Individual Growth Rates Research Articles

Disentangling the Factors That Contribute to the Growth of Betula spp. and Cunninghami lanceolata in China Based on Machine Learning Algorithms

Forests are indispensable materials and spiritual foundations for promoting ecosystem circulation and human survival. Exploring the environmental impact mechanism on individual-tree growth is of great significance. In this study, the effects of biogeoclimate, competition, and topography on the growth of Betula spp. and Cunninghamia lanceolata (Lamb.) Hook., two tree species with high importance value in China, were explored by gradient boosting regression tree (GBRT), k-nearest neighbor (KNN), and random forest (RF) machine learning (ML) algorithms. The results showed that the accuracy of RF was better than KNN, which was better than GBRT. All ML algorithms performed well for future diameter at breast height (DBH) predictions; the Willmott’s indexes of agreement (WIA) of each ML algorithm in predicting the future DBH were all higher than 0.97, and the R2 was higher than 0.98 and 0.90, respectively. The individual tree annual growth rate is mainly affected by the single-tree size, and the external environment can promote or inhibit tree growth. Climate and stand structure variables were relatively more important for tree growth than the topographic factors. Lower temperature and precipitation, higher stand density, and canopy closure were more unfavorable for their growth. In afforestation, the following factors should be considered in order: geographic location, meteorological climate, stand structure, and topography.

A registry of achondroplasia: a 6-year experience from the Czechia and Slovak Republic

BackgroundAchondroplasia (ACH) is one of the most prevalent genetic forms of short-limbed skeletal dysplasia, caused by gain-of-function mutations in the receptor tyrosine kinase FGFR3. In August 2021, the C-type natriuretic peptide (CNP) analog vosoritide was approved for the treatment of ACH. A total of six other inhibitors of FGFR3 signaling are currently undergoing clinical evaluation for ACH. This progress creates an opportunity for children with ACH, who may gain early access to the treatment by entering clinical trials before the closure of their epiphyseal growth plates and cessation of growth. Pathophysiology associated with the ACH, however, demands a long observational period before admission to the interventional trial. Public patient registries can facilitate the process by identification of patients suitable for treatment and collecting the data necessary for the trial entry.ResultsIn 2015, we established the prospective ACH registry in the Czechia and the Slovak Republic (http://www.achondroplasia-registry.cz). Patient data is collected through pediatric practitioners and other relevant specialists. After informed consent is given, the data is entered to the online TrialDB system and stored in the Oracle 9i database. The initial cohort included 51 ACH children (average age 8.5 years, range 3 months to 14 years). The frequency of selected neurological, orthopedic, or ORL diagnoses is also recorded. In 2015–2021, a total of 89 measurements of heights, weights, and other parameters were collected. The individual average growth rate was calculated and showed values without exception in the lower decile for the appropriate age. Evidence of paternal age effect was found, with 58.7% of ACH fathers older than the general average paternal age and 43.5% of fathers older by two or more years. One ACH patient had orthopedic limb extension and one patient received growth hormone therapy. Low blood pressure or renal impairment were not found in any patient.ConclusionThe registry collected the clinical information of 51 pediatric ACH patients during its 6 years of existence, corresponding to ~ 60% of ACH patients living in the Czechia and Slovak Republic. The registry continues to collect ACH patient data with annual frequency to monitor the growth and other parameters in preparation for future therapy.

Models Relating Individual Tree Basal Area Growth Rates to Tree Basal Areas in Even-Aged, Monoculture Forest Stands

As trees grow larger in even-aged, monoculture forests, stand density increases, taller trees shade smaller trees and a group of smaller, suppressed trees develops that may show little or no growth. Subsequent mortality is most common from this group. This work compares three models that may describe well the relationship between individual tree basal area growth rates and tree basal areas in a forest stand when a suppressed group of trees is present or not. The models are tested using a large collection of data from permanent sample plots in blackbutt (Eucalyptus pilularis Smith) forests in subtropical eastern Australia. An example is given for one stand showing how model parameter values may change as the stand ages; this illustrates how these models have potential for use in the first stage of model development to relate individual tree growth rates to tree sizes and stand characteristics. Such models may then be used widely across the forest population under consideration.

Inter-individual variation in mitochondrial phosphorylation efficiency predicts growth rates in ectotherms at high temperatures.

