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Simple Summary: In this study, we investigated the habitat use of the Antarctic toothfish (Dissostichus mawsoni) and the connectivity between nursery and feeding areas in the Atlantic sector of the Southern Ocean. We analysed the chemical signatures of otoliths (ear stones) from 45 individuals caught near the South Orkney Islands. These structures provide insights into the fish's life stages, from juvenile to adult. By examining the chemical composition of the otoliths, we identified potential nursery areas where juvenile fish develop. Our findings suggest that Antarctic toothfish migrate to deeper waters at approximately 11 to 13 years of life and that two distinct nursery areas contribute to the population in this region, supporting one of the hypotheses regarding its habitat use. However, further research is needed to fully understand the connections between breeding and nursery sites before excluding other potential explanations for their habitat use. This study is crucial for effective population management and the development of sustainable fishing practices in the Southern Ocean. We used otolith chemistry to test and complement current hypotheses regarding habitat use and connectivity between Dissostichus mawsoni sub-populations in Area 48 of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Sagittal otoliths from 45 fish sampled near the South Orkney Islands were analysed. Their elemental (Li, Na, Mg, Cr, Mn, Sr, Sn, and Ba relative to Ca) and isotopic (δ18O and δ13C) signatures were examined in both the nuclear and marginal regions, representing juvenile and adult stages. Potential nursery habitats were geo-located by comparing observed and expected δ18O values. Chemical differences between the nuclear and marginal regions indicated ontogenetic migrations to deeper offshore habitats, suggesting a distinct habitat shift between 11 and 13 years of life. The data supported the existence of two nursery origins contributing to the study area's population. However, the exact locations of these origins remain unclear and did not provide direct support for the hypotheses currently under consideration by the CCAMLR. Therefore, further assessment of the connectivity between nursery and adult habitats, as well as spawning site fidelity, is necessary before ruling out alternative hypotheses. [ABSTRACT FROM AUTHOR]

Abstract Failure to consider population structure when managing harvested fishes increases the risk of stock depletion, yet empirical estimates of population structure are often lacking for important fishery species. In this study, we characterise genetic variation in single nucleotide polymorphisms (SNPs) to assess population structure for three harvested species of tropical snappers across the broad (up to 300 km wide) and extensive (~ 4000 km) continental shelf of north-western Australia. Comparisons across ~ 300 individuals per species, showed remarkably similar patterns of genetic structure among Lutjanus sebae (red emperor), L. malabaricus (saddletail snapper) and Pristipomoides multidens (goldband snapper) despite subtle differences in biological and ecological traits. Low levels of genetic subdivision were reflected in an isolation by distance relationship where genetic connectivity increased with geographic proximity. This indicates extensive but not unlimited dispersal across the north-western Australian shelf. Our findings provide evidence of connectivity between current management areas, violating the assumption of multiple independent stocks. Spatial stock assessment models may be more suitable for the management of these species however demographic connectivity rates cannot be accurately estimated from the conventional population genetic approaches applied in this study. We recommend that managers aim to maintain adequate spawning biomass across current management areas, and assess stocks at finer scales, where practical.

Failure to consider population structure when managing harvested fishes increases the risk of stock depletion, yet empirical estimates of population structure are often lacking for important fishery species. In this study, we characterise genetic variation in single nucleotide polymorphisms (SNPs) to assess population structure for three harvested species of tropical snappers across the broad (up to 300 km wide) and extensive (~ 4000 km) continental shelf of north-western Australia. Comparisons across ~ 300 individuals per species, showed remarkably similar patterns of genetic structure among Lutjanus sebae (red emperor), L. malabaricus (saddletail snapper) and Pristipomoides multidens (goldband snapper) despite subtle differences in biological and ecological traits. Low levels of genetic subdivision were reflected in an isolation by distance relationship where genetic connectivity increased with geographic proximity. This indicates extensive but not unlimited dispersal across the north-western Australian shelf. Our findings provide evidence of connectivity between current management areas, violating the assumption of multiple independent stocks. Spatial stock assessment models may be more suitable for the management of these species however demographic connectivity rates cannot be accurately estimated from the conventional population genetic approaches applied in this study. We recommend that managers aim to maintain adequate spawning biomass across current management areas, and assess stocks at finer scales, where practical. [ABSTRACT FROM AUTHOR]

Objective: Estimates of Pacific salmon Oncorhynchus spp. stock composition in coastal fishery harvests are needed to balance fishing opportunities against conservation. Catch partitioning in some small‐scale fisheries can be hindered by insufficient resolution of modern stock classification tools (e.g., genetic stock identification). Methods: We used acoustic telemetry to investigate the stock composition of commercial landings in the Norton Sound district of Alaska by mimicking local fisheries to capture and tag 578 Coho Salmon O. kisutch in the contiguous Shaktoolik and Unalakleet commercial subdistricts over two seasons. Result: In total, 341 individuals that were last detected in demarcated spawning areas were assigned to a stock of origin based on putative natal site fidelity. Sex, location of capture, and timing of capture were predictors of stock membership. Models that were fitted to commercial harvest data from the project years (2020 and 2021) estimated that 32.9% of the Shaktoolik subdistrict catch was Shaktoolik stock, 51.5% was Unalakleet stock, and the remainder consisted of other transitory stocks. Conversely, 86.7% of landed Coho Salmon in the Unalakleet subdistrict were Unalakleet stock, whereas the Shaktoolik stock and transitory stocks made up less than 10%, respectively. Conclusion: These findings suggest that coastal salmon fisheries in Norton Sound have access to a variable mixture of stocks whose unique characteristics can be leveraged to examine the effects of directed harvest effort on stock health and diversity. Impact statementAcoustic telemetry identifies unique characteristics of adult Coho Salmon that can be used to differentiate among stocks in coastal mixed fisheries, allowing scrutiny of respective relationships with directed harvest effort. [ABSTRACT FROM AUTHOR]

Sustainable management of transboundary fish stocks hinges on accurate delineation of population structure. Genetic analysis offers a powerful tool to identify potential subpopulations within a seemingly homogenous stock, facilitating the development of effective, coordinated management strategies across international borders. Along the West African coast, the Atlantic chub mackerel (Scomber colias) is a commercially important and ecologically significant species, yet little is known about its genetic population structure and connectivity. Currently, the stock is managed as a single unit in West African waters despite new research suggesting morphological and adaptive differences. Here, eight microsatellite loci were genotyped on 1,169 individuals distributed across 33 sampling sites from Morocco (27.39°N) to Namibia (22.21°S). Bayesian clustering analysis depicts one homogeneous population across the studied area with null overall differentiation (FST = 0.0001ns), which suggests panmixia and aligns with the migratory potential of this species. This finding has significant implications for the effective conservation and management of S. colias within a wide scope of its distribution across West African waters from the South of Morocco to the North-Centre of Namibia and underscores the need for increased regional cooperation in fisheries management and conservation. [ABSTRACT FROM AUTHOR]

