Urbanization and technological advancements result in the dispersion of antropogenic electromagnetic fields (EMF) that can affect on ecosystems. Therefore, it is important to understand their impact on the environment. Aquatic ecosystems are subject to EMF as part of various electricity sources, e.g., high-voltage transmission lines (HVTL). We examined the impact of EMF generated by HVTL on the spatial arrangement and survival of pike (Esox lucius) embryos. Fertilized eggs were incubated under two HVTL configurations 110 kV and 220 kV compared with a control group devoid of anthropogenic EMF. Embryo orientation and survival were monitored until blastopore closure. The control group showed dominance in the arrangement of embryos along the N-S, NNW-SSE, and NNE-SSW axes, with a slight prevalence of northern directions. EMF originating from HVTL did not exert a significant influence on the spatial arrangement of pike embryos, although some deviations from the arrangement noticed in the control group were observed. Increased embryo mortality was observed only at 110 kV site, but probably due to factors unrelated to EMF. In conclusion, EMF generated by HVTL did not significantly change pike embryo orientation or chances of survival. However, longer exposure or higher EMF levels could provoke notable reactions, requiring ongoing evaluation as power networks continue to spread more widely.

The issue of microplastic contamination in seafood is progressively recognised as a significant global issue. This study presents novel findings regarding the detection of microplastics within the eggs of commercially available fish intended for consumption by humans. Eggs of Ompok bimaculatus, Heteropneustes fossilis, Mystus vittatus and Anabas testudineus collected from the Periyar River, Kerala, India were subjected to analysis for the potential presence of microplastics. Out of the 91 fishes (containing eggs) examined, microplastics were observed in the eggs of 2 species, i.e., Ompok bimaculatus and Mystus vittatus. The polymers recorded were polyethylene and polypropylene. Fish eggs are commonly consumed by humans and are highly esteemed as a delectable food. Considering the widespread consumption of fish eggs as a delicacy among humans, there exists a potential route for human exposure to microplastics, which raises concerns regarding public health.

Oncorhynchus mykiss, a significant aquaculture species, possesses compounds with numerous biological and pharmacological functions, including antioxidant, anticancer, anti-microbial, and anti-obesity effects. However, possible anti-inflammatory effects of lipids extracted from O. mykiss eggs on RAW264.7 cells induced by LPS have not been elucidated yet. The current study identified 13 fatty acids in lipids extracted from O. mykiss eggs that contained high amounts (51.92% of total fatty acids) of polyunsaturated fatty acids (PUFAs), especially DHA (33.66%) and EPA (7.77%). These O. mykiss lipids (100-400 μg/mL) showed significant anti-inflammatory effects by inhibiting NO and iNOS expression in LPS-stimulated RAW264.7 cells. They also inhibited expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α, while upregulating anti-inflammatory cytokines IL-10, IL-11, and TGF-β. These lipids from O. mykiss effectively inhibited LPS-induced expression CD86 as a surface biomarker on RAW264.7 cells. Additionally, O. mykiss lipids suppressed phosphorylation of p38, JNK, and ERK1/2 and the expression of phosphorylated NF-κB subunit p65. These findings indicate that O. mykiss lipids possess anti-inflammatory properties by inhibiting NF-κB and MAPK signaling pathways.

The Water-Sediment Regulation Scheme (WSRS) will deliver large amounts of water and sand to the Yellow River basin within a short period of time. This will significantly change the physicochemical environment of the Yellow River estuary and the surrounding marine ecosystem. Its effects on the spatial and temporal distribution patterns of ichthyoplankton are still unknown. In this study, six surface horizontal trawl surveys of ichthyoplankton were conducted during the WSRS in 2020 and 2021 using plankton nets. The results were as follows: (1) the estuarine sedentary fish Cynoglossus joyeri was the main species controlling the succession pattern of summer ichthyoplankton communities in the Yellow River estuary. (2) The WSRS influenced the ichthyoplankton community structure by changing the runoff, salinity, and suspension environment in the estuary. (3) The northern and southeastern parts of the estuary near Laizhou Bay were the main aggregation areas of the ichthyoplankton community.

Chemical liver injury is a common cause of liver disease primarily characterized by oxidative stress and inflammation. Sialoglycoproteins isolated from the eggs of Carassius auratus (Ca-SGP) have been proved to exhibit the antioxidant effect. However, the effect of Ca-SGP on liver injury remains unclear. Thus, this study was aimed to determine the effect of Ca-SGP on CCL4-induced chronic chemical liver injury and explore the underlying molecular mechanism. Results showed that Ca-SGP mitigated the elevated levels of serum alanine aminotransferase and aspartate aminotransferase, inhibited the systemic oxidative stress, and reduced the levels of pro-inflammatory factors TNF-α and IL-1β. Histologic results showed that Ca-SGP supplements alleviated hepatocyte necrosis and liver macrophage infiltration. Further, Ca-SGP supplement decreased endoplasmic reticulum stress-related proteins expression, including BiP, IRE-α, p-IRE-α, and TRAF2, and further inhibited the trigger of the NF-κB pathway. In summary, Ca-SGP might be a novel agent for liver injury treatment, and its potential mechanism was related to the inhibition of liver inflammation induced by the endoplasmic reticulum. PRACTICAL APPLICATION: The fish egg is an important by-product in fish processing. Carassius auratus is a common freshwater fish with large catches and low prices. However, the eggs of C. auratus are usually direct discard or processed into salted roe products, and the quality and value of these salted products are unsatisfactory. In this current study, we confirmed that sialoglycoproteins isolated from the C. auratus eggs have the potential for the treatment of liver injury and determined that its mechanism is related to the endoplasmic reticulum and inflammation, which put forward a new idea for solving the by-product of fish processing.