There is increasing evidence that aquatic ectotherms are especially vulnerable to global warming since their metabolic demands increase with ambient temperature while water-oxygen content decreases. The possible role of shrinking aerobic scope in limiting performance has been much discussed; however, less attention has been given to whether tissue-level changes in the efficiency of oxygen usage occur at elevated temperatures. Here, we show that this varies widely among individuals, with consequences for performance. We examined the inter-individual variation in growth rate and mitochondrial function from white muscle and liver of brown trout (Salmo trutta) acclimated to either high (19.5°C) or near-optimal temperature (12°C). Liver (but not muscle) mitochondria showed a positive relationship between growth rate and maximal oxidative phosphorylation at both temperatures, and a negative relationship between growth rate and ROS release. There was a positive correlation in both tissues between individual mitochondrial phosphorylation efficiency and growth rate, but only at 19.5°C. In this representative of aquatic ectotherms, an individual's liver mitochondrial efficiency thus seems to dictate its capacity to grow at elevated temperatures. This suggests that individual heterogeneity in cellular function may cause variation in the thermal limits of aquatic ectotherms and could adversely affect wild populations in warming environments.

Correlation of Total Lipid Content of Chlorella vulgaris With the Dynamics of Individual Fatty Acid Growth Rates

Microalgae are considered as a promising feedstock for the production of valuable fatty acids. In this study, individual fatty acid profiles during the growth period of Chlorella vulgaris were investigated. The results showed that the quantity and the type of fatty acids changed with varying rates during the growth of microalgal cells. Interchanging the fatty acid profiles may provide some metabolic information as a complementary method to radiolabeling studies. For C. vulgaris, two unsaturated fatty acids, oleic and linoleic acids, were the major components. Constant concentration of palmitic and oleic acids shows that they may serve as precursors for longer-chain fatty acids. Higher concentration of palmitic rather than palmitoleic acid (about 16 to 34 times depending on the cultivation day) shows that palmitic acid production rate is higher than its conversion rate to longer-chain fatty acids. In fact, palmitoleic acid might have been partly converted to oleic and linoleic acids. The fatty acid content variations during the growth period are not linear and can be fitted to a Sigmoidal model with R2 value higher than 0.98 and low RMSD values (except for oleic and palmitic acid).

What is the best fitness measure in wild populations? A case study on the power of short-term fitness proxies to predict reproductive value.

Fitness is at the core of evolutionary theory, but it is difficult to measure accurately. One way to measure long-term fitness is by calculating the individual’s reproductive value, which represents the expected number of allele copies an individual passes on to distant future generations. However, this metric of fitness is scarcely used because the estimation of individual’s reproductive value requires long-term pedigree data, which is rarely available in wild populations where following individuals from birth to death is often impossible. Wild study systems therefore use short-term fitness metrics as proxies, such as the number of offspring produced. This study compared two frequently used short-term metrics for fitness obtained at different offspring life stages (eggs, hatchlings, fledglings and recruits), and compared their ability to predict reproductive values derived from the genetic pedigree of a wild passerine bird population. We used twenty years of precise field observations and a near-complete genetic pedigree to calculate reproductive success, individual growth rate and de-lifed fitness as lifetime fitness measures, and as annual de-lifed fitness. We compared the power of these metrics to predict reproductive values and lineage survival to the end of the study period. The three short-term fitness proxies predict the reproductive values and lineage survival only when measured at the recruit stage. There were no significant differences between the different fitness proxies at the same offspring stages in predicting the reproductive values and lineage survival. Annual fitness at one year old predicted reproductive values equally well as lifetime de-lifed fitness. However, none of the short-term fitness proxies were strongly associated with the reproductive values. The commonly used short-term fitness proxies best predict long-term fitness when measured at recruitment stage. Thus, because lifetime fitness measured at recruit stage and annual fitness in the first year of life were the best proxies of long-term fitness in short-lived birds, we encourage their future use.

A test of frequency-dependent selection in the evolution of a generalist phenotype.

A solitary population of consumers frequently evolves to the middle of a resource gradient and an intermediate mean phenotype compared to a sympatric pair of competing species that diverge to either side via character displacement. The forces governing the distribution of phenotypes in these allopatric populations, however, are little investigated. Theory predicts that the intermediate mean phenotype of the generalist should be maintained by negative frequency‐dependent selection, whereby alternate extreme phenotypes are favored because they experience reduced competition for resources when rare. However, the theory makes assumptions that are not always met, and alternative explanations for an intermediate phenotype are possible. We provide a test of this prediction in a mesocosm experiment using threespine stickleback that are ecologically and phenotypically intermediate between the more specialized stickleback species that occur in pairs. We manipulated the frequency distribution of phenotypes in two treatments and then measured effects on a focal intermediate population. We found a slight frequency‐dependent effect on survival in the predicted direction but not on individual growth rates. This result suggests that frequency‐dependent selection might be a relatively weak force across the range of phenotypes within an intermediate population and we suggest several general reasons why this might be so. We propose that allopatric populations might often be maintained at an intermediate phenotype instead by stabilizing or fluctuating directional selection.