Small pelagic fish play an important role in marine trophic webs and human food security. Among those, Sardinella aurita represents an extremely valuable resource in West Africa, where it is assumed to conform a transboundary stock. During the last decade, quantitative stock assessment has not been possible in NW African waters due to the limitation of the indices used; however, a critical biomass decline has been observed, and the stock is considered overexploited. In order to delineate the population structure of the species in West Africa, twelve microsatellites were developed ad hoc and genotyped on some 1300 individuals collected from Morocco to Angola. The significant differentiation detected between the northernmost samples (Morocco to Guinea) and the southernmost ones (Liberia to Angola) was due to one candidate locus to positive selection. The signal of this locus resided uniquely in the frequency of allele SauMS002_131, which displayed a remarkable latitudinal cline. Allele frequency, starting around 47%–63% in Moroccan-Guinean waters and dropping to 0% off Gabon and southwards, accounts for the North–South declining trend and can be used as a meaningful tool to assist population structure outline for this species in West Africa for management purposes in order to ensure sustainable regionally shared fisheries. [ABSTRACT FROM AUTHOR]

Sustainable management of transboundary fish stocks hinges on accurate delineation of population structure. Genetic analysis offers a powerful tool to identify potential subpopulations within a seemingly homogenous stock, facilitating the development of effective, coordinated management strategies across international borders. Along the West African coast, the Atlantic chub mackerel (Scomber colias) is a commercially important and ecologically significant species, yet little is known about its genetic population structure and connectivity. Currently, the stock is managed as a single unit in West African waters despite new research suggesting morphological and adaptive differences. Here, eight microsatellite loci were genotyped on 1,169 individuals distributed across 33 sampling sites from Morocco (27.39°N) to Namibia (22.21°S). Bayesian clustering analysis depicts one homogeneous population across the studied area with null overall differentiation (FST = 0.0001ns), which suggests panmixia and aligns with the migratory potential of this species. This finding has significant implications for the effective conservation and management of S. colias within a wide scope of its distribution across West African waters from the South of Morocco to the North-Centre of Namibia and underscores the need for increased regional cooperation in fisheries management and conservation.

Morphometric variations across fish stocks have long been acknowledged as useful for determining population structure and identifying stocks. Schizothorax progastus (McClelland) is a common, dominant fish in most cold-water rivers and is considered a good sport fish and also delicious in taste. For the people of Ladakh, this fish is a significant source of nutrition. A total of 70 specimens were collected for this study. A total of 24 morphometric and six meristic characters were studied, with 18 morphometric characters assessed as percentages of total length and four characters analyzed as percentages of head length. Standard length and fork length had the strongest correlations with total length at 0.98 and 0.99, respectively. Overall, the findings demonstrated that all morphometric features had linear correlations and exhibited a high degree of association (P < 0.05). The meristic counts examined in this study were consistent among all fish of various sizes, suggesting that body size had no effect on them. The biological information generated from this study serves as an essential guideline for future management and conservation of S. progastus, an important food source in the Ladakh, Trans Himalayan region.

Accounting for marine stocks spatiotemporal complexity has become one of the most pressing improvements that should be added to the new generation of stock assessment. Disentangling persistent and dynamic population subcomponents and understanding their main drivers of variation are still stock-specific challenges. Here, we hypothesized that the spatiotemporal variability of density in two adjacent fish stocks is associated with spatially structured environmental processes across multiple spatiotemporal scales. To test this, we applied a generalized empirical orthogonal function and dynamic factor analysis to fishery-independent and -dependent data of red mullet, a highly commercial species, in the Western Mediterranean Sea. Areas with persistent and dynamic high aggregations were detected for both stock units. A large-scale climatic index and local open-ocean convection were associated with both stocks, while other variables exhibited stock-specific effects. We also revealed spatially structured density dynamics within the examined management units. This suggests a metapopulation structure and supports the future implementation of a spatial stock assessment. Considering the common—generally unrealistic—assumptions of panmictic structure and absence of connectivity with neighbouring stock units, our methodology can be applied to other species and systems with putative spatial complexity to inform more accurate population dynamics and structure. [ABSTRACT FROM AUTHOR]

Otoliths are widely employed in marine sciences to gain insights into fish growth, age, migrations, and population structure. This study investigates the relationships between morphometric measurements, otolith characteristics, and length size patterns in the brown comber (Serranus hepatus) from the Gulf of Cádiz, a species discarded in artisanal trawl fisheries. Our findings reveal significant changes in otolith shape indices as fish grow, with symmetry observed between left and right otolith measurements. Otolith size is found to be related to fish size, supporting its use in estimating body length at different life stages. Otolith shape analysis has potential applications in stock identification, detecting catch misreporting, and studying marine predator diets. Combining otolith shape analysis with other data types can clarify relationships among taxa and inform spatial management strategies, contributing to the long‐term sustainability of fish populations and the assessment of the impact of management strategies on fish size and growth. This study enhances our understanding of the broader implications of morphometric and otolith analyses in fisheries research and supports the development of more sustainable fisheries management practices. [ABSTRACT FROM AUTHOR]

Knowledge of the spatial structuring of stocks is essential to study the dynamics of fish populations, and thus to manage fisheries. In this study, sagittal otolith shape was used to understand the stock structures of populations of the main commercial species caught around La Réunion Island. A total of 1091 individuals, belonging to nine species of bentho-pelagic bony fishes (Aphareus rutilans, Cephalopholis aurantia, Epinephelus fasciatus, Etelis carbunculus, Lutjanus kasmira, Lutjanus notatus, Pristipomoides argyrogrammicus, Pristipomoides filamentosus, Variola albimarginata), were analyzed and compared between 10 areas around La Réunion. To describe the external shape of the otolith, normalized Fourier elliptical descriptors were extracted. For each species, the analysis of shape data was performed in two steps. The first step was investigating the potential effects of confounding factors such as fish size, symmetry between right and left otoliths, sexual dimorphism and spatial distribution. When location showed a significant effect on otolith shape, a second step coupling two complementary analyses was performed with hierarchical clustering (unsupervised machine learning) and linear discriminant analysis with jackknifed prediction (supervised machine learning), allowing characterization of the potential stock limits for each of the treated species. The results show that, for the nine species treated, only two species (Etelis carbunculus and Pristipomoides filamentosus) show spatial structuring around Reunion Island with, for each of them, two stocks potentially separated along a northwest/southeast axis. These results show that some species around La Réunion Island may have local subpopulations. [ABSTRACT FROM AUTHOR]

