Fish Eggs Research Articles

Investigating the Presence of Selenoneine, Ergothioneine, and Selenium-Containing Biomolecules in Fish and Fish-Derived Commercial Products.

Two potent antioxidants, selenoneine and ergothioneine, have been determined simultaneously for the first time in the muscle of highly consumed fish and in fish-derived products. The extraction methods were optimized, and their subsequent analysis was performed by HPLC-ESI-MS/MS. Best extraction efficiency (106 ± 3 and 104 ± 5%) was attained by performing a simple aqueous extraction containing 100 mmol L-1 ammonium acetate or ammonium formate as extractants. Selenoneine and ergothioneine were simultaneously detected in tuna (0.306 ± 0.006 and 3.5 ± 0.2 μg g-1) and swordfish (0.14 ± 0.02 and 1.1 ± 0.4 μg g-1) muscle tissues, while in fish roe and in farmed salmon, only ergothioneine was detected (with contents ranging 0.03-3.3 μg g-1). Moreover, the presence of their respective methylated forms was also considered. Additionally, Se-containing biomolecule profiles from water-soluble proteins were obtained by SEC-ICP-MS analysis. Results revealed similar profiles between fish and fish roe, whereas for ultraprocessed fish products, Se seems to be mostly associated with low-molecular-weight biomolecules. The results included in this work may contribute to a better understanding of the relations between selenoneine and ergothioneine in fishery products as well as their fate and potential modifications of Se-containing biomolecule profiles during fish processing.

DNA barcode reference library of the fish larvae and eggs of the South China Sea: taxonomic effectiveness and geographic structure

Fish early-stages constitute useful indicators of the states of marine ecosystems, as well as important fishery resources. Given the spectacular phenotypic changes during ontogeny, and the paucity of diagnostic morphological characters at the species level, the identification of fish early-stages is a challenging task. DNA barcoding, the use of the mitochondrial gene of the cytochrome c oxidase subunit I (COI) as an internal species tag, opened new perspectives for the identifications of both larval fish and fish eggs. However, the accuracy of the identifications assisted by DNA barcoding are dependent of the completeness of the DNA barcode reference libraries used to assigned unknown sequences to known species. Here, we built a DNA barcode reference library for 113 species of larval fish and 85 species of fish eggs involving the production of 741 newly generated DNA barcodes from South China Sea (63 localities). Together with 514 DNA barcodes mined from Genbank for 116 species from the South China Sea regions, a reference library including 1255 DNA barcodes for 308 species (248 locations) was assembled. The present study emphasizes the importance of integrating DNA barcoding to large scale inventories of early stages, as DNA-based species delimitation analyses delimited 305 molecular operational taxonomic units (MOTUs) and multiple cases of discordance with morphological identifications were detected. Cryptic diversity is detected with 14 species displaying two MOTUs and a total of 23 species were lumped into 11 MOTUs due to low interspecific divergence and/or mixed lineages.

Effect of Microplastic Exposure to the Reproductive Energy and Fecundity of Female Wami Tilapia (Oreochromis urolepis, Norman 1922) Fish

ABSTRACTThere is mounting evidence indicating that microplastics (MPs, < 5 mm) cause reproductive dysfunction in fish, yet information on the long‐term effects of MP exposure remains scarce. In this study, Wami tilapia fries were exposed to 38–45 µm polyethylene (PE) MPs for their first 2 months in treatment groups of control (0 PE MPs/mL), 1, 10, and 100 PE MPs/mL (with 60 individuals per group in triplicates), and subsequently maintained in a ratio of 3 females to 1 male for an additional 5 months. Reproductive proxies and parameters of female fish health were calculated, and models were developed according to the Akaike information criterion (AIC) and no significant differences in fecundity, relative fecundity, hepatosomatic index (HSI), weight, length, gonadosomatic index, and oocyte packing density were found between treatment groups (one‐Way ANOVA, p > 0.05). However, condition factors varied significantly between treatment groups (Kruskal–Wallis Test, p = 0.006), with the control group differing significantly from the groups exposed to 1 PE MPs/mL (p = 0.007), 10 PE MPs/mL (p = 0.03), and 100 PE MPs/mL (p = 0.001). Fecundity showed strong correlations with weight and length in all treatment groups except the group exposed to 10 PE MPs/mL (weight: r = 0.471, p = 0.346; length: r = 0.688, p = 0.131) and showed insignificant correlations with condition factors and HSI. Multiple regression models revealed that weight significantly contributed to fecundity in all treatment groups except the group exposed to 10 PE MPs/mL. Histopathological analysis indicated damage to livers and small intestines proportional to the dose of PE MPs. This study demonstrates that long‐term exposure of fish to MPs has no significant effect on fecundity but impairs fish health, which could potentially jeopardize the quality of fish eggs and recruitment.

