Mrigal Research Articles

Coexistence mechanisms and individual trophic niche variation between functionally analogous non-native and native carp species

Understanding the mechanisms that promote coexistence between functionally analogous non-native and native species that share similar prey is important for predicting the ecological consequences of their competitive interactions. Theory predicts that species coexistence is facilitated by stabilizing mechanisms that enhance inter-specific trophic niche partitioning, and/ or the equalizing mechanisms that reduce differences in the average fitness. Inter-specific niche partitioning, influenced by the ecological opportunity in prey resources, also affects intra-specific niche partitioning and individual niche expansion. These theories were tested using the non-native mrigal carp Cirrhinus mrigala and its congener native mud carp C. molitorella that coexist across the Pearl River basin, Southern China, with their trophic interactions analysed using DNA metabarcoding on fish gut contents sampled across the basin in both the dry and wet seasons of 2019 and 2021. The results revealed that the inter-specific trophic niche overlap was lower than their intra-specific trophic niche overlap, suggesting their coexistence was supported by stabilizing mechanisms. The ecological opportunity in prey resources was driving inter-specific niche partitioning and this partitioning then positively influenced intra-specific niche partitioning and individual niche expansion, especially in mrigal carp that had larger body sizes and occupied higher trophic positions at constricted individual niches. Fish body size also affected inter-specific niche partitioning and the relationship between inter- and intra-specific niche partitioning, with positive effects on both in mrigal carp but negative effects on both in mud carp. The results thus provide a mechanistic explanation on how closely related non-native and native species coexist and highlight the importance of dietary plasticity in facilitating the invasion of non-native species.

Myxobolus liuyangensis sp. n. (Myxosporea: Myxobolidae) from the gills of exotic mrigal carp Cirrhinus mrigala (Actinopterygii: Cyprinidae) in China.

A new species, Myxobolus liuyangensis sp. n., was found in the gills of the exotic mrigal carp Cirrhinus mrigala during a survey of the fauna of exotic fish myxospore in China. Plasmodia were elongated pyriform, measuring 0.42 mm long and 0.15 mm wide. The mature spores were elongated pyriform in the frontal view, tapered forward, rounded posterior end, and fusiform in the sutural view, measuring 17.3 ±0.5 (16.5-18.3) μm long, 6.2 ±0.3 (5.2-6.8) μm wide, and 4.8 ±0.2 (4.4-5.1) μm thick. The two equal polar capsules of elongated pyriform in shape measured 11.3 ±0.5 (10.6-12.3) μm long and 2.5 ±0.3 (2.0-3.1) μm wide, occupying more than half the capacity of the spores. The polar filaments were coiled with fifteen to sixteen turns. No mucous envelope and caudal appendages were found. The consensus SSU rDNA gene sequence obtained here for M. liuyangensis sp. n. did not match any sequences available in GenBank, but was most closely related to M. catlae that infects the gills of C. cirrhosis (MT003664, 97.99% similarity). Phylogenetic analysis indicated that the C. mrigala-infecting Myxobolus species were not clustered together, but dispersed in different clades. The present species clustered with M. catlae and M. orissae within the clade I of elongated pyriform spore shapes, revealing spore shapes may play an important role during the evolution of Myxobolus species. This is the second myxosporean infection report in the exotic mrigal carp C. mrigala.

The impact of host genetics on microbe assemblages in three types of mrigal carp (Cirrhinus mrigala)

Host–microbiota interactions are molecular and physical interactions between the microbiota and the host that play significant roles in the lifespan of animals. In the present study, two types of gynogenetic mrigal carp (GMCC and GMCW) and the original maternal mrigal carp (MC) were used as a models to investigate host–microbiota interactions. The two types of gynogenetic mrigal carps showed faster growth and better cold tolerance than the MC fish. Compared to those in MC, a large number of goblet cells and higher activity of cellulase and pepsin were detected in the intestine of gynogenetic fish. The composition and abundance of the microbial communities significantly differed among the three types of mrigal carp and water, with Proteobacteria, Firmicutes and Chloroflexi being the most dominant microbes in the GMCC, GMCW and MC fish, respectively. Pseudomonas, Lactococcus and Defluviicoccus were the biomarker genera in the GMCC, GMCW and MC fish. Network analysis revealed no relationships between fish and water, but the dominant genera was positively correlated with the abundance of certain enzymes. Functional analysis revealed the dominant genera associated with amino acid metabolism, fatty acid metabolism and bile acid biosynthesis. Our results suggested that host genetics may affected gut microbe assembly and that the specific metabolic functions of gut microbes may contribute to growth performance through the microbe-gut-liver axis.

