Fish Eggs Research Articles

The influence of the Black Sea rim current and the coastal quasi-stationary anticyclonic Eddie on the distribution of ichthyoplankton and jellyfish

This article describes the Black Sea quasi-stationary coastal anticyclonic eddy (CAE), with large accumulations of zooplankton and ichthyoplankton, which were registered in August 2021 off the northeastern Black Sea during the period of a tropical-type atmospheric mesocyclone. Intense rains (60–80 millimeters of precipitation) caused flooding and large volumes of terrestrial water entered the sea. Water flows came from rivers into the coastal area and flowed into the CAEs. As a result, there were favorable conditions for the growth of plankton, fish eggs and, larvae. Thus, in the Sochi CAE, against the background of a high concentration of chlorophyll a, and the abundance of small-sized fractions of the fodder zooplankton, there was an almost 30-fold increase in the number of fish larvae (947 ind.·m−2 in the CAE and 33.5 ind.·m−2 in the surrounding waters) and the accumulation of jellyfish Aurelia aurita (Linnaeus, 1758), which is their food competitor, with an abundance of up to 44 ind.·m−2. The data obtained indicates that the Black Sea coastal quasi-stationary anticyclones arise between the cyclonic rim current (Main Black Sea current) and the coast, which can be of great importance in the formation of fish abundance.

Assessing the Conservation Value of Artificial and Natural Reefs via Ichthyoplankton Spatio-Temporal Dynamics

The distribution of fish eggs and larvae (ichthyoplankton) reflects spawning and nursery areas as well as dispersal routes. This study’s goal is to demonstrate how the identification of ichthyoplankton species and stages and their spatial distribution among natural reefs (NRs) and artificial reefs (ARs) may serve as decision-making tools in conservation and fishery management. Natural reefs exhibited an eight-times higher abundance of eggs, as well as the highest abundance of larvae in the yolk-sac and preflexion phases. In contrast, ARs had the highest abundance of larvae in the flexion and postflexion phases. Natural reefs may serve as breeding grounds for Scaridae, Labridae, and Mugilidae; whereas, ARs may serve as breeding sites for Lutjanidae, Synodontidae, Carangidae, Fistularidae, and Haemulidae. Our study revealed differences between ARs and NRs, which demonstrate the potential of artificial reefs to expand the supply and settlement options of reef fishes and consequently can lead to increased fish production with potential benefits to adjacent fishing areas through connectivity. Thus, ARs as no-take sites can be effective tools for both fishery management and biodiversity conservation. The findings highlight the potential use of ichthyoplankton tools and the importance of considering both types of reefs in marine conservation and management efforts.

Metabolic effects of phospholipids extracted from capelin (Mallotus villosus) roe on HepG2 cells

This study aimed to evaluate the effects of capelin roe phospholipid (CPL) on lipid accumulation, fatty acid profile, oxidative stress, and changes in target macromolecular structure in HepG2 cells using multidimensional hyperspectral technique. The results showed that CPL significantly inhibited oleic acid-induced accumulation of intracellular lipids and increased the activity of intracellular antioxidant enzymes (CAT, GSH-Px, SOD). The control and CPL-treated groups promoted accumulation of unsaturated fatty acids and reduced deposition of saturated fatty acids. The therapeutic effects of CPL positively correlated with its concentration. Fourier transform infrared spectroscopy and two-dimensional correlation infrared analysis indicated that CPL decreased the relative contents of intracellular carbohydrate, nucleic acid, –CH2-, and ν(C=O)/νas (CH2+CH3), and maintained the order of intracellular protein structure. Fourier transform infrared spectroscopy could be used for label-free cell sorting. This work provided a direction for the subsequent development of functional lipids in aquaculture.