Distribution and environmental preferences of Saprolegnia and Leptolegnia (Oomycota) species in fish hatcheries in Hungary

We studied for the first time the abundance and species distribution of water molds (Oomycota, Saprolegniales) in fish hatcheries in Hungary, with a focus on Saprolegnia and Leptolegnia spp. A total of 182 water mold isolates were obtained from different developmental stages of fish (eggs, fry, and adults) and water samples collected during the spawning season of cyprinids and salmonids. Of the ten water mold species identified based on their ITS–rDNA sequences, S. parasitica, S. ferax, and S. australis were the most abundant. Statistical analyses of species proportions in relation to the sample source and host preference revealed that S. parasitica was significantly more abundant in the host than in water samples, whereas the opposite trend was observed for S. ferax and S. australis. In addition, our results confirmed previous findings that S. australis and S. ferax prefer warm water (+21–24 °C) and that S. parasitica has a wide temperature tolerance (+3–24 °C). The DNA sequence identity analysis showed that the species demarcation criterion for Saprolegnia spp. was approximately 98 % identity, based on ITS–rDNA sequences. Furthermore, our phylogenetic analyses suggest that taxonomic revision of Leptolegnia spp. is necessary.

The influence of lingonberry and sea buckthorn powder-aqua solutions on the nutritional value of sander roe

Fish roe is a rich source of polyunsaturated fatty acids, essential amino acids and several vitamins. The paper presents the possibility of using fish caviar treatment with berry solutions instead of traditional preservatives. The purpose of this study is to determine the effect of berry solutions from lingonberry powder (Vaccinium vitis-idea) and buckthorn (Hippophae rhamnoides) on the nutritional, biological value and safety of walleye caviar through the use of wild plants as preservatives. Samples of the caviar of the common walleye Sander (Sander lucioperca) were selected as research objects. The results showed that experimental caviar samples treated with berry solutions showed differences (p>0.05) compared to the control sample with saline solution, this proves an increase in the nutritional value and safety of fish caviar. It is also shown that the use of berry solutions from cranberries (LS) and sea buckthorn (SBS) combined with salt is 35% more effective compared to the control sample containing only salt (S). This means that using berry solutions significantly improves the results compared to the traditional canning method. This effect may be due to the additional beneficial properties of berry extracts, such as antioxidant and antimicrobial activity, which contribute to better preservation of caviar quality and safety. It was found that using a berry solution from cranberry powder revealed the best result. Also, it was shown that the greatest value and composition was possessed by the LS sample, which more satisfied the daily requirement of vitamins A, E and B group in comparison with other samples (p>0.05), the content of vitamin A (0.016±0.014); vitamin B (0.24±0.16); vitamin E (2.89±0.04); vitamin PP (2.1±0.05). This is because treating pikeperch caviar with berry solutions increases the amount of water-soluble and fat-soluble vitamins.

The influence and mechanism of fish collagen peptide and egg yolk lecithin on proliferation and lipid composition in feline adipocytes.

The influences of fish collagen peptide (FCP) and egg yolk lecithin (EYL) on the proliferation, fat accumulation and triglyceride content in feline adipocytes were investigated in this work, aiming at unveiling the mechanism of fat accumulation for cheek of feline animals. The lipogenic changes of adipocytes in the presence of FCP and EYL were determined by high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The results demonstrated that FCP of 10mg/mL had the strongest cell activity, with a relative increment rate of 156 ± 0.23%, and the triglyceride content reached 215.9 ± 3.86 mmol/L. By comparison, it was observed that an EYL concentration of 5mg/mL elicited the highest cell activity, exhibiting a relative increment rate of 152 ± 0.60%, and the level of triglyceride content was noted to reached 256.56 ± 25.68 mmol/L. After the feline adipocytes were treated with different concentrations of two active substances, fat formation and lipid droplets were found by oil red O staining. Liposome analyses confirmed that the formation of lipid compounds was regulated by FCP and EYL through pathways involved in lipid metabolism, notably including inositol phosphate insulin resistance, and phosphatidylinositol signaling pathways. This regulation was found to enhance cell vitality and facilitate fat accumulation. These findings provide a new strategy for the development of nutritional and healthy products or foods that promote feline cheek.

