Search

AbstractThe Ecuadorian site of Salango, with its 5500 years of pre-Columbian history, is of fundamental interest for understanding the relationships between people and the sea on the tropical Pacific coast of South America. In 2015, thousands of fish remains were found in foundational offering deposits of a perimeter wall built to protect a sanctuary of the Middle Guangala phase (AD 300–600). Approximately 3300 bones have been identified, and these represent the remains of 337 individuals belonging to 49 different species. The assemblage is largely dominated by pelagic species, particularly scombrids weighing 2–3 kg. The presence of dolphinfish, a taxon that has not been reported previously in the archaeological record of Salango, supports the hypothesis that fishing was mainly conducted offshore by boat. The preservation in situ of numerous anatomical connections and the large number of remains found virtually intact suggest that these fish were deposited whole. We suggest that these deposits were designed to represent the specific marine environment being exploited from Salango and, more broadly, the sea itself. In this respect, Salango presents an unusual manifestation of pre-Columbian sea-oriented ritual practice so far unique on the Ecuadorian coast. [ABSTRACT FROM AUTHOR]

Age-reading protocols for tuna species using annual growth zones in thin-cut transverse otolith sections have produced greater age estimates than previous methods. Lifespan estimates for yellowfin (YFT) and bigeye (BET) tuna (Thunnus albacares and T. obesus) were validated up to 16–18 years in the western North Atlantic Ocean using bomb 14C dating and the current study extends the approach to YFT and BET of the western and central Pacific Ocean (WCPO). Archived otoliths from young-of-the-year (YOY) tuna caught in the WCPO were analysed for 14C to establish a reference chronology covering 30 years (1989–2019). This YOY 14C time series exhibited strong concordance with existing coral-otolith 14C references for the tropical-subtropical Pacific Ocean and was combined as a single chronology. Otolith cores from YFT aged 1–14 years and BET aged 1–13 years from presumed annual counts were analysed for 14C. These measurements aligned with the reference chronology for the calculated hatch years for both species. These findings provide strong evidence that growth zones in thin-sectioned otoliths are deposited annually for YFT and BET of the WCPO and that age interpretation is correct using the current age reading protocol with little to no bias. [ABSTRACT FROM AUTHOR]

Scombridae is a family of pelagic marine fishes that comprises 16 genera and 51 species. This family has been of significant commercial importance throughout history; however, the phylogenetic relationships within the Scombridae have been disputed due to the unclear taxonomic boundaries of the suborder Scombroidei, which includes six families, including Scombridae. Despite this, only a limited number of studies have been conducted on the Scombridae. In our study, eight species covering five genera of the Scombridae were selected, and one nuclear (ITS) and three mitochondrial DNA markers (CO1, Cytb, and D-loop) were used to amplify gene fragments. Additionally, we included homologous sequences from other Scombridae fishes obtained from GenBank. Our analysis constructed phylogenetic relationships of 48 Scombridae species in 14 genera. The results demonstrated that the three phylogenetic trees (NJ, ML, and BI) exhibited similar topologies, containing three major clades. One major clade indicated that Grammatorcynus bilineatus and Grammatorcynus bicarinatus did not cluster with other species in the Scombridae; another clade comprised the genera Scomber and Rastrelliger; the third clade consists of the remaining Scombridae species. Notably, the study showed that Gasterochismatinae and Scombrinae were not sister groups; Allothunnus (tribe Thunnini) and Cybiosarda (tribe Sardini) clustered into a clade, suggesting that Sardini and Thunnini were non-monophyletic. Overall, this research enhances the understanding of phylogenetic relationships within the Scombridae and provides basic information to aid further research. [ABSTRACT FROM AUTHOR]

V.V. Bogachev (1933) described the scombrid fish Auxis caucasica based on an incomplete skeleton from the Sarmatian (Middle Miocene) of the North Caucasus (Stavropol Region). Subsequently, this species was assigned to the mackerel genus Scomber. New findings in the Sarmatian of the North Caucasus (Krasnodar Region, Pshekha River) revealed a significant reduction in the number of vertebrae in S. caucasicus (Bogatshov) (up to 28), which is extremely unusual for Scombridae, with at least 31 vertebrae. A new genus Mioscomber is established to accommodate the Sarmatian species of scombrids. The scombrids from the Sarmatian of the former Yugoslavia, originally described as Auxis vrabcensis Kramberger, 1882, A. thynnoides Kramberger, 1882 and Scomber sujedanus Steindachner, 1860, are assigned to the same genus—these also have a reduction in the number of vertebrae. The generic character of Mioscomber gen. nov. assumes correction of the diagnosis of the family Scombridae, from "Vertebrae 31–66" to "Vertebrae 28–66". [ABSTRACT FROM AUTHOR]

Tunas of the family Scombridae are of paramount importance for fisheries and the international seafood trade. In order to ensure a sustainable use of these valuable resources, it is crucial that stock delineation and management plans are in accordance. Here, we examined the population genetic structure of the two data-poor scombrid species wahoo (Acanthocybium solandri) and bigeye tuna (Thunnus obesus), both of growing significance in tuna fisheries. Our study employed whole-genome sequencing methods to conduct the most extensive genomic analysis of wahoo and bigeye tuna samples to date, collected from the Atlantic, Indian and Pacific Oceans. For both species, we observe genome-wide differentiation between samples from the Atlantic and the Indo-Pacific regions with little or no genetic structure within each of the ocean basins, indicative of high gene flow. However, by applying a set of extreme outlier tests, genomic differentiation between locations was identified within the Pacific Ocean for both species, as well as for wahoo within the Atlantic Ocean. Additionally, for bigeye tuna, we uncovered a putative chromosomal inversion with patterns of highly linked loci and strong population divergence, that may be involved in adaptive divergence across the distributional range of the species. Taken together, despite considerable gene flow, the detected substructures – most likely driven by local adaptation – challenge previously held assumptions of panmixia in both species. Our findings show that future stock assessment should consider genetic differences at both neutral and divergent loci to develop sustainable conservation and management actions for these valuable marine resources.

