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The Oyashio–Kuroshio Transitional Region (OKTR) is a nursery ground for pelagic fishes; thus, community succession of mesozooplankton is pivotal to understand prey availability, and it subsequently affects recruitment success. We investigated the surface distribution, biomass, and species composition of thaliaceans (salps and doliolids) that potentially have a significant impact on the food web and biogeochemical cycle by forming intensive blooms. A total of 11 thaliacean species were recorded from 62 locations along two transects at 36° N and 38.5° N extending from 142° E to 180° in May to June 1993. Salps and doliolids were found at 93% and 84% of the stations, respectively, and their biomass values varied widely in space (0.00011–79.56 and 0.00001–5.11 mg C m −3 for salps and doliolids, respectively). Thalia democratica was the most dominant salp and particularly abundant at stations east of 165°E on the 36°N-line; the abundance varied from 103 to 1379 ind m −3 . Dolioletta gegenbauri and Doliolum denticulatum were dominant doliolids, although their biomass values were far lower than that of salps. Multivariate statistical analysis with PRIMER revealed that the distribution of thaliaceans in the OKTR was not uniform in space and was affected by oceanographic conditions; doliolids tended to occur in much warmer (14.10–15.63 °C) and saline water mass (34.54–34.72) than salps (13.16–14.95 °C and 34.40–34.53). In terms of population clearance rates, the most dense salp blooms have the potential to sweep > 200% of their resident water per day, indicating that salp blooms cause deleterious feeding conditions for pelagic fishes through non-selective filter feeding.

To investigate the influence of parasitism of the copepod Pennella sp., which belongs to the family Pennellidae, on mortality in the Pacific saury Cololabis saira, we examined the seasonal changes in the following indices: prevalence (%; no. of infected fish × 100/no. of examined fish), mean intensity (total no. of infected Pennella sp./no. of infected fish), relative intensity (total no. of infected Pennella sp./no. of examined fish), and the maximum number of the parasites on a fish by age. A total of 32,376 Pacific sauries were collected from the central and western North Pacific, from May to December in 2016–2019, and analyzed. All indices were the highest in age-1 fish in May or June, and then decreased drastically. We also recorded the number of parasite debris (cephalothorax) left behind in the host bodies of 904 age-1 fish, but only six cephalothoraxes were found. Since it is unlikely that the cephalothoraxes could easily fall out after parasite death, our results indicated that decreases in prevalence and intensity were not caused simply by parasite death, but also as a result of host mortality. We need to quantitatively evaluate the impact of the Pennella sp. outbreak on resources of Pacific saury.

In recent years, the Northwest Pacific has seen a decline in Pacific saury ( Cololabis saira ) catch and an eastward shift of fishing grounds, both of which have posed increasing challenges for effective resource management. To identify environmental drivers underlying the formation of Pacific saury fishing grounds, we developed machine learning-based prediction models using spatial environmental variables. Our models combined fishing site and pseudo-absence data with high-resolution oceanographic data from the Japan Fisheries Research and Education Agency Regional Ocean Modeling System (FRA-ROMS). We employed three machine learning methods to evaluate three types of explanatory variable representations: averaged, vectorized, and spatially structured. The results demonstrated that preserving spatial structure using a two-dimensional grid layout improved model performance. Our prediction results reflected the recent eastward shifting fishing grounds, suggesting a strong influence of environmental factors, particularly water temperature derived from the ocean circulation model. The convolutional neural network model, which best replicated the eastward shift of fishing sites, achieved a recall of 45.0% and a precision of 95.4%, although its performance declined under higher environmental novelty, which was associated with low-catch years (2020-2022). By evaluating how different spatial representations of environmental variables affect model performance, this study demonstrates that incorporating spatial structure improves predictive ability and enables models to capture recent eastward shifts in fishing activity under changing ocean conditions.