Simple Summary: Sardinella maderensis, representing one of the most commercially important small pelagic fish species along the coast of West Africa, is suffering a drastic decline as a result of overfishing, the overcapacity of fishing fleets, the destruction of fish habitat, the use of inappropriate fishing gears and techniques, as well as environmental changes. The limited reliable information on their stock for sustainable management constitutes one of the problems facing small pelagic fish in general and Sardinella maderensis particularly along the coast of West Africa. The key goals of this study were to identify the parasites of Sardinella maderensis and to assess their potential use as biological tags for stock identification along the coast of West Africa (Benin and Ghana). The objectives of this study were to determine the morphological parameters (total length and body weight) of S. maderensis, identify their parasites in Benin and Ghana and select appropriate parasites with potential to be used as biological tags. The results suggest that the nematode Anisakis sp(p). and the cestode Tentacularia coryphaenae may serve as potential biological tags for the stock identification of Sardinella maderensis. This study is the first to provide information on the parasite fauna of Sardinella maderensis along the coasts of Benin and Ghana, and the first to investigate the potential use of parasites as biological tags in fish population studies in the area. It may thus serve as a starting point for upcoming studies. From February to June 2021, a total of 200 S. maderensis were sampled from the fishing port of Cotonou (Benin) and the Elmina landing site (Ghana). The prevalence and abundance of each parasite were recorded. The following are the outcomes of this study: Parasite species, such as Parahemiurus merus, Mazocraeoides sp. and Hysterothylacium fortalezae, were recorded along the coasts of Benin and Ghana, while Anisakis sp(p). and Tentacularia coryphaenae were only recorded along the coast of Benin. Parahemiurus merus was the most prevalent and abundant among all the parasites recorded. Anisakis sp(p). and T. coryphaenae were selected as having potential in the stock identification of S. maderensis. Both parasites were only recorded along the coast of Benin at a low prevalence. As a result, examinations of more S. maderensis from each location for these parasites may justify their use in stock identification studies. [ABSTRACT FROM AUTHOR]

A meta-analysis of research on fishstock identification in India was performed to examine the trends and patterns of work conducted in fish-stock identification between 2000 and 2021. The publication data extracted from the Web of Science database with different sets of keywords resulted in a total of 214 research articles dealing with fish-stock identification. The common methods applied for stock identification are mtDNA sequencing, microsatellite markers and truss morphometrics. Published records showed that 14.49% of the research used different stock-identification methods in a single study to arrive at an accurate result on the stock structure of the studied species. Teleosts were the most studied group, followed by crustaceans, bivalves and elasmobranchs, and most of the studies focused on the fishes belonging to the orders Cypriniformes and Siluriformes. Fishes caught from the wild populations accounted for most of the studies, rather than the farmed ones. The study highlighted pitfalls in the stock-identification studies in India, viz. fewer studies on the marine realm and more specifically on elasmobranchs, farm escapees into the wild, threatened species, etc. The study also highlighted the need for strengthening stock-identification studies so that they aid in data-driven fisheries management measures. Intraspecific diverstity of a fishery resource should be treated as a strategic unit for the sustainable management of fishery resources. Stock identification is one of the important fields in fisheries science and it is gaining importance in India. The review gives baseline data on different methods used and the fishes for which stock-identification study has been conducted. Further, we have highlighted a few issues that need to be considered in the future. [ABSTRACT FROM AUTHOR]

Serranus hepatus is a bycatch species in the Mediterranean trawl fishery for which knowledge on biological features such as otolith morphology is generally poor in the Mediterranean Sea. In the present study, the weight–length relationship, age, growth and ten otolith morphometric variables of this species were investigated in two distant areas, the Eastern Ionian and southwestern Aegean Seas. Isometric growth in weight was defined in both areas. Growth parameters also did not differ between the two study areas. Six of the otolith variables (radius, otolith length, otolith width, otolith area, perimeter and ellipticity) showed a significant relationship with size without significant differences between the two areas. Significant differences between the two areas were only defined for five of the morphometric variables (otolith length, width and area being the most important). Further studies to discriminate between potential stocks of S. hepatus seem to be necessary, information that is needed for stock identification, stock assessment and fisheries management. [ABSTRACT FROM AUTHOR]

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Simple Summary: Discrimination of geographic origins in seafood is crucial to safeguard and control food security and quality for consumers. We could successfully discriminate the origins of wild and cultured freshwater eel, Anguilla japonica, which is one of the most valuable fish in East Asia with high market demand, by means of trace elements' fingerprints (TEF) in the otoliths. Spatiotemporal variability of TEF was examined in the eels collected in wild and cultured environments in East Asia. Discriminant function analysis showed less temporal variation but high spatial variation, suggesting that otolith TEF reflect each habitat or aquaculture environment. The otolith TEF can be a reliable tool to discriminate the geographic origin of the fish. To secure traceability along supply chains of foodstuffs, the spatiotemporal variability of trace elements' fingerprints (TEF) in fish otoliths provides a powerful tool to determine and discriminate the origin. Spatiotemporal variability of TEF was examined in a commercially important seafood, Japanese eel (Anguilla japonica), by means of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). Six elemental ratios (Na:Ca, Mg:Ca, P:Ca, K:Ca, Sr:Ca, and Ba:Ca) were determined in the otoliths of specimens originating from four aquaculture farms to examine the spatial variability and from one wild habitat over three years to examine the temporal variation. Significant temporal variation was found in Mg:Ca and Sr:Ca ratios; however, discriminant function analysis showed a lower temporal variation (50%) for the three years. Spatial variations were significant in Sr:Ca and Ba:Ca ratios, and discriminant function analysis showed high (80%) spatial variation among the four farms. Otolith TEF in the Japanese eel showed specific spatial variation among aquaculture farms but intangible temporal variation, suggesting the otolith TEF reflect each aquaculture environment. The present study shows that otolith TEF can be a reliable tool to discriminate the geographic origin of the Japanese eel. [ABSTRACT FROM AUTHOR]

As a first step in stock identification of estuarine round herring Gilchristella aestuaria, a morphometric analysis of multiple standardised traits and body condition was conducted on samples from sites across the distribution range of the species, including freshwater and estuarine populations. Multivariate analyses, including a principal component analysis (PCA), revealed that sites on the same river system and sites in close geographic proximity tend to share morphometric traits. Most of the variation in PCA was due to caudal fin length (CFL). Single traits were analysed with generalised additive models with river system location as the smooth term. CFL was strongly related to river systems, and to a lesser extent salinity and turbidity. Unlike previous local‐scale studies, this broad‐scale study did not support the notion of ecotypes based on eye diameter. Condition indices like body depth and relative weight were related to climatic conditions, salinity and turbidity, more than to river system. The findings agree with previous studies on phylogenetic history and limited gene flow in G. aestuaria, and suggest variation in environmental productivity that affects body condition in different populations. Subsequent research should examine temporal changes in traits like CFL and body condition based on long‐term seasonal sampling. Safeguarding this potential resource may be enabled by adopting appropriate management methods based on delineation of stocks with different levels of productivity and connectivity, before widespread fishing of this species is promoted. [ABSTRACT FROM AUTHOR]

Populations of chondrichthyans are particularly sensitive to elevated fishing mortality due to their low reproductive potential and very low population growth.Dipturus brevicaudatus is a common and endemic skate from waters of Argentina and is frequently caught as by‐catch and is therefore extremely vulnerable to commercial fishing. There are signs of overfishing in both the northern and southern Argentine Sea and the species has been classified as 'Vulnerable' by the International Union for Conservation of Nature.A parasitological examination of 96 skates revealed 1,913 individual macroparasites belonging to 18 species and one myxozoan. Three parasite species were long‐lived and were suitable biological tags, resulting in statistically significant differences between North Patagonic and both Buenos Aires and South Patagonic regions and therefore can be used to identify stocks of D. brevicaudatus. The inclusion of short‐lived parasites in the analyses suggested the existence of three stocks.Parasite assemblages from the northern Argentine Sea (Buenos Aires, Argentine biogeographical province) and from Patagonian waters (North and South Patagonic, Magellanic biogeographical province) varied in terms of parasite infracommunity species richness and the relative abundance of parasite guilds.Using parasites to infer the existence of three stocks of D. brevicaudatus provides the basis to help establishing management and recovery strategies to preserve the diversity of this vulnerable skate in the south‐west Atlantic Ocean.Due to the low host specificity of the long‐lived parasite tags, there is potential to extend this methodology to other skate species that are commercially exploited in the region, whose population structures remain unknown. [ABSTRACT FROM AUTHOR]