Biochemical analysis and fertilization success of Cirrhinus mrigala ova during induced spawning

Fish egg quality is very crucial in aquaculture sector for production of healthy seed. Egg yolk is an energy reservoir for growth and development of embryo. This study evaluated the biochemical composition and quality of Cirrhinus mrigala eggs at three different hatchery sites of Pakistan, (Site 1= Fish Seed Hatchery, District Pakpattan; Site 2= Sidhuwan Hatchery, Head Balloki, District Kasur; Site 3= Chenab Fish Hatchery, Rangpur, District Muzaffargarh) during induced breeding. For this, a total of 36 (18 males and 18 females) fish brooders, 12 (06 males and 06 females) from each site were utilized. Fatty acids analysis revealed significant differences among three different sites. Saturated fatty acids i.e., palmitic acid (C16:0) and stearic acids (C18:0) were higher at site 2 compared to the others sites. Monounsaturated fatty acids i.e., Oleic acid (C18:1) and polyunsaturated fatty acids i.e., Docosahexaenoic acid (DHA) (C22:6) exhibited considerably greater values at site 2 than those of other two sites. Egg mineral contents unveiled remarkable differences, particularly at site 2 indicating significantly higher mineral contents except copper (Cu) in comparison to the other sites. Significant variation exists in fertilization and hatching rates during induced spawning, with the highest values recorded at site 2. It is concluded that biochemical composition of egg especially fatty acid profile and mineral content greatly influences the embryonic development and hatching success of farm reared Cirrhinus mrigala.

Latitudinal variation in zooplankton over the Emperor Seamounts (34°–44° N, 170°–171° E) during the summer of 2019

During a research expedition to the Northwest Pacific between July 13 and August 11, 2019, we collected oceanic zooplankton samples over the Emperor Seamounts (Koko, Jingu, Nintoku, and Suiko guyots). We analyzed the horizontal and vertical distributions of abundance and biomass and also the structure of the zooplankton in the highly productive but poorly studied ocean waters between 34° and 44° N. The zooplankton was represented by four genera of amphipods, seven genera of pteropods, 39 genera of copepods, and larvae of benthic invertebrates and fish. The abundance and biomass of zooplankton increased towards higher latitudes along the series Koko < Jingu < Nintoku < Suiko guyots. The highest index of diversity was recorded over the Koko and Jingu guyots; the highest species richness occurred over the Jingu and Nintoku guyots. Small-sized copepods, appendicularians, chaetognaths, euphausiids, and fish eggs and larvae concentrated in the epipelagic; large copepods and ostracods concentrated in the mesopelagic. We identified three types of zooplankton assemblages: a Subtropical assemblage between 34°–35° N characterized by tropical/subtropical forms; a Transition assemblage characterized by subtropical, subarctic, and widespread species between 38°–41° N; and a Subarctic assemblage characterized by subarctic and widespread species between 43°–44° N. The spatial distribution of zooplankton was a function of environmental variables such as surface salinity, temperature at 200-m, and, to a certain extent, by surface Chl-a concentrations.

Synthesis and properties of the natural ultraviolet absorber gadusol in Komagataella phaffii

