species that is rich in unsaturated fatty acids (FAs) that are beneficial to human health. However, the genes and mechanisms regulating seed oil biosynthesis in pecan are not well understood. Here, we analyzed the expression patterns of genes involved in seed oil biosynthesis in two different varieties of pecan with distinct fruit maturation schedules and oil contents. We cloned the C. illinoinensis WRINKLED 1 (CiWRI1) gene, a homolog of ArabidopsisWRINKLED1 (AtWRI1), which plays a key role in FA synthesis. Overexpressing CiWRI1 restored lipid synthesis in the Arabidopsiswri1-1 mutant and rescued other phenotypic defects such as plant height, root length, and germination rate, suggesting that CiWRI1 is an ortholog of the AtWRI1 and is involved in the regulation of FA synthesis. To investigate the mechanism of CiWRI1 regulation, we cloned C. illinoinensis BIOTIN CARBOXYL CARRIER PROTEIN ISOFORM2 (CiBCCP2) and determined that the CiWRI1 protein directly binds to an ASML1/WRI1 (AW)-box motif in the CiBCCP2 gene promoter and thereby activates its transcription. CiBCCP2 overexpression partly rescued the phenotypic defects of the wri1-1 mutant, indicating that it is directly regulated by CiWRI1. Thus, de novo FA biosynthesis in seed is conserved across plant species; moreover, CiWRI1 regulates oil synthesis by directly controlling CiBCCP2 expression. These findings present novel potential targets for molecular-marker-assisted breeding of this commercially important plant.

Reproduction of Atlantic bluefin tuna

AbstractThe reproductive success of fish populations depends on their reproductive potential and offspring survival to maturity. The reproductive potential affects recruitment and hence populations’ resilience and productivity. Extensive research carried out throughout the current century has improved our understanding of the reproductive biology of the Atlantic bluefin tuna (ABFT), Thunnus thynnus. Yet, crucial questions still remain unresolved. This paper examines key factors that drive ABFT reproductive performance (maturity, spawning frequency, fecundity, sex ratio, spawning habitat). Some reproductive variables (spawning at age, spawning omission, egg and offspring viability, parental effect) remain poorly investigated due to the enormous challenge of implementing the required research across the distribution range and over time. These fundamental traits of the reproductive life history, however, provide valuable information to fish stock assessment models and hence require further attention. There is a major debate as to the extent of similarity in reproductive traits between eastern and western ABFT stocks. Both stocks have been considered to display differing maturity schedules, which would result in different spawning rates and reproductive outputs. Yet, similarities have been found in major reproductive aspects suggesting that discrepancies between stocks may not be as broad as often assumed. Though substantial, the information acquired on ABFT reproduction over the years is still incomplete for adequately advising fisheries management. The present report provides a synthesis of the existing information on the reproductive biology of ABFT. It also identifies major research needs and analyses future research actions towards bridging current gaps in ABFT reproduction science.

Phenotypic plasticity in life-history characteristics of invasive blue catfish, Ictalurus furcatus

Blue catfish, Ictalurus furcatus, are an invasive species in the Chesapeake Bay region, where they negatively impact native species of ecological, economic and cultural value. Management of blue catfish is, however, hindered by a lack of information on their population dynamics. We studied decadal changes in growth and body condition and made inferences about maturity schedules of blue catfish in two Chesapeake Bay subestuaries (James and York rivers). Specifically, we quantified the dynamic responses of these populations to biotic and abiotic characteristics experienced by fish during two stages of invasion (1998−2000 or “early” period and 2015−2017 or “recent” period). In general, somatic growth rate, body condition and reproductive allocation were greater in the early, less dense populations, which also exhibited larger mean size-at-maturity. We observed sexual dimorphism in growth patterns where males reached larger asymptotic sizes than females in both rivers. Such sex-specific and density-dependent responses in life-history characteristics provide information critical for the development of quantitative models and deployment of effective management plans. Our results highlight the need for management plans to consider dynamic feedback mechanisms: efforts to decrease population density may diminish the negative impacts of blue catfish on native species, but this will be offset by increased growth rates and higher reproductive output.