ANTISAPROLEGNIA ACTIVITY OF METHANOLIC EXTRACT OF ZINGIBER OFFICINALE IN BUNNEI (BARBUS SHARPEYI) HATCHERY

Usage of chemicals such as malachite green to disinfect fish eggs in aquaculture has been banned in many countries around the world due to its environmental negative impact. This study aimed to evaluate the Zingiber officinale rhizomes extract as an antifungal agent during incubation period of Bunnei eggs and comparison of its effects with malachite green. For this purpose 24 hours after fertilization, methanolic extract of Zingiber officinale rhizomes in four groups with a concentration of 500, 750, 1000, and 1250 mg/L and three replications per concentration in a (10 minute) bath every 12 hours and malachite green group with a concentration of 0.1 mg/L for (6 minutes) bath was used twice a day and control group without antifungal agents under the same physiochemical conditions as other treatments were tested. The present study showed that the highest percentage of fungal infection was 41.82±0.5 % for the control group and the lowest 0.3±0.5 % was obtained for the treatment of 1250 mg/L of Zingiber officinale rhizomes. Also, the results showed that there were significant differences between treatments of different concentrates of Zingiber officinale rhizomes and with malachite green group in fungal infection, percentage of fertilization and survival do not exist (P>0.05.) No apparent deformity and abnormality were observed in the hatched larvae of Bunnei, so the extract of Zingiber officinale rhizomes with concentration 500 mg /L can be used to disinfect Bunnei eggs during Incubation period and safe material for humans and the environment.

Seasonal modulation of the testis transcriptome reveals insights into hibernation and reproductive adaptation in Onychostoma macrolepis.

The Onychostoma macrolepis have a unique survival strategy, overwintering in caves and returning to the river for reproduction in summer. The current knowledge on the developmental status of its testes during winter and summer is still undiscovered. We performed RNA-seq analysis on O. macrolepis testes between January and June, using the published genome (NCBI, ASM1243209v1). Through KEGG and GO enrichment analysis, we were able to identify 2111 differentially expressed genes (DEGs) and demonstrate their functions in signaling networks associated with the development of organism. At the genomic level, we found that during the overwintering phase, genes associated with cell proliferation (ccnb1, spag5, hdac7) were downregulated while genes linked to testicular fat metabolism (slc27a2, scd, pltp) were upregulated. This indicates suppression of both mitosis and meiosis, thereby inhibiting energy expenditure through genetic regulation of testicular degeneration. Furthermore, in January, we observed the regulation of autophagy and apoptosis (becn1, casp13), which may have the function of protecting reproductive organs and ensuring their maturity for the breeding season. The results provide a basis for the development of specialized feed formulations to regulate the expression of specific genes, or editing of genes during the fish egg stage, to ensure that the testes of O. macrolepis can mature more efficiently after overwintering, thereby enhancing reproductive performance.

Long-term dataset for contaminants in fish, mussels, and bird eggs from the Baltic Sea

Widespread persistent contaminants are a global environmental problem. In the Baltic Sea, wildlife contamination was first noticed in the 1960s, prompting the Swedish Environmental Protection Agency to establish a comprehensive Swedish National Monitoring Programme for Contaminants in Marine Biota (MCoM) in 1978 run by the Swedish Museum of Natural History. Eight species have been analysed, four fish species (Atlantic herring, Atlantic cod, European perch, viviparous eelpout), one bivalve species (blue mussel), and egg from three bird species (common guillemot, common tern, Eurasian oystercatcher). Here, we present a dataset containing MCoM data from its start until 2021. It includes 36 sets of time-series, each analysed for more than 100 contaminants. The longest time-series is for common guillemot and starts in 1968. We describe the structure of MCoM including historic changes to the number of stations, sample treatment, analytical methods, instruments, and laboratories. The MCoM data is available at the Bolin Centre repository and on GitHub through our R package mcomDb. The latter will be updated yearly with new MCoM records.