Evaluation of the skill of length-based indicators to identify stock status and trends

Abstract In data-poor situations, length-based indicators (LBIs) and reference points based on life history parameters have been proposed to classify stocks according to conservation status and yield optimization. Given the variety of potential LBIs, life history traits, and fisheries, it is necessary to evaluate the robustness of length-based advice to ensure that despite uncertainty that management objectives will still be met. Therefore, a simulation procedure was employed where an Operating Model conditioned on life history parameters was used to generate pseudo data. Receiver operator characteristics and the true skill score were then used to screen LBIs based on their ability to identify overfishing and recovery. It was found that LBIs performed better for long-lived species with low individual growth rates, those aimed at ensuring the conservation of mature fish performed better than those aimed at the conservation of immature fish, are better at indicating trends than at quantifying exploitation level, and in general were robust to uncertainty about dynamic processes.

Biphilic jumping-droplet condensation

Jumping-droplet condensation on rough superhydrophobic surfaces exhibits increased heat-transfer rates when compared with dropwise condensation on smooth hydrophobic surfaces. However, the performance of superhydrophobic surfaces is limited by the low individual droplet growth rates associated with their extreme apparent advancing contact angles. Here, we report that biphilic surfaces having smooth, low-surface-energy spots on a superhydrophobic background exhibit a 10× higher jumping-droplet condensation heat-transfer coefficient when compared with homogeneous superhydrophobic surfaces. Our detailed condensation heat-transfer modeling coupled with numerical simulations of binary and coordinated droplet coalescence show that spot wettability should not be optimized toward minimizing droplet nucleation energy barriers. Rather, spot wettability should be optimized to minimize droplet adhesion while maximizing individual droplet growth rates. Model-predicted design optimization of a variety of biphilic surfaces is validated against experiments. Our findings provide design guidelines for biphilic surface development to maximize condensation heat transfer.

The regulating effect of growth plasticity on the dynamics of structured populations

Plasticity is the extent to which life history processes such as growth and reproduction depend on the environment. Plasticity in individual growth varies widely between taxa. Nonetheless, little is known about the effect of plasticity in individual growth on the ecological dynamics of populations. In this article, we analyse a physiologically structured population model of a consumer population in which the individual growth rate can be varied between entirely plastic to entirely non-plastic. We derive this population level model from a dynamic energy budget model to ensure an accurate energetic coupling between ingestion, somatic maintenance, growth and reproduction within an individual. We show that the consumer population is either limited by adult fecundity or juvenile survival up to maturation, depending on the level of growth plasticity and the non-plastic individual growth rate. Under these two regimes, we also find two different types of population cycles which again arise due to fluctuation in, respectively, juvenile growth rate or adult fecundity. In the end, our model not only provides insight into the effects of growth plasticity on population dynamics, but also provides a link between the dynamics found in age- and size-structured models.

Effect of tax dynamics on linearly growing processes under stochastic resetting: A possible economic model

We study a system of N agents, whose wealth grows linearly, under the effect of stochastic resetting and interacting via a tax-like dynamics —all agents donate a part of their wealth, which is, in turn, redistributed equally among all others. This mimics a socio-economic scenario where people have fixed incomes, suffer individual economic setbacks, and pay taxes to the state. The system always reaches a stationary state, which shows a trivial exponential wealth distribution in the absence of tax dynamics. The introduction of the tax dynamics leads to several interesting features in the stationary wealth distribution. In particular, we analytically find that an increase in taxation for a homogeneous system (where all agents are alike) results in a transition from a society where agents are most likely poor to another where rich agents are more common. We also study inhomogeneous systems, where the growth rates of the agents are chosen from a distribution, and the taxation is proportional to the individual growth rates. We find an optimal taxation, which produces a complete economic equality (average wealth is independent of the individual growth rates), beyond which there is a reverse disparity, where agents with low growth rates are more likely to be rich. We consider three income distributions observed in the real world and show that they exhibit the same qualitative features. Our analytical results are in the N → ∞ limit and backed by numerical simulations.