Inclusion of near‐threatened micronutrient‐rich small indigenous species (SIS) dhela (Osteobrama cotio) in pond aquaculture

AbstractDue to their high content of micronutrients, small indigenous species (SISs) of fish play a vital role in the diets of people. Dhela (Osteobrama cotio) is one of the most important micronutrient‐rich SISs and was once abundant but is currently disappearing from inland waters. This study investigated the culture suitability of dhela with carp species in polycultures in a pond aquaculture system. The stocking density of the carp species was the same in all the treatments, with Labeo catla, Labeo rohita and Cirrhinus cirrhosus at 10,800/ha. Dhela were cultivated at a density of 10,000/ha in treatment 2 (Dhela‐10K) and 15,000/ha in treatment 3 (Dhela‐15K), and no dhela were cultivated in treatment 1 (Dhela‐0). After 7 months of culture, there were no significant differences in total production among the treatments, with yields of 3393.27 ± 120.70, 3534.52 ± 57.03 and 3687.34 ± 244.41 kg/ha in Dhela‐0, Dhela‐10K and Dhela‐15K, respectively. Notably, a significantly greater (p < 0.05) net profit and benefit‒cost ratio were found in Dhela‐10K and Dhela‐15K than in Dhela‐0, but no significant difference was found between Dhela‐10K and Dhela‐15K. The inclusion of dhela in pond polycultures with carp species demonstrates the potential benefits of diversifying aquaculture systems. Farmers could consider incorporating SISs into their existing aquaculture practices to increase overall production and improve economic returns.

Density‐dependent trophic consequences of invasive mrigal carp on native mud carp in Chinese fresh waters

Abstract Understanding the strength, direction and consequences of the trophic impacts of invasive fish on functionally analogous native fishes is important in invasion impact assessment and for informing management programmes. As functionally analogous native and invasive fishes can share prey resources, there is high potential for competitive interactions, which could affect trophic niche sizes and positions. The highly invasive mrigal carp Cirrhinus mrigala and native mud carp Cirrhinus molitorella now co‐exist in many freshwaters in southern China, raising concern on the consequences for mud carp. The trophic interactions of the two species and their consequences (for growth rates and trophic niche sizes as the isotopic niche, calculated using δ13C and δ15N) were tested in a pond enclosure experiment based on additive and substitutive treatments using fish in allopatric and sympatric contexts, with results compared with invaded wild communities. In the experiment, specific growth rates decreased significantly as fish abundance in treatments increased. These density‐dependent effects were observed in both species and were independent of whether the treatment was allopatric or sympatric. In allopatric treatments, isotopic niches of mud carp increased in size with fish number. Conversely, in sympatric treatments, mud carp isotopic niche size decreased with increased mrigal carp number. For mrigal carp, isotopic niche sizes decreased as fish number increased in both allopatric and sympatric treatments. In sympatric experiment treatments, the isotopic niches of mud carp and mrigal carp were always divergent. This was, however, in contrast to four invaded wild communities, where the isotopic niches of the two fishes always had some overlap. Experimental and field data suggest that although native mud carp could be impacted by mrigal carp, these impacts might only manifest when the species are at very high abundances and inter‐specific competitive interactions could be intense. These results also suggest the two species have mechanisms that reduce their inter‐specific interactions to minimise their competitive interactions, thus any ecological impacts from mrigal carp might manifest more from indirect than direct processes.

Comparative transcriptomic analysis of the brain-liver Axis reveals molecular mechanisms underlying acute cold stress response in Gynogenetic Mrigal carp