Estuarine front dynamics drive ichthyoplankton assemblage in the tidal freshwater zone of the Río de la Plata, South America

Frontal zones are critical in the retention and dispersal of ichthyoplankton. This study evaluates the response of ichthyoplankton assemblage to frontal zone dynamics in one of the world's largest estuaries, the Río de la Plata, South America. Surveys were conducted between October 2014 and December 2017 in a nearshore habitat of the tidal freshwater zone of the estuary. Ichthyoplankton was collected using conical nets, and physico-chemical variables were registered in situ. The frontal zone dynamics were evaluated through the turbidity front (TF) location, determined by satellite imagery. Although most larval taxa belonged to the freshwater category, the estuarine category had the highest abundances. The highest species richness and abundance occurred during spring and summer, linked to the season and proximity of spawning areas. The dynamics of the TF emerged as the primary driver of interannual variability in ichthyoplankton assemblages within the tidal freshwater zone. A seaward shift of the TF correlated with a reduction in total abundance and the prevalence of freshwater larvae, whereas a retraction of the TF location corresponded to an increased abundance of marine larvae in the tidal freshwater zone. These interannual shifts in TF location and fish larvae assemblages were closely tied to significant variations in river discharges resulting from the ENSO events during the study period. The findings suggest that marine and estuarine fish eggs exhibit effective retention near the frontal zone and the outer regions of the estuary. In contrast, larvae from these categories disperse along the main axis of the estuary in response to the displacement of the frontal zone. Finally, we discuss into the role of the frontal zone in the Río de la Plata as a pivotal environmental cue for fish larvae, influencing their behavior to regulate dispersal patterns.

Selenium-mercury interactions and relationship to aquatic toxicity: A review.

A review of the literature pertaining to selenium-mercury (Se/Hg) interactions in aquatic species was performed to provide insight into the mechanisms allowing for the reported changes in bioaccumulation and toxicity that have been observed when the two elements occur at elevated concentrations. Selenium (Se) has been shown to protect against mercury (Hg) toxicity in all animal models evaluated (fish, birds, mammals, and plants). To explore the interaction between the two elements, data are presented on concentrations of both elements in wild-caught fish at numerous locations. The data show that most fish have Se/Hg ratios >1.0. The importance of this ratio has been reported, with suggestions that the protective interaction is due in large part to the formation of HgSe. Data show that when the Se/Hg molar ratio is <1.0 in the diet of fish and animals, Hg toxicity will be expressed, provided that the Hg concentration is sufficiently high. This toxicity is likely the result of Se deficiency leading to an excess of reactive oxygen species. Laboratory fish toxicity studies reviewed show that Se toxicity can be reduced or eliminated when Hg is added to the diet in moderate amounts. Field studies have shown reduced accumulation of Hg when Se concentrations are increased. When Hg in the diet is significantly elevated (usually >10 µg/g), toxicity is expressed regardless of the Se present. Likewise, amelioration of Se toxicity by Hg occurs over a limited range. Tissue thresholds for Se toxicity have been derived primarily from studies where fish eggs were extracted from wild fish and embryo deformities were observed; however, the amount of Hg in the fish or ovaries was not considered, which could lead to uncertainty in the toxicity threshold. It is recommended that both elements be measured and evaluated when performing risk assessments and setting water quality criteria. Integr Environ Assess Manag 2024;00:1-11. © 2024 SETAC.

Single Bale-Bale Technology: Sustainable Utilization of Flying Fish Eggs in the Waters of the Aru Islands, Indonesia

The waters of Eastern Indonesia constitute a potential area for the utilization of flying fish eggs. The capture of fish eggs relies on the behavior of parent fish that deposit their eggs on floating objects at the sea surface. The technology is known by the name drifting FAD or its local name, “bale-bale”. However, the tendency of fishermen is to design double bale-bale for maximum utilization without considering the sustainability of the fishery resources. This research aims to develop single bale-bale technology for sustainable utilization of flying fish eggs in the waters of the Aru Islands, Indonesia. The vertical single bale-bale is an innovative system designed to enhance the efficiency of capturing flying fish eggs, reduce environmental impact, and support sustainable utilization. The research methodology involves the design and implementation of bale-bale, followed by performance evaluation and environmental impact analysis. The results of the study indicate that the vertical single bale-bale is more effective and sustainable compared to horizontal single bale-bale, mixed, or double configurations. Consequently, this research contributes to improving economic and ecological resilience while promoting environmentally friendly fishing practices.