Gadusol, an efficient natural ultraviolet (UV) absorbing substance with antioxidant capacity, is ubiquitous in aquatic organisms such as microorganisms, algae, and fish eggs. In order to address issues such as its low natural extraction yield and environmental unfriendliness, we introduced the gadusol synthesis pathway from zebrafish into Komagataella phaffii and successfully constructed the recombinant strain capable of synthesizing gadusol. The xylose assimilation genes derived from Scheffersomyces stipitis were further introduced into the recombinant strain to increase the content of the key substrate sedoheptulose 7-phosphate (S7P). The results showed that the utilization of xylose was an effective strategy to increase the yield of gadusol. In the medium with only xylose as the substrate, the yield of gadusol reached 141.8 mg/L (32.3 mg/g dry cell weight, DCW), which was about 46 times of that in the medium with only glucose as the substrate. The product showed obvious absorption in the range of 275-305 nm, with the maximum absorption at 290 nm. Moreover, the product demonstrated antioxidant capacity. After reaction for 5 h, the ferric ion reducing antioxidant power (FRAP), 2, 2'-azino- bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rates changed by 90.83%, 25.50%, and 131.80%, respectively, which suggested that the product may be used as a long-acting antioxidant. This study demonstrated the great potential of K. phaffii as a chassis for the biosynthesis of natural UV absorbers. The biosynthesized gadusol has good UV absorption and antioxidant properties, which provides a theoretical basis for the industrial production and application of gadusol.

Internet of Things Based Water Quality Control System

Fish incubation, which involves the hatching of fish eggs, represents the process of embryogenesis until the embryo emerges from its protective shell. This intricate developmental journey is influenced by a combination of internal and external factors. External factors can be influenced by water quality that is not suitable for hatching fish eggs. Water quality, which includes temperature, dissolved oxygen, light intensity, salinity, and pH, is an important and limiting factor for living creatures that live in water, including chemical, biological, and physical factors. Poor water quality can prevent fish eggs from hatching and even cause death. The primary objective here is the creation of an Internet of Things (IoT)-based system designed for controlling water quality during fish incubation. This system is intended to aid fish farmers in effectively control the environmental conditions within their incubation ponds. The method used in designing IoT device is research and development, and it uses the Arduino Mega microcontroller as the main device to run pH sensors, turbidity sensors, oxygen sensors, temperature sensors, and relay modules. Water Quality Control System The fish incubation was successful. The average time needed to change the water temperature from 28.5 to 29 degrees Celsius is 4 minutes and 7 seconds; change the dissolved oxygen level from 11 to 11.5 is 3 minutes and 33 seconds; change the pH value of the water from 6.9 to 7.1; and maintain turbidity below 5 with an average time of 5 minutes and 58 seconds. Controlling water quality can speed up the fish egg incubation process for 8 hours.

Transglutaminase mediates the hardening of fish egg envelope produced by duplication of factor XIIIA gene during the evolution of Teleostei.

During the fertilization of fish eggs, the hardening of the egg envelope is mediated by transglutaminase (hTGase). After fertilization, TGase undergoes processing. We isolated hTGase from extracts of unfertilized and water-activated rainbow trout eggs. Rainbow trout hTGase (Rt-hTGase) appeared as an 80 kDa protein, and its processed form was 55 kDa. Their N-terminal amino acid sequences were nearly identical, suggesting processing in the C-terminal region. The specific activities were not significantly different, indicating that C-terminal processing does not activate the enzyme itself. We cloned the cDNA by reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers followed by RACE-PCR. The deduced amino acid sequence of the cDNA was similar to that of factor XIII subunit A (FXIIIA). Molecular phylogenetic and gene syntenic analyses clearly showed that hTGase was produced by duplication of FXIIIA during the evolution to Teleostei. The 55 kDa processed form of Rt-hTGase is predominantly composed of an enzyme domain predicted from the amino acid sequence of the cDNA. It is hypothesized that the C-terminal domain of Rt-hTGase binds to egg envelope proteins, and that processing allows the enzyme to move freely within the egg envelope, increasing substrate-enzyme interaction and thereby accelerating hardening.

P22-03 Concentrations of toxic elements in freshwater fish (Cyprinus carpio) blood and eggs: potential health implications

P22-03 Concentrations of toxic elements in freshwater fish (Cyprinus carpio) blood and eggs: potential health implications

Effect of Sperm Extender and Dilution Ratio on The Sperm Motility, Fertility, and Hatching Rates of Depik Fish Rasbora Tawarensis (Pisces: Cyprinidae) Eggs