In this study, we produced a population of gynogenetic mrigal carp (Cirrhinus mrigala, GMCJ) through artificial gynogenesis using UV-inactivated white crucian carp spermatozoa. The GMCJ exhibited a faster growth rate and strong resistance to low temperatures, surviving natural winter conditions with temperatures below 10 °C. To gain a deeper insight into GMCJ's molecular response to acute cold stress (a decrease in water temperature from 26 °C to 14 °C within 1 h at a rate of 0.2 °C/min), we conducted a comparative analysis of the histology and transcriptomics of the brain-liver axis. Transmission electron microscopy of the heart tissues revealed that acute cold stress result in widened myofilament spacing, along with enlarged, deformed mitochondria that developed vacuoles and ruptured. We identified differentially expressed genes (DEGs) in the brain (2463 upregulated and 3288 downregulated genes) and liver (1210 upregulated and 1224 downregulated genes). Analysis of the DEGs' correlations indicated that major pathways involved in immunity, disease, metabolism, and growth were active and interconnected. KEGG functional analysis showed that the most enriched pathways in the brain-liver axis involved the regulation of the glucagon pathway, PI3K-Akt signaling pathway, and herpes simplex infection. Numerous genes associated with the nervous-endocrine system were activated, suggesting a coordinated response of the brain-liver axis to acute stress. These findings enhance our understanding of how farmed, particularly gynogenetic fish respond to acute cold stress.

Niche overlap between native Cirrhinus molitorella and potential invasive competitors

Biological invasion is one of the important reasons for the decline of freshwater biodiversity in China and even in the world. The Pearl river basin is one of the most threatened areas in China by biological invasion. Over the past four decades, mrigal carp Cirrhinus mrigala and rohu Labeo rohita have invaded the Pearl river. They potentially pose a huge threat to a well-known economic species, native mud carp Cirrhinus molitorella. However, little is known about the likely habitat distributions of these two invasive species, which limits our management of them. In this study, we detected the stable isotope ratios of nitrogen and carbon for fish and quantified their niche overlap with nicheROVER in R. The result showed that the individuals of two invasive species had a higher probability to be found in niche region of native C. molitorella (i.e., 65 % for C. mrigala and 74 % for L. rohita). Moreover, to increase understanding of their habitat distributions and potential range of spread, the existing habitats data of these three fish species obtained from previous literatures and the high-resolution bioclimatic parameters from WorldClim were analyzed via Maxent model. The results stressed that niche overlap was high among species, which could have an impact on local biodiversity in future. Furthermore, the visualization of habitat distributions could help show the dynamic habitat changes of invasive and native species over time, while also provide new insights into the subsequent prevention and control for invasive species in other river regions around the world.

PARASITIC DISEASES OF FISH IN THE CONDITIONS OF FARMING PONDS OF "AQVAREST" AND "AQUACITY" LLC IN THE ODESSA REGION

The article provides data on the spread of parasitic diseases in carp and grass carp in the farming ponds of Aqvarest LLC and Aquacity LLC of the Odesa region. Fish diseases are registered both in natural reservoirs and in fish farms, as a result of which the growth rates, reproductive capacity, marketability of fish decrease, quality indicators and biological value deteriorate; in addition, mass kills of fish may occur. The causes of diseases can be both non-contagious (adverse environmental conditions) and contagious (viruses, bacteria, parasitic diseases). Thus, constant monitoring of fish parasitofauna in pond farms of Ukraine is necessary, since the study of patterns of occurrence and spread of fish diseases, forecasting of these diseases affects the effectiveness of aquaculture breeding and preservation of fish products.
 The purpose of the work was to monitor parasitic diseases in carp and white amur in the farming ponds of Aqvarest LLC and Aquacity LLC of the Odesa region.
 During the parasitological examination of this year's and two-year-old carp and white amur in the ponds of LLC "Aqvarest" and LLC "Aquasti" of Odesa region, five diseases were diagnosed, the causative agents of which were: Gyrodastylus birmani, Dactylogyrus vastator, Khavia sinensis, Caryophyllaeus fimbriceps and Philometroides lusiana.
 Gyrodastylus birmani and Caryophyllaeus fimbriceps were recorded the most in the deep pond of "Aqvarest" LLC with the extent of invasion of 25.7%, in two-year-old carp and two-year-old white amur - 21.4%. In the shallow reservoir of "Aquacity" LLC, Gyrodastylus birmani (31.4%) and Caryophyllaeus fimbriceps (25.7%) were most recorded in two-year-old carp, and in two-year-old white amur Khavia sinensis (28.5%) and Caryophyllaeus fimbriceps (32.1 %).
 The intensity of infestation with cestodoses (caviasis and caryophyllosis), as well as nematodes (phyllometroidosis) was low, 1-2 or 3-4 specimen for fish, and clinical manifestations of the disease were not always recorded. However, the presence of these pathogens in the fauna represents a significant danger for the development of commercial fish species, namely carp and white carp.

