Freshwater Fish Research Articles

Improving gel properties of low-salt silver carp surimi through single-mode microwave-assisted processing

Surimi, a product derived from low-value fish, is widely used to produce high-value items such as imitation crabsticks and fish balls. However, surimi from freshwater fish like silver carp generally exhibits inferior gel properties compared to marine fish. This study investigated the effects of 915 MHz single-mode microwave-assisted processing on the gel properties of low-salt silver carp surimi. Traditional water bath processing served as the control for comparison. Gel strength, texture, water-holding capacity (WHC), whiteness, protein secondary structure, and microstructure, along with thermal processing efficiency for microbial inactivation were evaluated. The results demonstrated that single-mode microwave processing significantly improved gel properties compared to water bath processing. Compared with the optimal water bath treatment, the gel strength of microwave processed samples increased significantly from 479.32 g·cm to 821.74 g·cm, while WHC increased from 0.77 to 0.87. The microwave processed surimi exhibited a more uniform microstructure. Because it enhanced the dissolution and cross-linking of myofibrillar proteins, leading to superior gel formation characterized by a lower α-helix content (10.31%) and higher β-sheet content (61.70%). Furthermore, microwave processing achieved faster heating rates, reducing the time spent in the critical gel deterioration temperature range, thereby improving overall gel quality. Single-mode microwave-assisted gelation also provided better thermal processing uniformity and efficiency, achieving pasteurization standards. The study highlights the potential of 915 MHz single-mode microwave processing to produce high-quality, low-salt surimi products, meeting contemporary health and convenience demands. These findings offer valuable insights for the industrial application of single-mode microwave technology in surimi production, promoting the development of innovative processing techniques to enhance the quality of surimi-based food products.

Freshwater Habitats Promote Rapid Rates of Phenotypic Evolution in Sculpin Fishes (Perciformes: Cottoidea).

AbstractInvasions of freshwater habitats by marine fishes provide exceptional cases of habitat-driven biological diversification. Freshwater habitats make up less than 1% of aquatic habitats but contain ∼50% of fish species. However, while the dominant group of freshwater fishes (Otophysi) is older than that of most marine fishes (Percomorphaceae), it is less morphologically diverse. Classically, scientists have invoked differences in the tempo and/or mode of evolution to explain such cases of unequal morphological diversification. We tested for evidence of these phenomena in the superfamily Cottoidea (sculpins), which contains substantial radiations of marine and freshwater fishes. We find that the morphology of freshwater sculpins evolves faster but under higher constraint than that of marine sculpins, causing widespread convergence in freshwater sculpins and more morphological disparity in marine sculpins. The endemic freshwater sculpins of Lake Baikal, Siberia, are exceptions that demonstrate elevated novelty akin to that of marine sculpins. Several tantalizing factors may explain these findings, such as differences in habitat stability and/or habitat connectivity between marine and freshwater systems.

Effect of low-salinity seawater transient on antioxidant capacity, muscle quality and intestinal microorganism of crucian carp (Carassius auratus gibelio)

Freshwater fish are frequently disliked by consumers due to their fishy odor and loose texture. Therefore, salinity treatment before market release is crucial for improving the muscle quality of freshwater fish. In this study, Carassius auratus gibelio was temporarily reared in low-salinity seawater (6 ppt) for 15 days, and changes of antioxidant levels, muscle texture, and intestinal microbial were determined. After temporary rearing in seawater, the hardness, gumminess, and chewiness of the muscle texture improved, and the relative contents of fishy and fatty odors decreased. This indicated that low-salinity treatment can enhance muscle quality and flavor while reducing fishy odor. According to microbiome research, low-salinity saltwater temporarily reduced the relative abundance of some opportunistic pathogens, such as Vibrio (from 47.61% to 0.1%) and Shewanella (from 15.20% to 5.86%) in the intestinal tract of crucian carp, and increased the relative abundance of beneficial bacteria, such as Sphingomonas (from 2.52% to 28.38%). This study can provide a reference for using low-salinity seawater for temporary rearing to enhance the quality of fish prior to marketing.

Egg Size Scales Negatively With System Size in a Periodic Fish Species.