The otolith chemistry is one of the most commonly used tools to elucidate the structure of fish stocks. The correct application of this methodology depends on the fulfillment of several assumptions. One of the most relevant assumptions is that the otoliths and water chemistries vary at appropriate spatio-temporal scale in relation to the hypotheses being addressed. Due to the increase in the number of publications where this assumption is not properly considered, it is essential to discuss and order different concepts to contribute to the correct interpretation of the information provided by the otolith chemistry applied to the delimitation of stocks. Herein, the opportunity for dispersal concepts in otolith chemistry-based stock discrimination methods is discussed integrating the space-time scales, and biogeographic foundations. Additionally, a graphic guide was developed to facilitate hypothesis testing and their respective interpretations. This article encourages further use and attention on age and growth data, dispersal ability and life history, but further integration of the issue of biology versus management, as well as how the integration of other approaches may assist, is recommended, as most likely there will be no single approach to resolve stock structure. [ABSTRACT FROM AUTHOR]

Atlantic herring in International Council for Exploration of the Sea (ICES) Divisions 6.a, 7.b–c comprises at least three populations, distinguished by temporal and spatial differences in spawning, which have until recently been managed as two stocks defined by geographical delineators. Outside of spawning the populations form mixed aggregations, which are the subject of acoustic surveys. The inability to distinguish the populations has prevented the development of separate survey indices and separate stock assessments. A panel of 45 single-nucleotide polymorphisms, derived from whole-genome sequencing, were used to genotype 3480 baseline spawning samples (2014–2021). A temporally stable baseline comprising 2316 herring from populations known to inhabit Division 6.a was used to develop a genetic assignment method, with a self-assignment accuracy greater than 90%. The long-term temporal stability of the assignment model was validated by assigning archive (2003–2004) baseline samples (270 individuals) with a high level of accuracy. Assignment of non-baseline samples (1514 individuals) from Divisions 6.a, 7.b–c indicated previously unrecognized levels of mixing of populations outside of the spawning season. The genetic markers and assignment models presented constitute a ‘toolbox’ that can be used for the assignment of herring caught in mixed survey and commercial catches in Division 6.a into their population of origin with a high level of accuracy.

Background: Perna viridis (Linnaeus, 1758), the Asian green mussel, is native to the Asia-Pacific region. The species is extensively distributed in the Indian subcontinent and is a candidate species for aquaculture in the Southeast Asian region. Availability of genetic information on wild populations is essential for the effective conservation and management of Perna species. The present study assessed the genetic variation and population structure across the distribution range of this species from the Indian peninsula by using microsatellite markers to determine the genetic structuring among the species. Methods: A total of 15 microsatellite loci with M13 labeling were used for the genetic characterization of P. viridis along Indian waters. Genotyped data were analyzed using analytical software to determine the genetic stocks and understand the genetic variability across the populations. Results: We identified 15 polymorphic markers to understand the genetic stocks and variability across Perna populations. The mean value of the observed heterozygosity (Hobs: 0.741) for all populations was closer to the expected heterozygosity (Hexp: 0.75). The pairwise Fst values between the west and east coasts of India varied significantly, indicating the existence of significant genetic structure between the populations. Conclusions: Genetic stock identification using software analysis exhibited two distinct stocks, one along the west coast (Arabian Sea) and another along the east coast (Bay of Bengal). Bottleneck analysis indicated the genetic stability of species in the wild. P. viridis is a commercially vital species in Indian peninsular regions. The present study suggests the adoption of stock-specific relaying programs of the species from Indian waters in future studies. [ABSTRACT FROM AUTHOR]

Abstract Background The population genetics of U.S. honey bee stocks remain poorly characterized despite the agricultural importance of Apis mellifera as the major crop pollinator. Commercial and research-based breeding programs have made significant improvements of favorable genetic traits (e.g. production and disease resistance). The variety of bees produced by artificial selection provides an opportunity to characterize the genetic diversity and regions of the genome undergoing selection in commonly managed stocks. Results Pooled sequencing of eight honey bee stocks found strong genetic similarity among six of the stocks. Two stocks, Pol-line and Hilo, showed significant differentiation likely due to their intense and largely closed breeding for resistance to the parasitic Varroa mite. Few variants were identified as being specific to any one stock, indicating potential admixture among the sequenced stocks. Juxtaposing the underlying genetic variation of stocks selected for disease- and parasite-resistance behavior, we identified genes and candidate regions putatively associated with resistance regulated by hygienic behavior. Conclusion This study provides important insights into the distinct genetic characteristics and population diversity of honey bee stocks used in the United States, and provides further evidence of high levels of admixture in commercially managed honey bee stocks. Furthermore, breeding efforts to enhance parasite resistance in honey bees may have created unique genetic profiles. Genomic regions of interest have been highlighted for potential future work related to developing genetic markers for selection of disease and parasite resistance traits. Due to the vast genomic similarities found among stocks in general, our findings suggest that additional data regarding gene expression, epigenetic and regulatory information are needed to more fully determine how stock phenotypic diversity is regulated.

Abstract Identification of stocks and quantification of their relative contribution to recruitment are major objectives toward improving the management and conservation of marine exploited species. Next‐generation sequencing allows for thousands of genomic markers to be analyzed, which provides the resolution needed to address these questions in marine species with weakly differentiated populations. Greenland Halibut (Reinhardtius hippoglossoides) is one of the most important exploited demersal species throughout the North Atlantic, in particular in the Gulf of St. Lawrence, Canada. There, two nurseries are known, the St. Lawrence Estuary and the northern Anticosti Island, but their contribution to the renewal of stocks remains unknown. The goals of this study were (a) to document the genetic structure and (b) to estimate the contribution of the different identified breeding stocks to nurseries. We sampled 100 juveniles per nursery and 50 adults from seven sites ranging from Saguenay Fjord to offshore Newfoundland, with some sites sampled over two consecutive years in order to evaluate the temporal stability of the contribution. Our results show that after removing sex‐linked markers, the Estuary/Gulf of St. Lawrence represents a single stock which is genetically distinct from the Atlantic around Newfoundland (FST = 0.00146, p‐value = .001). Population assignment showed that recruitment in both nurseries is predominantly associated with the St. Lawrence stock. However, we found that the relative contribution of both stocks to the nurseries is temporally variable with 1% contribution of the Newfoundland stock one year but up to 33% for the second year, which may be caused by year‐to‐year variation in larval transport into the Gulf of St. Lawrence. This study serves as a model for the identification of stocks for fisheries resources in a context where few barriers to dispersal occur, in addition to demonstrating the importance of considering sex‐linked markers and temporal replicates in studies of population genomics.