The copepod family Shiinoidae Cressey, 1975 currently comprises nine species of teleost parasites with unusual morphology and a unique attachment mechanism. Female shiinoids possess greatly enlarged antennae that oppose a rostrum, an elongate outgrowth of cuticle that originates between the antennules. The antennae form a moveable clasp against the rostrum which they use to attach to their host. In this study, we use micro-computed tomography (microCT) to examine specimens of Shiinoa inauris Cressey, 1975 in situ attached to host tissue in order to characterize the functional morphology and specific muscles involved in this novel mode of attachment and to resolve uncertainty regarding the segmental composition of the regions of the body. We review the host and locality data for all reports of shiinoids, revise the generic diagnoses for both constituent genera Shiinoa Kabata, 1968 and Parashiinoa West, 1986, transfer Shiinoa rostrata Balaraman, Prabha & Pillai, 1984 to Parashiinoa as Parashiinoa rostrata (Balaraman, Prabha & Pillai, 1984) n. comb., and present keys to the females and males of both genera. [ABSTRACT FROM AUTHOR]

This article discusses a scientific study on the relationship between gill raker numbers and the early growth of Pacific bluefin tuna. The study found that fish with fewer gill rakers experienced better growth during the early life stage, particularly before metamorphosis. The researchers suggest that gill raker number can be used as a tool for monitoring early growth and potentially predicting survival and recruitment success. The study was conducted with the assistance of fisheries laboratories and associations in Japan and was funded by the Research and Assessment Program for Fisheries Resources. [Extracted from the article]

Carbon stable isotopes (δ13C) are widely used in ecological studies to understand diet, food web dynamics, and movements of marine fishes. Still, δ13C is influenced by lipid content and often requires chemical extraction or mathematical correction. Here, we developed a species-specific mathematical lipid correction for white muscle tissue of yellowfin tuna (Thunnus albacares), a highly migratory finfish of considerable economic and ecological value. Lipid extraction was conducted on yellowfin tuna white muscle tissue (C:N range: 2.96–6.49), and both linear and non-linear lipid correction models for δ13C were fitted and assessed. Lipid extraction increased δ13C, and to a lesser extent, δ15N values in yellowfin tuna white muscle tissue, but had no effect on δ34S. Both non-linear models provided better fits to the data than the linear model, suggesting an asymptotic relationship between C:N and ∆δ13C. Results support the growing body of evidence that C:N ratios can be used to predict lipid corrected δ13C and highlight the value of mathematical correction approaches. We provide species-specific parameter estimates that can be used for lipid correction of white muscle tissue for δ13C analysis in yellowfin tuna and similar species for which species-specific models have yet to be developed. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to identify the presence of parasite infections and cystic formation in Scomber japonicus, Scomber scombrus, and Thunnus thynnus. Euryphorus brachypterus and Clavellisa scombri were identified from Thunnus thynnus and Scomber scombrus, respectively. Anisakis pegreffii was identified from Scomber japonicus and Scomber scombrus by using molecular methods. Additionally, Anisakis typical was determined from Scomber japonicus. [ABSTRACT FROM AUTHOR]

In the Northwest Atlantic (NWA), the Atlantic mackerel (Scomber scombrus) has a northern and a southern contingent, which spawn in Canada and the United States (U.S.), respectively. Both contingents mix mostly along the U.S. shelf during overwintering. The discrimination of individuals from each contingent in fisheries could improve the management of this depleted species in both countries. Here, we used genome-wide markers (>10 000 single nucleotide polymorphisms (SNPs)) to assess genomic differences between mackerel of both contingents, and possibly infer the proportions of each contingent in NWA management units. Small but significant genetic differentiation was observed between the northern and southern contingents (FST = 0.0010). Genetic assignments to reference samples from the two contingents were performed with predictive accuracy > 85%. Fish from both contingents were present along the U.S. shelf during late winter and early spring but also, without prior evidence of this, likely in Canadian waters from late spring to fall. Genetic assignments could be used as a stock discrimination tool so that fishery removals can be effectively determined and managed on a contingent level. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Age and growth of little tunny (Euthynnus alletteratus) were assessed by examination of annual growth increments in cross-section of first dorsal spines from 207 fish (85–1030 mm Straight Fork Length, SFL) sampled between 2017 and 2021 from the northeastern Atlantic and Mediterranean Sea. Some analysis and recommendations are provided for using the first dorsal fin spine for age estimation of little tunny. The comparative analysis of the sectioning location, with transverse sections collected at 0.5, 1.0, and 1.5 times the width of the condyle base measured from the base of the spine, showed that the 1.0 cross-section distance proved to be the most reliable option. Fish ages ranged 0–10 years old and the growth parameters estimates based on standard von Bertalanffy growth function were (for sexes combined): L ∞ (asymptotic length) = 99.77 cm; k (growth coefficient) = 0.445 year−1; and t 0 (age at zero length) = − 0.072 year−1. In order to ensure comparable results, it is crucial to implement a reproducible protocol for future studies on the age and growth of little tunny. • A standardized method to estimate the age of little tunny was proposed. • Age and growth of little tunny was developed by examination of cross-section spines. • The 1.0 condyle width cross-section distance proved as the most dependable choice. • Growth parameters for little tunny were provided. [ABSTRACT FROM AUTHOR]

Carbon stable isotopes (δ13C) are widely used in ecological studies to understand diet, food web dynamics, and movements of marine fishes. Still, δ13C is influenced by lipid content and often requires chemical extraction or mathematical correction. Here, we developed a species-specific mathematical lipid correction for white muscle tissue of yellowfin tuna (Thunnus albacares), a highly migratory finfish of considerable economic and ecological value. Lipid extraction was conducted on yellowfin tuna white muscle tissue (C:N range: 2.96–6.49), and both linear and non-linear lipid correction models for δ13C were fitted and assessed. Lipid extraction increased δ13C, and to a lesser extent, δ15N values in yellowfin tuna white muscle tissue, but had no effect on δ34S. Both non-linear models provided better fits to the data than the linear model, suggesting an asymptotic relationship between C:N and ∆δ13C. Results support the growing body of evidence that C:N ratios can be used to predict lipid corrected δ13C and highlight the value of mathematical correction approaches. We provide species-specific parameter estimates that can be used for lipid correction of white muscle tissue for δ13C analysis in yellowfin tuna and similar species for which species-specific models have yet to be developed.