Optimal egg size theory implies that female organisms balance between fecundity and individual offspring investment according to their environment. Past interspecific studies suggest that fishes in large marine systems generally produce smaller eggs than those in small freshwater systems. We tested whether intraspecific egg size variation reflected a similar pattern by comparing egg size among yellow perch (Perca flavescens) populations inhabiting a range of system sizes. In 2018, 2019, and 2023, we collected yellow perch egg samples from 12 locations in systems ranging in surface area from 37 to 5,390,492 ha. First, we found that egg diameter significantly increased with maternal total length in five of eight individually tested populations. After accounting for these maternal effects, we found a significant interaction, where females inhabiting larger lakes, such as the main basins of Lakes Erie and Michigan, produced smaller eggs than those in smaller inland lakes, and the greatest differences were demonstrated among females of greater total length. This egg size variation in the largest females is consistent with interspecific egg size comparisons between marine and freshwater fishes. However, by examining a single species across vastly different environments, we were able to support theoretical expectations that maternal investment in offspring should vary with environmental conditions controlling early-life resource acquisition and competition.

Coral reef fish visual adaptations to a changing world

Abstract Coral reef ecosystems show fluctuations in their prevailing light environment in response to both regular (e.g. between seasons) and more prevalent stochastic events (e.g. human‐induced sediment runoff). In these shifting environments, phenotypic plasticity provides an essential mechanism for coral reef fishes to adjust their visual capability to meet changing sensory requirements. Here, we evaluate the growing area of research that highlights the many genetic and ecological mechanisms that affect the plastic responses of coral reef fish vision to environmental cues. With an increasing number of disturbances in the marine environment, it is critical to understand the extent and limits of visual plasticity under natural and disturbed conditions. With our current knowledge and drawing upon a large body of work in freshwater fishes, we speculate whether coral reef fishes can adapt to the changes to their visual environment and where the limitations could lie. Whilst coral reef fishes have shown visual adaptations under different light environments, the degree of plasticity is inconsistent between species. Thus, plasticity may not only be functionally significant in maintaining the performance of visually guided behaviours for single species but, more broadly, is likely key to sustaining ecosystem function. Read the free Plain Language Summary for this article on the Journal blog.

Immediate Genetic Augmentation and Enhanced Habitat Connectivity Are Required to Secure the Future of an Iconic Endangered Freshwater Fish Population.

Genetic diversity is rapidly lost from small, isolated populations by genetic drift. Measuring the level of genetic drift using effective population size (N e) is highly useful for management. Single-cohort genetic N e estimators approximate the number of breeders in one season (N b): a value < 100 signals likely inbreeding depression. Per-generation N e < 1000 estimated from multiple cohort signals reduced adaptive potential. Natural populations rarely meet assumptions of N e-estimation, so interpreting estimates is challenging. Macquarie perch is an endangered Australian freshwater fish threatened by severely reduced range, habitat loss, and fragmentation. To counteract low N e, augmented gene flow is being implemented in several populations. In the Murrumbidgee River, unknown effects of water management on among-site connectivity impede the design of effective interventions. Using DArT SNPs for 328 Murrumbidgee individuals sampled across several sites and years with different flow conditions, we assessed population structure, site isolation, heterozygosity, inbreeding, and N e. We tested for inbreeding depression, assessed genetic diversity and dispersal, and evaluated whether individuals translocated from Cataract Reservoir to the Murrumbidgee River bred, and interbred with local fish. We found strong genetic structure, indicating complete or partial isolation of river fragments. This structure violates assumptions of N e estimation, resulting in strongly downwardly biased N b estimates unless assessed per-site, highlighting the necessity to account for population structure while estimating N e. Inbreeding depression was not detected, but with low N b at each site, inbreeding and inbreeding depression are likely. These results flagged the necessity to address within-river population connectivity through flow management and genetic mixing through translocations among sites and from other populations. Three detected genetically diverse offspring of a translocated Cataract fish and a local parent indicated that genetic mixing is in progress. Including admixed individuals in estimates yielded lower N e but higher heterozygosity, suggesting heterozygosity is a preferable indicator of genetic augmentation.

