Stock Structure Research Articles

Population genetic structure of intensively exploited pikeperch (Sander lucioperca) in Lake Balaton (Hungary)

Pikeperch (Sander lucioperca Linnaeus, 1758) is a wide-ranged percid predator fish characterised by a great ecological value in the Eurasian freshwater and brackish ecosystems. It is also one of the most famous fish species of Lake Balaton (Hungary), where a unique (genetically separated) pikeperch stock lives. However, until now, no detailed information was available about the pikeperch population genetic structure in Lake Balaton. In the present study, the population genetic structure of the pikeperch assemblages in the lake was revealed by using microsatellite markers. Commercial fishery and angler catch data going back more than 100 years verified that the pikeperch has always been a key element of Lake Balaton’s fish stock utilization. Results of genetic data analyses showed that the pikeperch in the Lake Balaton forms a metapopulation system, in which only the westward stocks show certain separation. Moreover, it seems that the exploitation and mass fish kills that happened in the 1960s and 1970s may have had only a slight impact on the population genetic structure of Balaton pikeperch stocks. The information about genetic features and utilization changes of pikeperch stocks can help to develop area-specific management plans and ensure the long-term survival of this carnivore fish species characteristic of Lake Balaton.

Otolith shape analysis as a tool for stock identification of two commercially important marine fishes: Helicolenus dactylopterus and Merlucciusmerluccius

Stock identification studies are essential to understanding fish population structure and connectivity across wide geographical areas, and thus contribute to efficient fisheries management. The blackbelly rosefish, Helicolenus dactylopterus, and European hake, Merlucciusmerluccius, are two economically important marine fishes, but there are still gaps in knowledge regarding their present stock structure. Our objective was to assess the ability of otolith shape to define stock structure for the two species along the Northeastern Atlantic Ocean and the Mediterranean Sea, based on samples from eight and seven areas, for blackbelly rosefish and European hake, respectively. Shape analysis was obtained through Wavelet analysis. Canonical analysis of principal coordinates provided significant evidence for different population units with a clear separation between the Atlantic and Mediterranean populations for both species. However, random forest procedures indicated that the discrimination power varied with species and locations. For blackbelly rosefish, various Atlantic populations were more evident than for European hake. Overall, the usefulness of otolith shape to delineate stock structure of two species with distinct life history traits across a broad spatial region from the mid-Atlantic isles to the polar region, as well as the Mediterranean was demonstrated. Moving forward, it will be key to align our growing understanding of population structure with our increasing knowledge on species’ biological traits to ensure management units reflect population structure.

From rookeries to foraging grounds: understanding regional connectivity and genetic diversity in hawksbill turtles

This study investigated the genetic structure, diversity, and migratory patterns of hawksbill turtles (Eretmochelys imbricata) from two nesting locations in Papua New Guinea (PNG) using mitochondrial DNA (mtDNA) sequencing and satellite telemetry. Tissue samples collected from nesting female hawksbill turtles (n=75) in PNG revealed a total of 6 haplotypes from the Conflict Group site and 5 haplotypes from Kavieng site, with the Conflict Group and Kavieng samples significantly differing from one another and all other known Asia-Pacific stocks. This finding expands our understanding of the genetic stock structure of hawksbill turtles in the Asia-Pacific region, resulting in 9 Management Units (MUs) now published. Satellite tracking of 15 hawksbill turtles revealed that all individuals migrated from the Conflict Group westerly towards foraging areas in eastern Australia (93%) and PNG (7%). With a mean migration path distance of 1241 ± 108 km, three distinct migration strategies were used by the 10 hawksbill turtles that made it to their foraging grounds in the I) eastern Torres Strait, II) Far North Queensland, and III) western PNG waters. A broad scope of home-range strategies and sizes (95% UD) were used, and in comparison to other studies further postulates that hawksbills are connected to non-specific foraging grounds associated with food source availability. This study provides for the first time in PNG essential insights into hawksbill turtle population structure and connectivity in the western Pacific region, highlighting the importance of effectively conserving and managing this critically endangered species as distinct population stocks. Furthermore, we make recommendations for national and regional conservation strategies and transboundary management to ensure the long-term survival and recovery of western Pacific’s hawksbill turtle populations.