The Brazilian sardine (Sardinella brasiliensis) sustains the most important pelagic fishery off Brazilian waters. The present study evaluated the existence of distinct population-units inferred from body geometric morphometrics and otolith shape analyses using two and three-year-old individuals collected in Rio de Janeiro and Santa Catarina, the two main Brazilian fishery grounds. Univariate and multivariate statistics were performed for the entire dataset and separated by age groups. Re-classification success for combined ages achieved an overall re-classification rate of 84% and 89% for body and otolith signatures, respectively. Moreover, the combination of both techniques improved the overall re-classification success to 93%. However, when both techniques were conducted by age group, it allowed to unravel a more detailed population structure scenario, and a complete group separation (100% re-classification success) was obtained using otolith shape analyses for two-year-old individuals. Both techniques indicated the existence of two different population-units considering the Brazilian geographical extremes of the species' fishing area. Such regional differences are probably related to distinct oceanographic conditions affecting the feeding regime and fish growth. This study clearly shows that S. brasiliensis caught off southeast-south Brazil corresponds to two distinct population-units, and recommends a finer regional fishery management for the species. [ABSTRACT FROM AUTHOR]

Background. Since the formation of the research group in marine biology at the CCBA, different aspects of this discipline have been developed. One of them is the identification of populations and possible stocks of fish of commercial importance, using different techniques. The stock delineation (or population structure) are central considerations for fishery assessment and strategic management of marine natural resources and have to be addressed from a meta-population perspective where complementary technical approaches meet to enable the best picture to delineate complex stock structures. Objective. To review the current knowledge on the stock concept and the use of a multidisciplinary approach to properly assess commercially important marine stocks in the coastal waters of the Yucatan peninsula. Methodology. We present the research explored so far by the marine biology laboratory (LABIOMA by its acronym in Spanish) of the Autonomous University of Yucatán regarding the marine resources off the coast of the Yucatan peninsula, and the future lines of investigation pursued by our personnel, from fishing gear selectivity, abundances and catchability estimates, traditional morphometrics, parasitological and life history traits as biological tags, to more precise analyses such as fish otolith shape or even stable isotope analysis, genotypic markers, and marine natural products chemistry. Main findings. Single technical approaches are insufficient to delineate complex stock structures, especially in wide marine open access ecosystems, and there is a need to harness the full power of complementary and synergistic multidisciplinary approaches to improve fishery assessment and management efficiency in marine natural resources from the coastal areas of the Yucatan peninsula. Implications. Most stock assessment models are based on a single unit stock assumption, however the full impact of management actions, including identifying the complexity of the stock of any marine species subject to fishing, could affect the perpetuity of its abundances if the population subunits are not properly located. Conclusion. Identification of stocks is necessary for several reasons including allocation of catches, recognition and protection of nursery and spawning areas, and for development of optimal harvest and monitoring strategies. To this end, the LABIOMA are strengthening the assessments of commercially important marine stocks by using multidisciplinary approaches, whose lines of research represent basic aspects to be known and would be of great help to decision makers at the time of establishing more precisely, catch quotas, fishing areas, closed seasons, and therefore make more efficient the management strategies.

Delineation of population structure (i.e. stocks) is crucial to successfully manage exploited species and to address conservation concerns for threatened species. Fish migration and associated movements are key mechanisms through which discrete populations mix and are thus important determinants of population structure. Detailed information on fish migration and movements is becoming more accessible through advances in telemetry and analysis methods however such information is not yet used systematically in stock structure assessment. Here, we described how detections of acoustically tagged fish across a continental‐scale array of underwater acoustic receivers were used to assess stock structure and connectivity in seven teleost and seven shark species and compared to findings from genetic and conventional tagging. Network analysis revealed previously unknown population connections in some species, and in others bolstered support for existing stock discrimination by identifying nodes and routes important for connectivity. Species with less variability in their movements required smaller sample sizes (45–50 individuals) to reveal useful stock structure information. Our study shows the power of continental‐scale acoustic telemetry networks to detect movements among fishery jurisdictions. We highlight methodological issues that need to be considered in the design of acoustic telemetry studies for investigating stock structure and the interpretation of the resulting data. The advent of broad‐scale acoustic telemetry networks across the globe provides new avenues to understand how movement informs population structure and can lead to improved management. [ABSTRACT FROM AUTHOR]

Meristic variation among stocks of greater lizardfish Saurida tumbil through the western coasts of the Arabian Gulf and Sea of Oman was examined using meristic characters. Statistical analysis of meristic traits proposed that there is constrained migration of populations of greater lizardfish along the western coast of the Arabian Gulf and Sea of Oman. Overlapping of the two samples from the northern part of the Arabian Gulf (Iraq‐Kuwait waters), three samples from the middle region of the Arabian Gulf (Bahrain‐Qatar‐Saudi Arabia) and two samples from the southern part of the Arabian Gulf/Sea of Oman (United Arab Emirates–Sultanate of Oman) suggested that there are three self‐recruiting populations in the studied area. Inspection of the role of each meristic trait variable to Canonical discriminant analysis showed that changes among samples appeared to be linked with the pattern of distribution of water temperature and configuration of current in both the Arabian Gulf and Sea of Oman areas. [ABSTRACT FROM AUTHOR]

To discriminate potential stock units of the Atlantic horse mackerel Trachurus trachurus within the putative Moroccan–Saharan stock, we investigated the morphological variation of this species from three fishing areas (from the north to the south: Larache, Safi and Dakhla) in the Moroccan Atlantic coastal waters. We used a geometric morphometric approach based on 30 truss measures derived from 14 landmarks in 165 fish specimens. We compared fish from three areas using a multivariate analysis including discriminant analysis and Procrustes technique. We found indications of at least two subunits: a differentiated subgroup in the north off Larache, probably a self-recruiting population or a locally adapted morphotype, and two overlapped subunits, respectively in the mid and southern Moroccan Atlantic coast off Safi and Dakhla. Examination of the contribution of each morphometric variable to canonical functions indicated that differences among samples seemed to be associated with morphological changes in the anterior and posterior parts of body, which may indicate adaptations to local environmental conditions and habitat use. Further investigations using other methods are needed to confirm the identified stock units. The present study and the obtained results on such a vulnerable declining small pelagic species are of great importance for fish stock assessment management and practice, but also have ecological and evolutionary implications related to local adaptations in fish populations that are under intense fishing pressure as an induced evolutionary selective force, which affects several adaptive traits. [ABSTRACT FROM AUTHOR]

Otoliths are calcified structures and the information contained within their chemistry or shape can be used to infer life history events, migration patterns, and stock structure of a fish population. Understanding how otolith chemistry is affected by temperature, salinity, interactive effects of abiotic factors, ontogeny, physiology, etc. is essential for the reconstruction of the environment that affected the fish. Otolith shape is also affected by environmental conditions in addition to the genotype. The applications of otolith chemistry and shape for stock discrimination have increased in recent years because of the advancements in analytical methods and the related software. The stock identification methods sometimes provide variable results but if we use complementary approach the information generated could be more reliable which can be used to prepare effective management and conservation strategies. It appears warranted to generate more information on the factors influencing otolith chemistry and shape especially when two or more factors exert synergetic influence. Therefore, the objectives of this review paper were to provide comprehensive information on various factors influencing the otolith chemistry and shape, and the utility of otolith chemistry and shape for fish stock discrimination with an emphasis towards the research areas needing additional studies. [ABSTRACT FROM AUTHOR]

