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The chub mackerel (Scomber japonicus) is one of the most influential small pelagic fish in the Northwest Pacific Ocean, and accurate modeling approaches and model selection are critical points in predicting the Scomber japonicus fishing grounds. This study investigated the changes in catches and fishing days on no moonlight and bright moonlight days (2014-2022) and compared the differences in predictive performance between the LightGBM and RF models on three datasets under the two modeling approaches [those based on the light fishing vessels operational characteristics (Approach one) and those not (Approach Two)]. The results were as follows: 1) Stronger moonlight intensity (e.g., full moon) can limit the fishing efficiency of light fishing vessels, with most years showing a trend of a higher percentage of fishing days on bright moonlight days than catches percentage, i.e., no moonlight days resulted in higher catches with lower fishing days; 2) Compared to Modeling Approach Two, under Modeling Approach one, RF model achieved better predictive performance on dataset B, while the LightGBM model achieved better predictive performance on both datasets A and B; 3) Overall, the Approach One achieved more satisfactory prediction performance, with the optimal prediction performance on the complete dataset C improved from 65.02% (F1-score of the RF model, Approach Two) to 66.52% (F1-score of the LightGBM model, Approach Two); 4) Under the optimal modeling approach (Approach One) and the optimal model (LightGBM model), the differences in the importance of the variables on dataset A (no moonlight days) and dataset B (bright moonlight days) were mainly centered on the environmental variables, with CV, SLA, and SSS being the most important in dataset A, and CV, DO, and SLA being the most important in dataset B. This study provides a more scientific and reasonable modeling undertaking for the research of light purse seine fishing vessels, which is conducive to guiding fishermen to select the operating area and operating time of the Scomber japonicus fishery more accurately and comprehensively and realizing the balanced development of fisheries in terms of ecology and economy. [ABSTRACT FROM AUTHOR]

The Northwest Pacific chub mackerel (Scomber japonicus) is one of the most productive, economically important fishery resources worldwide. Accurately assessing this species and ensuring adherence to total allowable catch limits are crucial owing to fluctuations in their abundance and distribution. Acoustic target strength measurements of S. japonicus were conducted at 38, 70, and 120 kHz using a split-beam echosounder of individuals from nine size groups (mean fork length, 10.8–28.3 cm) swimming freely in a net cage within a seawater tank. An underwater camera was utilized to simultaneously measure swimming angle. Least-squares regression analysis revealed that when the slope was constrained to 20, as per the generally applicable morphometric equation, the resulting values for the constant term (b20) were −67.7, −66.6, and −67.3 dB at 38, 70, and 120 kHz, respectively. S. japonicus mean swimming angle across the groups was −10.5–9.6° (standard deviation [SD], 16.3–33.3°). Furthermore, the ratio of swimbladder height to swimbladder length, the ratio of swimbladder length to fork length, and the tilt angle of the swimbladder (mean ± SD) were 0.191 ± 0.060, 0.245 ± 0.055, and 9.6 ± 3.0°, respectively. These results can be used for the acoustic stock assessment of S. japonicus in the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

In order to explore the growth regularity of Scomber japonicus in Northwest Pacific Ocean, 210 samples collected by the "Songhang" from 2021 to 2022 used landmarks based on geometric morphometrics. Compared with other methods, the use of landmark methods can effectively reveal the phenotypic diversity of fish, reflect the changes in fish at different stages, and explore their individual growth regularity. The results showed that there were significant differences in the external morphology of S. japonicus across different fork length groups. Both principal component analysis and multivariate analysis of covariance showed that S. japonicus with smaller fork length had more distinct zones, with overlapping zones among the three different fork length groups. Different fork length groups had the same growth regularities. The growth rate of S. japonicus gradually decreased with increasing fork length. The thin-plate spline indicates that the smaller the fork length of S. japonicus, the smaller their abdomen and tail. The morphology of S. japonicus changes with the change of fork length. The conclusion is that the morphology of S. japonicus gradually changes with increasing fork length in Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

The Northwest Pacific chub mackerel (Scomber japonicus) is one of the most productive, economically important fishery resources worldwide. Accurately assessing this species and ensuring adherence to total allowable catch limits are crucial owing to fluctuations in their abundance and distribution. Acoustic target strength measurements of S. japonicus were conducted at 38, 70, and 120 kHz using a split-beam echosounder of individuals from nine size groups (mean fork length, 10.8–28.3 cm) swimming freely in a net cage within a seawater tank. An underwater camera was utilized to simultaneously measure swimming angle. Least-squares regression analysis revealed that when the slope was constrained to 20, as per the generally applicable morphometric equation, the resulting values for the constant term (b20) were −67.7, −66.6, and −67.3 dB at 38, 70, and 120 kHz, respectively. S. japonicus mean swimming angle across the groups was −10.5–9.6° (standard deviation [SD], 16.3–33.3°). Furthermore, the ratio of swimbladder height to swimbladder length, the ratio of swimbladder length to fork length, and the tilt angle of the swimbladder (mean ± SD) were 0.191 ± 0.060, 0.245 ± 0.055, and 9.6 ± 3.0°, respectively. These results can be used for the acoustic stock assessment of S. japonicus in the Northwest Pacific Ocean.

In this study, 75 chub mackerels that were caught in the Canakkale Strait in Türkiye between October to December, 2019, were examined for the presence of parasites. The length and weight of all fish were measured and the external body area, oral cavity, nostrils, fins, and gills were examined. Gill samples were examined under a stereomicroscope and all suspicious findings were preserved in 99.99% ethanol. The mean length and weight of fish were 24.84±0.39cm and 146.01±7.16 gr, respectively. It was determined that the collected parasite is Grubea cochlear, a monogenic helminth belonging to the Mazocraeidea family. The chub mackerel, in which the specimen of G. cochlera was isolated among the gill filaments, was a female with a total length of 18.5 cm and a weight of 49.80 gr. This finding of Grubea cochlear isolated from the gills of chub mackerel is the first record of this species in this region.