Variability of the period between germination and heading in spring barley accessions from Dagestan

Background. The genetic variability of the period between the germination and heading phases was analyzed in barley accessions from the Republic of Dagestan planted in the southern area of Dagestan (Derbent) and the Northwest of Russia (Pushkin, St. Petersburg). Testing barley development rates under contrasting climate conditions of Russia makes it possible to assess the paratypic variability and a norm of reaction in the tested accessions in order to identify environmentally adaptable plant forms useful for breeding.Materials and methods. Under spring sowing, 173 spring barley accessions were studied for the duration of the period from germination to heading. To compare the earliness of accessions planted at two sites with different sowing schedules, “the rate by which the germination-to-heading period of an accession exceeded its minimum value across the sample” was used as a criterion for calculations.Results and conclusions. Accession k-15013 was the earliest at both test sites during two years of studying. In Dagestan, accessions k-11439 and k-11475 with a low norm of reaction in 2016 and 2017 were also identified as early. Environmental conditions were found to have a significant effect on the development rate of barley accessions in Derbent and St. Petersburg. Dagestani barleys in the North-west of Russia ripened earlier than in the south of Dagestan during all the years of study. Vernalization temperatures proved to be the main factor affecting maturation schedules of local Dagestani barleys in the area of their distribution. A longer day and the absence of high temperatures in St. Petersburg contributed to the earliness of barley accessions.

Ecocentrism: Resetting Baselines for Virtue Development

From a planetary perspective, industrialized humans have become unvirtuous and holistically destructive in comparison to 99% of human genus existence. Why? This paper draws a transdisciplinary explanation. Humans are social mammals who are born particularly immature with a lengthy, decades-long maturational schedule and thus evolved an intensive nest for the young (soothing perinatal experience, responsive care, extensive breastfeeding, multiple responsive caregivers, positive social support, self-directed free play with multi-aged mates in the natural world). Neurosciences show that evolved nest components support normal development at all levels (e.g., neurobiological, social, psychological), laying the foundations for virtue. Nest components are degraded in industrialized societies. Studies and accounts of societies that provide the nest, particularly nomadic foragers, the type of society in which humanity spent 99% of its genus history, indicate a more virtuous human nature than that industrialized societies think is normal or possible. Nest-supported human nature displays Darwin’s moral sense whereas unnested individuals show dysregulation and a degraded moral sense—a species-atypical human nature. Original virtue is about flourishing—of self, human community and the more than human community—within all circles of life, based in a deep awareness of humanity’s dependence on the rest of nature to survive. The pillars of original virtue include relational attunement (engagement ethic), communal imagination, and respectful partnership with the natural world. All are apparent in human societies that provide the nest to their young, fostering connectedness throughout life. They maintain communal imagination through cultural practices that enhance ecological attachment and receptive intelligence to the natural world.

Timing of the reproductive cycle of waved whelk, Buccinum undatum, on the U.S. Mid-Atlantic Bight

Development of the unmanaged waved whelk (Buccinum undatum) fishery on the Mid-Atlantic continental shelf of the United States has initiated investigation into fisheries-related biological and population attributes of the species in this region. Maturation and reproduction timing vary by location for this species and are likely linked to bottom water temperature. This study examined the seasonal fluctuations in relevant body metrics and gonadosomatic index in relation to bottom temperature to assess the timing of the reproductive cycle of the B. undatum population in the southern-most extent of this species’ range in the Atlantic. To characterize variation over the maturation schedule, nine locations in the Mid-Atlantic Bight (MAB) were sampled five times between January 2017 and September 2017. Maturity was assessed macroscopically, with morphological methods, and via gonadosomatic indices. Male behavioral maturity estimates, based on a penis length to shell length index (PL50), were compared to estimates made using other methods for assessing maturity to test the efficacy of this commonly used ratio. Mature whelk were found in all months and peak reproductive activity was observed in spring and early summer. This timing suggests that ideal sampling to visually identify maturity to estimate size of maturity would be late winter or early spring. Unique oceanographic dynamics in the MAB, such as strong seasonal stratification results in large changes in annual bottom temperature which appears to be closely linked to the reproductive cycle in this region. Our data suggest that B. undatum in the MAB experience spawning and development at ~ 7–8 °C; temperatures warmer than Canadian populations and cooler than some UK conspecifics. To our knowledge, this is the first study to document the annual reproductive cycle of waved whelk in the United States.