Evaluation of circulating insulin-like growth factor (IGF)-I and IGF-binding proteins as growth indices in rainbow trout (Oncorhynchus mykiss)

Circulating insulin-like growth factor (IGF)-I has been proposed as a growth index in several teleosts, including salmonids, and its level in circulation is stabilized by multiple IGF-binding proteins (IGFBPs). Three IGFBPs, IGFBP-2b, -1a, and -1b, are consistently detected in salmonid blood and are suggested to be indices of positive or negative growth, although their applicability to rainbow trout (Oncorhynchus mykiss) is unclear. The present study examined the usefulness of IGFBPs along with IGF-I as a physiological indicator of growth rate in rainbow trout through a rearing experiment. Two groups of underyearling rainbow trout were pit-tagged and either fed or fasted for 33 days. A third group was fasted for 22 days, followed by refeeding for 11 days. Serum IGF-I levels were reduced after fasting for 22 days, but refeeding did not retore its levels to those of the fed control. Nevertheless, there was a positive relationship between serum IGF-I levels and individual growth rates over 33 days of experimentation, confirming its validity as a growth index. Ligand blotting using labeled human IGF-I revealed two IGFBP bands at 43 and 32 kDa, which corresponded to IGFBP-2b and an unidentified form, respectively. In contrast, bands corresponding to IGFBP-1a and -1b, which usually increase after fasting, were hardly detected, even in the fasted fish. The responses of circulating IGFBP-2b to fasting and refeeding were similar to those of circulating IGF-I and positively correlated with growth rate and IGF-I levels. The intensity of the serum 32-kDa IGFBP band was higher in constantly fed fish than in the fasted fish; however, its correlation with growth rate was weaker than those of IGF-I and IGFBP-2b. The present study shows that IGF-I and IGFBP-2b can be used as growth indices for rainbow trout. In contrast, circulating IGFBP-1a and -1b may not serve as negative growth indices in rainbow trout under regular aquaculture conditions because they are rarely detected by ligand blotting or respond to fasting/refeeding.

Is infarct core growth linear? Infarct volume estimation by computed tomography perfusion imaging.

Current guidelines for recanalization treatment are based on the time elapsed between symptom onset and treatment and visualization of existing penumbra in computed tomography perfusion (CTP) imaging. The time window for treatment options relies on linear growth of infarction although individual infarct growth rate may vary. We aimed to test how accurately the estimated follow-up infarct volume (eFIV) can be approximated by using a linear growth model based on CTP baseline imaging. If eFIV did not fall within the margins of +/- 19% of the follow-up infarct volume (FIV) measured at 24h from non-enhanced computed tomography images, the results would imply that the infarct growth is not linear. All consecutive endovascularly treated (EVT) patients from 11/2015 to 9/2019 at the Helsinki University Hospital with large vessel occlusion (LVO), CTP imaging, and known time of symptom onset were included. Infarct growth rate was assumed to be linear and calculated by dividing the ischemic core volume (CTPcore ) by the time from symptom onset to baseline imaging. eFIV was calculated by multiplying the infarct growth rate with the time from baseline imaging to recanalization or in case of futile recanalization to follow-up imaging at 24h, limited to the penumbra. Collateral flow was estimated by calculating hypoperfusion intensity ratio (HIR). Of 5234 patients, 48had LVO, EVT, CTP imaging, and known time of symptom onset. In 40/48 patients (87%), infarct growth was not linear. HIR did not differ between patients with linear and nonlinear growth (p>.05). As expected, in over half of the patients with successful recanalization eFIV exceeded FIV. Infarct growth was not linear in most patients and thus time elapsed from symptom onset and CTPcore appear to be insufficient parameters for clinical decision-making in EVT candidates.

Changes in the direction of the diversity–productivity relationship over 15 years of stand development in a planted temperate forest