Information on survival and growth during the early life stage is essential to understand the mechanism of interannual variations in fish recruitment. Chub mackerel Scomber japonicus is a commercially important pelagic fish widely distributed in the northwestern Pacific. Its catch showed large fluctuations with changes in distribution and migration under climate change and strong fishing. We determined the hatch dates and growth rates of young-of-the-year of chub mackerel through otolith microstructure using samples collected in the Oyashio water in autumn 2018. Results show that the ages of young chub mackerel ranged between 120 and 180 d, and the estimated hatch date lasted from mid-January to late May with a peak from mid-March to mid-April. Average otolith daily increment width during the early life stages (from hatching to 25 d) showed an increasing trend. Chub mackerel grows slowly in the first 10 d, and then grows faster during the 10th to 25th d. Three groups with dissimilar growth histories and migration routes were identified using unsupervised random forest clustering analysis, but all eventually converge on the same nursery ground. The faster growth of young-of-the-year chub mackerel leads to better recruitment due to the hypothesis of growth-dependent mortality. Most chub mackerels hatched in March and April, the spawning period is longer and earlier, which could lead to strong year classes. These findings on population composition and life history traits of young-of-the-year of chub mackerel provide valuable information on its recruitment processes during the period of stock recovery. [ABSTRACT FROM AUTHOR]

Standardized catch per unit effort (CPUE) data not only yield precise and biologically meaningful abundance indices but also provide crucial insights into the spatio-temporal distribution of fisheries resources, critical for their sustainable utilization and management. In this study, we integrated chub mackerel fishery statistics from the Northwest Pacific Ocean (NPO) and marine remote sensing environmental data, and constructed CPUE standardization models for chub mackerel based on the generalized linear mixed model (GLMM) and spatio-temporal GLMM (Vector Autoregressive Spatio-Temporal, VAST) and evaluated their performance. GLMM is a statistical technique extending GLM with random effects for complex datasets with non-independent observations and correlations or hierarchies. The VAST model is a statistical model for multivariate time series data with observations at different spatial locations, displaying both temporal autocorrelation and spatial dependence. Additionally, influence analysis and simulation testing were employed to quantify the effects of explanatory variables on the differences between nominal CPUE and standardized CPUE, and to assess the estimation accuracy of different models in CPUE standardization, respectively. Finally, the distribution pattern of chub mackerel in the NPO was analyzed by estimating centers of gravity (COGs). The results indicated that: 1) The GLMM model containing all explanatory variables was considered the best model with the smallest conditional Akaike Information Criterion (CAIC), while the VAST model, with only the covariate SST, performed the best. 2) Interactions of year and spatial effects in GLMM and the spatio-temporal variable in VAST, exerted a notable influence on annual standardized CPUE and should be accounted for in the model. 3) Based on simulation testing results, the VAST model exhibited lower model error (root mean square error, RMSE) and model bias, outperforming the GLMM model in CPUE standardization. 4) From 2014 to 2018, chub mackerel exhibited high biomass density widely distributed throughout almost the entire NPO, which shifted to the central-north region from 2019 to 2021. There was no significant northing and easting shift in COGs for the population (P > 0.05). The findings of this research enhance our understanding of the variations in resource abundance indices and spatio-temporal distribution patterns of chub mackerel in the NPO.

Summary: Fish spoilage is significantly influenced by the microbiota composition, in which the specific spoilage organisms are the main factors. In this article, we used the 16S rRNA V3–V4 hypervariable areas of bacteria to assess the microbial community and metabolic function of Scomber japonicus during storage at 4 °C for 9 days. The physicochemical and microbiological indices including total viable counts (TVC), total volatile basic nitrogen (TVB‐N) and biogenic amines (BAs) were determined. Observations revealed that TVC, TVB‐N and BAs content dramatically increased over the storage, TVB‐N, histamine, cadaverine and tyramine content reached 54.18 mg/100 g, 621.26, 190.93 and 57.48 mg kg−1, respectively, at the end of storage. The decrease of alpha diversity indicated the decrease of microbial community plenty and diversity. Pseudomonas, Acinetobacter and Moraxellaceae unclassified occupied the dominant position during storage. The accumulation of histamine and cadaverine correlated positively with Pseudomonas and Brochothrix while negatively with Acinetobacter, Arthrobacter and Flavobacterium. Putrescine production and Photobacterium showed a strong favourable association. Amino acid metabolism and glucose metabolism were the two primary metabolic routes during the storage of S. japonicus, according to the Kyoto Encyclopedia of Genes and Genomes (KEGG). Overall, this study explored the interrelationships among the microbial community, functional metabolisms and spoilage characteristics during the storage of S. japonicus, which aimed to identify the specific spoilage organisms and help to deepen the understanding of roles that this microbiota played during spoilage. [ABSTRACT FROM AUTHOR]

This study aims to realize the head, tail and ventral dorsal orientation of fish bodies in conveyors using machine vision technology. The Scomber japonicus was taken as the object of study. The morphological and physical characteristics of the fish were used to design the mackerel body lifting device, the fish body separation device, the fish body head, fishtail and ventral dorsal directional conveying device, the fish body return conveying device, and the directional control system to form the mackerel body directional arrangement conveying device. The fish body lifting device included a spacer conveyor belt and brush rollers to separate and convey the fish upwards; the fish body separation device included a fish sliding mechanism and brush rollers to guide the fish from the lifting device to the fish separating device, in order to separate and convey the fish; the fish body head, tail and ventral dorsal directional conveying device consisted of an image acquisition device, head- and tailand ventral-dorsal directional actuator to convey the fish in a set head, tail and ventral dorsal directional direction. The fish return conveyor was used to return the fish with the wrong head and tail orientation, in order to the fish lifting device for reorientation. The mackerel dataset was created. The image data was then enhanced with brightness enhancement, Gaussian noise and rotation to enrich the number of training datasets. The annotation of the image data was finally realized. YOLOv5s was selected as the fish head, tail and ventral and dorsal orientation detection model, with an accuracy of 99.76%, a recall of 99.59%, and an average detection accuracy value of 99.5%. The head, tail and ventral and dorsal orientation of the fish were detected in real time on the device. The orientation control system consisted of an Arduino UNO controller, a computer and detection program, a CMOS industrial camera, a head and tail orientation actuator cylinder, a ventral and dorsal orientation actuator cylinder, a solenoid valve, an optocoupler isolated relay, a photoelectric sensor and a power supply. The orientation control system controlled the head, tail and ventral dorsal orientation of the mackerel using the identification results of the fish head, tail and ventral dorsal orientation model, and finally realized that the fish were transported forward in a certain head, tail and ventral dorsal orientation. As such, a prototype of the fish body directional arrangement conveying device was tested to verify the conveying effect of the fish body lifting device at different conveying speeds using the single fish body lifting success rate as the evaluation index. At the same time, the directional success rates of the fish body head and tail, as well as ventral and dorsal were used as evaluation indexes, and the conveying speed of the fish body lifting device, the conveying speed of the fish body separation conveying device, the fish body head, tail and ventral and dorsal directional conveying. A series of tests were performed on the effect of the directional transport of fish in a directional arrangement transport device. The test results show that the fish lifting device effectively separated and lifted the fish at different conveying speeds, and there was no overlapping of the fish upwards. The directional conveying speed of the fish body reached 15 pieces/min when the conveying speed of the fish lifting device was 0.05 m/s, the conveying speed of the fish separating device was 0.45 m/s, and the conveying speed of the fish head, tail and ventral dorsal orientation device was 0.60 m/s. The finding can offer a strong reference for the development of freshwater fish orientation conveyors. [ABSTRACT FROM AUTHOR]

