The European seabass (Dicentrarchus labrax) is one of the most emblematic coastal fish species in the Northeast Atlantic, with high commercial value for fisheries and aquaculture, and importance for sport and recreational fishing. Despite its socio-economic importance, the Iberian divisions, Cantabrian Sea (8c) and the Atlantic Iberian waters (9a), defined by the International Council for the Exploration of the Sea (ICES), lack stock delimitation data. Moreover, this species is missing basic biological information, a seasonal reproductive fishing ban, and the annual landings in this region are more than double the levels recommended by ICES. To investigate the population structure of D. labrax in these areas, 140 adult individuals (36–51 cm of total length) were collected between January and March 2025 in three locations along the Atlantic coast of the Iberian Peninsula: Avilés (n = 47), Peniche (n = 48), and Lagos (n = 45). Fish from each location were analyzed for body geometric morphometrics (truss network) and otolith shape contour (Elliptical Fourier Descriptors). Data were evaluated using univariate and multivariate tests to assess spatial differences and reclassification success among locations. Results revealed regional differences using body morphometry and otolith shape analyses. The overall reclassification success was 68% for truss networking, 51% for otolith shape, and 65% when both methods were combined. Despite the observed differences, the absence of clear, isolated populations supports the ICES definition of a single, though not homogeneous, European seabass stock in the Atlantic Iberian coastal waters. Nevertheless, individuals from Avilés exhibited distinctive morphometric patterns and otolith shapes, suggesting possible adaptations to local selective pressures in slightly different environments. Further studies integrating genetic tools, otolith chemistry, parasitic fauna and telemetry analyses, as well as other fish samples from adjacent areas such as the Bay of Biscay, are recommended to achieve a more comprehensive understanding of the population structure and migration patterns of this key species in the Atlantic Iberian coastal waters.

Otolith shape has been widely used as a tool to investigate the population structure of marine fish, as it reflects environmental, physiological, and genetic influences throughout the lives of individuals. The morphological variability of Pomatomus saltatrix sagittal otoliths along the southeastern–southern coast of Brazil was assessed using Elliptic Fourier Descriptors (EFDs) and Wavelet Transform Descriptors (WTDs). A total of 74 individuals from Rio de Janeiro (RJ, N = 25), São Paulo (SP, N = 24), and Santa Catarina (SC, N = 25) were analyzed. The coefficients obtained from both methodologies were subjected to multivariate analyses, including Permutational Multivariate Analysis of Variance (PERMANOVA) and Flexible Discriminant Analysis (FDA), combined with Jackknife Cross-Validation (JKC). The results showed high similarity in otolith shape among the sampled locations. Overall, PERMANOVA detected significant spatial differences for both EFD and WTD, although the proportion of variation explained by sampling location was low for both descriptors (<5%). After Bonferroni correction, no pairwise differences remained significant for EFD, whereas WTD indicated significant differences between SC and the other two sampling locations. Nevertheless, FDA indicated partial discrimination among sampling sites, with some overlap among groups for both descriptors. Despite this, JKC rates were high, reaching 92% for EFD and 87% for WTD. Overall, the results point to a pattern of weak spatial structuring in P. saltatrix along the southeastern–southern coast of Brazil. Although subtle morphological heterogeneity was detected among the analyzed locations, the evidence does not support the existence of completely isolated stocks. The observed patterns indicate weak spatial phenotypic differentiation and may be consistent with population connectivity; however, connectivity cannot be directly inferred from otolith shape alone and represents only one possible interpretation, as similar environmental conditions, shared growth histories, or limited discriminatory power of otolith morphology could also contribute to the observed scenario. Thus, the study reinforces the utility of otolith morphometry as a complementary tool for population studies and highlights the importance of integrating it with other phenotypic and genotypic approaches for a more comprehensive understanding of the structure of the species’ stocks.

Introduction: Fish stock identification and delineation are fundamental requirements for preventing local depletion and promoting the sustainable exploitation of marine resources. The blackspot seabream, Pagellus bogaraveo, is the most commercially valuable sparid species across the Northeast Atlantic and the Mediterranean Sea. To effectively discriminate fish stocks, researchers increasingly rely on the use of natural tags, which reflect both environmental and genetic influences, providing critical information regarding fish movements and population structure. Objective: To broaden the understanding of P. bogaraveo stock structure, samples originally obtained for a parasite-based discrimination study were used to provide complementary insights through otolith shape and geochemical signatures. Methodology: A subset of 150 individuals (30 per location) collected across five Portuguese locations (Portugal mainland: Matosinhos, Figueira da Foz, and Sagres; and Archipelagos: Azores and Madeira) was selected for otolith analyses. Otolith contour phenotypic variation was quantified through Elliptical Fourier Descriptors (EFDs) and Shape Indices (SIs), while elemental signatures (element: Ca) were analyzed using solution-based inductively coupled plasma mass spectrometry (SB-ICP-MS). Statistical analyses involved both univariate (one-way ANOVA, followed by Tukey tests, if needed) and multivariate approaches (MANOVA and LDFA), considering both individual and combined datasets. Results: EFDs + SIs yielded the lowest discriminatory power, with an overall reclassification accuracy of 38%. In contrast, Ca signatures provided the highest discrimination at 79%. The combination of both markers resulted in a slightly lower overall accuracy of 75%, likely due to the higher variance associated with the morphological data. Conclusions: In agreement with the previous parasite assessment, these otolith-based approaches confirm that the Macaronesian archipelagos consist of distinct stocks, separate from the Portuguese continental shelf. Furthermore, significant differences in otolith geochemical signatures between Sagres and Figueira da Foz point to a further subdivision of stocks. These findings are consistent with recent genetic data identifying three distinct stocks along the western and southern Iberian Peninsula, reinforcing the need for localized management of P. bogaraveo populations to ensure long-term fishery sustainability.

