Chub Mackerel Scomber Japonicus Research Articles

Influence of ice storage period before freezing on quality of frozen chub mackerel Scomber japonicus fillets and considerations regarding high-quality frozen sashimi products

Influence of ice storage period before freezing on quality of frozen chub mackerel Scomber japonicus fillets and considerations regarding high-quality frozen sashimi products

Development of a polymerase chain reaction (PCR)-based genetic sex identification method in the chub mackerel Scomber japonicus and blue mackerel S. australasicus

Chub mackerel Scomber japonicus and blue mackerel S. australasicus have become important aquaculture target species in Japan. For an efficient and stable aquaculture production of mackerels, it is desirable to work with a female-biased broodstock and thus to be able to manage precisely their sex ratio. As these two mackerel species do not have any external sexual dimorphism, direct biopsy of the gonads or measurement of sex hormone plasma levels is used in research to determine their phenotypic sex. However, these methods are associated with handling stress that results in gonadal atresia. Besides, it is difficult to identify sex using these methods in immature individuals. Therefore, genetic sexing would be desirable in these species to overcome these problems. In this study, we developed molecular sex identification tools for both chub and blue mackerels using sex-specific single-nucleotide variations (SNVs) identified by pool-sequencing (pool-seq) analyses. Genomic DNA was isolated from 30 males and females, in each species, and sequenced as pooled samples. Results of these pool-seq analyses identified a clear XX/XY male heterogametic sex-determination system in blue mackerel and a ZZ/ZW female heterogametic system in chub mackerel. Using this pool-seq information, we designed primer sets for genetic sex identification in both species. Results demonstrated that these primer sets are robust and accurate in assessing the genotypic sex of both blue and chub mackerels (accuracy > 99.5% in the chub, and > 94.5% in the blue mackerel) in various geographical samples of different ages. This method can now be applied for the efficient management of sex ratios in both mackerel aquaculture populations and wild-caught animals for fisheries management.

Information support for chub mackerel Scomber japonicus fishery in the Pacific waters of the Russian Federation

Methods of machine learning were applied for forecasting of chub mackerel fishing grounds in the South Kuril fishery district. The problem of perspective fishing area definition was reduced for a binary classification task, i.e. the sets of environmental conditions corresponded with presence or absence of fishing operations were determined for each point within the district. The fishery statistics for 2016–2020 and the data on SST with delay of 4–7 days from the date of catch, spatial SST gradients calculated using Belkin algorithm, and day-to-day SST variations were processed using LightGBM machine learning algorithm. The model was trained on the data for 2016–2019 and verified on the data for 2020. The AUC (as an aggregate measure of performance across all possible classification thresholds) varied from 0.65 to 0.92. In the fishery season of 2020, AUC was 0.69, on average, growing to 0.75 in the period of the highest catches. Approximately 75 % of the annual catch of chub mackerel was caught at the predicted sites in 2020; this portion reached 84 % in the period of the highest catches.

Diet Composition of the Chub Mackerel Scomber japonicus in the Coastal Waters of the South Sea of Korea

Diet Composition of the Chub Mackerel Scomber japonicus in the Coastal Waters of the South Sea of Korea

Length–length and Length–weight Relationships for Four Dominant Small Pelagic Fishes in the Kuroshio–Oyashio Current System

Length–length and length–weight relationships in various length measurement standards were estimated for dominant small pelagic fishes in the Kuroshio–Oyashio current system (Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, chub mackerel Scomber japonicus, and spotted mackerel Scomber australasicus). Fish samples were collected from surface–midwater trawl surveys and commercial purse-seine fisheries between September and October of 2020 in the western North Pacific. Total length (TL), fork length (FL), and standard length (SL) were measured to 0.01 cm, and total body weight (W) was measured to the nearest 0.01 g for each individual. All length–length relationships (TL–FL, TL–SL, and FL–SL) were highly significant (p 0.98 in all species. Length–weight relationships (W–TL, W–FL, and W–SL) were also highly significant (p 0.98 in all species. This study provides new comprehensive information on length–length and length–weight relationships in various length measurement standards for the four small pelagic fish species. These data will be useful references for biological studies and stock assessments of these small pelagic fishes.