Sardinops melanostictus and Scomber japonicus, as the main associated species in the northwest Pacific Ocean, are of great scientific significance for the management and sustainable use of fishery resources to study their potential habitat distribution and differences in response to environmental changes in this area. The fishery data of S. melanostictus and S. japonicus in the northwest Pacific Ocean from May to November in 2017-2021 were used, combined with sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH ), chlorophyll-a (Chl. a), eddy kinetic energy (EKE ), and water temperature at different depths (50, 100, 150, 200 m) to construct a maximum entropy model. According to the response curves of the two to the key environmental factors of each month, the inter-month changes of the key factors on the potential habitats of S. melanostictus and S. japonicus were obtained, and the map of potential habitat distribution from May to November for S. melanostictus and S. japonicus was stimulated. The key factors affecting the change of suitable habitats from June and August to October were SSH, SST, and Chi. a, and their suitable ranges were not much different. The results show that the potential habitat changes of S. melanostictus and S. japonicus are consistent with the actual operating location, and with the increase of months, and they all show a trend of moving first to the northeast and turning back in the southwest direction, and their potential habitat positions overlap widely in each month. The key factors affecting the change of suitable habitat in May, July and November are different. The key factors affecting the change of suitable habitat in May, July and November are different, and the key factors of S. melanostictus are SSH, EKE, SST, the key factors in July are SSH, SST, Chl. a. The key factors in November are EKE, SST, Chl. a, while the key factors of S. japonicus are SSH, EKE, Chl. a in May, and the key factors in July are SST and Chl. a, SSS, while the key factors in November are SSH, SST, Chl. a, and the suitable range of environmental factors varies from month to month. In addition, as the number of months increases, the optimal habitat area of S. japonicus gradually decreases northward, with a minimum area in July and November, while the optimal habitat area of S. melanostictus tends to increase, extending to the area north of 37° north latitude in November. The study showed the changes of SSH, SST and Chi. a have an important impact on the distribution of potential habitats of S. japonicus and S. melanostictus in the northwest Pacific Ocean, and EKE and SSS are the main causes for the difference in the distribution of potential habitats. [ABSTRACT FROM AUTHOR]

In the East China Sea (ECS), chub mackerel Scomber japonicus constitutes an important coastal-pelagic fishery resource that is mainly exploited by Chinese, Japanese, and Korean light-purse seine fisheries. Because the early life history of chub mackerel plays a significant role in its recruitment, we developed an individual-based model to study the distribution, growth, and survival rate of chub mackerel larvae and juveniles in the ECS to improve our understanding of the chub mackerel population structure and recruitment. Our results show that as body length rapidly increases, the swimming capacity of chub mackerel larvae and juveniles improves quickly, and their spatial distribution depends more on their habitat conditions than the ocean currents. Correspondingly, the juveniles from the central and southern ECS spawning ground are scarcely recruited into the Japan/East Sea (JES) or the western Pacific Ocean, but a significant proportion of juveniles from the northern ECS spawning ground still enter the JES and there are exchanges between the stocks in the ECS and JES. Thus, it seems more reasonable to assess and manage the chub mackerels in the ECS and JES as a stock. The water temperature and ocean primary production in the ECS are two important factors influencing the chub mackerel habitat conditions and their spatial and temporal distribution are significantly different as the spawning time changes. Therefore, the spawning time and location play an important role in the growth and survival rate of the larvae and juveniles. Generally, when chub mackerel spawns at the southern ECS spawning ground in March, the larva and juvenile growth and survival rate is relatively high; as spawning time moves forward, higher growth and survival rates would be expected for the chub mackerel spawned coastward or northward. For specific spawning sites, early or delayed spawning will reduce the survival rate. [ABSTRACT FROM AUTHOR]

Changing ocean conditions driven by anthropogenic activities may have a negative impact on fisheries by increasing stress and disease. To understand how environment and host biology drives mucosal microbiomes in a marine fish, we surveyed five body sites (gill, skin, digesta, gastrointestinal tract [GI], and pyloric ceca) from 229 Pacific chub mackerel, Scomber japonicus, collected across 38 time points spanning 1 year from the Scripps Institution of Oceanography Pier (La Jolla, CA). Mucosal sites had unique microbial communities significantly different from the surrounding seawater and sediment communities with over 10 times more total diversity than seawater. The external surfaces of skin and gill were more similar to seawater, while digesta was more similar to sediment. Alpha and beta diversity of the skin and gill was explained by environmental and biological factors, specifically, sea surface temperature, chlorophyll a, and fish age, consistent with an exposure gradient relationship. We verified that seasonal microbial changes were not confounded by regional migration of chub mackerel subpopulations by nanopore sequencing a 14,769-bp region of the 16,568-bp mitochondria across all temporal fish specimens. A cosmopolitan pathogen, Photobacterium damselae, was prevalent across multiple body sites all year but highest in the skin, GI, and digesta between June and September, when the ocean is warmest. The longitudinal fish microbiome study evaluates the extent to which the environment and host biology drives mucosal microbial ecology and establishes a baseline for long-term surveys linking environment stressors to mucosal health of wild marine fish.IMPORTANCE Pacific chub mackerel, Scomber japonicus, are one of the largest and most economically important fisheries in the world. The fish is harvested for both human consumption and fish meal. Changing ocean conditions driven by anthropogenic stressors like climate change may negatively impact fisheries. One mechanism for this is through disease. As waters warm and chemistry changes, the microbial communities associated with fish may change. In this study, we performed a holistic analysis of all mucosal sites on the fish over a 1-year time series to explore seasonal variation and to understand the environmental drivers of the microbiome. Understanding seasonality in the fish microbiome is also applicable to aquaculture production for producers to better understand and predict when disease outbreaks may occur based on changing environmental conditions in the ocean.

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office 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.)

Chub mackerel, Scomber japonicus, is heavily farmed and harvested due to its demand as a high-quality protein source rich in fatty acids. However, the effects of environmental cues on sexual maturation of the fish remain understudied. We aim to elucidate the effect of light manipulation on the hormones related to reproduction and on the stress response in the species. Mackerel were exposed to different photoperiods (12 h light:12 h dark or 14 h light:10 h dark) and light wavelengths (provided by white fluorescent bulbs or green LEDs). Total RNA extracted from the brain was assayed with quantitative polymerase chain reaction (a powerful technique for advancing functional genomics) and blood plasma was analyzed via immunoassay using ELISA kits. The mRNA expression of gene-encoding gonadotropin-releasing hormone, gonadotropin hormone, follicle-stimulating hormone, and luteinizing hormone were significantly increased through the use of an extended photoperiod and green wavelength, which also increased testosterone and 17β-estradiol plasma levels. Plasma levels of cortisol and glucose, which are indicators of a stress response, were significantly decreased through green LED exposure. Our results indicate that environmental light conditions affect the production of pituitary and sex hormones, and reduce the stress response in S. japonicus. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department 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.)