A Review on the Use of Azolla Meal as a Feed Ingredient in Aquatic Animals’ Diets

The aquaculture industry’s insatiable demand for fishmeal has led to a price surge, prompting the search for a sustainable alternative protein source. Enter Azolla meal, a plant protein that could be a viable substitute for fishmeal. This cost-effective supplemental feed could be a game-changer for small-scale producers looking to expand their aquaculture production. Numerous experiments have been conducted on replacing fishmeals with Azolla meals in fish diets, and the results have sparked further research. This review delves into Azolla’s composition, comparing it to fishmeal in terms of proteins, amino acids, fatty acids, vitamins, and minerals. It also explores the value of employing Azolla in fish feeds and the various methods to mitigate its adverse effects through feed additives during the feed formulation. This review discusses the essential effects of Azolla meal on the growth of various fish species, including tilapia (Oreochromis niloticus), catfish (Clarias batrachus), thai silver barb (Barbonymus gonionotus), common carp (Cyprinus carpio), rohu (Labeo rohita), and catla (Catla catla) and mrigal (Cirrhinus cirrhosus). Azolla’s potential extends beyond its use as a fish feed ingredient. It could also be utilized for bioremediation to remediate hazardous chemicals in water resulting from aquaculture, industrial, and household waste. Further research is needed to optimize the use of Azolla meal in fish feed and to develop cost-effective production methods. This review is a valuable resource for farmers looking to maximize profit when using Azolla in aquafeed and potentially sustainably enhance aquaculture production. With its promising potential, the Azolla meal could be the key to meeting the growing demand for fishmeals while reducing the industry’s environmental impact.

Integration of transcriptome and metabolome reveals molecular mechanisms responsive to cold stress in gynogenetic mrigal carp (Cirrhinus mrigala)

Cold stress is a major environmental stimulus affecting the physiological and metabolic activities of farmed fish. In our previous study, we obtained gynogenetic mrigal carp (Cirrhinus mrigala, GMC) with significantly improved cold tolerance compared with the wild individuals. To gain a comprehensive and unbiased understanding of the molecular mechanism of cold tolerance in GMC, transcriptomes and metabolomics of liver tissues were comparatively analysed. After cold treatment at 14 °C for 48 h, histology analysis revealed that the hepatocyte nucleus was shifted, blurred and disintegrated; the terminus of the gill filament was enlarged; and the number of mucus cells and their secretions were increased. A total of 4844 differentially expressed genes (DEGs), including 2420 upregulated and 2424 downregulated genes, were identified. The upregulated KEGG pathways were mainly involved in oxidative phosphorylation, the proteasome and the citrate cycle, while the downregulated pathways were involved in staphylococcus aureus infection, systemic lupus erythematosus and leishmaniasis. A total of 160 differential metabolites (DMs) were identified, including 39 increased and 121 reduced metabolites. The KEGG pathway analysis revealed significant enrichment in retinol metabolism and folate biosynthesis. KEGG function analysis showed that the DEGs and DMs were both highly enriched in purine metabolism, neuroactive ligand–receptor interaction and galactose metabolism. Correlation analysis between DEGs and DMs revealed that multiple pathways were active and strongly related to immunity and disease, metabolism and growth under cold stress. This study can facilitate our understanding of the molecular mechanisms of fish response to cold stress and provide insight into the application of gynogenesis in farmed fish.

Different stocking densities and species combinations effects the growth and production in carp polyculture

A comparative experiment was undertaken to assess the effectiveness of different carp species i.e., Rohu (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus cirrhosus), and Silver Carp (Hypophthalmicthys molitrix) with variable stocking densities. Three treatments each with three replicates were maintained and the stocking densities of carps were 40, 80, and 120 fish/decimal in T1, T2, and T3, respectively. The stocking ratio of Rohu, Catla, Mrigal, and Silver Carp was 2:1:2:1. The experimental diet included rice bran (25%), wheat bran (25%), fish meal (25%), and mustard oil cake (25%), with a total protein content of 28%. This dietary supplement was administered twice daily. The fish were supplemented with 5% of their body weight for the first month, 4.5% for the next three months, and 2% for the final two months. The water quality parameters i.e., pH, temperature, dissolved oxygen and transparency were measured every 14 days interval. In T1, Silver Carp obtained the highest weight (188.86±17.86g) followed by Mrigal (106.78±14.23g), Catla (74.0±3.80g), and Rohu (67.72±6.03g). In T1, Silver Carp also attained the highest length at 26.33±0.63 cm, followed by Catla at 14.40±2.10 cm, Mrigal at 14.09±0.89 cm, and Rohu at 14.07±0.59 cm, respectively. Nevertheless, both weight gain and length gain were lowest for all species in T3. The highest SGR% was found in T1 for Silver Carp (3.22±0.06), whereas the lowest SGR% was found in T3 for Catla (1.69±0.06). In addition, T2 yielded the highest production (3090.91±119.57 kg/ha), followed by T3 (2949.80±137.67 kg/ha) and T1 (2946.21± 129.00 kg/ha). The experimental findings suggest that, the stocking density of 80 fingerlings/decimal (T2) yielded the highest production in carp polyculture.