Unicolax mycterobius (Vervoort, 1965) is redescribed based on specimens of both sexes recovered from the nasal cavity of the frigate tuna Auxis thazard (Lacépède, 1800) (Pisces, Scombridae) in Japan. This species possesses the lateral processes in the oral area. [ABSTRACT FROM AUTHOR]

This report provides the first confirmed identifications of wahoo (Acanthocybium solandri) and striped marlin (Kajikia audax) in the Red Sea, expanding the known ranges of these species into the basin. Potential mechanisms responsible for the lack of regional documentation of the two species are further discussed. These findings illustrate the need for systematic biodiversity surveys of pelagic fish assemblages in the Red Sea. [ABSTRACT FROM AUTHOR]

Background: The bullet tuna (Auxis rochei) is an epipelagic fish with a worldwide distribution that is highly targeted by fisheries. Genetic diversity and population genetics are good indicators of population structure and thus, essential tools for fisheries management. Knowing which factors (biotic and abiotic) might be shaping such structure is crucial for management plans. In the present study, we assessed the population structure of the bullet tuna in the western and central Mediterranean Sea. Methods: We used two types of genetic data: the mitochondrial DNA control region and seven microsatellite loci. The analysis of 431 sequences with a length of 386 bp from the mtDNA CR and the results from 276 individuals were genotyped by seven microsatellite loci. Results: Both types of markers coincided in showing significant genetic differences between an Iberian Peninsula–Strait of Gibraltar stock in comparison with a North African stock. Conclusions: We argue that this differentiation pattern is likely caused by reproductive strategies such as coastal spawning, larval retention, and natal homing behavior. These results should endorse the implementation of management plans for a resource that currently is not being managed. Thus, to ensure sustainability, these new policies should consider the presence of at least two genetically identified stocks. [ABSTRACT FROM AUTHOR]

A fossil mackerel Scomber collettei sp. nov. (Percomorpha, Scombroidei, Scombridae) is described from the Tarkhanian (lowermost Middle Miocene) of the northwestern Caucasus (Krasnodar Region, Pshekha River) based on several skeletons. This is the first discovery of a fossil representative of the genus Scomber in the Tarkhanian regional stage. The new species differs from the more ancient, late Oligocene to early Miocene mackerels from the Eastern Paratethys—S. cubanicus and S. gnarus—in having a different ratio of the abdominal and caudal vertebrae (14 + 17 vs. 15 + 16), and wider separated dorsal fins. S. collettei sp. nov. is also characterized by its unusually large teeth and lachrymal. [ABSTRACT FROM AUTHOR]

Pacific chub mackerel (Scomber japonicus) is a relevant fishery resource shared among three countries in the northeastern Pacific. The spatiotemporal distribution of larvae has been related to the convergence of oceanographic mesoscale structures, which can generate considerable variability in the morphology of fish larvae. The main goal of this work was to describe the shape changes of larval S. japonicus and their relationship with oceanographic variability, through geometric morphometric analysis to assess the seasonal variability of 10 homologous landmarks distributed on the pre‐anal section of 331 larvae from off the western coast of the Baja California Peninsula (WCBCP), Mexico (2006–2008). The results showed two principal morphotypes in Pacific chub mackerel larvae: The first morphotype had a more hydrodynamic body (longer and shallower head), influenced by increased sea surface flow and colder sea surface temperatures mainly during spring, and the second morphotype had robust larvae (shorter and deeper head) under slower current flow and warmer sea surface temperatures during winter and summer. We concluded that changes in larval body shape are influenced mainly by sea surface flow and sea temperatures, probably associated with the ability to reach higher swimming speeds during feeding success. [ABSTRACT FROM AUTHOR]

In this study, we examined the feasibility of germ cell‐less hybrids, produced by a cross between female blue mackerel (Scomber australasicus) and male chub mackerel (S. japonicus), as recipients in order to develop a surrogate broodstock technology for mackerels, which is attracting attention as a new aquaculture target. Donor testicular cells, isolated from the testes of a chub mackerel, were transplanted into the peritoneal cavity of 500 hybrid mackerel larvae. Of the 42 male recipients that survived to 1 year of age, 35 matured and produced donor‐derived chub mackerel sperm. Amongst them, 22 produced only donor‐derived sperm, with none of the recipient's own sperm detected. Two of the six females that survived to 1‐year‐old produced donor‐derived eggs, and one of two matured females produced only donor‐derived eggs. Notably, when the mature recipients were housed in a single fish tank, some spontaneously mated, and normal hatchlings arising from fertilization of donor‐derived chub mackerel eggs and sperm were successfully obtained. Although the efficiency of this method needs to be improved in the future, hybrid mackerel can be used as surrogates for mackerel species breeding. This technology is expected to make a significant contribution to the breeding of mackerels. [ABSTRACT FROM AUTHOR]

Microplastics are one of the major pollution problems nowadays, have been found in both marine environments and various fish species worldwide. In this study, the presence of microplastics in the digestive systems and the gills of 6 species from the Scombridae family on the coast of Karachi in Pakistan was investigated. A total of 336 fish were examined for the presence of microplastic in gills and the digestive systems. Microplastics were detected in digestive systems and gills in 11.11%-19.51% and 58.62%-85.71% of total individuals, respectively. The number of microplastics varied from 0.19 to 1.12 items.ind-1 in digestive system and 1.5 to 7.04 items.ind-1 in gill. Fibre was dominant in both gills (98.67-99.17%) and digestive systems (100%). More extensive and further investigations are needed on microplastic contamination of the biota on the Pakistan coast. [ABSTRACT FROM AUTHOR]