Fishery resources play an important role in the national economy and ecological diversity in China; it is of great significance to evaluate and rationally exploit the fishery resources. Most fisheries off the coast of China are data-limited, as the complex assessment models are not suitable for its resource assessment. Therefore, data-limited models for fishery resources assessment in China are among the current research hotspots. In this paper, two new data-limited assessment models (Bayesian state–space implementation of the Schaefer production model (BSM) and Monte Carlo MSY estimation model (CMSY)) were used to evaluate the fishery resources of Scomber japonicus and Muraenesox cinereus in the East China Sea. The results showed that the estimated value of MSY of S. japonicus was 220 × 103 t to 240 × 103 t, the estimated value of F/FMSY was greater than one, and the estimated value of B/BMSY was very close to one, indicating that the fishery in the East China Sea had been overfished. The estimated value of MSY for the M. cinereus fishery in the East China Sea ranged from 140 × 103 t to 170 × 103 t. The estimated value of F/FMSY at the biological reference point was greater than one and the estimated value of B/BMSY was less than one, indicating that the fishery had been overfished and resources had declined. Both models can be used for data-limited fisheries offshore of China. To better understand the impact of uncertainty on fishery resource assessment, more research should be carried out on these two data-limited assessment models. [ABSTRACT FROM AUTHOR]

In order to explore the hot air drying characteristics of scomber japonicus, the drying kinetics at different hot air drying temperatures (70,80 and 90 °C) were investigated. The effects of different drying temperatures on the quality of dried fish were studied using texture properties, color, TBA value and water distribution as indicators. Results show that the hot air drying of scomber japonicus muscle mainly underwent a slow-down drying stage. The effective water diffusion coefficient ranges from 4.856 7x 10-10 to 9.411 1x10-10 m²/s,and the diffusion activation energy is 33.587 7 kJ/mol. By comparing the fitting results of four drying models, the Page and Logarithmic models were obtained to describe the hot air drying process of scomber japonicus. With the increase of hot air drying temperature, the hardness and chewiness of scomber japonicus increase significantly, and the TBA value, a* and b* values increase significantly. The non-mobile water is the most abundant water in dried scomber japonicus, and its content decreases from 93.06% to 90.25% as the drying temperature increases from 70 °C to 90 °C. The study results can provide theoretical reference for the production of dried scomber japonicus meat by hot air drying. [ABSTRACT FROM AUTHOR]

IntroductionWith a higher degree of automation, fishing vessels have gradually begun adopting a fishing monitoring method that combines human and electronic observers. However, the objective data of electronic monitoring systems (EMS) has not yet been fully applied in various fishing boat scenarios such as ship behavior recognition.MethodsIn order to make full use of EMS data and improve the accuracy of behaviors recognition of fishing vessels, the present study proposes applying popular deep learning technologies such as convolutional neural network, long short-term memory, and attention mechanism to Chub mackerel (Scomber japonicus) fishing vessel behaviors recognition. The operation process of Chub mackerel fishing vessels was divided into nine kinds of behaviors, such as “pulling nets”, “putting nets”, “fish pick”, “reprint”, etc. According to the characteristics of their fishing work, four networks with different convolutional layers were designed in the pre-experiment. And the feasibility of each network in behavior recognition of the fishing vessels was observed. The pre-experiment is optimized from the perspective of the data set and the network. From the standpoint of the data set, the size of the optimized data set is significantly reduced, and the original data characteristics are preserved as much as possible. From the perspective of the network, different combinations of pooling, long short-term memory(LSTM) network, and attention(including CBAM and SE) are added to the network, and their effects on training time and recognition effect are compared.ResultsThe experimental results reveal that the deep learning methods have outstanding performance in behaviors recognition of fishing vessels. The LSTM and SE module combination produced the most apparent optimization effect on the network, and the optimized model can achieve an F1 score of 97.12% in the test set, surpassing the classic ResNet, VGGNet, and AlexNet.DiscussionThis research is of great significance to the management of intelligent fishery vessels and can promote the development of electronic monitoring systems for ships.

An individual-based model of Scomber japonicus in the East China Sea (ECS) was developed to simulate the effects of physical environment on the transport and distribution of eggs, larvae and juveniles of S. japonicus from 1978 to 2013. The results showed that there were interannual differences in the transport and distribution of eggs, larvae and juveniles of S. japonicus in the ECS due to different physical environments from 1978 to 2013, and this difference was extremely obvious in some specific years. The current in the drift path of eggs and juveniles controlled and affected the transport process and distribution characteristics. In April, the distribution of eggs and larvae was mainly controlled by the Taiwan Warm Current (TWC). The number of eggs and larvae transported into the northeastern waters of the ECS was positively correlated with the intensity of TWC. In May, it was mainly regulated by the TWC and the Tsushima Strait Warm Current (TSWC). In June, the number of larvae and juveniles entering the Tsushima Strait and the Pacific Ocean was determined by the TSWC. In general, in the years with high number of larvae and juveniles into the Tsushima Strait, the catch of 0-year-old S. japonicus was also higher. In addition, the number of larvae and juveniles entering the Tsushima Strait in El Niño years was less than that in La Niña years. In July, the transport was mainly controlled by the Kuroshio Current (KC), and the eddy within the KC strongly affected its distribution. [ABSTRACT FROM AUTHOR]

We modified Quinn's size-based model for the assessment of chub mackerel (Scomber japonicus) stock in Korean waters, using annual data about body lengths (fork lengths), fishery catches, and catch-per-unit-effort. One of the strengths of Quinn's size-based model is the construction of an imaginary age structure for a fish population, allowing the estimation of year- and age-based population sizes. Our modification was twofold. First, we applied a likelihood theory for numerical optimization, instead of the least squares method that Quinn et al. (1998) used. Second, we not only made point estimates of parameters, but also measured their uncertainties, using ADMB (automatic differentiation model builder) software. Estimates of annual biomass from 2001 to 2017 ranged from 1.01 × 106 to 2.15 × 106 MT, and estimates of annual fishing mortality from 1996 to 2017 ranged from 0.11 to 0.32 per year. Using a sensitivity analysis, we obtained the natural mortality of the stock, which was 0.1 per year. [ABSTRACT FROM AUTHOR]

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.