Response of Different Fish Species to Highly Saline Water under Desert Climate Condition - Finding Options for Local Food Security

Fresh water shortage is indeed a global issue that affects many areas of the world, including desert regions like the Thar Desert of Pakistan. Recurring droughts have badly affected the marginal communities of these areas. The desert has wide spread lenses of saline groundwater. There is a pressing need for exploring ways to use saline groundwater and identifying alternative sources of livelihood under the prevailing conditions. Therefore, a research study on saline aquaculture was conducted. Twenty fish fingerlings (40-50 g) of the varieties namely rahu labeo (locally kurh’rho), silver carp, mrigal carp (morakhi) and grass carp were stocked into the earthen fish pond. Saline groundwater having electrical conductivity (EC) between 8.5 - 9.0 dS/m was used to fill the pond. The overall yield of silver carp was the highest (1275 g/fish) followed by grass (1093 g/fish), mrigal carp (965 g/fish) and rahu labeo (610 g/fish). However, meal yield of grass variety was the highest followed by mrigal carp, silver and lowest of rahu labeo. Silver carp varieties had 330 g/fish of egg in their bodies. Hence, for the massive fingerling development, silver carp is recommended for saline aquaculture. However, for meal production and high economic return, grass carp should be selected for saline aqua-culturing.

Growth Performance and Muscle Composition of Carps (Labeo rohita, Catla catla, Cirrhinus cirrhosus and Hypophthalmichthys molitrix) at Different Protein Diets under Polyculture Farming

This study investigated the effects of three supplemental diets varying in protein percentage (T1- 28%, T2- 30%, and T3- 32%) on the fillet composition of Rohu (Labeo rohita), Catla (Catla catla), Mrigal (Cirrhinus cirrhosus), and Silver Carp (Hypophthalmichthys molitrix) reared in ponds with supplemental diets. The control treatment with no supplemental feeding was also included to conduct the experiment. Fish from control ponds had substantially lower mean muscle protein concentrations than fish from ponds that received supplemental feeding, with 28% and 30% protein diets producing the most muscle protein. Compared to other treatments, fish fed a diet containing 32% protein had significantly (p<0.05) higher muscle lipid concentrations (2.22%). The muscle carbohydrates were greater in fish from ponds fed 28% protein diets. The Rohu (L. rohita) had the highest percent of muscle protein among the three sampled fish species, while Silver carp (H. molitrix) had the lowest, with all other species having intermediate values. The Mrigal (C. cirrhosus) and Silver Carp (H. molitrix) had the highest carbohydrate in their muscles, while Rohu (L. rohita) had the least carbohydrate content. During polyculture of cyprinids in ponds, the supplemental feeding of diets with protein ranging from 28 to 30% protein can be recommended as an optimal protein diet to attain the higher growth performance of carps avoiding the wastage of feed at the farmer’s level in semi-intensive polyculture farming.