Three decades before, the gillnet was the major gear in Andaman and Nicobar Islands(ANI), India, because of the less expensive and simple method of operation with non-motorised small dinghies or without craft. Earlier, the gillnet landing was 39% of the total landings and a further report said 27%, which indicated the decrease in gillnet landings. The present study was carried out from 2014 to 2018 at four main fish landing centers (FLCs) Junglighat, Dignabad, Guptapara and Wandoor of ANI to investigate the present status of major gillnet landings. Altogether 1097 visits were carried out at all FLCs and 63.1% of visits occurred at Junglighat. The total landings of all FLCs were 3880.6 tons, of which 98.6% were recorded at Junglighat. The total gillnet landings were 330.4tons, of which Driftnet covered 82.1%, followed by bottom plastic(9.8%) and bottom nylon(8%) gillnets. Significant landings (P<0.0001) of Scombridae family were recorded through Drift gillnet (182.47tons) compared to other families. The family of Carangidae(7.71tons) and Clupeidae(16.54tons) were recorded dominantly through bottom plastic and bottom nylon gillnets, respectively. The gillnetters explored 31 fishing grounds in the South, Middle, North and Little Andamans sectors. The significant (P<0.0001) fish catch was recorded from the South Andaman sector. A total of 17 validation experiments carried out in each Potential Fishing Zone (PFZ) and Non-PFZ by using PFZ advisories indicated a significant(P<0.0001) catch from PFZ(3.5:1). There was a decline of 18.5% in the landings of gillnet than earlier studies. It is suggested that the fishermen may follow the PFZ forecast for a better catch. The gillnet fishing to be promoted to under-exploited pelagic fishes of these islands will benefit the gillnetters. [ABSTRACT FROM AUTHOR]

This study presents information about trophic relationships between juvenile albacore (ALB, Thunnus alalunga) and skipjack tuna (SKJ, Katsuwonus pelamis) in the Gulf of Cadiz (East Atlantic Ocean). Data on stomach contents (SCA) and stable isotope ratios of carbon and nitrogen (SIA) were analyzed to ascertain foraging patterns and trophic niche breadths and overlapping. SCA showed that European anchovy (Engraulis encrasicolus) and Atlantic chub mackerel (Scomber colias) were the most important prey species in both tuna species. A PERMANOVA analysis of the SCA data revealed interspecific differences in the diet (p < 0.05). δ15N and δ13C values from ALB muscle and liver tissues were higher than those from SKJ samples. As with SCA, the PERMANOVA analysis of isotopic data indicated significant interspecific differences in both muscle and liver samples (p < 0.01). Isotopic trophic niche values estimated by Bayesian standard ellipse corrected areas (SEAC) showed low (muscle) or no (liver) overlap between ALB and SKJ. Taken together, the present results suggest that, although juveniles of the two species fed for an extended period of time in the same area and shared some prey species, there is evidence of food resource partitioning, thus preventing trophic competition. [ABSTRACT FROM AUTHOR]

One of the most promising aquaculture species is the Atlantic bluefn tuna (Thunnus thynnus) with high market value; disease control is crucial to prevent and reduce mortality and monetary losses. Microsporidia (Fungi) are a potential source of damage to bluefn tuna aquaculture. A new microsporidian species is described from farmed bluefn tunas from the Spanish Mediterranean. This new pathogen is described in a juvenile associated with a highly severe pathology of the visceral cavity. Whitish xenomas from this microsporidian species were mostly located at the caecal mass and ranged from 0.2 to 7.5 mm. Light and transmission electron microscopy of the spores revealed mature spores with an average size of 2.2 x 3.9 μm in size and a polar flament with 13--14 coils arranged in one single layer. Phylogenetic analysis clustered this species with the Glugea spp. clade. The morphological characteristics and molecular comparison confrm that this is a novel microsporidian species, Glugea thunni. The direct life-cycle and the severe pathologies observed makes this parasite a hard risk for bluefn tuna cultures. [ABSTRACT FROM AUTHOR]

The feeding ecology of juvenile Pacific bluefin tuna (PBF) Thunnus orientalis in the Sea of Japan was examined to better understand the survival process before fishery recruitment. Stomach content analysis showed that the main prey items were fish, especially Japanese anchovy Engraulis japonicus, cephalopods, mainly small squid Enoploteuthis chunii, and copepods. In addition, although both fish prey and cephalopods were important for large juveniles (100-300-mm fork length, FL), the stomach contents of small juveniles (40-99 mm FL) mainly included fish prey. The strong possibility of cannibalism was also suggested, although its contribution to total food consumption was limited. The size of fish prey increased significantly with the FL of PBF. Nitrogen isotope ratios (i.e. δ15N) also increased with increasing FL (12-227 mm), suggesting that the trophic level increases rapidly during the juvenile stage because of the active feeding on fish by PBF. Such feeding habits, especially feeding on fish, would be essential to achieve a high growth rate and would therefore be associated with the survival of juvenile PBF before recruitment in the Sea of Japan. In addition, PBF exhibited a decrease in stomach fullness during the night-time, and their estimated gastric evacuation rate was 0.36 h-1. [ABSTRACT FROM AUTHOR]

Despite being an important source of wealth and food security for many countries, most of the small tuna stocks in the Atlantic Ocean and Mediterranean Sea remain unassessed. In this study, we summarized the current state of knowledge of this group of species reviewing the information available on life history parameters, stock structure, historical catches, size frequency distributions and current knowledge of stock status. In relation to the life history parameters, data are overall scarce and mainly missing in the Eastern Atlantic where small tunas are relevant in small-scale fisheries. From the 27 defined stocks, only 11 have been quantitatively assessed. From those, the Northwest wahoo and the Southeast little tunny stocks may be experiencing overfishing, deserving priority management attention. Length-based rather than catch-based methods showed a more promising applicability for small tunas, although representative length distributions from the catch are scarce for some stocks. Historical catch time series for small tuna are still incomplete, however, the last two decades are the most accurate and could be considered in future assessment methods. The gaps of knowledge related mainly to life history parameters and historical catches are the main reason why most of these stocks remain unassessed and unmanaged. [ABSTRACT FROM AUTHOR]

Background: The bullet tuna (Auxis rochei) is an epipelagic fish with a worldwide distribution that is highly targeted by fisheries. Genetic diversity and population genetics are good indicators of population structure and thus, essential tools for fisheries management. Knowing which factors (biotic and abiotic) might be shaping such structure is crucial for management plans. In the present study, we assessed the population structure of the bullet tuna in the western and central Mediterranean Sea. Methods: We used two types of genetic data: the mitochondrial DNA control region and seven microsatellite loci. The analysis of 431 sequences with a length of 386 bp from the mtDNA CR and the results from 276 individuals were genotyped by seven microsatellite loci. Results: Both types of markers coincided in showing significant genetic differences between an Iberian Peninsula–Strait of Gibraltar stock in comparison with a North African stock. Conclusions: We argue that this differentiation pattern is likely caused by reproductive strategies such as coastal spawning, larval retention, and natal homing behavior. These results should endorse the implementation of management plans for a resource that currently is not being managed. Thus, to ensure sustainability, these new policies should consider the presence of at least two genetically identified stocks.