Areas of Assessment and Regional Differences in the Volume and Qualitative Structure of the Housing Market in Russia

Residential real estate is one of the most important types of assets, the lack of which becomes impossible the existence and development of the economy. For an entire sector of households, dwellings are not only a source of livelihood, but also determine the cost of living. Moreover, in the 2008 SNA Manual the production of housing services by homeowners for their own consumption is included in the production boundary (as in earlier versions of the UN SNA). This once again emphasizes the importance of studying the housing stock as the most important basis for the real estate market. In addition, the volume, dynamics and structure of the housing stock in various areas of classification is an important factor in the formation of the real estate market, its object-by-object basis, as well as the development of the activities of the subjects of this market. The above considerations determined the relevance of studying the composition and structure of the housing stock of the Russian Federation, including regional differences in the housing stock in the context of a complex of classification features.

Optimization of welding parameters for improving welded joints used in rolling stock structures using experimental and Taguchi technique

Optimization of welding parameters for improving welded joints used in rolling stock structures using experimental and Taguchi technique

Fine-scale population structure of the northern hard clam (Mercenaria mercenaria) revealed by genome-wide SNP markers.

Aquaculture is growing rapidly worldwide, and sustainability is dependent on an understanding of current genetic variation and levels of connectivity among populations. Genetic data are essential to mitigate the genetic and ecological impacts of aquaculture on wild populations and guard against unintended human-induced loss of intraspecific diversity in aquacultured lines. Impacts of disregarding genetics can include loss of diversity within and between populations and disruption of local adaptation patterns, which can lead to a decrease in fitness. The northern hard clam, Mercenaria mercenaria (Linnaeus, 1758), is an economically valuable aquaculture species along the North American Atlantic and Gulf coasts. Hard clams have a pelagic larval phase that allows for dispersal, but the level of genetic connectivity among geographic areas is not well understood. To better inform the establishment of site-appropriate aquaculture brood stocks, this study used DArTseq™ genotyping by sequencing to characterize the genetic stock structure of wild clams sampled along the east coast of North America and document genetic diversity within populations. Samples were collected from 15 locations from Prince Edward Island, Canada, to South Carolina, USA. Stringent data filtering resulted in 4960 single nucleotide polymorphisms from 448 individuals. Five genetic breaks separating six genetically distinct populations were identified: Canada, Maine, Massachusetts, Mid-Atlantic, Chesapeake Bay, and the Carolinas (F ST 0.003-0.046; p < 0.0001). This is the first study to assess population genetic structure of this economically important hard clam along a large portion of its native range with high-resolution genomic markers, enabling identification of previously unrecognized population structure. Results of this study not only broaden insight into the factors shaping the current distribution of M. mercenaria but also reveal the genetic population dynamics of a species with a long pelagic larval dispersal period along the North American Atlantic and Gulf coasts.

Population structure of Pacific green turtles: a new perspective from microsatellite DNA variation

This study builds upon the current understanding of green turtle population genetic structure in the Pacific that has largely been based on mitochondrial DNA (mtDNA), by examining nuclear DNA (nDNA) diversity, regional connectivity, and male-mediated gene flow. A total of 1,111 nesting green turtle samples were analyzed with 10 microsatellite markers from 20 Pacific rookeries. Population differentiation (FST) was significant (p &amp;lt;0.05) in all but 8 of 190 pairwise rookery comparisons. PairwiseFSTvalues and discriminant analysis of principal components (DAPC) revealed a defined East-West split consistent with mtDNA studies. Additionally, isolation-by-distance was evaluated with estimated effective migration surfaces (EEMS). The data indicated structure throughout the Pacific rookeries largely in agreement with stock structure defined by mtDNA studies, except for some areas on the Central American and Australian continental shelves, providing evidence of possible male-mediated gene flow. The series of analyses performed did indicate that male-mediated gene flow has likely occurred where breeding migration corridors of separate populations overlap with courtship areas. This may occur primarily along the margins of continents, including along Mexico and Central America in the East Pacific. Our study provides an ocean-wide baseline nDNA dataset for green turtle rookeries in the Pacific and reexamines the current thinking regarding the role of male turtles in the population dynamics of management units (MU) and to what extent nuclear gene flow occurs among designated MUs.