«Wrong fish» or wrong hypotheses: what happens to nekton of the Pacific waters at Kuril Islands?

A phenomenon of undulating fluctuations of nekton abundance in the Kuroshio system is discussed on example of japanese sardineSardinops melanostictus, as the most abundant and the most fluctuating species. The so-called «sardine epochs» are distinguished according to this species abundance. The last such epoch ended in the early 1990s. Since 2014, structural changes occurred again in the nekton communities of the Pacific waters off Kuril Islands, caused by expansion of southern fish and squid species, primarily japanese sardine and chub mackerelScomber japonicus, and decreasing in abundance of japanese anchovyEngraulis japonicusand sauryCololabis saira. The scope of these changes allowed Russian fishermen to resume the fishery on japanese sardine and chub mackerel in the Russian exclusive economic zone since 2016. Annual catch of Japanese sardine increased steadily from 6,700 t in 2016 to 315,500 t in 2020. Over these 5 years, Russian fishermen landed 531,700 t of sardine and 167,900 t of chub mackerel. However, many Russian fishery forecasters believe that these reconstructions is only a «rehearsal» of the upcoming «sardine epoch», being based on formal climatic indices, without delving into the mechanisms of abundance fluctuations. The authors note that new «sardine epochs» cannot be predicted as completely similar to the previous ones. Several hypotheses on causes of the beginning and end of japanese sardine blooms are considered critically, and the conclusion is made that mechanisms which determine its year-classes strength are still unclear, as well as the reasons of undulating fluctuations of this species and some other nekton species abundance, because of high complexity of this problem.

Establishment of a tracing technique for transplanted bluefin tuna germ cells in recipient’s gonads using monoclonal antibodies specifically recognizing bluefin tuna spermatogenic cells

Our ultimate aim is to establish a small-bodied surrogate broodstock (e.g., mackerel) that produces functional gametes of the Pacific bluefin tuna Thunnus orientalis using xenogeneic germ cell transplantation. To accomplish this goal, we need to be able to sequentially trace transplanted donor cells in recipients. Here we succeeded in identifying two monoclonal antibodies that could specifically recognize the germ cells of bluefin tuna but not of the chub mackerel Scomber japonicus or the eastern little tuna Euthynnus affinis, which are promising recipient species. Using these antibodies, we developed a method to detect transplanted bluefin tuna germ cells in the gonads of xenogenic recipients. Since all stages of testicular germ cells can be recognized by these antibodies, donor germ cells can be observed throughout gametogenesis in the recipient’s gonads. Thus, the antibodies established in this study could be a powerful tool to observe survival, proliferation, and differentiation of the transplanted bluefin tuna germ cells in the gonads of small Scombridae recipients, and evaluate transplantation efficiency.

Evaluating Stock Status of 16 Commercial Fish Species in the Coastal and Offshore Waters of Taiwan Using the CMSY and BSM Methods

The waters around Taiwan are impacted by the Kuroshio and coastal currents, resulting in a high productivity and a high diversity of marine life. As a consequence, there are a multitude of fisheries around Taiwan, conducted by a fleet that has grown enormously in the last four decades. Here, we investigate the effect of the resulting fishing pressure on sixteen commercial fish stocks including demersal and pelagic species in the coastal and offshore waters of Taiwan using the CMSY and BSM methods. Both of these methods required principally catch time series, with the BSM methods also requiring CPUE data. The results show that of the 16 assessed stocks, 10 stocks have collapsed, 2 are severely overfished, 2 are overfished, 1 is slightly overfished and only 1 stock remains in a healthy status; these troubling results are attributed to excessive fishing pressure. However, climate-driven environmental variability may be another factor affecting the fishery resources around Taiwan, as evidenced by chub mackerel Scomber japonicus, the one stock deemed healthy, which is here attributed to favorable environmental condition. Using the fisheries reference points provided here, rebuilding plans could be provided for the other 15 species; however, such plans are not likely to be successful without reducing the size of the Taiwanese fishing fleet.