In this study, we developed an individual-based model for age-0 Pacific saury Cololabis saira focusing on the winter-spawned cohort to advance our understanding of the dynamic link between transport/migration and growth during the first year after hatching. The model individuals (superindividuals) were initially located in the spawning ground, and growth and transport/migration were calculated through bioenergetics and movement submodels using sea surface temperature, chlorophyll a, and velocity derived from satellite data. Comparative experiments for several migration algorithms and cues showed that the extended kinesis algorithm stimulated with growth rate condition yielded the most plausible results. Without considering mortality, the summer distribution predicted by the model was substantially different from observations. When distribution-based mortality was used, the model growth histories became qualitatively consistent with the otolith-derived growth histories. Furthermore, the formation mechanisms of the second peak in daily growth rates occurring from spring to summer of age-0 fish were investigated by selecting superindividuals with a growth history well-fitted to that derived from otoliths. For these superindividuals, the growth rate increased in accordance with the successful northward migration from spring to early summer, and decreased as they fell behind the rapid northward shift of the high productivity zone in mid-summer.

We collected samples of Pacific saury Cololabis saira (249–331 mm in knob length; ages 0 and 1) in the North Pacific Ocean from 154°E to 165°W during their northward migration in the early summers of 2013, 2014, and 2015, and measured the stable nitrogen and carbon isotope ratios (δ15N and δ13C) of their muscle tissues. A hierarchical cluster analysis based on δ15N and δ13C yielded three groups (G1–G3). G1 (mean δ15N: 12.9%; mean δ13C: –20.3%) had the highest δ15N and occurred only in the eastern area of 170° W in 2013 and 2015. G2 (δ15N: 9.3%; δ13C: −20.1%) and G3 (δ15N: 7.3%, δ13C: −20.9%) occurred in all years mainly in eastern and western areas of 170° W, respectively. The latter two groups presented reasonable δ15N and δ13C considering the trophic enrichment and potential prey such as Neocalanus copepods that exist in each area. In contrast, the substantially enriched δ15N of G1 was characteristic of organisms at higher trophic levels in the same area. Thus, this group is most likely an immigrant from outside the survey area. This study showed that Pacific saury utilize different ecosystems east and west of 170° W during their northward migration.

Fishery-independent surveys using sea surface trawl nets for Pacific saury Cololabis saira in the western North Pacific since 2003 have enabled the investigation of their annual distribution patterns and total biomass during June and July, prior to the main fishing season in Japan. We compared biomass estimates and their associated variances derived based on five different post-stratification approaches in a swept area method, and then observed that these approaches have little effect on biomass estimates and their precision, owing to well-organized survey designs and homogeneously allocated sampling stations. We were able to utilize decreasing biomass estimates for 15 years as an essential abundance index in the ongoing stock assessment. Notably, examination based on stratification along with longitudinal survey lines indicated that the estimated biomass had decreased in the western survey area, resulting in an eastward shift in the gravity center of Pacific saury distribution after 2010. We recommend biomass estimation in an east–west direction based on longitudinal stratification as an effective measure to develop population dynamics models which reflect westward migration into the fishing grounds around Japanese coastal waters, and to forecast the expected catch during the subsequent fishing period.

Background Tick-borne encephalitis virus (TBEV) is a significant threat to human health. The virus causes potentially fatal disease of the central nervous system (CNS), for which no treatments are available. TBEV infected individuals display a wide spectrum of neuronal disease, the determinants of which are undefined. Changes to host metabolism and virus-induced immunity have been postulated to contribute to the neuronal damage observed in infected individuals. In this study, we evaluated the cytokine, chemokine, and metabolic alterations in the cerebrospinal fluid (CSF) of symptomatic patients infected with TBEV presenting with meningitis or encephalitis. Our aim was to investigate the host immune and metabolic responses associated with specific TBEV infectious outcomes. Methods CSF samples of patients with meningitis ( n  = 27) or encephalitis ( n  = 25) were obtained upon consent from individuals hospitalised with confirmed TBEV infection in Brno. CSF from uninfected control patients was also collected for comparison ( n  = 12). A multiplex bead-based system was used to measure the levels of pro-inflammatory cytokines and chemokines. Untargeted metabolomics followed by bioinformatics and integrative omics were used to profile the levels of metabolites in the CSF. Human motor neurons (hMNs) were differentiated from induced pluripotent stem cells (iPSCs) and infected with the highly pathogenic TBEV-Hypr strain to profile the role(s) of identified metabolites during the virus lifecycle. Virus infection was quantified via plaque assay. Results Significant differences in proinflammatory cytokines (IFN-α2, TSLP, IL-1α, IL-1β, GM-CSF, IL-12p40, IL-15, and IL-18) and chemokines (IL-8, CCL20, and CXCL11) were detected between neurological-TBEV and control patients. A total of 32 CSF metabolites differed in TBE patients with meningitis and encephalitis. CSF S-Adenosylmethionine (SAM), Fructose 1,6-bisphosphate (FBP1) and Phosphoenolpyruvic acid (PEP) levels were 2.4-fold (range ≥ 2.3-≥3.2) higher in encephalitis patients compared to the meningitis group. CSF urocanic acid levels were significantly lower in patients with encephalitis compared to those with meningitis ( p  = 0.012209). Follow-up analyses showed fluctuations in the levels of O-phosphoethanolamine, succinic acid, and L-proline in the encephalitis group, and pyruvic acid in the meningitis group. TBEV-infection of hMNs increased the production of SAM, FBP1 and PEP in a time-dependent manner. Depletion of the metabolites with characterised pharmacological inhibitors led to a concentration-dependent attenuation of virus growth, validating the identified changes as key mediators of TBEV infection. Conclusions Our findings reveal that the neurological disease outcome of TBEV infection is associated with specific and dynamic metabolic signatures in the cerebrospinal fluid. We describe a new in vitro model for in-depth studies of TBEV-induced neuropathogenesis, in which the depletion of identified metabolites limits virus infection. Collectively, this reveals new biomarkers that can differentiate and predict TBEV-associated neurological disease. Additionally, we have identified novel therapeutic targets with the potential to significantly improve patient outcomes and deepen our understanding of TBEV pathogenesis.