Abstract In fisheries, the phenomenon known as fishing down food webs is supposed to be a consequence of overfishing, which would be reflected in a reduction in the trophic level of landings. In such scenarios, the resilience of carnivorous, top predator species is particularly affected, making these resources the first to be depleted. The Serra Spanish mackerel, Scomberomorus brasiliensis, exemplifies a predator resource historically targeted by artisanal fisheries on the Brazilian coast. The present work analyzes landings in three periods within a 50-year timescale on the Parana coast, Southern Brazil, aiming to evaluate whether historical production has supposedly declined. Simultaneously, the diet was analyzed to confirm carnivorous habits and evaluate the trophic level in this region. Surprisingly, the results show that from the 1970’s to 2019 Serra Spanish mackerel production grew relatively to other resources, as well as in individual values. The trophic level was calculated as 4.238, similar to other Scomberomorus species, consisting of a case where landings increase over time, despite the high trophic level and large body size of the resource. The results agree with a recent global assessment that has demystified a necessary correlation between high trophic level and overexploitation, but possible factors acting on the present findings are discussed.

The Atlantic chub mackerel (Scomber colias) is an important commercial fish species of the North-east Atlantic. Two-year-old individuals collected between January and April of 2018 at six sampling locations (45 fish per site) of the North-east Atlantic (Azores, Madeira, Canaries and mainland Portugal – Matosinhos, Sesimbra and Portimão) were used for body morphometrics and otolith-shape analyses. Data were analysed by univariate and multivariate statistics. Re-classification success using shape analyses and body morphometrics showed an overall rate of 51 and 74% respectively. Regional differences regarding the otolith-shape analyses suggested a single stock, not necessarily homogenous, with a discrete separation of two main groups (oceanic islands and mainland Portugal). However, body morphometrics showed a more detailed separation in two main groups (Canaries and the others, but with a slight differentiation between fish from Azores-Madeira and mainland Portugal). Moreover, joint analyses gave an overall re-classification success of 82% and allowed a more comprehensive scenario, showing the existence of three main groups (Canaries, Azores-Madeira and mainland Portugal). Regional differences are probably related with different oceanographic conditions influencing the feeding regime and fish growth. The hereby data suggest that S. colias caught in the North-east Atlantic are different population units, and we recommend a fishery management at a finer regional scale. Two-year-old Atlantic chub mackerels (Scomber colias) collected between January and April of 2018 at four main regions of the North-east Atlantic were used for body geometric morphometrics and otolith-shape analyses. Data suggested that S. colias in these main fishery areas is not a homogenous single stock, and should be regarded as different population units for fisheries management purposes. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the presence of anisakids in three Scombridae fish species from Tunisian coasts (Mediterranean Sea): Scomber japonicus, Scomber scombrus and Auxis rochei. A total number of 188 chub mackerel (S. japonicus), 32 Atlantic mackerel (S. scombrus) and 31 bullet tuna (A. rochei), were collected from four Tunisian regions: Bizerte, Tunis, Nabeul and Mahdia. The parasite specimens were morphologically identified as Anisakis spp. type I larvae. 87.1% of bullet tuna were infected, followed by Atlantic mackerel (56.3%) and chub mackerel (20.7%). Prevalence, mean intensity and mean abundance values varied from one region to another. The majority of larvae were recovered in the visceral cavity. In 4% of examined fish, Anisakis spp. larvae were isolated from muscles. Moreover, the level of infection was associated with seasons, and the highest prevalence was registered during summer. The data suggest that studied fish species may present high-risk for anisakiasis zoonotic disease, and that parasitological control of seafood should be reinforced in order to protect consumers. [ABSTRACT FROM AUTHOR]

The Spanish mackerel Scomberomorus brasiliensis is an epipelagic species with coastal habits and is a fundamental part of artisanal fishing along the Brazilian coast as a species with high economic value. The present work aimed to report the first occurrence of Cybicola buccatus (Copepoda) in S. brasiliensis in northeastern Brazil. The fish were purchased at the public terminal in Aracaju/SE between March 2016 and June 2019 and transported to the laboratory for identification, necropsy and parasite collection. Of the sixteen fish analysed, six were parasitized by C. buccatus with a prevalence of 37.50%, an mean intensity of 1.33 and an mean abundance of 0.50. This occurrence is a new record of this ectoparasite for the locality, as it had not yet been reported in S. brasiliensis on the northeastern coast of Brazil. The results presented here contribute to the existing knowledge about the distribution of this copepod and the parasitic fish fauna along the Brazilian coast. [ABSTRACT FROM AUTHOR]

In response to perceived, but unknown variation among the size selection of narrow-barred Spanish mackerel (Scomberomorus commerson) by artisanal gillnetters off Iran, and the need for such data to control exploitation as a precursor to balanced harvesting, the effects of two common mesh sizes (130 and 140 mm stretched mesh opening made from multifilament twine) on catches were investigated over one fishing year (nine months encompassing autumn to spring). Both mesh sizes mostly caught S. commerson at fork lengths (FL) larger than mean sizes at maturity (>67 cm), with the mean size selection incrementally increasing in the 130-mm mesh gillnet from autumn, and especially during spring. The greater selection occurred concurrent with an increasing condition factor (CF) among S. commerson, which typically spawn in late spring/early summer. Conversely, the relative size-selection of the 140-mm mesh gillnet decreased in spring, attributed to increasing CF precluding the capture of larger fish. Such seasonal variation in size selection might be countered by increasing mesh size to ~145 or 150 mm in spring. However, the existing 140-mm mesh might positively affect stock biomass by allowing larger, more fecund fish to avoid capture during spawning. The data support the strong influence of biological and environmental factors on gillnet size selection, which might also extend to other migratory, pelagic species. [ABSTRACT FROM AUTHOR]

Se encontraron seis especímenes de Scomber japonicus peruanus (Jordan y Hubbs, 1925) de Curiñaneo (39°41?S; 73°22?W), Chile. Este es el nuevo límite más austral de la distribución de la especie en la costa chilena (500 km más al sur de Valparaíso). A partir de la presencia de esta especie y de los clasmobranquios Myliobatis chilensis y Galeorhinus zyopterus en la zona alrededor de los 40°S, se presenta una discusión sobre el calentamiento periódico de la masa de agua, lo que permite la extensión de especies de aguas más cálidas en estas aguas frías.