Relationship between fish body and sagittal otolith morphometrics in the pool barb Puntius sophore (Hamilton, 1822) from the Ganga and Punpun rivers of Bihar, India

The present study estimated the morphometric relationships between body and sagittal otolith of the economically and nutritionally important pool barb Puntius sophore (Hamilton, 1822). A total of 266 fish specimens were collected monthly from the Ganga and Punpun rivers of Bihar, India from September 2021 to March 2022 Length-weight relationships (LWRs), length frequency distribution, condition factor and otolith aspect ratio were assessed. The fish length and weight ranged from 5.57 cm to 11.17 cm and 1.18 g to 18.98 g, respectively. The b value in LWRs (b&gt;3) were estimated as 3.20 and 3.17 for Ganga and Punpun, respectively. Condition factors indicated optimal growth conditions for this species in both the rivers. The fish and otolith morphometrics showed a positive correlation, and the highest coefficient of determination (R2) was observed between total fish length and otolith weight (R2= 0.942) followed by fish length and otolith length (R2=0.90). All of these relationships are significant to fisheries management and useful for future time series studies on food-feeding habits, stock structure, environmental change and resource conservation. Keywords : Coefficient of determination, Condition factor, Fish otolith, Growth, Length-weight relationship

An Analysis of Capital Structure, Stock Ownership Structure, and Profitability as Intervening Variables in Firm Value Testing

Value is one metric that identifies a company's sustainability. Financing assets or paying off a company's debt are two alternatives to the capital structure and stock ownership structure. Businesses can also use profitability indicators to decide whether a capital structure is necessary and how much stock should be owned. The purpose the The link between capital structure and return, as well as the profitability of capital structure for each of these attributes on equity, were examined and empirically established in this study. business value. Manufacturing firms registered on the Indonesia Stock Exchange between 2014 and 2016 made up the sample population for this study. Additionally, the sample used for the 2014–2016 period included 10 manufacturing firms in the food and beverage subsector. Descriptive analysis and partial least squares (PLS) data analysis were the methods employed in this investigation. Indicators were also included as sub-variables affected by latent variables in a reflective model. The measurement model testing also made use of the outer and inner models. The study's findings showed that the latent variable of profitability is significantly influenced by the ownership structure of stocks and the capital structure. Furthermore, there is a connection between the latent variables of corporate value and profitability. the latent variables of business value or capital structure, however, are unaffected by the stock ownership structure

Stock structure analysis of the white-spotted spine foot fish (Siganus canaliculatus) along the Indian coast using Truss morphometry

The white-spotted spine foot, Siganus canaliculatus is a reef-associated pelagic fish widely distributed and consumed all along the Indian waters. The purpose of this study was to examine the stock structure of Siganus canaliculatus using truss morphometric data. A total of 434 specimens were collected from four different fish landing centers along the Indian subcontinent, namely Mangalore, Vizhinjam, Mandapam, and Vishakhapatnam. Morphological data including 28 truss distances were measured for each specimen and these data were subjected to analysis using several multivariate methods such as Principal component analysis (PCA), Discriminant function analysis (DF), and Hierarchical cluster analysis (HCA). The PCA results demonstrated that the first two components (PC1 and PC2) accounted for over 52.6% of the total morphometric variance (PC1%-37% and PC2%-14%). PC1 and PC2 represented the posterior abdomen and the caudal peduncle region of the fish, and both components exhibited a positive correlation. The DF analysis identified 15 out of 28 variables as effective discriminators among the different locations. Additionally, the cluster analysis revealed the existence of two distinct stocks within the four samples groups. Specifically, the Vishakapatnam samples formed group I, forming a separate cluster while the remaining three samples were grouped together as group II indicating a common cluster. The result of DF and HCA confirmed the presence of different stocks of Siganus canaliculatus across the Indian coast.