Bird‐mediated endozoochory as a potential dispersal mechanism of bony fishes

The dispersal of fish into distant and isolated habitats remains a topic of continuous discussion in the field of fish biogeography. This is particularly relevant due to the perceived limitation of fish movement to what is known as active dispersal. Fish migration is often confined to interconnected water bodies, underscoring the significance of dispersal for fish inhabiting isolated aquatic habitats. However, empirical evidence for a natural (i.e. not human‐mediated) mechanism has been limited. Here we explore and provide evidence for waterbird‐mediated endozoochory as a possible dispersal mechanism in various fish species and families. We force‐fed mallards Anas plathyrynchos with fertilised eggs of nine bony fish species, covering nine taxonomic families. We recovered viable embryos of five fish taxa in the faeces of mallard, proving the ability of fish eggs to survive the passing of the digestive system of waterbirds. Moreover, the recovered eggs successfully hatched into larvae in two fish species. Taking into the flight speed and numerosity of mallards, as well as the high abundance of fish eggs, our results highlight endozoochory of fish eggs by waterbirds as a possible significant, although likely rare natural dispersal mechanism that can occur across more species than previously known in freshwater fish.

How the Water-Sediment Regulation Scheme in the Yellow River affected the estuary ecosystem in the last 10 years?

The Yellow River, renowned as the most sediment-laden river globally, grapples with sediment deposition issues compromising reservoir functionality and elevating downstream riverbeds, posing threats to human life and property safety. In response, the Water-Sediment Regulation Scheme (WSRS) has been innovatively implemented to address these challenges. While effectively mitigating sediment deposition, WSRS has concurrently disrupted the equilibrium of the estuarine ecosystem. This paper addresses the understudied but crucial topic of the interannual impact of WSRS on the estuarine ecosystem. Drawing upon physical, chemical, and biological data gathered through field surveys conducted before, during, and after WSRS from 2011 to 2022, the analysis delves into the interannual changes in the estuarine environment, fish eggs and larvae abundance, and species diversity under the influence of WSRS. The findings reveal an interannual decreasing trend in terrestrial material input due to WSRS, juxtaposed with an interannual increasing trend in fish eggs and larvae around the estuary, as well as the species diversity index. Notably, these trends became more pronounced post-2014. Compared to pre-2014, nutrient concentrations experienced a ~20 % decrease, chlorophyll-a concentration increased by 44 %, fish eggs proliferated approximately 1 time, and the species diversity index transitioned from a declining trend to an ascending trajectory. After 12 years of continuous WSRS implementation, the impact on the estuarine ecosystem has demonstrably diminished. This research aims to furnish reference experience and scientific basis for water and sediment regulation in major rivers around the world in terms of estuarine ecology.

Removal of dead fish eggs by Asellus aquaticus as a potential biological control in aquaculture

The objective of the present experimental study was to gain a better understanding of the foraging activity of Asellus aquaticus during fish egg incubation. A. aquaticus were introduced into experimental setups of dead eggs, viable eggs and hatched larvae of zebrafish (Danio rerio), a commonly used model organism. The amount of A. aquaticus and the duration of their exposure to the eggs significantly affected the proportion of consumed dead eggs in each experimental cycle. A. aquaticus belongs to the group of aquatic detritivores, and no predatory behavior was observed during the experiments. These crustaceans could distinguish between the dead eggs and those containing living embryos. Furthermore, zebrafish larvae remained unharmed by A. aquaticus, even in the absence of alternative food source. These findings underscore the potential sanitary role of these crustaceans in natural waters and offer new perspectives on their possible use as biological control organisms in aquaculture hatcheries. Additionally, our results suggest a potential application of A. aquaticus in combating pathogens by reducing the growth substrates for bacteria and fungi.