Abstract There is no known artificial breeding method for depik fish Rasbora tawarensis. Sperm extender and the dilution ratio are crucial factors in the artificial breeding of fish. The current study aimed to assess the effect of several common fish sperm extenders and its dilution ratio on sperm characteristics and fertilization of depik fish eggs. Two series of experiments were performed to find the best extender and its dilution ratio. In the first experiment, five types of extenders were tested: Ringer’s solution, physiological solution, coconut water, sugarcane water, and roomie water. The second experiment studied four dilution levels of sperm and extender (v/v): 1:20, 1:30, 1:40, and 1:50. Every treatment was conducted in four replicates and the experiments were conducted consequently so that the findings in the first experiment were applied in the second. The first experiment showed that Ringer’s is the best extender for depik sperm with sperm motility, fertilization and hatching rates of 71.00%, 69.30%, and 53.66%, respectively; and the second experiment revealed that Ringer’s at dilution ratio 1:40 gave higher sperm motility, fertilization, and hatching rates of 74.66, 70.33, and 59.00%, respectively. In conclusion, Ringer’s solution was the most favorable extender for sperm which yielded best fertilization results at 1:40 dilution ratio (sperm:extender, v/v) in depik fish.

Straightforward high-temperature antibody immobilization for rapid and simple microfluidic paper-based ELISA for detection of β’-component (Onc k 5) protein, a major IgE-binding protein in salmon roe

Detection of allergenic proteins in food is required for maintaining the health of persons with food allergies. Enzyme-linked immunosorbent assay (ELISA) is a common technique for the detection of proteins. However, conventional ELISA is expensive, time-consuming, and needs technical expertise. Here, a microfluidic paper-based analytical device (µPAD) combined with a sandwich ELISA technique is developed for rapid, simple, and sensitive colorimetric detection of β’-component protein, a major allergen in salmon roe. The developed µPAD-ELISA employs a capture antibody and enzyme-labeled detection antibody. In addition to the µPAD, a technique for immobilization of the capture antibody has been developed, which completes the immobilization within 5 min by drying the antibody solution on a paper substrate in an oven at 50 °C without any chemical modification. The immobilized antibody exhibited higher binding capability to an antigen and stability against washing processes than those immobilized at room temperature. Since this technique allows simple and rapid preparation of the ELISA in the µPAD, the present µPAD-ELISA completed the analysis within only 15 min, including the immobilization step, compared to a conventional ELISA, which takes about 19 h. This µPAD-ELISA offered a good limit of detection of 1.59 ng mL−1 and reduced the amounts of reagents by a factor of about 17–67, which decreases the analysis cost. This µPAD-ELISA approach employing the present antibody immobilization is expected to be an effective strategy for the detection of allergenic proteins in food.

Characterization of Bacterial Communities on Trout Skin and Eggs in Relation to Saprolegnia parasitica Infection Status.

We have investigated the changes in the microbial communities on the surface of trout eggs and the skin of adult trout in relation to the presence of Saprolegnia parasitica. This pathogen causes saprolegniosis, a disease responsible for significant losses in salmonid farms and hatcheries. It is known from other disease systems that the host-associated microbiome plays a crucial role in the defence against pathogens, but if the pathogen predominates, this can lead to dysbiosis. However, analyses of the effects of S. parasitica on the diversity, composition, and function of microbial communities on fish skin and eggs are scarce. Thus, we have collected skin swabs from injured and healthy trout (N = 12), which differed in S. parasitica load, from three different fish farms in Croatia (Kostanjevac, Radovan, and Solin), while trout egg samples (N = 12) were infected with S. parasitica in the laboratory. Illumina sequencing of the V4 region of the 16S rRNA marker gene showed that infection with S. parasitica reduced the microbial diversity on the surface of the eggs, as evidenced by decreased Pielou's evenness and Shannon's indices. We further determined whether the bacterial genera with a relative abundance of >5.0% in the egg/skin samples were present at significantly different abundances in relation to the presence of S. parasitica. The results have shown that some genera, such as Pseudomonas and Flavobacterium, decreased significantly in the presence of the pathogen on the egg surface. On the other hand, some bacterial taxa, such as Acinetobacter and Janthinobacterium, as well as Aeromonas, were more abundant on the diseased eggs and the injured trout skin, respectively. Finally, beta diversity analyses (weighted UniFrac, unweighted UniFrac, Bray-Curtis) have shown that the sampling location (i.e., fish farm), along with S. parasitica infection status, also has a significant influence on the microbial communities' composition on the trout skin and eggs, demonstrating the strong influence of the environment on the shaping of the host surface microbiome. Overall, we have shown that the presence of S. parasitica was associated with changes in the diversity and structure of the trout skin/egg microbiome. The results obtained could support the development of new strategies for the management of saprolegniosis in aquaculture.