Freshwater habitat invaders: Impacts on artificial flow refuge use by native fish under pulsed flows

Flow regulation and the spread of invasive species are significant threats to freshwater biodiversity, including native fish communities in rivers across the globe. The bleak (Alburnus alburnus), an invasive fish currently widespread throughout the main rivers of the Iberian Peninsula, threatens native fish biodiversity, mostly via trophic competition and hybridisation. In this study, we assessed the impacts of bleak presence and rapid flow fluctuations (both main and interactive effects) on the use of artificial habitats (a flow refuge) and the stress physiology of barbels. We examined how bleak's presence influenced the selection of flow refuges by the native Iberian barbel (Luciobarbus bocagei) under base (continuous 7 L s−1 flow stimulus) and pulsed (7 L s−1 to a 60 L s−1 pulse) flows in an indoor flume. We quantified habitat use within three specific regions of two installed flow refuges and two physiological responses (glucose and lactate) associated with the stress axis. The results indicated that the presence of bleak significantly reduced flow refuge use by barbels and this effect was more prominent during pulsed flows. Additionally, barbels exhibited higher levels of glucose and lactate in the presence of bleaks. These results show that bleaks compete with barbels for habitat under fluctuating flows and induce physiological adjustments that may reduce the ability of barbels to find low-velocity areas to shelter. Overall, the bleaks had a competitive advantage under high flow variability. This underscores the need for further studies and effective management strategies to protect native freshwater fish communities in the context of biological invasions and anthropogenic flow variability.

Early Pleistocene freshwater fish from Dursunlu (Ilgın Basin, south-western Türkiye): Implications for early hominin dispersals out of Africa

Dursunlu, located in the Ilgın Basin (south-western Türkiye), represents one of the most prolific sites to explore early human occupations in Anatolia. This paper describes the lacustrine fish assemblage from this site during the Early Pleistocene (Günz glaciation). The fish community comprised two families, namely Cyprinidae and Cobitidae. Within the cyprinids, the genera had a wide range of ecological diversity. The most frequently observed genera in Dursunlu are Chondrostoma and Squalius, but Capoeta and Barbus are also present. These genera prove that a very shallow and well-oxygenized paleolake occupied the Ilgın Basin with a dense palustrine vegetation belt and partially rocky-gravelly substrate. This paleolake constituted a hotspot for the presence and early dispersal out of Africa of the genera Homo in this region and Eurasia during the Lower Paleolithic/Early Pleistocene.

Interbasin trade worsens the state of freshwater fish biodiversity in China

Interbasin trade worsens the state of freshwater fish biodiversity in China

Azoxystrobin induced genotoxicity in Pethia conchonius, a freshwater fish of river Teesta, India

Azoxystrobin, a widely used fungicide, can contaminate water bodies through surface run-off, posing a risk to aquatic organisms. This study aimed to assess the genotoxic effects of azoxystrobin on the fish Pethia conchonius. The 96-hour lethal concentration (LC50) of azoxystrobin was determined to be 0.514 mg/L. Based on LC50, three sub-lethal concentrations (SLCs) of 0.025 mg/L, 0.0514 mg/L, and 0.103 mg/L were used to expose fish for 96 hours. The blood and gill samples were collected at 24-hour intervals for analysis. The Micronucleus (MN) and Comet assays were used to evaluate nuclear abnormalities and DNA damage, respectively. The results showed that the frequency of nuclear abnormalities and DNA damage in the exposed groups was significantly higher than the control, with increasing concentrations and duration of exposure. The highest levels of micronuclei, notched and blebbed nuclei, and DNA damage parameters were observed in the group exposed to SLC III for 96 hours. These findings indicate that azoxystrobin is highly genotoxic to fish causing severe DNA damage.