Estimation of spawning stock biomass and spawning areas of sardine, (Sardina pilchardus) with winter time ichthyoplankton sampling in the Sea of Marmara, Türkiye

The spawning areas and spawning stock biomass of sardine were studied with ichthyoplankton sampling in the winter period from the 32 stations, in the Marmara Sea. The mean fish egg and larvae biomass in a unit area were calculated as 18.4 ± 5.3 eggs/10 m2 and 2.5 larvae/10 m2, respectively. Three main spawning areas were detected as Karacabey Floodplain area, Gönen, and Büyükçekmece estuarine area. The larvae are mostly located in the western part. The batch fecundity of sardine was detected between 2415.9 and 16738.3, with a mean of 6899.8 ± 255.7 eggs. The sex ratio (R), spawning fraction (S), mortality rate, and daily egg production (Po) were calculated as 0.53, 0.098, 0.62, and 9.25 eggs/m2 in the Marmara Sea. The spawning stock biomass (B) is estimated at 2998 tonnes in the Marmara Sea. Both ichthyoplankton biomass and spawning stock biomass were found relatively lower. It is recommended to apply stricter management sanctions for the sustainability of sardine stocks.

Fluorescence of plankton fish eggs of Black Sea Mullus barbatus ponticus for test-analysis of the cell fertilization and development

The autofluorescence of fish eggs from the Black Sea Mullus barbatus ponticus Essipov was studied in order to identify the state of their fertilization and development in the ichthyoplankton. The study differed from the earlier genetic fish investigations with artificial fluorescent dyes. In our experiments, among the eggs were the objects with various stages of development: from unfertilized and just-fertilized cells emitted in blue to well-seen embryos that fluoresced in red. Red-fluorescing embryonal probes were peculiar to living eggs, unlike blue-fluorescing cells with damaged structures. The fluorescent method (luminescence microscopy with or without microspectrofluorimetry) allows us to identify the earlier stages of development of the fish eggs. The autofluorescence of the fish eggs of the species studied was possible to recommend for the testing of fertilized and living eggs at the early stages of development that may be applied to the fish industry in the future.

Effects of Flow Turbulence on the Entire Development Process of Drifting Fish Eggs

Excessive flow turbulence poses a threat to the development of drifting fish eggs, leading to mortality or developmental malformations and ultimately depleting early fish resources. Currently, there is a scarcity of quantitative studies investigating the effects of flow turbulence on the entire process of drifting fish egg development, from fertilized egg division to hatching. In this paper, the effects of different flow turbulence conditions (FTCs), including turbulent kinetic energy and shear stress, and action times on different stages of fish egg development were quantitatively explored using a transverse-oscillating-grids turbulence tank. Empirical formulas were established to predict the proportion of normal fish egg development under different FTCs within a selected range. The research findings provide a quantitative basis for protecting early fish resources, mitigating the biological invasion of specific fish, constructing fish-breeding facilities, and ensuring safe transfer and transportation.

Fluorescent imaging and toxicology study of alga-derived carbon dots in zebrafish

With the widespread application of carbon dots (CDs) in fluorescence imaging, their toxicity has become a focal point of concern. The potential toxicity of CDs synthesized from different raw materials remains an unresolved issue. Laver and wakame, which are commonly popular sea vegetable foods rich in nutrients, were utilized to investigate whether synthetic CDs derived from these alga sources retain medicinal value. Herein, two types of fluorescent alga-derived CDs were prepared through hydrothermal synthesis using laver and wakame respectively. Zebrafish were immersed in both types of CDs to observe their fluorescence imaging effects within the zebrafish bodies. It was observed that laver-derived CDs and wakame-derived CDs exhibited similar luminescence properties but differed in terms of fish egg imaging localization. Additionally, intestinal flora sequencing revealed varying degrees of influence on the zebrafish gut microbiota by the two types of CDs, suggesting that both alga-derived CDs could enhance the abundance of intestinal flora in zebrafish.

