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A new anchovy species, Stolephorus falco sp. nov ., is described based on three museum specimens collected from northern Sumatra, Indonesia. Although the new species resembles S. baganensis Delsman, 1931, S. dubiosus Wongratana, 1983, S. taurus Hata, Lavoué & Motomura, 2022, and S. tri (Bleeker, 1852) in having a predorsal scute and a spine on the pelvic scute, it differs from all four of these taxa in having a distinctively deeper body, fewer scales on the longitudinal series, and additional differences in a number of other characters.

Fish parasite communities can be directly influenced by characteristics of host species. However, little is known about the host-parasite relationships in commercially important fish of the southeastern Atlantic. To address this knowledge gap, a comparative analysis of the parasite communities of three sympatric Clupeiformes was conducted. Cetengraulis edentulus (Engraulidae), Opisthonema oglinum (Clupeidae) and Sardinella brasiliensis (Clupeidae) were collected from an estuarine lagoon near Rio de Janeiro, Brazil. Prevalence, abundance and aggregation were estimated for infrapopulations; richness, diversity, evenness and dominance for infracommunities. The three component communities were compared using both quantitative and qualitative components. Canonical discriminant analysis was used to determine if a host population could be characterised by the component community of its parasites. Multivariate models revealed that host species, a proxy for diet and phylogenetic relationships, was the main factor influencing the composition of parasite infracommunities. Diet was found to be the main factor shaping the communities of endoparasites, in which digeneans were dominant and best indicator of host population. Ectoparasites (copepods, isopods and monogeneans) displayed strong host-specificity with some species restricted to a single host population. The similarity of the component communities of the two clupeid populations demonstrated the influence of host phylogeny. Parasite infracommunities exhibited low diversity and high dominance, with many taxa restricted to a single host species (specialists) and few occurring in more than one (generalists). Host phylogeny and by extension, diet, morphology and coevolution with parasites appear to be important factors in determining the host-parasite relationships of clupeiform fish in the southeastern Atlantic.

The anchovy family (Engraulidae) holds significant economic and ecological value in seas around China, playing a crucial role in fisheries and marine ecosystems in these regions. This study analyzed the complete mitochondrial genome data of 18 Engraulidae species from seas around China, integrating molecular evidence to systematically investigate mitochondrial genome structure, codon usage patterns, and phylogenetic relationships within the family. The mitochondrial genomes of Engraulidae exhibited a highly conserved structure, characterized by significant A + T richness and variable control region lengths. Codon usage analysis in seven Thryssa species revealed that base composition, particularly GC content at the third codon position (GC3s), along with purifying selection, jointly influenced codon usage patterns. Phylogenetic analyses supported the division of the 18 species into two subfamilies, Engraulinae and Coiliinae, and highlighted variability in the phylogenetic placement of Setipinna depending on the inclusion of third codon positions. Furthermore, the genus Thryssa was supported to be polyphyletic: T. baelama and T. kammalensis formed one clade, while T. dussumieri, T. hamiltonii, T. setirostris, T. vitrirostris, and T. mystax constituted a separate branch. These findings provide novel molecular evidence for species identification and the taxonomic classification of Engraulidae, while offering a foundation for further exploration of their evolutionary relationships and systematic taxonomy. In this study, we utilized the complete mitochondrial genomes of 18 Engraulidae species to analyze their basic genomic features and reconstruct the phylogenetic relationships within the family. We examined the codon usage bias in the genus Thryssa, explored the evolutionary relationships among the species within the genus, and we also provide some insights into the taxonomic revision of this genus.

Small pelagic fishes in the Mediterranean Sea constitute about half of the total landings, of which almost one-third is European anchovy. Anchovy abundance mainly depends on early life stage and juvenile survival and growth, which are susceptible to shifts in environmental processes. Due to the commercial importance of this species, it is necessary to elucidate the processes affecting recruitment strength for effective fishery management, using environmental indices to set more appropriate harvesting limits. Here, we constructed a simple index to capture synchronicity between enrichment and retention/concentration processes, which are known to affect anchovy abundance, during the first year of life. Three ecosystems in the Mediterranean were examined: Gulf of Lions, Adriatic Sea, and Strait of Sicily. The synchronicity index (SI) represented the synergic evolution over time of the chlorophyll-a concentration (CHL, enrichment process) and mixed layer depth (MLD, concentration/retention processes), and was related with the abundance of anchovy recruits obtained from published survey reports. Considering different ecosystems, when the SI was significantly higher, anchovy recruitment was promoted. This result indicated SI is consistent across ecosystems in explaining anchovy abundance fluctuations and thus could be used to enhance fisheries management and extended to assess the impact of projected environmental changes.