Interactions between Marine Growth and Life History Diversity of Steelhead from the Situk River, Alaska

AbstractSteelhead (the anadromous form of Rainbow Trout Oncorhynchus mykiss) exhibit a complex life history that is described by variable freshwater and ocean residency and maturation schedules. This diversity confers resilience but complicates their monitoring and management. The Situk River in Southeast Alaska has the longest running set of biological data and scale samples for steelhead in the state, and it is of particular interest because it supports the largest known population of steelhead in Alaska and is free of hatchery influence. We used a retrospective analysis of scales that were collected from 525 individuals over 11 years (1999–2012) to examine the relationships among freshwater growth, early ocean growth, and life history in a mixed‐effects modeling framework. Specifically, we examined the relationships among annual growth stanzas and adult length and we determined how age at maturity varied by sex and growth history while allowing these relationships to vary randomly among calendar years of growth. Within individuals, freshwater and first ocean‐year growth were positively correlated, while second ocean‐year growth was negatively correlated with earlier growth stanzas. Early‐maturing steelhead (returning after two ocean years) grew more quickly during their first ocean year, and they then grew more slowly during their second ocean year and attained smaller adult length than did later‐maturing steelhead (those that returned after three ocean years). Second ocean‐year growth was more variable than first ocean‐year growth and adult length were. Males tended to mature earlier than females did, and later‐maturing males attained larger freshwater growth than their earlier‐maturing male counterparts did and grew larger in overall length than did females. Our analyses identified divergent growth trajectories that were associated with age at maturity that began in freshwater periods but were most pronounced during early ocean residency. We found retrospective scale‐growth analysis to be a useful tool for better understanding the connections between ocean growth and demography in this important sport fish.

Resolving associative patterns in life history parameters among marine fish stocks in the Northeast Pacific Ocean

Knowledge of life history characteristics in marine fishes, including natural mortality, somatic growth, maturity schedule, productivity and others, is essential for successful management and long-term sustainability of marine resources. Patterns exist among these traits within and among taxa to maximize individual fitness and offspring survival, and trade-offs are typical. In this study, we examined life history data from 42 fishery stocks in the Northeast Pacific Ocean using principal component analysis (PCA) and clustering techniques. We identified discrete clustering patterns of stocks corresponding to ecological, taxonomic, and management criteria. Our results revealed additional resolution for complex structure among stocks based on combinations of life history traits, well beyond what was described before, for the diverse group of Sebastes rockfish, which have not been examined in this context previously. One example is clear differentiation between Sebastes demersal species, and those caught with midwater gear, particularly with addition of stock-specific fecundity data; another is bocaccio rockfish, whose life history patterns our results shed new light on. Our results also provide an empirical basis for grouping stocks in meta-analytic studies, which are often used to inform unknown or difficult to estimate parameters in stock assessment. Our results supported important core aspects of previous studies, and rectified others, among a wide range of stocks including highly migratory, coastal pelagic and groundfish stocks. They also reinforce fishery management strategies grounded in life history, among stocks in the Northeast Pacific Ocean and around the world.

Labor and Finance: The Role of Financial Reporting Quality

We examine the role of financial reporting quality in facilitating corporate employment around debt maturities. As firms’ long-term debts approach maturity, information problems and conflicts of interest among capital providers create refinancing risk that can constrain borrowing. Refinancing risk is particularly relevant for funding labor, because wage rigidity creates operating leverage and human capital lacks collateral value, both of which increase credit risk and the importance of information in debt markets. We use firms’ predetermined debt maturity schedules to identify firms with significant long-term debt approaching maturity and find that higher quality financial reporting mitigates the negative effect of maturing debt on firms’ net hiring. This result is stronger when wages are more rigid, when other sources of collateral are limited, and for firms with higher default risk. Higher quality financial reporting is also associated with lower employee quit rates as debt approaches maturity, consistent with a related labor supply channel. Overall, our results are consistent with unique frictions in labor and debt markets creating an important role for financial reporting quality in facilitating firm-level employment.