Determining the temporal community composition of fish eggs in particular regions and understanding the reproductive times of regional fish taxa are key aspects of the management and regulation of regional fish stocks. However, it is extremely difficult to accurately identify fish eggs due to the absence of diagnostic morphological characters. We sampled fish eggs in the lower Hongshuihe River (an upper mainstem of the Pearl River) between May and September 2020. We then used DNA barcoding to determine the species composition of the egg pool and to predict the spawning periods of the identified species. A total of 641 eggs and 17 larvae were chosen for molecular identification; 397 eggs and 17 larvae yielded high-quality barcoding sequences. The high failure rate (~38%) was most likely due to long-term storage in low concentrations of ethanol prior to molecular analysis. We successfully classified 392 eggs into 10 species and 13 larvae into four species using public databases. Most of the species identified in the egg pool were small and/or benthic, and migratory species were rare. This may partially reflect the adverse effects of hydropower cascade development in this river section. We also found that spawning periods tended to be species-specific. Our study provides a reference for the conservation and management of regional fishery stocks.

Fish eggs of the ovate sole Solea ovata and black porgy Acanthopagrus schlegelii were identified through DNA barcoding of cytochrome c oxidase subunit I (COX1). Visual taxonomic features were achieved, and photographs of the eggs of both species at different developmental stages were reported for the first time. In addition, the dissolution of oil globules caused by ethanol as egg fixatives was observed. This result showed the importance of using formalin as egg fixatives in the case of morphometric analysis and the necessity of combining molecular and visual taxonomic method for morphological study.

Understanding the anthropogenic impact of oyster farms is essential for the management and conservation of marine fishes. In Japan, Hiroshima Bay is the region with the most intense oyster farming and thus suitable to study the impact of these farms. Here, we surveyed spherical planktonic eggs of the black sea bream Acanthopagrus schlegelii, one of the most abundant fish in the Bay. Our survey was performed at fourteen stations which included places with oyster farms and historical spawning grounds. We found the highest egg densities in four stations, one with historical spawning aggregations and three with major oyster farms. Besides, surveys at the innermost part of Hiroshima Bay, where two major rivers discharge, showed a low density of eggs indicating that black sea bream avoids spawning in low salinity areas. Our study suggests that oyster farms benefit spawners of black sea bream by providing more food sources than historical spawning grounds for efficient spawning. Yet, whether oyster farms represent a full advantage for the species remains unclear, particularly because they are known to host jellyfishes that prey on eggs and limit water flow that can influence the survival of fish eggs.

Coral reefs are an important part of the ocean ecosystem and are a vital spawning ground for marine fish. Microorganisms are abundant in this environment and play a key role in the growth and development of host species. Many studies have investigated the microbial communities of fish with a focus on the intestinal microbiome of laboratory-reared adult fish. Little is known about the relationship between fish eggs and their microorganisms, especially as microbial communities relate to wild fish eggs in coral reefs. In this study, we analyzed the microbial communities of two species of coral fish eggs, Acanthopagrus schlegelii and Halichoeres nigrescens, using 16S rRNA gene amplicon sequencing technology. Pseudomonas, Archromobacter, and Serratia were the main bacterial genera associated with these fish eggs and are known to be bacteria with potentially pathogenic and spoilage effects. The microbial community structures of Acanthopagrus schlegelii and Halichoeres nigrescens eggs were separated based on the 30 most abundant operational taxonomic units (OTUs). Principal coordinate analysis (PCoA) and non-metric multidimensional scaling analysis (NMDS) further confirmed that the microbial communities of coral fish eggs differ by species, which may be due to host selection. A functional prediction of the microbial communities indicated that most of the microbial communities were chemoheterotrophic and involved in nitrogen cycling. Our results showed that the microbial communities of coral fish eggs were distinct by species and that key microorganisms were potentially pathogenic, leading to the spoilage of fish eggs, high mortality, and low incubation rates. This study provided new insights for understanding the relationship between microorganisms and wild fish eggs.

Changes in the proportions of river- and lake-produced eggs of a landlocked amphidromous fish, ayu (Plecoglossus altivelis altivelis) in the Lake Biwa water system, Japan, were monitored by stable isotope analysis, based on different δ15 N and δ13 C values of prey organisms between the lake and its tributaries. During the 3 month reproduction season, the δ15 N values of spawned eggs decreased with time. This result implies that there was a shift from lake-produced eggs to river-produced eggs within a reproductive season, based on the observation that adult fish in the lake had previously been shown to have eggs with distinctly higher δ15 N values in their ovaries than those in the tributaries. This explanation was also supported by the change in δ13 C values of the spawned eggs. Furthermore, eggs with lower δ15 N and higher δ13 C values tended to be spawned at less variable depths, suggesting that females spawning river-produced eggs selected the spawning sites from a narrower range. We conclude that stable isotope ratios of spawned eggs can be indicators of the relative contributions of different food chains and can enable comparisons of reproductive characteristics between types of egg.