Impact of triflumezopyrim (insecticide) on blood and serum biochemistry of freshwater fish, subadult Labeo rohita (Hamilton, 1822)

The impact of insecticides on water bodies can be evaluated by studying the physiology and health of fish. These chemicals pose a significant and direct risk to aquatic ecosystems and hence aquatic animals like fish. Therefore, this study was designed to investigate the toxic effects of sub-lethal concentrations of triflumezopyrim, a novel synthetic insecticide commonly used in crop protection, on the biochemical and hematological parameters of freshwater sub-adult Labeo rohita L. Here, fish were subjected to sub-lethal doses of triflumezopyrim at various concentrations (1.41 ppm, 3.27 ppm, and 4.97 ppm) for 21 days. In addition, fish were grown in an insecticide-free control group to determine the toxic effects of the insecticides. The obtained data on various biochemical and hematological parameters of the fish were analyzed using state-of-the-art statistics. Our findings suggest that triflumezopyrim exposure has a significant effect on blood variables. However, variable response, such as mean corpuscular volume, hemoglobin concentration, neutrophils, and eosinophils were unaffected by insecticide treatment, regardless of the dose. Our interhematological parameter analysis revealed varying interrelationships at various insecticide doses. Similarly, triflumezopyrim exposure significantly affected the response of serum biomarker profiles i.e., the difference in mean treatment pairs (control and three doses of triflumezopyrim) had a significant effect on the response of most serum profile parameters.

Incorporating Implicit Information to Disentangle the Impacts of Hydropower Dams and Climate Change on Basin-Scale Fish Habitat Distribution.

The loss of freshwater fish habitats, exacerbated by climate change and dam constructions, poses a critical environmental concern. The upper Yangtze River basin, noted for its abundant fish fauna and concentrated dam development, serves as a crucial locale for investigating the impacts of climate shifts and dam construction. This study aims to disentangle the impacts of hydroelectric dams and climate change on fish habitat distribution by analyzing species presence data across different periods. Species distribution models were constructed using Maxent for Coreius guichenoti (a warm-water endangered fish) and Schizopygopsis malacanthus (a cold-water endangered fish). The model accuracy was assessed using the area under the curve of the receiver operating characteristic. Habitat distribution modeling and prediction for the pre-dam period (1970-2000) and post-dam period (2001-2020), as well as future climate change under two shared socioeconomic pathways scenarios, were conducted. The impacts of climate change and dam construction on the habitat suitability of two fish species were quantified. The results revealed dam construction predominantly diminished habitat suitability and range, with high-suitability habitats in the post-dam period decreasing by 56.3% (720.18 km) and 67.0% (1665.52 km) for the two fishes, respectively. Climate change would enhance the habitat suitability of Coreius guichenoti, while it would decrease the habitat suitability of Schizopygopsis malacanthus. The impact of dam construction is greater that of climate change for them. This study underscores the profound impacts of dam construction on fish habitats, particularly for cold-water species, and highlights the critical need for habitat restoration in sustainable hydropower development. Our method of disentangling these factors also provides a new approach to evaluating environmental impacts in large river basins.

Effect of hydrochemical parameters of ponds on the quality of fish seeds in the conditions of the Kherson industrial and experimental hatchery for growing common freshwater fish

Effect of hydrochemical parameters of ponds on the quality of fish seeds in the conditions of the Kherson industrial and experimental hatchery for growing common freshwater fish

Whether hypoxia tolerance improved after short-term fasting is closely related to phylogeny but not to foraging mode in freshwater fish species.

The combined stresses of fasting and hypoxia are common events during the life history of freshwater fish species. Hypoxia tolerance is vital for survival in aquatic environments, which requires organisms to down-regulate their maintenance energetic expenditure while simultaneously preserving physiological features such as oxygen supply capacity under conditions of food deprivation. Generally, infrequent-feeding species who commonly experience food shortages might evolve more adaptive strategies to cope with food deprivation than frequent-feeding species. Thus, the present study aimed to test whether the response of hypoxia tolerance in fish to short-term fasting (2 weeks) varied with different foraging modes. Fasting resulted in similar decreases in maintenance energetic expenditure and similar decreases in Pcrit and Ploe between fishes with different foraging modes, whereas it resulted in decreased oxygen supply capacity only in frequent-feeding fishes. Furthermore, independent of foraging mode, fasting decreased Pcrit and Ploe in all Cypriniformes and Siluriformes species but not in Perciformes species. The mechanism for decreased Pcrit and Ploe in Cypriniformes and Siluriformes species is at least partially due to the downregulated metabolic demand and/or the maintenance of a high oxygen supply capacity while fasting. The present study found that the effect of fasting on hypoxia tolerance depends upon phylogeny in freshwater fish species. The information acquired in the present study is highly valuable in aquaculture industries and can be used for species conservation in the field.