Abstract Experiments manipulating diversity in both forests and grasslands have often observed a positive diversity–productivity relationship (DPR) which tends to strengthen during plant community development. This pattern is generally attributed to an increase in niche complementarity or facilitation. Most analyses do not examine species dominance and density, which also change over time. Moreover, how neighbourhood‐scale interactions among tree species affect the DPR is not well‐understood. We analysed growth and mortality data from the Simplex experiment, a part of the BIOTREE tree diversity experiment. Simplex consists of 36 plots each planted with four common and commercially important tree species to create a gradient of tree species evenness at two tree densities (6667 and 3556 trees ha−1). We test whether: (a) the effect of evenness on total above‐ground biomass productivity increase with stand development (year), (b) the effect of evenness on productivity is stronger in dense plots; and (c) intraspecific competition from neighbours negatively affect the growth of dominant species more strongly compared to co‐dominant species, and whether this negative effect is stronger in denser plots. The direction of DPR was initially negative because the fast‐growing long‐lived pioneer Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) dominated. However, with time, shade‐tolerant Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) increased in abundance (by biomass), and the relationship between evenness and biomass increment changed from negative to positive in high‐density plots. Neighbourhood analyses revealed that for Douglas fir and Norway spruce, conspecifics reduced individual growth rates across density levels and years. Synthesis. We observed a shift in the diversity–productivity relationship over 15 years in our experiment. Over time, increasing intraspecific competition limited the increment of the abundant Douglas fir in uneven plots, and a persistent increase in the abundance (by biomass) of shade‐tolerant Norway spruce and European beech in even plots led to a higher community biomass increment, which led to a positive DPR. Emergence of a positive DPR in temperate forest plantations requires significant time and is importantly promoted by diversity at the neighbourhood scale (intimate mixtures) as well as higher density planting.

Optimum growth temperature declines with body size within fish species.

According to the temperature-size rule, warming of aquatic ecosystems is generally predicted to increase individual growth rates but reduce asymptotic body sizes of ectotherms. However, we lack a comprehensive understanding of how growth and key processes affecting it, such as consumption and metabolism, depend on both temperature and body mass within species. This limits our ability to inform growth models, link experimental data to observed growth patterns, and advance mechanistic food web models. To examine the combined effects of body size and temperature on individual growth, as well as the link between maximum consumption, metabolism, and body growth, we conducted a systematic review and compiled experimental data on fishes from 52studies that combined body mass and temperature treatments. By fitting hierarchical models accounting for variation between species, we estimated how maximum consumption and metabolic rate scale jointly with temperature and body mass within species. We found that whole-organism maximum consumption increases more slowly with body mass than metabolism, and is unimodal over the full temperature range, which leads to the prediction that optimum growth temperatures decline with body size. Using an independent dataset, we confirmed this negative relationship between optimum growth temperature and body size. Small individuals of a given population may, therefore, exhibit increased growth with initial warming, whereas larger conspecifics could be the first to experience negative impacts of warming on growth. These findings help advance mechanistic models of individual growth and food web dynamics and improve our understanding of how climate warming affects the growth and size structure of aquatic ectotherms.

Evolutionary game of life-cycle types in marine benthic invertebrates: Feeding larvae versus nonfeeding larvae versus direct development

Many marine invertebrates have a benthic adult life with planktonic long feeding larval stages (planktotrophy). In other species, planktonic larvae do not eat, and after a rather short period, they settle and initiate their benthic stages (lecithotrophy). Still other species skip planktonic larval stages altogether, and adults produce benthic offspring (direct development). In this paper, we develop an evolutionary game among different life-cycle types and examine the conditions for each life-cycle type to win in a seasonal environment. The growth rate and mortality of benthic individuals are the same among all three life-cycle types, the local habitat (patches) for benthic individuals have a finite longevity, and adults may engage in a limited dispersal just before breeding. Planktotrophy evolves if the planktonic stages are more efficient in terms of biomass gain than benthic life. Otherwise, lecithotrophy or direct development should evolve. Among them, direct development is more advantageous than lecithotrophy if the cost of having planktonic larvae is large, the habitat for benthic individuals is stable, and adults engage in some dispersal.

On the intraspecific competition of yellowfin sole Limanda aspera (Pallas, [1814]) (Pleuronectidae) in the eastern part of the Sea of Okhotsk

Based on the longterm observations for 1963–2019, the article provides an assessment of the yellowfin sole generation mortality dynamics depending initial abundance and population dynamics in view of abundance and biomass. Individual growth and matiration rates were evaluated in generations with different initial abundance and in different states of population dynamics. Results indicated about intraspecific competition in yellowfin sole in the eastern part of the Sea of Okhotsk, expressed in specifics of the dynamics of stock abundance, growth and maturation. Forming generation stock abundance in early and later ages has different character. The more exceeding number of parental eggs spawned, the more generation abundance of yearlings getting exactly compensated by mortality (complete compensation). Older generations demonstrate the phenomen of “overcompensation”, when mortality of generations appeared in the years of higher egg production exceeds fertility. In the period of population growth and stabilization at a high level the period of the Yellowfin sole abundance fluctuation cycle gets shorter and the amplitude – smaller. Effects of intraspecific competition on the growth of individuals are revealed. Negative effects of the competition authentically revealed in elder age groups were not observed in younger age groups. An increase of the Yellowfin sole abundance brings negative effects on maturation rate of males with almost no such effects on females. To the greatest extent such effects can be seen in young age groups, at the beginning and middle stage of maturation.