Using multivariate autoregressive state‐space models to examine stock structure of Greenland halibut in the North Atlantic

AbstractAccurate information on population structure is essential for effective fisheries management. Greenland halibut (Reinhardtius hippoglossoides) in the North Atlantic is managed as four separate offshore stocks. We use Multivariate Autoregressive State‐Space (MARSS) models to assess population structure by means of abundance and biomass trends in four regions (Norwegian Sea, Iceland, Southeast Greenland, and Northwest Atlantic) where three offshore stocks are recognized: (1) Baffin Bay–Davis Strait (Northwest Atlantic stock), (2) Southeast Greenland and Iceland (West Nordic stock (WNS)), and (3) the Barents and Norwegian Seas (Northeast Arctic stock). We formulated model alternatives, using bottom trawl survey data from each region for 1996–2019, to evaluate support for different population structures. Abundance and biomass observations from each region were linked to growth rate parameters in MARSS models and the impact of climate (North Atlantic Oscillation Index) and fishing (commercial catches) on stock dynamics was investigated. Top models identified the Northwest Atlantic as an independent population. Best‐fit models treated Greenland halibut in the WNS as two independent populations (east and west), with potential connections between eastern Iceland and the western Barents Sea. These results suggest a mismatch between current stock perception and management boundaries in the Northeast Atlantic.

Looking for Parasites as Potential Biological Tags for Pacific Thread Herring, Opisthonema libertate (Günther, 1867) (Clupeiformes, Dorosomatidae), in the Gulf of California

The Pacific thread herring, Opisthonema libertate, is a fishery resource in the eastern tropical Pacific, yet its population dynamics are poorly understood. The aims of this work were to document the metazoan parasite species in O. libertate from the Gulf of California in Mexico, determine latitudinal changes in their infection levels, and assess their potential as biological tags. Six parasitic species were identified: Myosaccium ecaude and Parahemiurus merus digeneans, Cribromazocraes cf. travassosi and Mazocraeoides georgei monogeneans, Pseudoterranova sp. nematodes, and Lepeophtheirus sp. copepods. The monogenean and copepod species are reported for the first time in O. libertate. Many fish were infected with digeneans, and there was a rare occurrence of other parasites. While the prevalence and median intensity of M. ecaude and P. merus significantly varied among sampling localities, a multivariate analysis revealed a distinct separation between some localities; these results suggest that individual fish form several discrete populations. However, the utility of these parasites as biological tags will be further probed because they cannot satisfy all requirements for good biological tags. The present results might be helpful in complementing other techniques to determine the movement and stock structure of O. libertate, albeit with certain limitations.

Improved size selection and estimated at-vessel mortalities for an Australian whiting (Sillago spp.) boat seine

In response towards more species in New South Wales (NSW), Australia being managed via quotas, efforts have recently focused on developing more efficient fishing methods with concomitantly low unaccounted fishing mortality and/or other environmental impacts. The present study contributes information towards this initiative by investigating the relative selectivity of a boat seine with a traditional vs modified codend when targeting eastern school whiting, Sillago flindersi and stout whiting, S. robusta—species historically caught in NSW using otter trawls. The traditional boat seine represented those used in other Australian jurisdictions, tapering from an 85-mm stretched mesh opening in the body to a codend comprising 38.5-mm diamond-shaped mesh ('T0') throughout, and was alternately fished with a modified codend made entirely from 40.9-mm mesh to match the grith of mature individuals of both whiting species and orientated 90° ('T90') with shortened lastridge ropes. Regardless of codend, the boat seine was very efficient at quickly harvesting large quantities of whiting (i.e. often >3 tonnes 60 min deployment–1), with a total discarded-to-retained catch weight ratio (0.44:1) much less than for conventional otter trawls used across similar areas (e.g. >2:1). At-vessel mortalities were high (>95%) for both whiting species, but all were retained. Mortalities were lower for two key discards, bluespotted, Platycephalus caeruleopunctatus (61%) and longspine flathead, P. grandispinis (82%) and both were negatively affected by the total catch weight. The mortality of bluespotted flathead was also negatively correlated to their total length. The T90 codend allowed many immature eastern school whiting to escape, however there were issues with fish being entangled in meshes. We conclude boat seining could represent an effective and relatively selective method for harvesting whiting in NSW, but future work is required to progress an appropriate codend configuration (possibly with fewer T90 meshes) and also address any impacts of rapid, regional depletions on the overall stock structures of both whiting species.