Fishing vessels have been ever-increasing to adopt the monitoring system for the combination of human and electronic observers, particularly with a high level of automation in the world. The data processing has required a simple configuration in the electronic monitoring system at present. It is urgent to improve the automation degree of the electronic monitoring system and the management efficiency of relevant fishing. In this study, the combined Convolutional Neural Network (CNN) with the Long Short Term Memory module (LSTM) was used to apply to the traditional electronic monitoring systems for the data extraction from the fishing vessel behavior of Japanese mackerel fishing in the light fishery. Nine types of fishing operations were divided, including sailing, putting net, waiting, pulling net, waiting for fish, organizing fish box, fish in, fish picking and reprinting, according to the operational characteristics of Japanese mackerel fishing boats. Four groups of parallel experiments were designed to compare the performance of a 3-layer CNN, a 3-layer CNN with an LSTM module (3-layer CNN-LSTM), an 8-layer CNN, and an 8-layer CNN with an LSTM module (8-layer CNN-LSTM) in a Japanese mackerel fishing boat during behavior extraction. Both CNN with LSTM modules were designed before the fully connected layers. The behaviors of nine fishing vessels presented the specific time characteristics, such as “pulling net” and “putting net”. Therefore, the 100 consecutive frames were then stitched horizontally to design the dataset during data processing. The frames per second of the video data was 25, and 100 was determined as the length of each dataset. The reason was that the human eye was normally observed the EM video data for 2-4 s to distinguish the two behaviors. Each data sample also contained certain time dimension information in the LSTM module. The test results show that the comprehensive evaluation index, the F1 score of the models that trained by the 3-layer CNN, 3-layer CNN-LSTM, 8-layer CNN, and 8-layer CNN-LSTM in the test set reached 0.794, 0.799, 0.966, and 0.972, respectively. In addition, the average detection speed of each model on three devices was measured to fully detect the detection efficiency of each model, including a laboratory supercomputer, small mobile workstation, and personal computer. The test samples of 5 000 data sets were taken 34.66, 34.50, 37.41, and 37.61 ms to process each piece using 3-layer CNN, 3-layer CNN-LSTM 8-layer CNN, and 8-layer CNN-LSTM on the supercomputer, respectively. In a small workstation, they were 85.47, 86.10, 120.13, and 121.15 ms in PC2, respectively, whereas, 93.77, 102.27, 118.51, and 124.50 ms in PC3, respectively, in the personal computer. Consequently, the network depth significantly improved the efficiency of the model within the specific range, but the detection time also increased significantly. Specifically, the F1 score of the 8-layer CNN increased from 0.794 to 0.966, while the training time increased from 23.028 to 29.624 h, compared with the 3-layer CNN. The LSTM module enhanced the performance of the network model with the sound detection time. Therefore, the CNN-LSTM modules presented excellent application prospects in the high real-time and high-precision scenarios of electronic monitoring systems. The finding can be expected to improve the automation degree of electronic monitoring systems for the better management efficiency of fishing boats. [ABSTRACT FROM AUTHOR]

The Pacific mackerel Scomber japonicus aquaculture is receiving growing attention, and further development of this industry is expected to protect wild stocks. Information on S. japonicus hematology is very limited. Therefore, the present study aimed to provide the hematological and serum chemistry profiles associated with sex and some seasonal variations in Pacific mackerel from Todos Santos Bay, Baja California, Mexico. Fish were sampled in April (spring) and August (summer). Results showed that the condition factor and all blood parameters analyzed in male and female mackerel were not affected by sex (P > 0.05). The seasonality effect on the mackerel was observed in some blood parameters such as mean corpuscular hemoglobin, total protein, globulin, and triglycerides that exhibited lower values in April compared to August (P < 0.05). While white blood cell count was higher in August (P < 0.05) compared with April. The fish sampled during the two sampling times were possibly a heterogeneous group of ages (1 to 3 years) with lengths ranging from 20 to 30 cm. Consequently, there is an urgent need to follow doing reference interval databases to assess Pacific mackerel health status under different conditions. [ABSTRACT FROM AUTHOR]

The accurate estimates of the maximum length of fish within a population are significant issues. Because the parameters related to maximum length, weight and age of fish communities in the ecosystem are constantly used in population dynamics and stock estimation studies, recording of such data is vital for determining the life history of fish. In this connection, a single specimen of Scomber japonicus was captured off Kabatepe Bight (Gallipoli Peninsula) with handline by a commercial fisherman on 21 September 2013. This specimen was 370.00 g in total weight and 34.6 cm in total length (32.0 cm in fork length), corresponding to the second maximum size recorded for Turkish waters. This study aims to contribute to the scientific literature.

Chub mackerel (Scomber japonicus) is an important commercial fish in the Northwest Pacific Ocean. Accurate target strength (TS) underpins acoustic stock assessment but the TS of S. japonicus is still poorly understood. In this study, the Kirchhoff-ray mode (KRM) model was used to estimate the TS of S. japonicus and its relationship with sound wave frequency and fish morphology. The results revealed that TS values varied with pitch angle shifts, with the impact on fish scattering strength being greater at higher frequency. This is less important because 38 kHz has been used for the biomass assessment of these fish resources. At frequencies of 38 kHz, 70 kHz, 120 kHz and 200 kHz, TS was greatest at a pitch angle range of -10° to 0°, which was related to the angle of the swim bladder tilt. There were almost no differences between TS estimated using the measured pitch angle distributions and using the universal distribution. When the measured pitch angle was N[-3°,4°], the average TS of S. japonicus with body length of 12.04–22.17 cm at four frequencies was -48.88 dB, -49.14 dB, -49.75 dB and -48.55 dB, respectively. The regression intercept (b20) in TS–body length equation was -73.27 dB, -73.56 dB, -74.18 dB and -73.46 dB, respectively. Variation in TS range at 0–300 m depth was about 10 dB. The simulated broadband target strength spectrum shows the scattering characteristics of individuals with different swim bladder length between 0–250 kHz. These results could be used for identification of S. japonicus in echograms and provide reference for acoustic stock assessment of S. japonicus in the Northwest Pacific Ocean.

Spatio-temporal distribution of chub mackerel Scomber japonicus is strongly susceptible to climate variability. In this study, a weighting-based habitat suitability index (HSI) model was established to assess the impacts of Pacific Decadal Oscillation (PDO) on habitat range and distribution of S. japonicus in the East China Sea (ECS) using vertical water temperature at depths of 2.5 m, 25 m and 50 m. Results showed that the optimal HSI model selected from ten weighting scenarios can yield reliable predictions. Correlation analysis revealed a significant negative relationship between the PDO index and water temperature anomaly at different depths. The water temperatures at three different layers on the fishing ground of S. japonicus tended to be low in the warm PDO phase and high in the cold PDO phase, respectively. The range of suitable habitats and its spatial distribution exhibited large differences between the warm and cold PDO regimes. During a warm PDO phase, vertical water temperature became cool, and the monthly preferred water temperature at each depth for S. japonicus shifted southeastward. Consequently, habitat quality dramatically decreased, and suitable habitat ranges also reduced and moved southeastward. Conversely, in a cool PDO phase, with the warmer vertical water temperature and northwestward shift of the preferred water temperature, the suitable habitats enlarged and migrated in the same direction. Our findings indicate that the PDO produced significant impacts on habitat range and distribution of S. japonicus in the East China Sea. [ABSTRACT FROM AUTHOR]

Chub mackerel, Scomber japonicus, is heavily farmed and harvested due to its demand as a high-quality protein source rich in fatty acids. However, the effects of environmental cues on sexual maturation of the fish remain understudied. We aim to elucidate the effect of light manipulation on the hormones related to reproduction and on the stress response in the species. Mackerel were exposed to different photoperiods (12 h light:12 h dark or 14 h light:10 h dark) and light wavelengths (provided by white fluorescent bulbs or green LEDs). Total RNA extracted from the brain was assayed with quantitative polymerase chain reaction (a powerful technique for advancing functional genomics) and blood plasma was analyzed via immunoassay using ELISA kits. The mRNA expression of gene-encoding gonadotropin-releasing hormone, gonadotropin hormone, follicle-stimulating hormone, and luteinizing hormone were significantly increased through the use of an extended photoperiod and green wavelength, which also increased testosterone and 17β-estradiol plasma levels. Plasma levels of cortisol and glucose, which are indicators of a stress response, were significantly decreased through green LED exposure. Our results indicate that environmental light conditions affect the production of pituitary and sex hormones, and reduce the stress response in S. japonicus.