The fishing industry is an important economic sector in Namibia and South Africa, with the shallow-water hake Merluccius capensis being an important target species. Recent genetic studies of M. capensis found two stocks in the Benguela Current Large Marine Ecosystem, one in the north (17–29° S) and one in the south (29–36° S), and a proposed mixed stock in the Orange River area (around 29° S). The present study investigated the use of otolith shape analysis for purposes of stock-structure analysis of M. capensis. Merluccius capensis otolith samples were collected during demersal-trawl surveys along the Benguela, for the years 1992, 2004 and 2005. Different years were selected to investigate temporal stability in otolith shape in the northern Benguela. A total of 1 628 otolith images were analysed using the shapeR library in R. Otolith shape was analysed using wavelet transformation, and ANOVA-like permutation tests indicated no significant differences between the northern (17°31′–25°29′ S) and central (25°30′–29°05′ S) Benguela for all years but showed significant differences between the northern and southern (29°05′–35°50′ S) Benguela. This study therefore demonstrated that otolith shape could be used for stock discrimination of M. capensis. It confirmed one stock of M. capensis in the northern and central Benguela and another in the southern Benguela, which supports the current, separate management approach for this species. It also showed some differences in otolith shape from the 1990s to the 2000s, which could be explained by increased movement of the southern Benguela stock to the northern Benguela and increased hybridisation in the later years. [ABSTRACT FROM AUTHOR]

Otolith shape analysis is a powerful method for fish stock identification. We compared the otolith shape of Pagrus pagrus (Linnaeus 1758) along with its distribution in four south‐western Atlantic regions where it is commercially fished: Rio de Janeiro, Rio Grande do Sul in southern Brazil, the Argentine‐Uruguayan Common Fishing Zone (UA) and the Argentinian Exclusive Fishing Zone (AR). Otolith shapes were compared by Elliptical Fourier and Wavelet coefficients among specimens in a size range with similar otoliths, morphometric parameters and ages. Four potential stocks were identified: one in the AR, a second along the UA which included specimens from southern Brazil with well‐marked opaque bands in its otoliths (MRS), the third in southern Brazil with faint or absent opaque bands in its otoliths (FRS) and the fourth along Rio de Janeiro. The difference in the otolith shape among regions followed differences reported using other stock identification techniques. The similarity between otoliths from UA and MRS (ANOVA‐like, P > 0.01) can be explained by seasonal short‐range migrations. Otoliths shape differences between MRS and FRS (ANOVA‐like, P < 0.01) suggest that P. pagrus does not form a homogeneous group in southern Brazil. [ABSTRACT FROM AUTHOR]

Identification of stocks and quantification of their relative contribution to recruitment are major objectives toward improving the management and conservation of marine exploited species. Next‐generation sequencing allows for thousands of genomic markers to be analyzed, which provides the resolution needed to address these questions in marine species with weakly differentiated populations. Greenland Halibut (Reinhardtius hippoglossoides) is one of the most important exploited demersal species throughout the North Atlantic, in particular in the Gulf of St. Lawrence, Canada. There, two nurseries are known, the St. Lawrence Estuary and the northern Anticosti Island, but their contribution to the renewal of stocks remains unknown. The goals of this study were (a) to document the genetic structure and (b) to estimate the contribution of the different identified breeding stocks to nurseries. We sampled 100 juveniles per nursery and 50 adults from seven sites ranging from Saguenay Fjord to offshore Newfoundland, with some sites sampled over two consecutive years in order to evaluate the temporal stability of the contribution. Our results show that after removing sex‐linked markers, the Estuary/Gulf of St. Lawrence represents a single stock which is genetically distinct from the Atlantic around Newfoundland (FST = 0.00146, p‐value =.001). Population assignment showed that recruitment in both nurseries is predominantly associated with the St. Lawrence stock. However, we found that the relative contribution of both stocks to the nurseries is temporally variable with 1% contribution of the Newfoundland stock one year but up to 33% for the second year, which may be caused by year‐to‐year variation in larval transport into the Gulf of St. Lawrence. This study serves as a model for the identification of stocks for fisheries resources in a context where few barriers to dispersal occur, in addition to demonstrating the importance of considering sex‐linked markers and temporal replicates in studies of population genomics. [ABSTRACT FROM AUTHOR]

Abundance and structure of feeding aggregations of chum salmon are analyzed on the results of the otoliths processing sampled in different areas of the Okhotsk Sea in 2011-2014 and scheme of their autumn migrations in dependence on the sea surface temperature (SST) patterns, using the data on catching the fish with the otoliths marked in hatcheries. The migrations were similar for all chum groupings from the Okhotsk Sea and adjacent waters: their juveniles moved to Kamchatka coast until SST decreasing to 11оС in October, where they formed mixed aggregations, then density of the aggregations increased until SST 9-10оС, after that the aggregations moved to the central part of the sea and further southward passing the Kuril Straits in November under SST 7-8оС. The portion of marked fish from hatcheries in mixed catches was 2.1-7.8 % (on average 3.9 %). Taking into account these values and the ratio between marked and non-marked fish for certain hatcheries, the ratio between wild stocks and hatchery release of different origin is determined. The portion of chum salmon from Japanese hatcheries is estimated as 9.6-41.6 % (on average 27.3 %), the portion of chum from Russian hatcheries is considerably lower - 0.5-2.6 % (on average 1.2 %), and chum salmons of natural origin dominate in all years with the portion 55.8-89.9 %. For the fish of artificial origin, the ratio between the number of juveniles feeding in the sea and their release from hatcheries is estimated as 3.0-4.2 % (on average 3.6 %) for Japanese hatcheries and 0.3-0.7 % (on average 0.5 %) for Russian hatcheries. So, survival of chum from Japanese hatcheries is higher in 8 times on average, and total abundance of the feeding artificial chum salmons of Japanese origin is higher than those of Russian origin in more than 20 times. However, the hatcheries in Sakhalin and Kuril Islands has similar efficiency as Japanese ones, in opposite to other areas. The abnormally low estimations of the efficiency for some Russian hatcheries allow us to suppose that the otolith marking program is not realized correctly in some regions of Russian Far East, possibly the marks don’t correspond exactly to the schemes of marking.