Simulation of the Progress of the Decarbonization Process in Poland’s Road Transport Sector

In the years ahead, the majority of the EU member states will be implementing their energy and climate plans. These plans are aimed at fulfilling obligations related to the strategy for the Sustainable and Smart Mobility Strategy and the “Fit for 55” package. The European Commission has presented highly challenging proposals for the decarbonization of the transport sector through electrification and support for innovation. The decarbonization of transport will not be possible without cooperation and mutual understanding between manufacturers, suppliers, and customers, or without proper organization of the transport process itself. High-emission means of transport must be replaced with low-emission ones. In the EU, road transport generates 70% of all transport emissions. There are few scalable decarbonization opportunities in the transport sector. Various kinds of solutions should be promoted, yet at the same time, it is imperative to analyze the current situation and forecast desirable potential future outcomes. By employing optimization theory tools, specifically the SOLVER add-in—an Excel-based optimization tool—the optimum structure of the stock of road transport vehicles in Poland’s commercial road transport sector was searched for. Several research hypotheses were formulated, primarily focusing on the potential for electric vehicles to reduce emissions significantly. These findings suggest a promising outlook for this transition, with particular implications for decision-makers in the field of shaping transport policy. As a result of the conducted analyses and simulations, the hypothesis—that the application of selected elements of optimization theory tools allows us to determine the optimum stock structure of the Polish road transport sector in terms of propulsion system type (emission performance) in the context of pollutant emission targets set for the sector resulting from the EU’s climate policy targets, the European Green Deal, and the EU’s transport policy in terms of decarbonization, taking into account determinants and constraints included in the analysis—was confirmed. An important finding and result is the statement that, in its current state, the Polish road transport sector is not ready for the challenges related to the new goals of climate policy, the European Green Deal, and EU transport policy in the context of decarbonization.

Seasonal migration, site fidelity, and population structure of European seabass (Dicentrarchus labrax)

Abstract Large-scale electronic tagging is a very powerful tool to study how fish movements and migrations shape the internal dynamics of populations. This knowledge, crucial for improving fishery management, was still limited for the European seabass, whose stocks in the Northeast Atlantic have declined drastically over the last decade. To better understand the species ecology and the spatio-temporal structure of the population, we tagged seabass in the North Sea, the English Channel, and the Bay of Biscay, from 2014 to 2016. Out of 1220 deployed DSTs, 482 have been recovered by November 2022. Approximately half of them included a period of potential spawning migration. Reconstructed trajectories confirmed seabass to be a partial migratory species, as individuals exhibited either long-distance migrations or residence. Most migrants exhibited fidelity to summer feeding areas and winter spawning areas. Our dataset enriches the knowledge of seabass biological traits (e.g. temperature and depth ranges, vulnerability to predation and fishing). Our results suggest a spatial structure of the Atlantic population that differs from the stock structure currently considered for assessment and management. The consequences should be explored at both the European level and by regional managers involved in conservation outcomes.

Mitochondrial DNA revealed a single stock structure of the Spotted sardinella Amblygaster sirm (Walbaum, 1792) (Teleostei; Clupeidae) in Tanzanian coastal waters

Mitochondrial DNA revealed a single stock structure of the Spotted sardinella Amblygaster sirm (Walbaum, 1792) (Teleostei; Clupeidae) in Tanzanian coastal waters

Seasonal patterns in the structure of the fish larvae assemblages in the lower Amazon River