Fishery resources play an important role in the national economy and ecological diversity in China; it is of great significance to evaluate and rationally exploit the fishery resources. Most fisheries off the coast of China are data-limited, as the complex assessment models are not suitable for its resource assessment. Therefore, data-limited models for fishery resources assessment in China are among the current research hotspots. In this paper, two new data-limited assessment models (Bayesian state–space implementation of the Schaefer production model (BSM) and Monte Carlo MSY estimation model (CMSY)) were used to evaluate the fishery resources of Scomber japonicus and Muraenesox cinereus in the East China Sea. The results showed that the estimated value of MSY of S. japonicus was 220 × 103 t to 240 × 103 t, the estimated value of F/FMSY was greater than one, and the estimated value of B/BMSY was very close to one, indicating that the fishery in the East China Sea had been overfished. The estimated value of MSY for the M. cinereus fishery in the East China Sea ranged from 140 × 103 t to 170 × 103 t. The estimated value of F/FMSY at the biological reference point was greater than one and the estimated value of B/BMSY was less than one, indicating that the fishery had been overfished and resources had declined. Both models can be used for data-limited fisheries offshore of China. To better understand the impact of uncertainty on fishery resource assessment, more research should be carried out on these two data-limited assessment models.

Length-weight, condition factors, age, and growth of Scomber japonicus were investigated. The specimens were collected monthly from Alexandria landing centers during 2017 and caught using night purse seine ranging from 12.9 to 34.4 (TL) (average, 21.00 ± 4.1) cm and from 15.10 to 391.49 (TW) (average, 92.81 ± 59.17) g. The exponent “b” of the length-weight relationships were “>3” for females (b = 3.24), males (b = 3.25), and all samples (b = 3.15), reflecting the positive allometric mode of growth. Moreover, the positive allometric mode of growth was observed for the relationship between forked length (FL) and standard length (SL) with weight. The annual average of absolute condition was 0.89 ± 0.06, with the highest value during April (0.96 ± 0.05). The annual average relative condition was 1.01 ± 0.06, with the highest value (1.10 ± 0.10) during August. The absolute condition (Kc) increased with the increasing length. However, the relative condition showed an inverse trend. The age of S. japonicus was determined using length-frequency analysis giving five age groups at mean lengths of 14.09, 19.29, 23.82, 28.25, and 31.76 cm for the 1st, 2nd, 3rd, 4th, and 5th age groups, respectively. The third age group (III) was the most frequent one (38.89%). The estimated growth parameters were L∞ of 38.11 cm; W∞, 534.74; K, 0.33 year-1; growth performance (Ø), 2.68; and t-max, 8.89 years. In conclusion, the present data reflected a good stock status with the suitability of living habitats. Further continuous monitoring is recommended for better fishery management and conservation. [ABSTRACT FROM AUTHOR]

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Species-specific ecological traits in fishes are likely to vary between populations or stocks due to differences in regional oceanic conditions, such as latitudinal temperature. We examined potential intraspecific differences in the swimming performance and metabolism of Pacific chub mackerel (Scomber japonicus) from the Northwest and Northeast Pacific stocks, which are distributed on opposite sides of the North Pacific at similar latitudes, but where the temperature contrast is large. Swimming bioenergetics and metabolic data of Northwest stock mackerel were measured at 14, 18, and 24°C using variable-speed swim-tunnel respirometers, and then the resulting bioenergetic parameters were compared with previous findings from the Northeast stock. At a given size, the maximum sustainable swimming speed (Umax) of the Northwest stock showed no significant difference compared to the Northeast stock at 18 and 24°C, but was lower at 14°C. In addition, the oxygen consumption rate (MO2) of the Northwest stock showed lower mass dependence and different temperature dependence at a given swimming speed than in the Northeast stock. Combined with stock-specific data on growth and experienced temperatures in the wild, these bioenergetic differences indicate that the swimming performance and metabolism of the two stocks are specific to their local environment to maximize bioenergetic efficiency.

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]

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ABSTRACT Changing ocean conditions driven by anthropogenic activities may have a negative impact on fisheries by increasing stress and disease. To understand how environment and host biology drives mucosal microbiomes in a marine fish, we surveyed five body sites (gill, skin, digesta, gastrointestinal tract [GI], and pyloric ceca) from 229 Pacific chub mackerel, Scomber japonicus, collected across 38 time points spanning 1 year from the Scripps Institution of Oceanography Pier (La Jolla, CA). Mucosal sites had unique microbial communities significantly different from the surrounding seawater and sediment communities with over 10 times more total diversity than seawater. The external surfaces of skin and gill were more similar to seawater, while digesta was more similar to sediment. Alpha and beta diversity of the skin and gill was explained by environmental and biological factors, specifically, sea surface temperature, chlorophyll a, and fish age, consistent with an exposure gradient relationship. We verified that seasonal microbial changes were not confounded by regional migration of chub mackerel subpopulations by nanopore sequencing a 14,769-bp region of the 16,568-bp mitochondria across all temporal fish specimens. A cosmopolitan pathogen, Photobacterium damselae, was prevalent across multiple body sites all year but highest in the skin, GI, and digesta between June and September, when the ocean is warmest. The longitudinal fish microbiome study evaluates the extent to which the environment and host biology drives mucosal microbial ecology and establishes a baseline for long-term surveys linking environment stressors to mucosal health of wild marine fish. IMPORTANCE Pacific chub mackerel, Scomber japonicus, are one of the largest and most economically important fisheries in the world. The fish is harvested for both human consumption and fish meal. Changing ocean conditions driven by anthropogenic stressors like climate change may negatively impact fisheries. One mechanism for this is through disease. As waters warm and chemistry changes, the microbial communities associated with fish may change. In this study, we performed a holistic analysis of all mucosal sites on the fish over a 1-year time series to explore seasonal variation and to understand the environmental drivers of the microbiome. Understanding seasonality in the fish microbiome is also applicable to aquaculture production for producers to better understand and predict when disease outbreaks may occur based on changing environmental conditions in the ocean.