Technological influence on the current state of the species composition of the ichthiofauna of the r. Samara in the Novomoskov District of the Dnipropetrovsk Region

The species composition of the ichthyofauna of the Samara River under the influence of man-made factors in the Novomoskovsk district of the Dnipropetrovsk region is presented. The environmental problem of the Samara River in the Novomoskovsk district is characterized, and the man-made influence on the species composition of the ichthyofauna of the Samara River is revealed. The species composition of the ichthyofauna of the Samara River in the Novomoskovsk district was analyzed based on literature data, and field and ichthyological studies were also conducted to determine the species composition of the ichthyofauna of the Samara River. The results of the influence of technogenic factors on the ichthyofauna of the Samara River in Novomoskovsk in modern realities have been revealed. The obtained results are summarized and analyzed in relation to technogenic influence on the species composition of ichthyofauna. In the studied area, it was found that there are the largest population of the following species: Neogobius fluviatilis Pallas, 1814; Alburnus alburnus Linnaeus, 1758; Carassius auratus gibelio Bloch, 1782; Scardinius erythrophthalmus Linnaeus, 1758; Perca fluviatilis Linnaeus, 1758; Rutilus rutilus Linnaeus, 1758; Lepomis gibbosus Linnaeus, 1758; Esox lucius Linnaeus, 1758. The restoration of natural water bodies on the example of the study model of technogenic influence on the species composition of the ichthyofauna of the Samara River, Novomoskovskiy district, Dnipropetrovsk region, is subject to study in the context of scientifically useful interest. Technogenic factors have a significant impact on the reservoir and the formation of species composition of ichthyofauna in it. Own research was conducted in the water area of ​​the Samara River to study the species composition under the influence of man-made factors. A table of fish species living in the Samara River was compiled and their status and distribution were indicated. We compared and summarized the obtained data with research materials of previous years. To improve the species composition of the ichthyofauna of the Samara River, mechanical and biological reclamation and stocking of the Samara River with white carp, crucian carp, and carp are proposed. Therefore, it was concluded that the processes of changing the ichthyocenosis under the influence of technogenic factors of pollution require the necessary optimizing interventions and require the attention of researchers and monitoring.

Morphological variability of the white carp (Hypophthalmichthys molitrix) during domestication

Acclimatized in the last century in the reservoirs of Russia, the white silver carp is the only consumer of phytoplankton in our country. In conditions of artificial reproduction and domestication, uncontrolled deterioration of fish habitus often occurs. In this regard, a comparative analysis of the variability of the most informative morphological parameters, namely length, mass, head length, body girth and their main indices in the samples of the white silver carp of varying degrees of domestication, was carried out. The Chinese, Amur and local lineages, the Ergenin sample and the Romanian population were studied, of which the least domesticated is the Chinese line. The presented materials show that the Chinese white carp line of the second generation of domestication differs in a smaller head, high indices of relative head length and physical development from the local and Ergeninsky fish samples domesticated for several decades. In pond lines domesticated in several generations, there is an increase in the relative size of the head and a deterioration in the index of physical development, which indicates the presence of selection for fitness to insufficient food supply in conditions of weak flow. It is recommended in the breeding program when growing reproductive herds of white carp in ponds to provide for selection to preserve the commercial qualities of fish.

Organoleptic qualities and proximate composition of fish grown in good aquaculture practice-based carp fattening pond

Organoleptic qualities and proximate composition of fish grown in carp fattening pond were studied under three treatments of feed and fertiliser management. Treatment T1 was designed with the use of organic fertiliser and stocking of silver carp, T2 with both organic and inorganic fertilisers and silver carp and T3 with both organic and inorganic fertilisers but excluding silver carp. One day in a week feeding restriction was followed in all the treatments. Fishes were stocked with a stocking density of 2470 fishes ha–1. Three fishes (Gibelion catla, Labeo rohita and Cirrhinus cirrhosus) were selected for organoleptic and proximate assessment. Cyanobacteria along with total phytoplankton cell density was significantly higher at treatment T2 followed by T3 and T1. However, in terms of productivity (Chl-a) treatment T2 was 27.1 and 13.3% higher compared to T1 and T3 respectively. Parameters assessed for proximate composition analysis did not vary across treatments and organoleptic test revealed comparatively higher acceptability of fishes collected from treatment T1 followed by T2 and T3 for all the fishes. Overall acceptability was higher for L. rohita from treatment T1. This study concluded that, inorganic fertilisation along with silver carp can improve the organoleptic properties of carps in pond.