In the Pacific Ocean, air and ocean temperatures, atmospheric carbon dioxide, landings of anchovies and sardines, and the productivity of coastal and open ocean ecosystems have varied over periods of about 50 years. In the mid-1970s, the Pacific changed from a cool \"anchovy regime\" to a warm \"sardine regime.\" A shift back to an anchovy regime occurred in the middle to late 1990s. These large-scale, naturally occurring variations must be taken into account when considering human-induced climate change and the management of ocean living resources.

Most data sets of ichthyoplankton contain a high frequency of zeros, and, not considering the possible inflation of zero counts, as in most studies, may result in incorrect model predictions. Thus, we modeled abundance of Engraulis anchoita eggs and larvae sampled during 18 oceanographic cruises conducted between 1974 and 2010 using zero-inflated (ZI) models. ZI models are mixture models with 2 components: (1) containing false zeros (due to design, survey or observer errors) modeled using a binomial generalized linear model (GLM); (2) containing abundance data that may produce zeros (true zeros), and modeled with a negative binomial GLM (ZINB). Although ZINB has been used in other areas of research, we are not aware of its previous use for ichthyoplankton. Common to larvae and eggs, the probability of false zeros was lowest in the southern area of the southeastern Brazilian Bight and higher at deeper station depths. The probability of false zeros was higher in 0.505 mm mesh-size samples than in 0.333 mm mesh only for eggs. Egg and larval abundance was negatively related to temperature in the count portion of the model; only larval abundance was negatively related to salinity. Egg abundance was higher in years sampled with 0.333 mm mesh under conditions of moderate/strong El Niño. The high interannual variability in the abundance and distribution of eggs emphasizes the importance of long-term studies to better understand patterns of fluctuations in the occurrence of ichthyoplankton that are related to environmental conditions.

As top predators and environmental sentinels in marine ecosystems, seabirds face significant pressure from global fisheries in competing for fish resources. For the critically endangered Chinese crested tern (Thalasseus bernsteini), characterizing its dietary requirements is a fundamental step in assessing how food availability and potential fishery‐induced resource shifts may impact its recovery. This study, conducted on breeding islands (Xiangshan island and Nanji Island) in Zhejiang, analyzed 12S and COI regions from fecal samples (n = 50) using DNA metabarcoding technology to systematically analyze the diets of mixed‐colony terns (Chinese crested terns and greater crested terns [T. bergii]) across the breeding season (breeding stage and nestling stage). The results for both species combined revealed a highly specialized diet, primarily focused on epipelagic schooling fish, with Engraulidae (occurrence frequency, FO = 72.73%) and Scombridae (FO = 27.27%) being the dominant taxa (combined relative read abundance, RRA > 54%). The key species were Engraulis japonicus, Setipinna tenuifilis, and Thryssa kammalensis. Our multi‐scale taxonomic analysis revealed that the dietary structure of these terns was conserved at higher taxonomic levels but highly dynamic at the species level. PCoA indicated no significant segregation between breeding stages or islands at the family level, whereas distinct, significant differences emerged between breeding stages at the species level, with nestling‐stage diets exhibiting greater diversity (significant higher Chao index), reflecting increased flexibility in resource utilization during the provisioning period. By integrating our findings with data from Australia and South Africa, we identify a universal foraging characteristic of T. bergii and T. bernsteini as a specialist predator primarily dependent on epipelagic schooling fish across its global range. Although the waters surrounding the study islands serve as an important spawning ground for various commercial fish species, the diet of these terns contains economically valuable fish in very low proportions (relative sequence abundance < 5%), indicating niche separation from direct fishery competition. Additionally, the first detection of freshwater fish in 6.82% of samples (3 out of 44) in the tern diet within this study area highlights the behavioral plasticity of terns in human‐modified environments and the potential for novel human‐bird conflicts at these sites. Our study emphasizes that securing these shared prey resources, particularly Engraulidae, is essential for the breeding success of these mixed colonies. Conservation strategies must extend beyond traditional habitat protection to incorporate coastal human activities into risk management frameworks, thereby enhancing the recovery of the critically endangered Chinese crested tern by protecting its primary food base. This study employs DNA metabarcoding to analyze the diet composition of the critically endangered Chinese crested tern and the greater crested tern during their breeding season in Zhejiang. The terns primarily consume epipelagic schooling fish like anchovies and mackerel, with minimal overlap with commercial fisheries (< 5% commercial fish). The detection of freshwater prey indicates behavioral adaptability to human‐altered coastal environments.