Chub mackerel (Scomber japonicus) is a pelagic fish widely distributed in temperate and subtropical zones throughout the Indian and Pacific Oceans and is commercially exploited, particularly in the North Pacific. Although highly targeted in this region, little is known about their life history aspects. The objectives of this study are to evaluate the growth heterogeneities and ageing analysis of this species. We describe the length-at-age, weight-at-length, relative condition factor relationships, spatiotemporal heterogeneity and compare estimated growth parameter values to those reported from other regions. This study used data obtained from Chinese fishing vessels collected from 2016–2020 in the northwest Pacific Ocean. Length-weight data from 2686 specimens (40–294 mm, fork length; 0.8–311.8 g body weight) were analyzed, and the Length-weight relationship was W = (1.41 × 10−6) × FL3.37. Seven linear mixed-effects models (LMEM) were used to analyze the heterogeneity of length-weight relationships of Chub mackerel. The Length-weight relationships for Chub mackerel were best described by a model with random effects with both year and season (spring, summer, autumn) with the scalar parameter a. Age estimates were obtained from 175 specimens, and the length-at-estimated ages relationship was described using three non-linear candidate growth models. The von Bertalanffy growth model fit the data best for Chub mackerel in the northwest Pacific Ocean. Comparing the results to that of previous studies, we observed that individual Chub mackerel exhibited a slower growth rate than that observed in previous studies. In addition, relative condition factors varied among years, seasons, and regions. Information presented in this study provides an effective scientific basis for stock assessment and fishery management of Chub mackerel in the northwest Pacific Ocean.

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]

• VAST model outperforms GLMM in standardizing CPUE for chub mackerel, with higher conditional R 2 and lower CAIC. • Year × spatial interaction (GLM/GLMM) and spatio-temporal variable (VAST) strongly impact standardized CPUE. • Highly influential explanatory variables in CPUE standardization models may not impact nominal and standardized CPUE differences. • There was no significant shift in COGs for the population (P > 0.05). • First step for sustainable conservation and utilization of chub mackerel. Standardized catch per unit effort (CPUE) data not only yield precise and biologically meaningful abundance indices but also provide crucial insights into the spatio-temporal distribution of fisheries resources, critical for their sustainable utilization and management. In this study, we integrated chub mackerel fishery statistics from the Northwest Pacific Ocean (NPO) and marine remote sensing environmental data, and constructed CPUE standardization models for chub mackerel based on the generalized linear mixed model (GLMM) and spatio-temporal GLMM (Vector Autoregressive Spatio-Temporal, VAST) and evaluated their performance. GLMM is a statistical technique extending GLM with random effects for complex datasets with non-independent observations and correlations or hierarchies. The VAST model is a statistical model for multivariate time series data with observations at different spatial locations, displaying both temporal autocorrelation and spatial dependence. Additionally, influence analysis and simulation testing were employed to quantify the effects of explanatory variables on the differences between nominal CPUE and standardized CPUE, and to assess the estimation accuracy of different models in CPUE standardization, respectively. Finally, the distribution pattern of chub mackerel in the NPO was analyzed by estimating centers of gravity (COGs). The results indicated that: 1) The GLMM model containing all explanatory variables was considered the best model with the smallest conditional Akaike Information Criterion (CAIC), while the VAST model, with only the covariate SST , performed the best. 2) Interactions of year and spatial effects in GLMM and the spatio-temporal variable in VAST, exerted a notable influence on annual standardized CPUE and should be accounted for in the model. 3) Based on simulation testing results, the VAST model exhibited lower model error (root mean square error, RMSE) and model bias, outperforming the GLMM model in CPUE standardization. 4) From 2014 to 2018, chub mackerel exhibited high biomass density widely distributed throughout almost the entire NPO, which shifted to the central-north region from 2019 to 2021. There was no significant northing and easting shift in COGs for the population (P > 0.05). The findings of this research enhance our understanding of the variations in resource abundance indices and spatio-temporal distribution patterns of chub mackerel in the NPO. [ABSTRACT FROM AUTHOR]

In this study, fishing efficiency was analyzed by using different colored feathers in chub mackerel fishing (Scomber japonicus Houttuyn 1782) at Gökçeada. Catching lengths of green, brown (grayed), pink, white and orange feathers were determined to be 33.7 cm, 34.2 cm, 33.6 cm, 34.7 cm and 35.9 cm, respectively. When the fishing efficiencies of different colored feathers used in the study were compared at the end of the study, brown (grayed) color was found to have caught 164 individuals, having a catching rate of 35%. Orange colored feather was found to have caught 95 individuals, having a catching rate of 21% while white colored feather was found to have caught 49 individuals, having a catching rate of 11%. Green colored feather was found to have caught 70 individuals, having a catching rate of 15% and pink colored feather was found to have caught 82 individuals, having a catching rate of 18%.

Chub mackerel Scomber japonicus is an economically important fish species, extensively distributed in the East China Sea, the Yellow Sea and the Sea of Japan. Climate variability has strong impacts on its habitat. In this study, an integrated habitat suitability index (HSI) model was constructed to examine habitat suitability of S. japonicus in the East China Sea, and evaluate the relationship with the El Niño and La Niña events, with three crucial environmental variables (sea surface temperature (SST), sea surface height (SSH) and net primary production (NPP)) as predictors. The HSI model was developed using data over 2006–2013 and validated using data in 2014 and 2015. Results showed that the HSI model with the best model performance yielded robust predictions of habitat suitability for S. japonicus . The decreasing catch and CPUE (catch per unit effort) of S. japonicus during 2006–2015 were highly consistent with substantial shrinkage of suitable and optimal habitats, and enlargement of normal and poor habitats. Similar movement pattern was also found between the latitudinal gravity centers of fishing effort for S. japonicus fishery and the gravity centers of potential habitat. In addition, spatial correlation analysis indicated that the HSI value was significantly positively related to the SST anomaly (SSTA) and negatively correlated with the SSH anomaly (SSHA) and NPP anomaly (NPPA), on the main fishing ground between 25°–30 °N and 120°–130 °E. Furthermore, various intensity of the El Niño and La Niña event may lead to different variations in the habitat suitability of S. japonicus . Comparing to the very strong El Niño, the moderate El Niño events would yield rising SSTA and lowing SSHA and NPPA, leading to dramatically enlarged suitable habitat of S. japonicus . The habitat quality in La Niña events with different intensity depended on the local environmental variability on the fishing ground. Our findings suggested that the El Niño and La Niña events prominently affected the habitat suitability of S. japonicus in the East China Sea. However, the impacts varied with the intensity of each anomalous climatic event. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department 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.)