REPRODUCTIVE POTENTIAL OF POTATO ACCESSIONS FROM THE VIR COLLECTION IN MURMANSK PROVINCE

Background. Knowledge of the reproductive potential in plants is of vital importance for potato cultivation in the Arctic environments.Materials and methods. From 2008 through 2017, 1594 potato cultivars with diverse maturation schedules from VIR’s collection were studied at the Polar Experiment Station of VIR. The material was evaluated according to the timing of their phenological phases (germination, budding, and flowering) and the possibility of their reproductive organs’ development.Results: With the same agricultural practice applied, cultivars of different maturation groups began to germinate and produce shoots at about the same time within the growing season, with a slight difference from 0.2 days (2010) to 3.3 days (2015). Further passing of phenological phases under the conditions of the Arctic depended on the mean daily air temperature and precipitation. The duration of the period from germination to flowering was largely affected by the temperature regime. The emergence of mass shoots was observed on average 18.5 ± 2.9 days after planting. The budding phase started 31.9 ± 4.7 to 43.0 ± 6.9 days after planting. The beginning of flowering occurred at the beginning of the third decade of July or 46.8 ± 4.9 to 57.5 ± 7.5 days after planting. The duration of the mass flowering of potato plants on average covered the time frame from the end of July to the middle of the third ten-day period of August. To move a potato plant from the budding phase to the flowering/mass flowering phase, a sum of effective July temperatures of 300°C is required. During the growing season, for all the years of the study, 97% of the varieties, as related to the total number of accessions, were able to set up buds; 85.7% entered the flowering stage; 63.3% moved to the stage of mass flowering; and 22.2% were able to set berries from self-pollination. According to the data of the long-term analysis of perennial agrometeorological data, the most favorable conditions for setting berries after potato self-pollination recurred every five years in the north. These conditions were formed under the sum of active air temperatures from 1170 to 1300°С (for June, July, and August), combined with insufficient provision of precipitation. Under the natural conditions in the north, the lack of moisture stimulates plants to enter the stages of flowering and fruit setting quicker and more intensively.Conclusion: The study made it possible to identify the optimal conditions for the fruit to be set by a potato plant in the north and also to acquire more data on the reproduction characteristics of potato cultivars.

DIVERSITY OF THE PUMPKIN COLLECTION AND ITS HEREDITARY POTENTIAL. RESULTS AND PROSPECTS OF BREEDING PRACTICE

Background. Pumpkin is an important food, feed and medicinal crop. It is widely used by national cuisines in many countries and utilized as raw material for canning industry and in pharmacy to prepare drugs. The Kuban Experiment Station of VIR, where the collection of pumpkin genetic resources is maintained and regenerated for long-term storage in the genebank, conducts comprehensive research work to analyze the genetic diversity of pumpkin accessions and disclose the potential of its hereditary variation.Objective. The aim of this study was to screen various species from the global pumpkin collection and identify sources of traits valuable for breeders in order to develop promising cultivars and hybrids.Materials and methods. The pumpkin collection was studied and the breeding work was performed using the guidelines worked out by VIR’s scientists. The work included botanical description, study of variability and inheritance of traits, hybridization, inbreeding, mutagenesis, and different selection techniques (individual, group, individual/ family, and mass selection). In the first stages of the study, inbreeding was employed to select best plants from the collection in order to set up a trait-specific collection and incorporate its accessions into the hybridization process. Self-pollination was usedfor several years to obtain self-pollinated lines, sufficiently uniform in the selected trait. The hybrid progenies from crosses between parental forms were analyzed to throw light on the inheritance of major traits and their genetic control. The accessions were assessed for their earliness, productivity and quality. Evaluation of disease resistance was carried out in the field under natural infection pressure.Results and discussion. Targeted breeding efforts resulted in releasing cultivars of Cucurbita pepo L., C. maxima Duch. and C. moschata Duch. ex. Poir. having different maturation schedules and approved for cultivation in various regions of Russia: ‘Kustovaya oranzhevaya’, ‘Lechebnaya’, ‘Kustovaya zolotaya’, ‘Malyshka’, ‘Matreshka’, ‘Krasavitsa’, Zimnyaya sladkaya’, ‘Zhemchuzhina’, ‘Yantarnaya’ and ‘Mariya’. These cultivars are in demand among both agricultural producers and individual growers. New sources of valuable morphobiological and agronomic characters have been identified as useful for modern plant breeding trends: KL 625, ZhZM 692, L-180, L-193, KPL 168, KL 568 and KL 570. New bushy lines of C. maxima and C. moschata selected from cultivar and hybrid populations are now tested in an elite test nursery in order to submit the best of them to the State Variety Trials.

${H}_{\infty }$ Filtering for Fuzzy Jumping Genetic Regulatory Networks With Round-Robin Protocol: A Hidden-Markov-Model-Based Approach

In this article, a method to design the filter for fuzzy jumping genetic regulatory networks is explored. The case when the filters cannot directly utilize the mode information of the plant is taken into account. A hidden Markov model is introduced to address such a problem. Furthermore, a mature scheduling method, namely round-robin protocol, is employed to optimize the data transmission in genetic regulatory networks. On the basis of the fuzzy model approach and the stochastic analysis technique, some novel conditions ensuring the $H_{\infty }$ performance and stochastic stability of the error system are established. The parameters of the filter can be presented via addressing the convex optimization problem. The feasibility of results is finally illustrated by considering a repressilator model subject to stochastic jumping parameters.