The simultaneous use of the scale and otolith morphometry was assessed as a potential tool for the identification of Persian brown trout Salmo trutta stocks of the Lar Lake and five rivers from Lar Basin, Iran. Fourier coefficients (FC) and circularity, rectangularity, roundness, ellipticity and form factor shape indices (SI) were calculated for otolith and scale. Several SIs were significantly different among sites for both structures. Permutational multivariate analysis of variance revealed significant differences between several pairwise comparisons for otolith and scale (FCs and indices separately). Discriminant analysis showed otolith FCs (cross‐classification rates: 25–86%) and SI (20–45%) appear to be a relatively acceptable tool to discriminate between several locations. Comparatively, the scale morphometry showed lower discriminatory power (FC = 3–65%; SI = 15–34%), with the exception of SI for Elarm River (60%), Kamardasht River (56%) and Lar Lake (75%). Cross‐classification rates improved up to 100% when discriminate analysis incorporating all variables for otolith and scale was performed. The results showed a potential segregation between some water bodies, suggesting that the otolith and scale morphometry could be a useful tool to delimit S. trutta populations in relatively close freshwater environments. [ABSTRACT FROM AUTHOR]

Despite increased focus on ascertaining the status of elasmobranch fish, the stock units for many species are uncertain. Data from mark-recapture tagging studies undertaken from 1959–2017 were analysed for 13 batoid species. Data were most comprehensive for skates (Rajidae), with 22,374 released and 3342 (14.9%) returned. Most data related to thornback ray Raja clavata , blonde ray R. brachyura and spotted ray R. montagui. Tags were generally returned from areas less than 50 km from their release, and usually from the ICES Division in which they were released. However, straight-line distances travelled of up to 910 km (R. brachyura) and 772 km (R. clavata) were recorded, highlighting that individual skates are capable of longer-distance movements. The maximum time at liberty was 16.6 years (R. clavata). Whilst mark-recapture data indicated that the current stock units used by ICES are broadly appropriate, southward movements of several skate species tagged off Northern Ireland (Division 6.a) to the Irish Sea (Division 7.a) were observed. In contrast, skates tagged in the Irish Sea and Bristol Channel (Division 7.f) generally remained in that area, with only occasional recaptures from Division 6.a. [ABSTRACT FROM AUTHOR]

Assessing fish stocks has important implications for fisheries management and conservation biology. Gurnards are marine demersal fish that commonly occur in the Mediterranean, but their population in this region remains to be quantified. This study examines the population structure of the longfin gurnard Chelidonichthys obscurus (Walbaum, 1792) in waters off eastern Tunisia, using morphometry and parasite assemblages. A total of 134 fish are investigated from two studied zones – the Gulf of Hammamet and the Gulf of Gabès. Discriminant analysis is used to compare gurnard populations in the two studied zones using 13 morphometric characters and the infection parameters of seven parasites. Morphometric analysis reveals strong spatial variations between the studied zones, providing evidence for the existence of an ecological differentiation along the eastern Tunisian coast. Mahalanobis distances show that body height, pectoral fin length and first dorsal fin length are the most salient morphometric characters for determining the position of samples from the Gulf of Gabès. The effectiveness of using parasites to study longfin gurnard stocks is uncertain. The use of short-lived parasites as biological tags is questionable, at least in the present case. Future research, based on complementary approaches such as otolith microchemistry and genetics, may improve our understanding of the global stock structure of longfin gurnard to suitably inform regional organizations involved in fisheries management. [ABSTRACT FROM AUTHOR]

Auxis thazard (frigate tuna), is a commercially important fish species in Sri Lanka. Although Sri Lanka is fortunate to have a large resource of tuna, little information is available on the biology, genetics and stock structure of A. thazard. Hence, the present study was conducted to study the biology, genetics and stock structure of A. thazard in coastal waters around Sri Lanka. The fish samples were collected from October 2015 to September 2017 from day-boats operating in the Western, North Western, Eastern and Southern Provinces of Sri Lanka. For this period, the length-weight relationship and Fulton's condition factor (K) calculated for A. thazard using standard length measured in centimetres and weight measured in grams were shown as W = 0.1091L 3.3385 and 1.93, respectively, indicating a relatively healthy growth pattern and a comparatively unpolluted habitat. Studies on the stomach contents revealed that A. thazard are non-selective carnivors, feeding on diverse animal prey items such as small fish species, shrimps and cephalopods available in the surrounding waters. The fecundity of female A. thazard was shown to be 48,056 to 267,000 eggs. The calculated GSI values showed that the peak spawning period for male A. thazard extends from May to August and for the females from May to July. The phylogenetic analysis of the mitochondrial D-loop region sequences of 75 selected samples representing all the geographical regions studied showed that the fish of different regions are clustering together. Hence, for fisheries management strategies, A. thazard found in the coastal waters of the Western, North Western, Eastern and Southern Provinces of Sri Lanka could be considered as a single stock. [ABSTRACT FROM AUTHOR]

Landmark-based truss morphometry was used to identify stock structure of striped snakehead, Channa striata, in the river Ganga and its tributaries: river Yamuna and river Gomti. The fish samples were collected from Narora site of the river Ganga, Agra site of the river Yamuna and Lucknow site of the river Gomti from November 2012 to May 2016. Ten morphometric landmarks were selected to construct truss network on the fish body. Transformed truss network measurements were subjected to principal component analysis, discriminant function analysis and univariate analysis of variance. The first principal component (PC I) explained 40.2% of total variation while PC II and PC III explained 9.86 and 6.68%, respectively. The step-wise discriminant function analysis retained six variables that significantly discriminated the populations. Using these variables, 89.2% were correctly classified into their original groups. Of the total 35 transformed morphometric measurements, 28 exhibited significant differences among the populations. Results indicate the presence of different stocks of C. striata in the selected rivers of the Gangetic river system. [ABSTRACT FROM AUTHOR]

Morphometric variation can be very useful for discriminating 'phenotypic stocks' as groups with similar life-history traits. Such groups are of great importance for accurate population-dynamics modelling for purposes of fishery stock assessment and management, independent of their genetic differences or similarities. This study is a contribution to the stock identification of the sardine Sardina pilchardus off the Moroccan Atlantic coast. The objectives were to (i) assess whether specimens from stocks defined by the FAO correspond to different morphotypes, and (ii) compare the obtained results with those recently published on the genetic variability of the studied populations. Morphometric analyses, using truss variables and landmarks data from sardine sampled from four widely spaced ports of landing along the Moroccan Atlantic coast (from north to south: Larache, Safi, Tantan and Dakhla), were carried out using multivariate and geometric approaches. Principal components analysis of truss variables and cluster analysis of the average shape of the sardine revealed the existence of three distinct morphotypes: 'Larache,' 'Safi–Tantan' and 'Dakhla.' These correspond well with the FAO's stock subdivision. The morphometric variation might be related to the mesoscale hydrodynamic characteristics of the study area. However, these morphometric results do not fully accord with recently published data on genetic variability of the species. Those data indicated the genetic singularity of the Safi population, which could have led to the historical collapse of that sardine stock in the 1970s. Additional work is needed to validate the obtained results by taking into account seasonal variations and transitional areas between stocks. [ABSTRACT FROM AUTHOR]

Balinese Sardinella (Sardinella lemuru) is the main commodity in Indonesia. Despite, more research show that lemuru got the overfishing condition. In East Java region, likely Bali Strait, Southern-East Java water, and Madura Strait are the region which the most production of lemuru catch. So it needs identification stock of Sardinella lemuru on the third fisheries management east java sub-region, as it to be used as a reference to managing the sustainability of the catch sardinella lemuru for the future. Research carried out in January to May 2016 with the methods is the sample of random sampling on three different locations water representing Madura Strait, Bali Strait, and southern-East Java water. The each sample implemented were in four times during a period of months old different. Every the sample researchers get as 50-200 tail. Sardinella lemuru in accordance with the season fish. The sample which has been obtained taken to the laboratory of Marine Science University of Brawijaya to data take. The analysis used in this research was Truss morphometric and Factor analysis of the condition allometric. Based on the results of the analysis in the Madura Strait, Bali Strait, and Southern-East Java water are having a distinction of morphometric character amount 44 % with the character being very affected is PAL_FL, DFB_HL , PVL_FL, UPCL_FL, OD_HL, and PPL_FL. Around 64 % of the whole morphometric character that is 14 characters. Next, if it is seen from Allometric condition in the third these waters having b value different from each aquatic and after B-test that lemuru in the three the waters might otherwise dissimilar stock so management of Sardinella lemuru in the three waters should have been undertaken in separated.