Abstract This study assessed the phenology and functional structure of parental stocks of fish larvae, and evaluated how the species modulate their reproductive activities as a function of natural hydrological regimes in the lower Amazon River, Brazil. Larvae were collected using conical plankton nets monthly over two hydrological cycles between January and December 2013, and between May 2017 and April 2018. The collections were conducted around an alluvial island located near the municipality of Santarém, Pará, Brazil. After identification, individuals were classified into four functional groups (e.g., life‐history strategy, feeding habits, type of migration, and swimming‐performance/microhabitat‐use in the water column) based on species traits. The relationships between seasonal hydrology, environmental variables and larval assemblage structure were evaluated using multivariate analyses. A total of 31,347 fish larvae were collected, from nine taxonomic orders, 26 families, 40 genera and 53 species. The larval assemblages showed highly variable taxonomic and functional composition between different phases of the hydrological cycle (rising water, high water, receding water and low water) and were strongly influenced by environmental variables. Fish reproductive phenology in the lower Amazon is complex and distributed among the hydrological phases. The different ecological characteristics allow the species to withstand specific environmental conditions during each phase. Changes in the structure of larval assemblages indicate that hydrological variability is a key ecological factor influencing the reproductive dynamics of fish and reflects adaptive strategies used to reduce interspecific competition for space and food, maximising recruitment. The variation of fish reproduction across the hydrological cycle that we observed is a result of different ecological characteristics enabling species and functional groups to adapt to environmental conditions of each phase.

Analysing 25 years of bottlenose dolphin (Tursiops truncatus) strandings along the Atlantic coast of the USA: do historic records support the coastal migratory stock hypothesis?

Between June 1987 and March 1988, bottlenose dolphins (Tursiops truncatus Montagu 1821) along the US Atlantic coast experienced an epizootic. Monthly interquartile ranges of strandings during the epizootic were used to propose the Coastal Migratory Stock (CMS) of bottlenose dolphins (Scott et al., 1988). To date, the hypothesised CMS remains poorly understood. The goal of this study was to use a 25-year database to compare stranding patterns during the epizootic to those before (1972-1986) and after (1989-1997) the event. These comparisons reveal that monthly interquartile ranges during the epizootic are dissimilar to those before and after the event. The frequency distribution of total monthly strandings during the epizootic is also significantly different from those observed outside the event. Seasonal stranding patterns from 1989-1997 suggest more complex movements of dolphins along the US Atlantic coast than those of a single group ranging seasonally from Florida to New Jersey. In winter, for example, when the current model for the CMS predicts dolphin distributions concentrated in central Florida, the highest number of strandings occurred in North Carolina. Thus, these comparative analyses suggest that the pattern observed during the epizootic was anomalous, and not representative of stranding distributions for any other time period of the study. During the 15 years before the epizootic, and the nine years following, there was no clear picture of ‘migration’ of mortality along the coast. This study demonstrates how long-term, systematic collection of strandings data can be useful in testing hypotheses regarding the complex stock structure of coastal bottlenose dolphins. This knowledge will greatly enhance the ability to conserve and manage these animals as they recover from historic (i.e. directed takes and epizootic) and current sources of mortality.

Bayes and Empirical Bayes approaches to addressing stock structure questions using mtDNA data, with an illustrative application to North Pacific minke whales

Bayesian methods using mtDNA data are developed to compare single- and multiple-stock hypotheses. The likelihood of the data is assumed to be multinomial and the multivariate prior for the probability of an individual having a particular haplotype is assumed to be of the Dirichlet-b form. The values for the parameters of this prior are either determined using an Empirical Bayes approach or assumed to be distributed according to a log-normal hyper-prior (the ‘Full Bayes’ approach). The Empirical and Full Bayes methods are examined using simulation. The performance of the Empirical Bayes method is found to be much worse than that of the Full Bayes method. Illustrative comparisons for North Pacific minke whales based on the latter method confirm previous results that sub-areas 6 and 7 contain different stocks. Results of the application of this method to the mtDNA data for the sub-areas to the east of Japan, although generally uninformative, are nevertheless consistent with analyses based on hypothesis testing using allozymes and mtDNA. The results from this method should, however, be used for management purposes with some caution. This is because, although some testing of the Full Bayes method has been completed and suggests that when applied to data for two stocks that differ substantially in haplotype frequency, or when sample sizes are large and there is only one stock, performance is adequate, in common with most other methods for analysing genetics data, its performance has yet to be fully evaluated.

The structure of the brood stock and replacement herds of the beluga Huso huso linnaeus, 1758 formed at the sturgeon farm in the Astrakhan Region

The structure of the brood stock and replacement herds of the beluga Huso huso linnaeus, 1758 formed at the sturgeon farm in the Astrakhan Region