Feeding ecology of Sardina pilchardus considering co-occurring small pelagic fish in the eastern Adriatic Sea

Small pelagic fish with their significant biomass are connecting plankton production and higher trophic levels in marine ecosystems. The aim of this paper was to analyse feeding habits of sardine Sardina pilchardus (Walbaum, 1792), regarding the season and the spatial area, but also considering trophodynamics of other co-occurring small pelagic fish: anchovy Engraulis encrasicolus (Linnaeus, 1758), round sardinella Sardinella aurita (Valenciennes, 1847), chub mackerel Scomber japonicus (Houttuyn, 1782) and horse mackerel Trachurus trachurus (Linnaeus, 1758) in the eastern Adriatic Sea. Sardine revealed copepods (average contribution 30%), decapod larvae (18%), mysids (15%) and copepod eggs (9%) as their main source of energy. Seasonal oscillations of the sardine fullness index were determined, with highest values in the autumn and spring (%Jr = 0.71 and 0.66, respectively). Spatial analysis showed no significant difference in the diet of fish caught in offshore and coastal waters (ANOSIM, Global r = 0.034; p > 0.05). The ANOSIM test showed a significant difference in prey composition among five investigated species (Global r = 0.081, p < 0.05). The greatest difference in diet was observed between sardine and chub mackerel, as well as between sardine and horse mackerel. While copepods dominated in the sardine, anchovy and round sardinella stomach, horse mackerel and chub mackerel showed selectivity for larger prey as euphausiids, which dominated in terms of numbers, while the most frequent prey were decapod larvae. However, calanoid copepods, fish larvae, decapod larvae, decapod larvae–megalopa stage, copepod eggs, amphipods and isopods were present in the diet of all small pelagic fish. Interspecies diet overlap, besides being significant for marine food web modelling, is particularly important for future fishery management, since investigations in this field are still mostly based on a single-species diet approach.

Maturity and Spawning of the Chub Mackerel Scomber japonicus in the Korean Waters

Maturity and Spawning of the Chub Mackerel Scomber japonicus in the Korean Waters

Molecular characterization of kisspeptin 2 dodecapeptide in sixteen species of Scombridae

Kisspeptin is an endogenous ligand that modulates gonadotropin-releasing hormone (GnRH) secretion and plays an essential role in the reproduction of mammals. In fish, two subtypes of kiss genes (kiss1 and kiss2), which encode kisspeptins, have been reported. Our previous study showed that kisspeptin 2 receptor (KissR2) is highly expressed in the vicinity of GnRH1 neurons, and that centrally administered Kiss2, but not Kiss1, significantly increased gonadotropin synthesis in chub mackerel Scomber japonicus. The results of this latter study suggested that the kisspeptin system plays an important role in chub mackerel reproduction, and that Kiss2 in particular plays a dominant role in the regulation of the central reproductive axis. In the present study, we identified the functional form of Kiss2 peptide in 16 species of Scombridae. All the species possessed kiss2, and the deduced mature peptide had 12 amino acids, all of which were very highly conserved, except for the second amino acid from the N-terminal end that was found to vary across species. However, species specificity of the second residue did not affect signal transduction in chub mackerel KissR2, bluefin tuna Thunnus orientalis KissR2, or Japanese Spanish mackerel Scomberomorus niphonius KissR2. Therefore, the importance of the Kiss2 system, shown in studies of chub mackerel reproduction, may be relevant across all species of Scombridae.

Metabolic measurements and parameter estimations for bioenergetics modelling of Pacific Chub Mackerel Scomber japonicus

AbstractAs a crucial step in developing a bioenergetics model for Pacific Chub Mackerel Scomber japonicus (hereafter chub mackerel), parameters related to metabolism, the largest dissipation term in bioenergetics modelling, were estimated. Swimming energetics and metabolic data for nine chub mackerel were collected at 14°C, a low temperature within the typical thermal range of this species, using variable‐speed swim‐tunnel respirometry. These new data were combined with previous speed‐dependent metabolic data at 18 and 24°C and single‐speed (1 fork length per second: FL/s) metabolic data at 15 and 20°C to estimate respiration parameters for model development. Based on the combined data, the optimal swimming speed (the swimming speed with the minimum cost of transport, Uopt) was 42.5 cm/s (1.5–3.0 FL/s or 2.1 ± 0.4 FL/s) and showed no significant dependence on temperature or fish size. The daily mass‐specific oxygen consumption rate (R, g O2 g fish−1 day−1) was expressed as a function of fish mass (W), temperature (T) and swimming speed (U): R = 0.0103W−0.490 e(0.0457T) e(0.0235U). Compared to other small pelagic fishes such as Pacific Herring Clupea harengus pallasii, Pacific Sardine Sardinops sagax and various anchovy species, chub mackerel respiration showed a lower dependence on fish mass, temperature and swimming speed, suggesting a greater swimming ability and lower sensitivity to environmental temperature variation.