Thrissina splendida sp. nov., described from 19 specimens collected from the coastal areas of Korea and China, is closely related to Thrissina adelae (Rutter 1897), both species having a long maxilla with the posterior tip beyond the pectoral-fin insertion and the snout tip above the eye center level, and similar ventral scute and fin-ray numbers. However, the former is characterized by lower total gill raker numbers on the first, second, third, and fourth gill arches, higher numbers of longitudinal series scale rows, transverse scales, and vertebrae, a shorter snout and lower jaw, a shorter distance between the dorsal and anal-fin origins, and 4th and 5th anal-fin rays, and distinct paired dark lines along the dorsum from the occiput to the caudal-fin base.

Summary The identification of larval fish has been an important morphological issue in marine biology due to the dramatic transformations that most species undergo from early larval stages to adulthood. Insufficient morphological diagnostic characters in larval fishes made it easy to misidentify them and a difficult process to key to genus and species level. The experiment aims to find out, by applying DNA barcoding, how consistent the morphological identifications can be among larval fish. Larval fish were mainly collected using plankton nets around mangrove areas in Pendas (Johor), Setiu (Terengganu), Pekan (Pahang) and Matang (Perak) Malaysia between April 2015 and October 2015. A total of 354 samples were morphologically identified, mostly to the family level and a few to the genus level. Larval fish ranged from 1.5 mm to 31 mm of total length, with the most abundant individuals being <3 mm. Among them, a total of 177 individuals were selected for DNA barcoding analyses. Molecular works involved polymerase chain reaction (PCR) and sequencing of mitochondrial Cytochrome c Oxidase I (COI) gene fragment (655 base pairs) methods. DNA barcoding enabled all samples to be identified down to species level. The overall genetic identities ranged from 91% to 100%. Morphological identification classified the specimens into 19 families and 11 genera while DNA barcoding identified them into 19 families 33 genera and 40 species. A comparison between the two methods showed a mismatched identification of 42.6% where the accuracy percentage for morphological identification was moderate for the family level (67.8%) but was low for genus level identification (30%). The DNA barcoding method also managed to successfully identify 86.4% of the samples up to their species level where morphological method has failed to do so. The most misidentified families in the study were Blenniidae, Sparidae, Apogonidae Ambassidae and Monachantidae while almost all samples from the family Gobiidae and Engraulidae were correctly identified to family level because of their distinct morphology. In conclusion, taxonomic studies of larval fish should continue using combination of both morphology and DNA barcoding methods. Morphological identification should be more conservative i.e., when in doubt, it is better to key only to family and not to the genus and species level. DNA barcoding is a better method for deeper taxonomic levels identification with the existence of robust sequence reference libraries and should be able to validate the accuracy of traditional larval fish identification.

The mitochondrial genome provides important information for phylogenetic analysis and an understanding of evolutionary origin. In this study, the mitochondrial genomes of Ilisha elongata and Setipinna tenuifilis were sequenced, which are typical circular vertebrate mitochondrial genomes composed of 16,770 and 16,805 bp, respectively. The mitogenomes of I. elongata and S. tenuifilis include 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA), two ribosomal RNA (rRNA) genes and one control region (CR). Both two species' genome compositions were highly A + T biased and exhibited positive AT-skews and negative GC-skews. The genetic distance and Ka/Ks ratio analyses indicated that 13 PCGs were affected by purifying selection and the selection pressures were different from certain deep-sea fishes, which were most likely due to the difference in their living environment. Results of phylogenetic analysis support close relationships among Chirocentridae, Denticipitidae, Clupeidae, Engraulidae and Pristigasteridae based on the nucleotide and amino acid sequences of 13 PCGs. Within Clupeoidei, I. elongata and S. tenuifilis were most closely related to the family Pristigasteridae and Engraulidae, respectively. These results will help to better understand the evolutionary position of Clupeiformes and provide a reference for further phylogenetic research on Clupeiformes species.