Reference points for the length-based indicator Lmax5% for use in the assessment of data-limited stocks

Abstract In the absence of abundance indices from scientific surveys or commercial sources, reliable length frequency data from sampled commercial catches can be used to provide an indirect assessment of fishing mortality. Length-based indicators are simple metrics which describe length frequency distributions. The length-based indicator Lmax5%, the mean length of the largest 5% of individuals in the catch, combined with appropriately selected reference points, can be used to evaluate the presence of very large individuals in the catch and hence determine exploitation level. Using analytical per-recruit models, we derive reference points consistent with a spawning potential ratio of 40%. The reference points depend on the life history parameters for natural mortality, maturity, and growth (M, Lmat, L∞, k, CVL∞). Using available simulation tools, we investigate the sensitivity of the reference points to errors in these parameters and explore the usefulness of particular reference points for management purposes for stocks with different life histories. The proposed reference points are robust to uncertainty in length at first capture, Lc, and take into account the maturation schedule of a species. For those stocks with high M/k ratios (>1), Lmax5%, combined with the appropriate reference point, can be used to provide a data-limited stock assessment.

Evidence for trans-generational effects on egg maturation schedules in a syn-ovigenic parasitoid

The lifetime reproductive success of a female parasitoid is limited by (1) host (or time) limitation – the number of hosts available for oviposition during its lifetime; and (2) egg limitation – its egg supply. Host limitation is expected to select for increased longevity and/or foraging efficiency, while increased fecundity is predicted to evolve under egg limitation. If the limiting factor varies, phenotypic plasticity in egg maturation schedules may be advantageous, i.e. adjusting investment in egg production to host availability. In the polyembryonic parasitoid Copidosoma koehleri, environmental conditions experienced during development indeed influence resource allocation to egg maturation. However, whether parasitoids’ maternal environment also influences their daughters’ egg production has hardly been studied. To address this knowledge gap, we tested whether exposure of C. koehleri females to previously parasitized hosts (signaling intraspecific exploitation competition and risk of host limitation) reduces their daughters’ initial egg loads. We presented newly-emerged females with hosts that were either fresh or parasitized by conspecifics. The following day, we exposed both groups to additional fresh hosts, and reared out the daughters of these previously experienced, 24+ h old, individuals. The daughters’ egg loads and body sizes were similar under both experimental conditions. Nevertheless, their egg loads were ~30% higher, and body sizes were ~10% lower, than in daughters of just-emerged parasitoids. We suggest that female experience or age, but not conditions associated with host exploitation, trigger maternal effects on the reproductive and developmental physiology of their daughters.

Selection for small body size favours contrasting sex-specific life histories, boldness and feeding in medaka, Oryzias latipes

BackgroundStudying variation in life-history traits and correlated behaviours, such as boldness and foraging (i.e., pace-of-life syndrome), allows us to better understand how these traits evolve in a changing environment. In fish, it is particularly relevant studying the interplay of resource abundance and size-selection. These are two environmental stressors affecting fish in natural conditions, but also associated with human-induced environmental change. For instance, fishing, one of the most important threats for freshwater and marine populations, results in both higher mortality on large-sized fish and reduced population density.ResultsMedaka, Oryzias latipes, from lines selected for large or small size over ten generations, were exposed individually to high or low food availability from birth to adulthood. Maturation schedules, reproductive investment, growth, boldness and feeding were assessed to evaluate the effect of size-selection on the pace of life, and whether it differed between food contexts (high and low). Different food abundance and size-selection resulted in diverse life histories associated with different feeding and boldness behaviour, thus showing different pace-of-life-syndromes. High availability of food favoured faster growth, earlier maturation and increased shyness. Selection for small size led to slower growth in both males and females. But, the life-history trajectory to reach such growth was sex- and food-specific. Under low food conditions, females selected for small size showed earlier maturation, which led to slower adult growth and subsequent low willingness to feed, compared to females selected for large size. No line differences were found in females at high food conditions. In contrast, males exposed to selection for small size grew slower both as juvenile and adult, and were bolder under both feeding regimes. Therefore, the response to size-selection was more sensitive to food availability in females than in males.ConclusionsWe showed that size-selection (over ten generations) and resource abundance (over developmental time) led to changes in life history and behaviour. However, the effect of size-selection was sex- and context-specific, calling for precaution when drawing general conclusions on the population-level effects (or lack of them) of size-selective fishing. Conservation and management plans should consider this sex- and context-specificity.