The distribution and early growth of juvenile Pacific bluefin tuna (PBF) Thunnus orientalis were studied based on trawl surveys conducted around Sado Island, eastern Sea of Japan, from late August to early September in 2017 and 2018. Juvenile PBF were mainly collected in an area between the Tsushima Warm Current and land where the surface water (5-m depth) temperature ranged from 22.8 to 27.2 °C. The fork length (FL) of the fish ranged from 12 to 320 mm, and there were modes at 140–170 mm FL in the frequency distribution for both years. In 2018, there was also a mode at around 50 mm FL. Otolith microstructure analysis revealed that hatch date mainly peaked in early and mid July in both years, and in early and mid August in 2018, and corresponded with the modes of FL. In addition, differences in growth were observed between year classes, and between size classes in 2018. Total gill raker number increased with FL and was almost constant at around 100 mm FL. This study provides an update of the distribution of juvenile PBF in the Sea of Japan, which was found to be related to the Tsushima Warm Current, and indicates the importance of the eastern Sea of Japan as a nursery ground for PBF that hatch from July to August. [ABSTRACT FROM AUTHOR]

Many large predatory fishes are in decline and tuna sustainability is high on the global agenda. Slender tuna (SLT), Allothunnus fallai, is data‐poor and a rare contemporary example of a globally unexploited temperate tuna. This study analysed 214 otoliths for age and growth of fish collected in the South Atlantic. Observed ages varied between 9 and 42 years for a size range of 68–90 cm fork length. We reveal important life history data for SLT before exploitation and underline the relevance of data‐poor stocks in understanding wider questions for exploited tuna. [ABSTRACT FROM AUTHOR]

We developed a simple dry shipper method for cryopreserving the sperm of Scombridae fish in outdoor environments. First, we undertook a preliminary study to optimize the sperm cryopreservation conditions using bullet tuna, Auxis rochei (Risso, 1810) sperm. We found that the optimum cryomedium contained 90% foetal bovine serum (FBS) or 300 mM trehalose as an external cryoprotectant and 10% dimethyl sulfoxide (DMSO) as an internal cryoprotectant. Under these optimized conditions, the post‐thaw sperm had a duration of motility of 500 s and a motility rate of >70%. We then performed practical trials of the optimized protocol in various outdoor environments (e.g., fishing boats and ports) using the sperm of five Scombridae species: chub mackerel, Scomber japonicus (Houttuyn, 1782); blue mackerel, S. australasicus (Cuvier, 1832); skipjack tuna, Katsuwonus pelamis (Linnaeus, 1758); longtail tuna Thunnus tonggol, (Bleeker, 1851) and Pacific bluefin tuna, T. orientalis (Temminck & Schlegel, 1844). The post‐thaw sperm of all five of these species had a duration of motility of 650 s and a motility rate of >70%, indicating that this simple method can be used to obtain high‐quality cryopreserved sperm of various Scombridae species in outdoor environments. [ABSTRACT FROM AUTHOR]

The morphology and morphometry of olfactory systems of three fishes; Scomberoides commersonnianus, Rastrelliger kanagurta and Sphyraena obtusata were explored. The olfactory organs are round in S. commersonnianus and oval in the other two species. In the present study, 19 olfactory morphometric characters and 6 ratios (of some of the traits) are quantified. In the selected species, the mean values of all the traits and ratios were significantly different among the species (p < 0.001). The correlations between all olfactory traits and total length, standard length, head length and body weight are significant for all the species (p < 0.001). Principal Component Analysis revealed that the olfactory systems of studied species are dissimilar (both in size and shape) while, Cluster Analysis depicted that the difference is greater between the olfactory system of S. obtusata and the other two species. The traits that chiefly discriminate the olfactory systems of targeted species are length of both nostrils; length, width and volume of olfactory organ. [ABSTRACT FROM AUTHOR]

The present study assesses length-weight relationship (LWR) of Auxis thazard, Auxis rochei, Euthynnus affinis, and Katsuwonus pelamis caught by gill net along the Tuticorin coastal area. The fitted regression model resulted (log-transformed) in slope values extending from 2.9 to 3.8. The logarithmic data exhibiting the exponent value b > 3 and b < 3, confirms that the tuna species showed both negative and positive allometric growth. Particularly, K. pelamis (b < 3) indicated the negative allometric growth. The regression slope value for all the species was found to be highly significant (P < 0.05). All the species showed positive allometric growth, except K. pelamis, which exhibited negative allometric growth. Findings in the present study conclude that LWR does not follow the cubic relationship. Furthermore, studies should be carried out for more fish species to enlighten biologists about the status and growth condition of the fishes in the natural waters. [ABSTRACT FROM AUTHOR]

Near reef abundance and coast–offshore distribution of tuna larvae around Minicoy Island were studied based on three cruises carried out on board FORV Sagar Sampada during 2014–15. The samples were collected by oblique tows using bongo twin nets (300 micron) for three seasons (Fall inter-monsoon (FIM), Spring inter-monsoon (SIM) and Summer monsoon (SM)) in six on–offshore stations ranging from 1 to 20 km off-shore of the Minicoy. Results indicated that the tuna larvae aggregate in the near reef waters and total tuna larvae abundance (all the species combined) shows a decreasing trend towards off-shore. Tuna larvae are found to be more abundant during SM and FIM. Comparison of the species-wise variation in tuna larvae for one season (SM) indicated that the larvae of Euthunnus affinis (32.5%) dominated among the tuna species, followed by Auxis spp. (31.6%), Thunnus spp. (3.9%) and Katsuwonus pelamis (2.7%). A pattern of highest larvae abundance in the near reef areas was observed except for Thunnus larvae. GAM indicated that mean seawater temperature and mean seawater salinity are the major environmental factors that significantly influence the larvae abundance, particularly for Thunnus followed by Katsuwonus pelamis, E. affinis and Auxis spp. The study confirms that the environmental parameters show high variation between stations and among transects as a result of the complex oceanographic characteristics around the islands. Further studies with better understanding of the larvae dynamics and their association with the environmental parameters including physical processes are essential to elucidate these relationships more clearly. [ABSTRACT FROM AUTHOR]