Otolith oxygen isotope analysis and temperature history in early life stages of the chub mackerel Scomber japonicus in the Kuroshio–Oyashio transition region

To determine the temperature history of early life stages of chub mackerel (Scomber japonicus), otolith stable oxygen isotope ratios (δ18Ootolith) of larval and juvenile fish collected in the Kuroshio–Oyashio transition area during 2004–2015 were analyzed, and experienced temperatures were estimated accordingly. The δ18Ootolith values decreased with otolith growth during the larval stage, whereas those for juveniles were positively correlated with otolith radius and increased with increasing otolith size. Combinations of δ18Ootolith values, average otolith daily increment width, and daily age were representative of the differences between better and poorer recruitment years, the former being characterized by earlier spawning and faster growth (resulting from cooler experienced temperatures), and the latter by slower growth. Analyzed fish were sorted into larval and early juvenile growth stages by cluster analysis; the high-growth cluster exhibited higher δ18Ootolith values than the low-growth cluster. The conversion of δ18Ootolith values to water temperature indicated that the higher growth cluster experienced a water temperature ca. 2.0 °C cooler during the later juvenile stage. Therefore, our results suggest the presence of a growth positive spiral, wherein individuals with high initial growth proactively enter cooler water temperature areas, accessing a highly nutritious diet resulting in further rapid growth.

Effects of water temperature and prey density on recent growth of chub mackerel Scomber japonicus larvae and juveniles along the Pacific coast of Boso–Kashimanada

The effects of temperature and prey density on the recent growth rate (RGR) of chub mackerel, Scomber japonicus, were examined. Scomber spp. larvae and juveniles were collected along the Boso–Kashimanada Pacific coast in Japan between March and July in 2015 and 2016. Larvae and juveniles identified as S. japonicus using DNA were subjected to stomach-content and otolith-increment analyses. The effects of temperature and prey density on RGR were analyzed using a generalized linear mixed model (GLMM), which showed that temperature positively affected the RGR of larvae in the body length (BL) classes 11 mm classes and effects of prey density on RGR for larger (> 11 mm) larvae and juveniles were stronger than those for smaller (< 9 mm) larvae. S. japonicus larvae transform into juveniles at around 12 mm BL, and the increased feed demands of juveniles likely lead to prey-density-dependent growth. The otolith increment widths of larvae and juveniles were significantly narrower than those during the same stages in 1-year-old S. japonicus collected from purse seine fisheries operated in the Joban or Kashimanada areas, suggesting growth-dependent mortality.

Interannual Dynamics of the Fish Community’s Integral Characteristics in the Upper Epipelagic Layer of the Pacific Ocean’s Russian Part in June–September 2004–2018

Interannual dynamics of the integral characteristics of species structure in the fish community in the Pacific waters off the Kuril Islands in 2004–2018 is described. During that period, the species richness of the fish community was relatively low: 88 fish and fishlike species (annual average 41.06 ± 1.55) of three classes, 20 orders, 47 families, and 75 genera. It was revealed that species diversity and evenness of species structure are decreased because of subtropical species' mass migrations (chub mackerel Scomber japonicus and Japanese sardine Sardinops melanostictus) to the region in the warm season. Changes in the species structure of ichthyocene occurred in 2013–2014. The values of Simpson dominance index (from 4.85 ± 0.44 to 2.97 ± 0.29) and Pielou evenness species structure (from 0.41 ± 0.04 to 0.21 ± 0.03) decreased, while the measure of the concentration of species richness (Margalef index) did not significantly change (3.43 ± 0.14 on average). The hypothesis of the “Japanese sardine’s Epoch” onset is discussed.