Introduction: Understanding population structure is essential for the effective management of marine resources. The bluefish (Pomatomus saltatrix) is a widely distributed and commercially important species along the Brazilian coast, yet its population structure in the South–Southeastern region remains unclear. Objectives: This study aimed to assess the body morphological variation and to infer the population structure of P. saltatrix along the South and Southeastern coasts of Brazil using a landmark-based geometric morphometrics method. Methodology: Individuals were collected between August and October 2024 from artisanal fisheries in Rio de Janeiro (n = 46), São Paulo (n = 37), and Santa Catarina (n = 29). A total of 12 landmarks were used to derive a truss network and extract 25 transformed distances (DTs). Data were analyzed using univariate (one-way ANOVA, followed by Tukey’s test if needed, or Kruskal–Wallis followed by Dunn’s test if needed) and multivariate statistics (PERMANOVA and Flexible Discriminant Analysis (FDA)). Results: Significant regional differences were detected for most DTs, except DT3, DT4, DT6, DT9, DT13, DT24, and DT25. PERMANOVA revealed significant differences among all sampling locations, including pairwise comparisons (p < 0.05). FDA achieved an overall reclassification success of 93% of individuals to their original location. Conclusion: Despite the high reclassification accuracy, the results support the existence of a single stock with spatial structuring rather than completely distinct population units, indicating that P. saltatrix in this region is not homogeneous.

Introduction: Understanding population structure is essential for fisheries management and stock identification. In marine species, spatial differentiation may arise from environmental conditions and biological factors, even when populations appear continuous. Otolith shape and body analyses have been widely used as effective tools to detect such differences, as they reflect both genetic and environmental influences. Objectives: The main objective of this study was to assess the population structure of Sarpa salpa in three fishing grounds in the Northeast Atlantic using two geometric morphometric approaches. Methodology: A total of 133 individuals collected between November 2025 and March 2026 from Santa Maria (n = 48), Peniche (n = 36), and Olhão (n = 49) were analyzed using two geometric morphometric approaches. The first involved otolith contour analysis using Elliptical Fourier Descriptors (EFD), with 12 descriptors explaining 90% of the cumulative variance. The second approach used truss network analysis based on 11 body landmarks, corresponding to 22 transformed distances (TD). Statistical analyses included multivariate analysis of variance (MANOVA), Hotelling’s T-square tests (HT2) for multiple comparisons, and linear discriminant function analysis (LDFA), with reclassification success assessed using a jackknifed (leave-one-out) classification matrix (JKM). Results: EFD analysis showed significant differences for MANOVA, with significant HT2 between all locations, but LDFA indicated considerable overlap, with a global JKM reclassification rate of 60%. In contrast, TD also showed significant MANOVA results, with significant HT2 across all comparisons. However, LDFA demonstrated clear separation among the three groups, achieving a JKM overall reclassification success of 98%. Conclusions: The results indicate that geometric morphometrics based on body landmarks provides greater discriminatory power than otolith contour analysis for identifying population structure. These results suggest the existence of distinct population units of Sarpa salpa in the Northeast Atlantic, highlighting the importance of spatially explicit approaches for fisheries assessment and management.

Introduction: Understanding population structure is essential for effective fishery management, and otolith shape analysis provides a robust framework for detecting spatial variation in marine fish populations. The bluefish (Pomatomus saltatrix), a commercially important and widely distributed species along the southeastern and southern Brazilian coast, may exhibit subtle population structuring that is still not fully resolved. Methodology: Otolith contour variation was analyzed using two complementary approaches: Elliptical Fourier Descriptors (EFD) and Wavelet Transformed Descriptors (WTD). A total of 75 individuals (25/site) were sampled from Rio de Janeiro, São Paulo, and Santa Catarina, with total lengths ranging from 33.2 to 45.5 cm. Multivariate analyses included Permutational Multivariate Analysis of Variance (PERMANOVA), pairwise Hotelling’s t-tests (HT²), Flexible Discriminant Analysis (FDA), and jackknife reclassification matrices (JKC). Results: For the EFD approach, PERMANOVA showed no significant differences among localities, while FDA revealed partial overlap among groups and a JKC overall reclassification accuracy of 46%. In contrast, the WTD approach detected significant spatial differences, with PERMANOVA indicating overall variation among localities and HT² identifying significant differences between Santa Catarina and the other regions. FDA improved visual separation of Rio de Janeiro samples, although the JCK accuracy decreased to 35%. Conclusion: The combined results suggest the presence of weak to moderate spatial structuring in P. saltatrix along the studied coastline. However, inconsistencies among analytical approaches and relatively low reclassification success rate to the original site indicate that the observed differentiation is insufficient to conclusively define distinct population units, remaining compatible with either a single stock exhibiting spatial heterogeneity or weakly differentiated subpopulations.