Numerical Simulation of Habitat Restoration for Floating Fish Eggs in the Upper Yangtze River Tributaries

The upper reaches of the Yangtze River not only serve as a crucial waterway in China’s southwestern region but also function as a conservation area for rare fish species. Recognizing the tendency of current navigation channel improvement projects to overlook the impact on aquatic habitats and the limitations of existing habitat assessment systems, this study specifically focuses on the bifurcation section of the upper Yangtze River. To address these issues, a two-dimensional mathematical model is established to simulate and validate various improvement schemes. An analysis of the flow conditions necessary for fish migration and spawning in this section is conducted, determining optimal flow rates and water levels during spawning and migration periods. A suitability assessment system for spawning and migration is then established, utilizing the four major Chinese carps as representative fish species for evaluation. Through a comprehensive analysis of the results, rational improvement schemes are identified. The findings underscore the importance of considering elevation of dam crest during the construction of sub-dams to regulate the navigation channel, particularly regarding its impact on fish habitats during the dry season. In this plan, the weighted available area of the spawning ground increased by 189,251 m2, 165,860 m2, 89,527 m2, 66,542 m2, and 47,182 m2 under five conditions. Additionally, the evaluation indexes PPA, HFI, and CQI showed increases of 5.011%, 4.176%, and 2.901%, respectively. Moreover, this study refines fish habitats based on their reproductive and living habits, thereby enhancing existing habitat assessment models.

Incidence of microplastic translocation in freshwater fish eggs

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.

Whole transcriptome analysis of demersal fish eggs reveals complex responses to ocean deoxygenation and acidification

Ocean acidification and deoxygenation co-occur in marine environments, causing deterioration of marine ecosystems. However, effects of compound stresses on marine organisms and their physiological coping mechanisms are largely unknown. Here, we show how high pCO2 and low dissolved oxygen (DO) cause transcriptomic changes in eggs of a demersal fish (Sillago japonica), which are fully exposed to such stresses in natural environment. Overall gene expression was affected more strongly by low DO than by high pCO2. Enrichment analysis detected significant stress responses such as glycolytic processes in response to low DO. Increased expression of a group of glycolytic genes under low DO conditions is presumably because oxygen depletion disables the electron transfer pathway, complementing ATP production in the glycolytic pathway. Contrary to expectations, apparent mitigation of gene expression changes was dominant under combined stress conditions, and may represent an innate fish adaptive trait for severe environments.

Identification of pre-flexion fish larvae from the western South Atlantic using DNA barcoding and morphological characters.

Knowledge on species composition is the first step necessary for the proper conservation and management of biological resources and ecologically relevant species. High species diversity and a lack of diagnostic characters for some groups can impose difficulties for taxonomic identification through traditional methodologies, and ichthyoplankton (fish larvae and eggs) are a good example of such a scenario. With more than 35.000 valid species of fishes worldwide and overall similar anatomies in early developmental stages in closely related groups, fish larvae are often hard to be identified at the species or even more encompassing taxonomic levels. To overcome this situation, molecular techniques have been applied, with different markers tested over the years. Cytochrome c oxidase I (COI) is the most commonly used marker and now has the broadest public reference libraries, providing consistent results for species identification in different metazoan studies. Here we sequenced the mitochondrial COI-5P fragment of 89 fish larvae collected in the Campos Basin, coastal southeastern Brazil, and compared these sequences with references deposited in public databases to obtain taxonomic identifications. Most specimens identified are species of the Blenniiformes, with Parablennius and Labrisomus the most frequently identified genera. Parablennius included two species (P. marmoreus and P. pilicornis), while Labrisomus included three species (L. cricota, L. conditus and L. nuchipinnis). Anatomy of these molecularly identified specimens were then analyzed with the intention of finding anatomical characters that might be diagnostically informative amongst the early development stage (pre-flexion) larvae. Ventral pigmentation patterns are proposed as useful markers to identify Labrisomus species. However, additional specimens are needed to confirm if the character holds stability through the geographic distribution of the species.