Meat quality of frozen hybrid mackerel (Scomber australasicus × Scomber japonicus)

Frozen sashimi can be stored for a long time and transported over long distances, giving it a distinct advantage over fresh sashimi, and a stable supply of material for frozen sashimi products can be obtained using cultured fish rather than natural resources fish. Hybrids of blue mackerel Scomber australasicus and chub mackerel Scomber japonicus possess unique characteristics that are advantageous in aquaculture, such as a high temperature tolerance. To evaluate the quality of the meat in these hybrids after freezing, we compared the muscle properties of hybrid and chub mackerel that had been reared in a land-based tank. The hybrid mackerel had a lower gonadosomatic index and a higher crude lipid content than the chub mackerel. However, there were no significant differences in the breaking strengths of unfrozen and frozen–thawed muscles between the hybrid and chub mackerel. These findings suggest that the hybrid mackerel may be suitable for use in frozen sashimi products, and that it has unique characteristics that will give it added value as a branded fish.

Draft Genome Sequence of Streptomyces sp. Strain RFCAC02, Isolated from the Gut Microflora of the Pacific Chub Mackerel Scomber japonicus peruanus.

A new strain of Streptomyces sp., strain RFCAC02, was isolated from the gut of the Pacific chub mackerel Scomber japonicus peruanus This strain produces a variety of secondary metabolites. Further bioinformatic analysis revealed the presence of biosynthetic gene clusters putatively coding for compounds related to the polycyclic tetramate macrolactams (PTMs).

The Mitochondrial COI Gene Reveals the Genetic Diversity of Chub Mackerel (Scomber japonicus) in the Taiwan Strait and its Adjacent Waters

The Mitochondrial COI Gene Reveals the Genetic Diversity of Chub Mackerel (Scomber japonicus) in the Taiwan Strait and its Adjacent Waters

한국 연근해에 분포하는 고등어(Scomber japonicus) 난·자치어의 분포특성 및 초기 수송과정 연구

The horizontal distributions of eggs and larvae of chub mackerel Scomber japonicus were extensively surveyed in the vicinity of Korean waters between 31°75''N and 36°50''N during May and June in 2016 and 2017 (total of four sur veys). We used a coupled bio-physical model (DisMELS) that combines an individual-based model (IBM) incorpo rating vertical migration of larvae and temperature-dependent survival to understand transport processes in the early life stage. Using the distributions of eggs and larvae from surveys, the potential spawning grounds were estimated at the northwest and southeast of Jeju Island and the central East China Sea in May, and at the southwestern East Sea and southern West Sea in June by running the model backward in time. In forward experiments within 30 days from the backward results, most larvae were transported to both the Korean and Japanese sides of the East Sea through the Korea Strait. However, the larvae released in the central East China Sea were transported to the Japanese side only, while those released in the southern West Sea were retained within that region. The survival rates at 30 days after release based on the simulation incorporating temperature-dependent survival throughout May and June were 29.7% in 2016 and 28.8% in 2017.

Synchronous multi-species alternations between the northern Humboldt and Kuroshio Current systems

Synchrony of species alternations in the northern Humboldt (NHCS) and Kuroshio (KCS) Current systems was examined by comparing time series data of landings and population statistics of major small pelagic fish species along with climate indices from 1960 to 2015. Target species were anchovy Engraulis ringens, sardine Sardinops sagax, jack mackerel Trachurus murphyi and chub mackerel Scomber japonicus in the NHCS, and anchovy E. japonicus, sardine S. melanostictus, jack mackerel T. japonicus and chub mackerel in the KCS. The time series of total biomass and spawning stock biomass (SSB) of anchovy and sardine for the NHCS and the KCS were well correlated, as were the landings data. Landings of small pelagic fish including jack mackerel and chub mackerel indicated that multi-species alternations may also be synchronous at a community level between the two current systems. Peak landings of jack mackerel and chub mackerel were observed between peaks of anchovy and sardine in both current systems, although the relationships between jack mackerel and chub mackerel differed between the current systems. The species alternations between anchovy and sardine are most reasonably attributable to environmentally-induced changes in the biomass as a major mechanism, although the effect of fishing activity cannot be excluded. Future studies will be required to compare biological characteristics of multiple small pelagic fish species in the pelagic food chain in each current system.