The rationale for heterogeneous inclusion of ecosystem trends and variability in ICES fishing opportunities advice

Incorporation of ecosystem information into fish stock assessments and management advice, a cornerstone of delivering ecosystem-based fisheries management (EBFM), occurs often implicitly, faces multiple challenges, and remains often unquantified in terms of scope and scale. This paper provides a comprehensive overview of the inclusion of ecosystem trends and variability in ICES fishing opportunities advice in the Northeast Atlantic, by covering 87% of stocks corresponding to 99% of landings. Just under 50% of all stock assessments considered ecosystem information and the majority of management strategy evaluations did so in at least one way. Almost 73% of the data-rich stocks incorporated ecosystem trends and variability in at least one way, and almost 55% of short-term forecasts did so. Stock (individual growth rate) and fisheries (landings) characteristics largely explained the observed patterns of incorporation of ecosystem information into advice, with pelagic species and stocks with higher landings having higher instances of incorporation. Early stages of the advice process (closer to data analysis and methods development) had greater inclusion of ecosystem information, though this inclusion was generally implicit and not explicit, e.g. based on a hypothesis of environmental influence on stock dynamics. Moving towards explicit instructions and routine documentation of the inclusion of ecosystem information in fishing opportunities advice will accelerate the path to the EBFM in a consistent and transparent manner.

​Study of the Zootechnical Performance of Tilapia cabrae and Oreochromis schwebischi in a Controlled Environment: The Case of the Mbolet Fish Farm in Lambaréné, Gabon

Background: The study of the zootechnical performance of Tilapia cabrae and Oreochromis schwebischi was carried out at the Mbolet fish farm in Lambaréné in Gabon in order to evaluate the growth and reproductive performance of these two species. Methods: For this purpose, 226 fish (113 of T. cabrae with an average weight of 30.55±9.5 g and 113 O. schwebischi with an average weight of 20.64±10.5 g), were distributed in four 6 m2 tanks with two replicates per species for the growing phase which lasted 60 days. For the reproductive phase, 42 selected mature fish, including 6 males and 36 females of each species, were placed in six 2 m2 ponds with three replicates per species for 78 days. Result: The survival rate, the number of reproductions per species and the absolute, relative and system productivities were determined. It was found that the average weight gain, daily individual growth and specific growth rate were significantly (p less than 0.05) higher in T. cabrae, 48.1±5.51 g, 0.8±0.092 g/day and 1.57±0.066% g/day respectively, than in O. schwebischi, 27.11±9.23 g, 0.45±0.15 g/day and 1.38±0.051% g/day respectively. At the end of reproduction, the absolute productivity of T. cabrae (234.75±24.71 larvae/female/egg-laying) was significantly higher (p less than 0.05) than that of O. schwebichi (104.68±46.64 larvae/female/laying). System productivity was significantly higher (p less than 0.05) in O. schwebichi (11.34±2.29 larvae/m2/day) compared to that of T. cabrae (4.12±1.73 larvae/m2/day). Thus, on a fish farm, the use of these species may be possible.

Varying relationships between fish length and scale size under changing environmental conditions – Multidecadal perspective in Atlantic herring

Calcified structures are valuable indicators being used in fisheries research for the estimation of fish ages or back-calculations of fish lengths. Such back-calculations typically assume constant proportional growth of fish and calcified structures independent of internal or environmental factors. We analyzed extensive data (1935–2020) of scale measurements from Norwegian spring-spawning herring. We applied linear quantile regressions to investigate the fish length – scale size relationship and environmental influences on individuals growing at different rates. We demonstrated that the fish length – scale size relationship varied over time and between cohorts, individuals of the same year-class. Parts of this variation can be attributed to changing environmental conditions. We identified a negative effect of stock total biomass and a positive effect of temperature on fish length when conditioned on scale size. The effect of stock total biomass varied considerably but the effect of temperature was similar between fish characterized by different growth rates. Our results are essential for long-term studies highlighting potential biases associated with environmental effects and different growth rates of individuals. These biases should be accounted for in growth history reconstructions and applications of the calcified structures as ecological indicators.