Development and validation of a gas chromatography method for analysing polychlorinated biphenyls in fish roe

A method for determining polychlorinated biphenyls (PCBs) in fish roe by gas chromatography (GC) has been developed. The suitability (validation) of the process for the determination of 14 PCBs (PCB 18, PCB 31, PCB 28, PCB 52, PCB 44, PCB 101, PCB 149, PCB 118, PCB 153, PCB 138, PCB 180, PCB 170, PCB 194, PCB 209) in fish roe by GC using an electron capture detector (ECD) was evaluated according to the following criteria: selectivity, linearity, limits of detection (LOD), limits of quantification (LOQ), accuracy and precision. Automated Soxhlet extraction and sample clean-up by solid phase extraction (SPE) were proposed for extracting PCBs from fish roe. The results of the method selectivity study showed that the determination of PCBs in fish roe is not affected by other components in the sample. The correlation coefficients for fourteen PCBs ranged from 0.9962 to 0.9999 (R2 ≥0.995). The limits of detection (LOD) and limits of quantification (LOQ) of PCBs are below the maximum permissible levels set by the European Union (EU). The recovery percentage ranged from 81.5% to 107%, indicating the PCB extraction procedure's acceptability (R, 80 – 120%). The relative standard deviation (RSD, %) of the measurement results under convergence conditions ranged from 1.02% to 9.43% (RSD ≥15%). The obtained method suitability (validation) data meets the Commission Regulation (EU) No 589/2014 criteria.

Fish eggs in the diet of White Sea cod Gadus morhua marisalbi (Gadiformes: Gadidae): species identification using DNA-based methods

Trophic relationships reflect the peculiarities of the functioning of communities of aquatic organisms and analysis of their structure and dynamics can be used to improve fisheries management and assess the state of marine ecosystems. Populations at the margins of the species' range have particular adaptations, including feeding habits, to extreme conditions, which makes them a convenient model object for studying the possible consequences of ecosystem changes under the influence of global factors. The cod Gadus morhua marisalbi Derjugin, 1920 permanently inhabits the coastal waters of the subarctic White Sea, located at the northeastern margin of the geographic range of the Atlantic cod G. morhua Linnaeus, 1758. This coastal cod population strongly depends on the local environmental conditions and available food resources during the summer feeding period. In addition to the main food organisms (fish, polychaetes, crustaceans), the eggs of fish spawning in shallow coastal areas in summer are also important in the diet of cod at this time. According to published data, fish eggs found in significant quantities and most often in the stomachs of cod belonged to threespine stickleback and lumpfish, but this has not been confirmed by any experimental research. Besides, the possible presence of herring eggs in the diet of cod remains unproven due to the difficulties of its visual identification. In this work, we used molecular genetic methods for species identification of fish eggs found in cod stomachs. At the first stage, the species identification of DNA isolated from eggs was done using two sets of species-specific primers: the first which we designed for the mitochondrial COI gene of stickleback, cod, and herring, and the second, published for a microsatellite locus of herring. At the second stage, the species identity of DNA extracted from fish eggs was checked using DNA barcoding. The results showed that cod stomachs contained herring and stickleback eggs, and in a number of cases we found the co-occurrence of eggs of these species. Of the 29 DNA preparations studied, fourteen were successfully amplified with microsatellite primers for herring, and thirteen amplified with primers for stickleback. Interannual differences in the occurrence of herring eggs in samples were insignificant, while the frequency of occurrence of stickleback eggs in 2018 was higher than in 2017. Our analysis did not reveal significant intra-annual differences between the observed and theoretically expected number of cases of simultaneous occurrences of herring and stickleback eggs. The high frequency of occurrence of herring and stickleback eggs in cod stomachs revealed in this study indicates the importance of these components in the diet of cod and provides new knowledge on the trophic role of cod as a key species in the White Sea ecosystem. Analysis of available data on the spatial and temporal diet patterns of coastal White Sea cod shows that fish eggs can significantly contribute to the total amount of food consumed by this species during the summer.