Embryonic development of the world's smallest puffer fish, Carinotetraodon travancoricus - a threatened freshwater fish of the Western Ghats Biodiversity Hotspot.

The Malabar dwarf puffer, Carinotetraodon travancoricus is the smallest known pufferfish (family Tetraodontidae) and one of the smallest freshwater fishes of the Indian subcontinent. Due to their miniature size, wacky behaviour and appearance, they are much preferred in the international aquarium fish trade, although little is known regarding their breeding activity in captivity and their embryonic development. The purpose of this study was to fill these knowledge gaps. Wild-caught Malabar dwarf puffers were acclimatised to conditions, and pairs were introduced to breeding tanks. Adult fishes were fed with live and frozen diets including Artemia nauplii, moina and bloodworm. During spawning seasons, adult fish displayed elaborate courtship behaviour around sunset. Carinotetraodon travancoricus is a batch spawner releasing 1 to 5 eggs per diem. The eggs were spherical, and non-sticky, with a diameter of 1.48 ± 0.1 mm, and hatching took place after 108 to 116 h post-incubation. The newly hatched larvae were 3.5 ± 0.2 mm in length, and weighed 2.9 ± 0.4 mg. The early larvae have substantial yolk and oil globules as an energy reserve. Histological studies on mature females suggested the batch spawning nature of the species and low fecundity. Given its unique reproductive behaviour and characters, in situ protected habitats are required to ensure their continued survival in the wild, apart from encouraging captive breeding to augment the demand in the international aquarium fish trade.

Determining the efficient mass ratio of the extractant and the object of extraction and the equilibrium concentrations of the target components in them

The caviar and lecithin complex of freshwater fish can be widely used for the production of various food products, including those of functional orientation. The main technological operations in lecithin technology should include the processes of extraction of the initial caviar raw material and raffinate obtained after the first stage of selective extraction. The purpose of the study is to identify the rational mass ratio of extractant and raw material (module), on which the extraction efficiency depends, as well as the final concentration of extracted substances in the extract to determine its current value in the process of mass transfer to study the kinetics of extraction. The object of the study is the caviar-anchovy complex of fathead carp, carp, pikeperch and catfish, as well as the extract and raffinate from it. Summarizing the experimental data on revealing the rational module, as well as the final concentration of extracted substances in the extracts obtained, we can conclude that for caviar of the fish species under study, the rational hydromodule for its extraction with acetone is the ratio of dry caviar : extractant 1 : 4, and for its extraction with ethyl alcohol is the ratio of dry caviar : extractant 1 : 8. If the mass ratio refers to the fresh caviar of the studied fish species, then its rational indicator at its extraction with acetone is the ratio of fresh caviar : extractant 1 : 1.5, and at its extraction with ethyl alcohol is the ratio of fresh caviar : extractant 1 : 3. The average final concentration of extracted substances from dry caviar of the studied fish species in the extracts obtained, if acetone was used as a solvent under rational conditions of mass transfer, corresponds to the value of 1.3 %, and if ethyl alcohol was used as a solvent under rational conditions of mass transfer, corresponds to the value of 1.0 %.

DIGITAL MARKETING IN THE CREATIVE ECONOMY

The urgency of this research is focused on Mina Padi Integrated Agriculture education in order to increase rice production and freshwater fish production by Cibahayu Village farmers as well as digital marketing training in the creative economy of making fish-based culinary that has high economic value, as well as digital-based marketing education so as to increase economic opportunities from these marketing strategies. Through this research activity, it is hoped that digital literacy related to production marketing can be a provision in utilizing existing economic opportunities. The purpose of this research activity is to provide experience and knowledge for farmers to be able to carry out the mina padi system, besides that the community is able to apply the creative economy by making fish-based culinary, and understand the digital-based production marketing process.