A new genus and species of scombrid fish Caucombrus histiopterygius gen. et sp. nov. is described from the Lower Oligocene (Lower Maikopian, Pshekha regional state) of the north-western Caucasus (Russia) and Abkhazia (rivers Belaya, Pshekha and Gumista). The new taxon differs from the other known Scombridae, both fossil and Recent, by the high and sail-like first dorsal fin. Osteological characters of Caucombrus gen. nov. indicate its relationship with the Spanish mackerels (subfamily Scomberomorinae). It is assumed that either C. histiopterygius gen. et sp. nov. or the related species of Caucombrus gen. nov. inhabited the Mid-Oligocene sea basin in the territory of the Rhine Graben (Germany). [ABSTRACT FROM AUTHOR]

This dissertation describes gill specializations related to fast, continuous swimming in tunas, bonitos, and mackerels (family Scombridae), the billfishes (Istiophoridae, Xiphiidae) and the shortfin mako, Isurus oxyrinchus (Lamnidae). These fishes all require gill adaptations for increased gas exchange to meet relatively high aerobic demands and for added rigidity to withstand the forceful branchial flow produced by ram ventilation. Preliminary research for this dissertation, included as an appendix chapter and published as Wegner et al. (2006), examined gill specializations in the striped marlin, Kajikia audax (formerly Tetrapturus audax ), and the wahoo, Acanthocybium solandri, and sets the stage for Chapters 1-4. Chapter 1 documents changes in scombrid and billfish gill morphometrics which augment gill surface area above that of other fish groups and increase branchial resistance to slow and streamline ram-ventilatory flow. Many scombrids and billfishes also have gill fusions which provide support and secure the spatial relationship of filaments and lamellae. Chapter 2 details the structure, function, and distribution of these fusions within different species; they are most complex in large tunas and billfishes, which are obligate ram ventilators, but are absent in mackerels, which utilize active ventilation at slower swimming speeds. Chapter 3 investigates the convergence of mako and tuna gill structure in relation to high aerobic demands and ram ventilation and shows that although makos have relatively larger gill surface areas and shorter diffusion distances than those of other shark species, these features are not as specialized as those of tunas. This work suggests that differences in the gill design of elasmobranchs and teleosts may limit mako gill surface area and ultimately constrain mako aerobic performance in comparison to tunas. Chapter 4 tests this hypothesis with in vivo studies of gill function in makos swimming in a water tunnel. Mako gills are similar to those of tunas in terms of oxygen utilization, the total pressure gradient driving the ventilatory stream, and flow conditions along the respiratory surfaces. However, the interbranchial septum, an intrinsic feature of the shark gill, greatly contributes to mako branchial resistance, and this is compensated by changes to gill dimensions that ultimately limit gill surface area.

The complete mitochondrial genome of the doubled-lined mackerel, Grammatorcynus bilineatus, was determined by the combination of high-throughput sequencing (HTS) and Sanger sequencing. The constructed mitochondrial genome of G. bilineatus was 16,537 bp in length, which harbors a canonical 37 genes (13 proteins, two ribosomal RNAs, and 22 tRNAs) and two non-coding regions (origin of light-strand replication (OL) and the D-loop control region). Among 38 genes, nine were encoded on its light strand (L), while the other 28 were on its heavy strand (H). Besides COX1 (GTG) and ATP6 (CTG), the other eleven protein-coding genes (PCGs) begin with a typical start codon (ATG). The phylogenetic tree showed that G. bilineatus was not clustered with the other species in the Scombridae, forming a clade for Grammatorcynus. The genetic information of G.bilineatus will provide useful information for the scientific management and conservation of the species in the genus.

Vertebrate bone is composed of three main cell types: osteoblasts, osteoclasts and osteocytes, the latter being by far the most numerous. Osteocytes are thought to play a fundamental role in bone physiology and homeostasis, however they are entirely absent in most extant species of teleosts, a group that comprises the vast majority of bony 'fishes', and approximately half of vertebrates. Understanding how this acellular (anosteocytic) bone appeared and was maintained in such an important vertebrate group has important implications for our understanding of the function and evolution of osteocytes. Nevertheless, although it is clear that cellular bone is ancestral for teleosts, it has not been clear in which specific subgroup the osteocytes were lost. This review aims to clarify the phylogenetic distribution of cellular and acellular bone in teleosts, to identify its precise origin, reversals to cellularity, and their implications. We surveyed the bone type for more than 600 fossil and extant ray‐finned fish species and optimised the results on recent large‐scale molecular phylogenetic trees, estimating ancestral states. We find that acellular bone is a probable synapomorphy of Euteleostei, a group uniting approximately two‐thirds of teleost species. We also confirm homoplasy in these traits: acellular bone occurs in some non‐euteleosts (although rarely), and cellular bone was reacquired several times independently within euteleosts, in salmons and relatives, tunas and the opah (Lampris sp.). The occurrence of peculiar ecological (e.g. anadromous migration) and physiological (e.g. red‐muscle endothermy) strategies in these lineages might explain the reacquisition of osteocytes. Our review supports that the main contribution of osteocytes in teleost bone is to mineral homeostasis (via osteocytic osteolysis) and not to strain detection or bone remodelling, helping to clarify their role in bone physiology. [ABSTRACT FROM AUTHOR]