We examined specimens from the winter–spring cohort of the neon flying squid Ommastrephes bartramii caught off the coast of northeastern Japan in early summer and the following winter for mantle length, sex, maturity, and age to determine their hatching dates as well as their growth and migration patterns. Squid specimens were collected with a research driftnet in July 2018 in the northwestern Pacific and by squid jigging off the coast of northeastern Japan in November 2018 and January 2019. The ages of 300 specimens were estimated from statolith increment counts and used to back-calculate hatching dates. Hatching dates ranged from September 2017 to July 2018. The peak hatching dates varied with the survey season, even for the same winter–spring cohort. Squid caught in July 2018 hatched mainly from February to April, while those caught in November 2018 hatched mostly during April and May and those caught in January 2019 hatched principally during May and June. This pattern indicates that squid migrate among fishing grounds and that stocks are gradually replaced by late-hatching squid.

This study analyzes the actual transmitted power from 5G beamforming radio base stations (BF-RBSs) to clarify the effectiveness and issues of an actual maximum approach specified in the International Electrotechnical Commission 62232:2025. The actual maximum approach is a new compliance assessment method for electromagnetic field exposure levels from BF-RBSs based on time-averaged transmitted power. In this study, the actual maximum transmitted power every 5 or 30 min from more than 400 BF-RBSs using millimeter waves in urban areas in Japan was collected using a network management system over a period of one month. For each BF-RBS, normalized actual transmitted power was derived as the ratio of actual to configured maximum transmitted power. As a result of this measurement, the maximum value of normalized actual transmitted power was approximately −3 dB when the number of sets of user equipment (UEs) in the BF-RBS was less than two with high data traffic. Moreover, statistical analysis results of the measurement data shows that the actual maximum approach may underestimate the electromagnetic field exposure levels from a BF-RBS with three or fewer UEs when the actual transmitted power of the BF-RBSs is not monitored and controlled to maintain a level below the threshold.

We examine geographical differences in percentages of age-1 Pacific saury Cololabis saira with previous spawning experience collected from 143°E to 165°W during June and July of 2013 and 2014. Previous spawning experience of fish was determined using a new histological method involving Victoria blue (VB)-positive ovarian arterioles. We also compared the radius of the otolith annual ring (ROA), which indicates fish body size at the beginning of the breeding season, with the incidence of previous spawning experience. A generalized linear model was used that treats the occurrence of fish with VB-positive arterioles as a response variable, following the Bernoulli distribution of probability pi, where longitude, latitude, body length, ROA in age-1 fish, year (2013 or 2014), sea surface temperature, and days elapsed from a survey starting date, are used as fixed effect terms. An estimated regression coefficient of longitude was negative while that of ROA was positive, meaning that the probability of previous spawning increases with a latitudinal progression west, and with increased ROA. Our results suggest that differences in the percentage of previously spawned fish in different geographic areas are caused by differences in body length at the beginning of the breeding season.