Variations in the Abundance, Biodiversity, and Assemblage Structure of Larval Fish in the Restricted Waters of the Wang-an Light Fishery off Penghu, Taiwan

This study examined the abundance, biodiversity, and assemblage structure of larval fish inside and outside the restricted fishing zone of the Wang-an light fishery, which is located off Penghu, Taiwan. A total of 97 taxa belonging to 48 families of larval fish were identified through plankton tows conducted during the present investigation. Upeneus japonicus from the Mullidae family emerged as the dominant species in the surveyed area. Diurnal variation in larval fish abundance was evident, with higher abundance observed at night-time than during daytime. However, no significant difference was observed between the larval fish abundance inside and outside the restricted zone. Moreover, fish egg abundance and larval fish biodiversity did not exhibit notable differences between sampling locations or times. Cluster analysis revealed the presence of two groups of seasonal species. The major species in the spring group were Abudefduf vaigiensis and Pomacentrus coelestis, which prefer a low-temperature environment. The major species in the summer group was U. japonicus, which prefers a high-temperature environment. The seasonal succession of water masses under the influence of monsoon activity likely contributed to the observed grouping patterns of larval fish assemblages in the study area. These patterns were closely linked to the marine environmental conditions in this area. The study outcomes provide scientific insights and recommendations regarding the importance and benefits of establishing a restricted fishing zone for sustaining fishery resources.

Investigation of Antioxidant Activity of Protein Hydrolysates from New Zealand Commercial Low-Grade Fish Roes.

The objective of this study was to investigate the nutrient composition of low-grade New Zealand commercial fish (Gemfish and Hoki) roe and to investigate the effects of delipidation and freeze-drying processes on roe hydrolysis and antioxidant activities of their protein hydrolysates. Enzymatic hydrolysis of the Hoki and Gemfish roe homogenates was carried out using three commercial proteases: Alcalase, bacterial protease HT, and fungal protease FP-II. The protein and lipid contents of Gemfish and Hoki roes were 23.8% and 7.6%; and 17.9% and 10.1%, respectively. The lipid fraction consisted mainly of monounsaturated fatty acid (MUFA) in both Gemfish roe (41.5%) and Hoki roe (40.2%), and docosahexaenoic (DHA) was the dominant polyunsaturated fatty acid (PUFA) in Gemfish roe (21.4%) and Hoki roe (18.6%). Phosphatidylcholine was the main phospholipid in Gemfish roe (34.6%) and Hoki roe (28.7%). Alcalase achieved the most extensive hydrolysis, and its hydrolysate displayed the highest 2,2-dipheny1-1-picrylhydrazyl (DPPH)˙ and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidant power (FRAP). The combination of defatting and freeze-drying treatments reduced DPPH˙ scavenging activity (by 38%), ABTS˙ scavenging activity (by 40%) and ferric (Fe3+) reducing power by18% (p < 0.05). These findings indicate that pre-processing treatments of delipidation and freeze-drying could negatively impact the effectiveness of enzymatic hydrolysis in extracting valuable compounds from low grade roe.

Integrating visual and molecular approaches for fish eggs analysis: A study on formaldehyde fixation and storage procedures

AbstractAccurate taxonomic classification and developmental stage determination of fish eggs are crucial for ecological monitoring, conservation efforts, and stock assessments. Traditional methods for fish and fisheries rely on visual examination of morphological traits, but they face challenges due to species overlap especially for early stages. Molecular tools, such as DNA barcoding, offer higher resolution in taxonomic identification but may not provide developmental stage information. This study explores the effectiveness of different formaldehyde fixation concentrations and storage procedures on fish eggs collected from Lofoten, Norway, for both visual and molecular analysis. Visual analysis successfully identified developmental stage for all fixation solutions. Molecular barcoding using the 16S rRNA gene identified up to 100% of eggs at the species level, with decreasing success rates over time when stored in formaldehyde fixation. The highest DNA barcoding success rates were accomplished using 4% formaldehyde fixation for 12‐ or 24‐h following transfer to ethanol. Using 0.5% and 1% formaldehyde fixation up to 8 weeks also resulted in high DNA success rates, but results deteriorated with increasing storage time. This study provides valuable insights for integrating visual and molecular methods for fish egg analysis, with practical implications for sample preservation during marine surveys.