Mesoscale oceanic features such as eddies generate considerable environmental heterogeneity within the pelagic oceans, but their transient nature makes it difficult to identify both their spatial and temporal extent and their effects on the distribution of pelagic fauna. Simplifying these complex features using a biologically meaningful classification system will likely be a useful first step in understanding the extent of their influence in structuring openocean ecosystems. In this study, we present a tool to classify the pelagic environment in the Gulf of Mexico using seasurface height and temperatureatdepth data from the 1/25° GOM HYbrid Coordinate Ocean Model (HYCOM). Three "water types" were identified: Loop Currentorigin water (LCOW), Gulf common water (CW), and mixed (MIX) water, where the latter represents an intermediate state during the degradation of LCOW to CW. The HYCOMderived classifications were validated against in situ CTD data and microbial samples collected through 2015–2016 by the Deep Pelagic Nekton Dynamics of the Gulf of Mexico (DEEPEND) consortium. The validation data comprised classifications derived from both temperaturedepth (TD) and temperaturesalinity (TS) profiles and from microbial community analyses from the surface to mesopelagic depths. The HYCOM classifications produced an overall agreement rate of 77% with the TS/TD classifications, and 79% with the microbial classifications. With applicability across a wide range of spatial and temporal scales, we believe that the system provides a useful, complementary tool for biological oceanographers and resource managers interested in better understanding the effects of major mesoscale features on the pelagic biota. [ABSTRACT FROM AUTHOR]

Background: Digenean trematodes of the family Didymozoidae are tissue parasites that are particularly common in scombrid fish. These parasites can reduce the commercial value of fish, especially the ones occurring in the muscle. Purpose: In the present study and for the first time, we report the occurrence of didymozoids in muscle tissue of Atlantic chub mackerel (Scomber colias) collected in northeast Atlantic (Portuguese coast). Methods: The entire musculature of 64 Scomber colias was removed and examined macroscopically and under a stereomicroscope to search for parasites. Results: The prevalence (3.1%) and abundance (0.03) of infection detected were quite low, but the parasites cause muscle softening decreasing the quality of the infected fish. If the infection levels increase, this may constitute a cause of concern for the fisheries and canning industry. Conclusion: Didymozoids identified in this study are closely related to muscle parasites detected in other fish species of the genus Scomber, most probably the same species. Phylogenetic analysis also corroborates the hypothesis that muscle-parasitizing didymozoids are distinct from the ones parasitizing other fish organs. [ABSTRACT FROM AUTHOR]

Measuring the demographic parameters of exploited populations is central to predicting their vulnerability and extinction risk. However, current rates of population decline and species loss greatly outpace our ability to empirically monitor all populations that are potentially threatened.The scale of this problem cannot be addressed through additional data collection alone, and therefore it is a common practice to conduct population assessments based on surrogate data collected from similar species. However, this approach introduces biases and imprecisions that are difficult to quantify. Recent developments in hierarchical modelling have enabled missing values to be reconstructed based on the correlations between available life‐history data, linking similar species based on phylogeny and environmental conditions.However, these methods cannot resolve life‐history variability among populations or species that are closely placed spatially or taxonomically. Here, theoretically motivated constraints that align with life‐history theory offer a new avenue for addressing this problem. We describe a Bayesian hierarchical approach that combines fragmented, multispecies and multi‐population data with established life‐history theory, in order to objectively determine similarity between populations based on trait correlations (life‐history trade‐offs) obtained from model fitting.We reconstruct 59 unobserved life‐history parameters for 23 populations of tuna that sustain some of the world's most valuable fisheries. Testing by cross‐validation across different scenarios indicated that life‐histories were accurately reconstructed when information was available for other populations of the same species. The reconstruction of several traits was also accurate for species represented by a single population, although credible intervals increased dramatically.Synthesis and applications. The described Bayesian hierarchical method provides access to life‐history traits that are difficult to measure directly and reconstructs missing life‐history information useful for assessing populations and species that are directly or indirectly affected by human exploitation of natural resources. The method is particularly useful for examining populations that are spatially or taxonomically similar, and the reconstructed life‐history strategies described for the principal market tunas have immediate application to the world‐wide management of these fisheries. The described Bayesian hierarchical method provides access to life‐history traits that are difficult to measure directly and reconstructs missing life‐history information useful for assessing populations and species that are directly or indirectly affected by human exploitation of natural resources. The method is particularly useful for examining populations that are spatially or taxonomically similar, and the reconstructed life‐history strategies described for the principal market tunas have immediate application to the world‐wide management of these fisheries. [ABSTRACT FROM AUTHOR]

The larval growth of Pacific bluefin tuna (Thunnus orientalis) was compared between two main spawning areas, the Sea of Japan (SOJ) and the western North Pacific (WNP). Growth trajectories indicate that the larval survival depends on their growth in both areas. Until the flexion stage, larvae of the SOJ showed lower growth than those of the WNP, but after the post-flexion stage, there was no significant differences in larval growth between two areas. The observed growth differences were likely driven by the sea surface temperature (SST): the lower SST in the SOJ negatively affected the larvae until they reached to the flexion stage. Survival over the flexion stage is one of the major ontogenetic milestones during the larval development in the SOJ. Chlorophyll-a concentrations were negatively correlated with SST and tended to be higher in the SOJ than in the WNP. Prey availability was presumed to be higher in the SOJ. As larval swimming and feeding abilities improved with flexion, larvae would have been able to capitalize on the favorable feeding environment in the SOJ, thus eliminating the temperature mediated growth difference in pre-flexion larvae. [ABSTRACT FROM AUTHOR]

Biological aspects of butterfly kingfish Gasterochisma melampus were examined using Japanese longline fishery data and research data collected for over 20 years. Butterfly kingfish were distributed in a continuous band around the circumpolar region between 35°S and 45°S. The southern limit of distribution corresponded with the sub-Antarctic front. The estimated global total annual catch for butterfly kingfish ranged from 613 to 3699 t (mean 1859 t) with Japan taking the largest proportion of the total catch. Large, adult butterfly kingfish spawn in the south-eastern Pacific, whereas smaller, immature fish are distributed in feeding grounds in the area extending across the Atlantic and Indian Oceans to the south-western Pacific Ocean. Catch per unit effort (CPUE) data for fish in the feeding grounds from 1993 to 2016 were compared with the CPUE value from 1970. These data indicate that the stock is currently not likely to be depleted. [ABSTRACT FROM AUTHOR]

Hermaphroditic gonads were collected from three skipjack tuna Katsuwonus pelamis in the western and central Pacific Ocean. Both ovarian and testicular tissues were found in the same gonad lobe for each of the three fish. Histological sections of the hermaphroditic gonad from one K. pelamis showed postovulatory follicles, which is evidence of spawning. [ABSTRACT FROM AUTHOR]