Cortical and subcortical T1 white/gray contrast, chronological age, and cognitive performance

The maturational schedule of typical brain development is tightly constrained; deviations from it are associated with cognitive atypicalities, and are potentially predictive of developmental disorders. Previously, we have shown that the white/gray contrast at the inner border of the cortex is a good predictor of chronological age, and is sensitive to aspects of brain development that reflect cognitive performance. Here we extend that work to include the white/gray contrast at the border of subcortical structures. We show that cortical and subcortical contrast together yield better age-predictions than any non-kernel-based method based on a single image-type, and that the residuals of the improved predictions provide new insight into unevenness in cognitive performance. We demonstrate the improvement in age predictions in two large datasets: the NIH Pediatric Data, with 831 scans of typically developing individuals between 4 and 22 years of age; and the Pediatric Imaging, Neurocognition, and Genetics data, with 909 scans of individuals in a similar age-range. Assessment of the relation of the residuals of these age predictions to verbal and performance IQ revealed correlations in opposing directions, and a principal component analysis of the residuals of the model that best fit the contrast data produced components related to either performance IQ or verbal IQ. Performance IQ was associated with the first principle component, reflecting increased cortical contrast, broadly, with almost no subcortical presence; verbal IQ was associated with the second principle component, reflecting reduced contrast in the basal ganglia and increased contrast in the bilateral arcuate fasciculi.

Population density and temperature correlate with long-term trends in somatic growth rates and maturation schedules of herring and sprat.

We examine long-term trends in the average growth rates and maturation schedules of herring and sprat populations using survey data collected from the North Sea and west of Scotland since the 1960s and 1980s respectively. Otolith age data and maturity data are used to calculate time series of mean lengths at age, von Bertalanffy growth parameters, and probabilistic maturation reaction norms. As the growth and maturation of fish is known to be influenced by temperature and stock abundances, we account for these variables using Generalised Additive Models. Each of the herring populations displayed either steady declines in mean length across multiple age groups, or declines in length followed years later by some recovery. Depending on region, lengths at age of sprat increased or decreased over time. Varying temporal trends in maturation propensity at age and length were observed across herring populations. Many of the trends in growth rate and maturation were correlated to population abundance and/or temperature. In general, abundance is shown to be negatively correlated to growth rates in herring and sprat, and positively correlated with maturation propensity in herring. Temperature is also shown to be correlated to growth and maturation, and although the effect is consistent within species, the temperature effects differ between herring and sprat. This study provides detailed information about long-term trends in growth and maturation, which is lacking for some of these pelagic stocks, especially in the west of Scotland.

Recruitment variation disrupts the stability of alternative life histories in an exploited salmon population.

Males of many fish species exhibit alternative reproductive tactics, which can influence the maturation schedules, fishery productivity, and resilience to harvest of exploited populations. While alternative mating phenotypes can persist in stable equilibria through frequency‐dependent selection, shifts in tactic frequencies have been observed and can have substantial consequences for fisheries. Here, we examine the dynamics of precocious sneaker males called “jacks” in a population of sockeye salmon (Oncorhynchus nerka) from Frazer Lake, Alaska. Jacks, which are of little commercial value due to their small body sizes, have recently been observed at unusually high levels in this stock, degrading the value of regional fisheries. To inform future strategies for managing the prevalence of jacks, we used long‐term monitoring data to identify what regulates the frequencies of alternative male phenotypes in the population over time. Expression of the jack life history could not be explained by environmental factors expected to influence juvenile body condition and maturation probability. Instead, we found a strong positive association between the proportion of individuals maturing as jacks within a cohort and the prevalence of jacks among the males that sired that cohort. Moreover, due to differences in age‐at‐maturity between male phenotypes, and large interannual variability in recruitment strength, jacks from strong year‐classes often spawn among older males from the weaker recruitments of earlier cohorts. Through such “cohort mismatches,” which are amplified by size‐selective harvest on older males, jacks frequently achieve substantial representation in the breeding population, and likely high total fertilizations. The repeated occurrence of these cohort mismatches appears to disrupt the stabilizing influence of frequency‐dependent selection, allowing the prevalence of jacks to exceed what might be expected under equilibrium conditions. These results emphasize that the dynamics of alternative life histories can profoundly influence fishery performance and should be explicitly considered in the management of exploited populations.