Nano-selenium supplementation: improving growth, digestibility and mineral absorption in freshwater fish, Catla catla

BackgroundThis research investigated the impact of selenium-nanoparticles (Se-NPs) supplemented in sunflower meal (SM)-based diets on digestibility, mineral absorption, and growth performance of Catla catla. Se-NPs were added to seven test meals in varying amounts (0, 0.5, 1, 1.5, 2, 2.5 and 3 mgkg− 1). A total of 315 fish were evenly allocated three replicate tanks, with 15 fish per tank, and given diets equivalent to (5%) of their wet biomass daily for a period of 90 days.ResultsThe test diet (T-D) supplemented with 1.5 mgkg− 1 Se-NPs yielded remarkable results, including a significant increase in mean weight gain (14 g), an impressive average weight gain percentage (208%), a 100% survival rate, with no mortality observed and the highest specific growth rate (1.25). Moreover, 1.5 mgkg− 1 Se-NPs (T-D-IV) demonstrated superior nutritional digestibility (CP, 76%; CF, 79% and GE, 74%). Additionally, the diet 1.5 mgkg− 1 Se-NPs showed enhanced mineral absorption (K, P, Ca, Na, Zn, Cu and Fe) than other diets.ConclusionIt was practically proven that the growth indices, nutrient absorption, and mineral status of C. catla were significantly improved by Se-NPs supplemented SM-based diets, with the optimum level of supplementation being 1.5 mgkg− 1.

Unpredictable Repeated Stress in Rainbow Trout (Oncorhynchus mykiss) Shifted the Immune Response against a Fish Parasite.

Farmed fish are regularly subjected to various stressors due to farming practices, and their effect in the context of a disease outbreak is uncertain. This research evaluated the effects of unpredictable repeated stress in rainbow trout challenged with the ciliate Ichthyophthirius multifiliis, known to cause white spot disease in freshwater fish. Before and after the pathogen exposure, fish were handled with a random rotation of three procedures. At 7 days post-infection (dpi), the parasite burden was evaluated in fish and in the tank's water, and the local and systemic immune responses were investigated in the gill and spleen, respectively. The fish mortality was recorded until 12 dpi, when all the fish from the infected groups died. There was no statistical difference in parasite burden (fish and tank's water) and infection severity between the two infected fish groups. The immune gene expression analysis suggested a differential immune response between the gill and the spleen. In gills, a T helper cell type 2 immune response was initiated, whereas in spleen, a T helper cell type 1 immune response was observed. The stress has induced mainly upregulations of immune genes in the gill (cat-1, hep, il-10) and downregulations in the spleen (il-2, il-4/13a, il-8). Our results suggested that the unpredictable repeated stress protocol employed did not impair the fish immune system.

Future invasion risk assessment of the peacock bass in Neotropical ecoregions: A conceptual and testable model

Protecting freshwater biodiversity from non-native invasive species and their impacts is crucial for minimising both regional and global deterioration of ecosystem services. The yellow peacock bass Cichla ocellaris, a predatory freshwater fish endemic to the Amazon region, has been translocated within several Neotropical ecoregions, exhibiting harmful effects on biodiversity. In order to facilitate the prioritization of management efforts, which are essential for defining conservation actions in extensive and diverse areas, we propose a risk assessment index that integrates multiple ecological and environmental variables within a comprehensive framework, here applied for C. ocellaris. By considering fish species richness, occurrence frequency, and climate suitability, our index provides a more nuanced understanding of invasion risks. Within regions categorized as high and very high risk, where ecological impacts of C. ocellaris have been extensively documented (e.g., the Southern and North-East Brazilian regions, as well as Central American and Caribbean ecoregions), numerous environments are increasingly conducive to the establishment of this invasive species, exacerbated by a surge in dam constructions. Our analysis projects a significant increase in suitable habitats by 5% to 6.5%, with Southern and Northeastern Brazil and Central America identified as critical zones. Thus, our reproducible risk assessment framework, which considers freshwater ecoregions as conservation units, not only directs effective resource allocation for control measures but also enhances our ability to predict and mitigate the ecological impacts of non-native species introductions, providing a valuable tool for both policymakers and conservationists.