The antioxidant properties of the Pacific chub mackerel (Scomber japonicus) muscle protein hydrolysates prepared by enzymatic hydrolysis were investigated. After enzyme hydrolysis at 50°C for 60 min, more than 80% of theS. japonicusmuscle protein was hydrolyzed. The highest 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity (71.69%) occurred in whole muscle protein hydrolysates treated at 50°C for 30 min with Protamex, and the highest 2,2ʹ-azino-bis(3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) radical-scavenging activity (95.39%) was observed in white muscle protein hydrolysates treated at 50°C for 30 min with Neutrase. The highest superoxide dismutase (SOD)-like activity (32.84%) was recorded in white muscle protein hydrolysates treated at 50°C for 120 min with Protamex. Changes in the molecular weight distribution ofS. japonicusmuscle proteins after enzymatic hydrolysis were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A robust and a convenient enzyme hydrolysis technique for obtainingS. japonicusmuscle protein hydrolysates with useful biological activities, within a short time (<2 h) is proposed. [ABSTRACT FROM AUTHOR]

Chub mackerel ( Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full-life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na+/K+- ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na+/K+- ATPase in the gills decreased within 10 days after the low-salinity challenge, which implies the reduction of the energy-consuming active ion secretion under the low-salinity environment. The physiological capacity for adaptation to low-salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low-salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture. [ABSTRACT FROM AUTHOR]

Accurate prediction of the central fishing grounds of chub mackerel is substantial for assessing and managing marine fishery resources. Based on the high-seas chub mackerel fishery statistics and multi-factor ocean remote-sensing environmental data in the Northwest Pacific Ocean from 2014 to 2021, this article applied the gravity center of the fishing grounds, 2DCNN, and 3DCNN models to analyze the spatial and temporal variability of the chub mackerel catches and fishing grounds. Results:1) the primary fishing season of chub mackerel fishery was April–November which catches were mainly concentrated in 39°∼43°N, 149°∼154°E. 2) Since 2019, the annual gravity center of the fishing grounds has continued to move northeastward; the monthly gravity center has prominent seasonal migratory characteristics. 3) 3DCNN model was better than the 2DCNN model. 4) For 3DCNN, the model prioritized learning information on the most easily distinguishable ocean remote-sensing environmental variables in different classifications. [Display omitted] • Predicting chub mackerel fishery is important for food security, cost-saving, and sustainable development. • Gravity center and statistical analysis used to study chub mackerel fishery variability. • First demonstration of the importance of spatial and temporal scales for predicting fisheries using a deep learning model. • 2DCNN and 3DCNN models applied to predict chub mackerel fishery in the high seas. • Revealed key technology for predicting fishing grounds using marine remote sensing images. [ABSTRACT FROM AUTHOR]

Only one diagnostic sign is enough for differentiation of chub mackerel Scomber japonicus and blue mackerel S. australasicus working with mass material. It is a number of spines in dorsal fin: chub mackerel has 9-10 (often 9) and blue mackerel has 11-12 spines. Species identification may be done by relative distance between the spines: it is larger by half for chub mackerel. The species differ well by coloration of dorsal side: blue mackerel has «marbled» pattern with thin lines, in contrast to chub mackerel that has «zebra» pattern with thick lines.

The probability distribution of ichthyoplankton is important for enhancing the precision of sampling while reducing unnecessary surveys. To estimate the ichthyoplankton detection proportion (IDP) and its margin of error (ME), the monitoring information of the chub mackerel's (Scomber japonicus) ichthyoplankton presence-absence sampling data has been were collected over approximately 30 years (from 1982 to 2011) in the Korean coastal seas. Based on the computed spatial distributions of the mackerel's IDP and ME, the confidence interval (CI) range, defined as 2 ME, decreases from approximately 80% to 40% as the sample size n increases from 4 to 24 and the ME is approximately 40% in the typical (seasonal survey) case n = 4 per year. The IDP and ME off Jeju Island are relatively high at the 0.5-degree smoothing level. After increasing the spatial smoothing level to 1.0-degree, the ME decreased, and the spatial distribution pattern also changed due to the over-smoothing effects. In this study, the 0.5-degree smoothing is more suitable for the distribution pattern than the 1.0-degree smoothing level. The area of the high IDP and the low ME on the mackerel's ichthyoplankton was similar to the estimated spawning ground in the Korean peninsula. This information could contribute to enhancing for the spawning ecology surveys. [ABSTRACT FROM AUTHOR]

Mackerel is marketed at prices according to the species type,Scomber japonicusandScomber scombrus.Distinguishing these two species with the naked eye is difficult, and their differentiation becomes more difficult after they are processed by cooking, thereby leading to counterfeiting issues. Thus, in this study, we developed a method to differentiateS. japonicusfromS. scombrusby detecting polymorphisms in mitochondrial 16 s rRNA gene by using fluorescence melting curve analysis and locked nucleic acid probes. Our method could distinguishS. japonicusfromS. scombrusin a single experiment by using a single probe. The probes developed matched exactly withS. japonicusand had a melting temperature of 64 °C. However, the probes were mismatched withS. scombrus, resulting in a lower melting temperature of 46 °C. The high specificity of the locked nucleic acid probes resulted in this large difference in the melting temperatures. [ABSTRACT FROM PUBLISHER]

Se evaluó el efecto de las harinas de Salicornia bigelovii (SA) y Scomber japonicus, semiprocesada (HPS) como ingredientes en la formulación de dietas para camarón azul Litopenaeus stylirostris, en cultivo súper-intensivo. Se formularon tres diferentes dietas isoproteicas (40%) e isocalóricas (6 kcal g-1): (DSA), (DHPS), basal (DBA) y una dieta control (DCO). El peso obtenido con DSA y DHPS (0,9 ± 0,014 y 0,8 ± 0,015 g) fue similar a la dieta comercial DCO (0,9 ± 0,07 g), no existieron diferencias significativas (P > 0,05) en talla (cm), peso (g) y factor de conversión alimenticio (FCA). Los resultados obtenidos sugieren que DSA y DHPS son factibles de utilizar en la formulación de dietas para camarón por ser ingredientes de bajo costo que pueden sustituir a la harina de maíz y pescado tradicional, respectivamente sin efectos detrimentales en el crecimiento y supervivencia.The effect of semi-processed fishmeals (HPS) made using Salicornia bigelovii (SA) and Scomber japonicusas ingredients in the formulation of diets for blue shrimp Litopenaeus stylirostris undersuper-intensive farming was evaluated. Three different isoproteinic (40%) and isocaloric (6 kcal g-1) diets were formulated: DSA, DHPS, basal (DBA); a fourth control diet (DCO) was also used. The weights obtained with DSA and DHPS (0.9 ± 0.014 and 0.8 ± 0.015 g) were similar to those obtained with the commercial diet (DCO; 0.9 ± 0.07 g), and no significant differences (P > 0.05) were found for size (cm), weight (g), and the feed conversion ratio (FCR). The results suggest that the use of DSA and DHPS in the formulation of diets for shrimp is feasibleas these are low-cost ingredients that can be used as substitutes for cornstarch and traditional fishmeal, respectively, without detrimental effects for shrimp growth and survival.