Otolith shape analysis is an efficient fish stock identification tool. However, most applications used left and right otoliths or only one of them arbitrarily chosen without testing for biases resulting from potential directional bilateral asymmetry (DA) in otolith shape, i.e. a unimodal population-level deviation form bilateral symmetry between right and left otolith shapes. In this study, 560 bogues (Boops boops) were sampled from 11 geographical locations from the Canary Islands to the Aegean Sea and elliptical Fourier descriptors were used to describe their otoliths' shape. First, a significant otolith DA was observed at the global scale with an average amplitude of 2.77%. However, at the scale of sampling locations, DA was not always significant and varied in amplitude and direction. Second, population structure was investigated using the shape of either right otoliths or left otoliths or both together. Analyses based on right otoliths or both otoliths together, suggested three stock units: a North-Western Mediterranean Sea stock, an Eastern Mediterranean Sea stock, and a Central-Eastern Atlantic Ocean and South-Western Mediterranean Sea stock. In contrast, no coherent geographical pattern was found based on left otoliths. Our results highlight the importance of accounting for potential otolith DA in otolith shape-based stock identification. [ABSTRACT FROM AUTHOR]

Abstract Selective breeding of shrimp has major potential to enhance production traits, including growth and disease resistance. Genetic characterization of broodstock populations is a key element of breeding programs, as it enables decisions on inbreeding restrictions, family structure, and the potential use of genomic selection. Single Nucleotide Polymorphisms (SNPs) are suitable genetic markers for this purpose. A set of SNPs was developed to characterize commercial breeding stocks in Mexico. Individuals from local and imported lines were selected for sequencing using the nextRAD technique, resulting in the identification of 2619 SNPs. Genetic structure analysis showed three to five genetic groups of Ecuadorian and Mexican origins. A subset of 1231 SNPs has potential for stock identification and management. Further, three SNPs were identified as candidate sex-linked markers. The role of SNPs possibly associated with genes related to traits of importance to shrimp farming, such as growth and immune response, should be further investigated. Highlights • SNP markers were developed for the whiteleg shrimp Litopenaeus vannamei. • The genetic structure of cultivated shrimp in Mexico is described. • A set of markers can be used to genetically identify breeding stocks in Mexico. • Putative sex-associated SNPs are reported. • Match of SNPs with genes of interest are found. [ABSTRACT FROM AUTHOR]

In the late 1960s, two local herring stocks and one seasonal migratory herring stock in Icelandic waters collapsed primarily due to overfishing. While the stocks of Icelandic summer-spawning herring (ISSH) and Norwegian spring-spawning herring (NSSH) have recovered, Icelandic spring-spawning herring (ISPH) has not. The main objective of this work is to explore the existence of ISPH and identify potential signs of recovery. Analyses were based on samples from the autumn fishery and survey data from 1962 to 2016. In the autumn, local ISSH and ISPH cohabitated and mixed in the main fishery, where sampled fish were categorized into stocks on basis of maturity stage. The results indicate that the proportion of ISPH was in the range of 13–33% in the 1960s while below 5% and on average 1.4% during 1970–2016. Several year classes of ISPH exhibit notable differences from the general low levels and caused a slight increase in ISPH spawning-stock biomass for corresponding years. An increase in proportion of generally old ISPH around 2004 and 2013 occurred simultaneously with the reappearances of NSSH in the feeding areas east and north of Iceland, respectively. Altogether, it supports earlier suggestions that ISPH might require immigration from NSSH to recover, as these were considered closely related stocks. This is consistent with the source-sink theoretical model of stock size regulation. [ABSTRACT FROM AUTHOR]

The study on intraspecific variation of wild crossbanded barb, Puntioplites bulu stock in Peninsular Malaysia was investigated based on truss network analysis constructed from the fish body. A total of 90 samples were collected from three different populations, namely Kelantan River, Perak River and Pahang River (n= 30/population). The 22 truss characters were standardised by an allometric formula and analysed by multi and uni-variate analysis. The results showed significant differences (p< 0.05) between mean of the three populations. The loadings of the first and second discriminant function accounted for 81.3% and 18.7% respectively in terms of group variability, and they explained 100% of the total among group variability. The results showed significant variation of P. bulu in morphology based on truss network caught from three different populations. The morphological differences were located mainly on the head region, body depth and median region. These findings indicate the presence of morphometric variations between three populations of P. bulu in Peninsular Malaysia based on their locations. [ABSTRACT FROM AUTHOR]

Morphometrics is a beneficial, straightforward and relatively simple tool for fish stock delineation and identification. Analysis of spatial divergence, and morphological traits in relation to other factors, are of high interest both for management and in ecological studies. Morphology can help to delineate stocks, inform about local adaptations as well as ecological role the species play in the ecosystem. Morphological variation and differentiation of three-spined stickleback ( Gasterosteus aculeatus ) has been thoroughly studied in small freshwater systems, but less is known about differentiation of the species in an open marine system. The Baltic Sea inherits substantial environmental gradients in salinity, temperature, as well as in the nature and intensity of predation, gradients that all can foster local morphological adaptation and potential population differentiation. Previous studies have revealed some morphological differentiation of the species along the coast, but studies from the offshore are lacking. In this study we used traditional as well as geometric morphometrics to analyse divergence in morphological traits like body plate numbers, body- and otolith shape among sticklebacks from two major genetic clusters inhabiting different parts of the Baltic Sea. Our results show that fish from one area (Curonian Lagoon) representing one of the clusters had significantly higher number of body plates, potentially indicating a response to higher predation pressure compared to the other areas studied. Body shape also significantly differed among locations with deeper bodied fish in the Curonian Lagoon. The most conservative and least plastic trait studied, otolith shape, did, however, not show any divergence among the areas studied. Our results suggest morphological divergence in plastic traits like body plates and body shape in response to local environmental conditions. The lack of divergence in otolith shape further suggests that the degree of population differentiation is weak or rather recent, as also highlighted in earlier studies using molecular markers or synchrony in population abundances. In all, our study shows that at least the number of body plates can serve as an effective stock delineator among genetic clusters of three-spined sticklebacks in the Baltic Sea. [ABSTRACT FROM AUTHOR]