Effect of Traditional Cooking Method on the Heavy Metal Content of Four Selected Farmed Carp Species And Assessment of Possible Human Health Risk

The present study was conducted to evaluate the effect of traditional Bengal culinary practice on the heavy metal content of four carp species (Labeo rohita, Catla catla, Cirrhinus cirrhosus, and Hypophthalmichthys molitrix). Fish samples were collected from seven different farms located in the Rajshahi district of Bangladesh. The collected samples were processed and cooked in a traditional currying method and concentrations of five heavy metals (Pb, Co, Cr, Cd, and Ni) were assessed in raw and cooked fish using a flame atomic spectrophotometer. Heavy metal concentrations were significantly reduced in the cooked samples with a few exceptions. The metal pollution index (MPI) indicated that the most amount of heavy metals was lost in C. cirrhosus followed by H. molitrix, L rohita, and C. catla. Pb was the most abundant and consumed of the tested heavy metals in the cooked fish followed by Co, Ni, Cd, and Cr respectively. Health risk index (HRI) and target hazard quotient (THQ) revealed that individual heavy metal intake from cooked fish does not pose any threat to human health. However, the hazard index (HI) of the accumulated heavy metals in the cooked fish suggested that the long-term effect of consuming heavy metal contaminated fish could collectively lead to possible non-carcinogenic health complexities. Additionally, HI also implied that the highest degree of health risk is associated with the consumption of H. molitrix and the least with L. rohita.
 Vol. 9, No. 3, December 2022: 367-376

Gynogenetic Cirrhinus mrigala produced using irradiated sperm of Cyprinus carpio exhibit better cold tolerance

Artificial gynogenesis is an important method for accelerating the selective breeding of varieties and populations. In this study, ultraviolet-irradiated sperm of Common carp (Cyprinus carpio) was used to activate the mature eggs of mrigal carp (Cirrhinus mrigala, MC), after cold shock at 4–8 °C for 16 min to double the chromosomes, a population of gynogenetic mrigal carp (GMC) was obtained. The fertilization rate, hatching rate and survival rate of GMC exceeded 62.2%, 6.3% and 2.9%, respectively. Comparative analyses of morphological traits, DNA content, chromosome numbers and 5S rDNA sequences showed no significant differences between MC and GMC. However, microsatellite (MFW1, CCA15) analysis revealed that paternal DNA fragments were inserted and a parent DNA fragment was deleted in the GMC. The GMC population survived the natural winter for more than 50 days with a temperature below 10 °C, while all the normal MC individuals perished. In addition, lower critical thermal minimum (CTMin) and lethal temperature (TLD50) values were detected in GMC than that in MC. Our results indicated that the artificial gynogenesis method improved the cold tolerance of mrigal carp. The results of this study are of great significance for fish breeding and application.

HYDRO-ECOLOGICAI CONDITION OF LAKE LYMAN (DVS RP "LYMANSKE" OF KHARKIV REGION)

A comparative analysis of the hydro-ecological state of Lake Lyman (DVSRP "Lymanske" of the Kharkiv region) of the cooling reservoir of the Zmiyivska TPP (Siverski Dinets basin) was carried out for the study of ecological and genetic features of white (Hypophthalmichthys molitrix) and variegated (Aristichthys nobilis) carp using ISSR DNA markers during 2019-2020. The ecological state of water bodies is presented, the species composition of the biota, the natural fodder base and the factors influencing the environment on the conditions of aquaculture are defined; the ecological conditions of growing a population of different age groups of variegated (Aristichthys nobilis) and white carp (Hypophthalmichthys molitrix) in the conditions of the Lymanske DVSRP of the Kharkiv region were studied in 2019. The studied phytoplankton shows a rather significant increase in biomass compared to previous research results (1984-2010). A significant increase in the number of phytoplankton is also evidenced by the fixation of floating masses of phytoplankton in the reservoir with a layer of up to 2-3 cm, among which blue-green algae (Cyanophyta), dinophyta (Dinophyta), and diamond algae (Bacillariophyta) predominated in number. The zooplankton of Lake Lyman was represented by rather widespread forms of three main groups: Rotifera, Cladocera, Copepoda. The ichthyofauna of the cooling pond of the Zmiivskaya TPP, which now includes 28 species of fish from 8 families, was studied. The main factors in the formation of the composition of fish in the cooling reservoir are the thermal load of the station, fishing activity and regular supply of river water to the reservoir. Changes in the composition of the fish fauna in recent years are due to the massive spread of evribiont fish-intervenors (needle fish, stickleback), a decrease in the power plant's working capacity (chub fish, gustera, or whitefish), as well as the release of fish from cages when the latter are broken.

BIOTESTING OF THE ANTHROPOGENIC IMPACT ON AREAS OF THE R. ROS AND R. PROTOKA ON THE VIABILITY OF CARP FISH EGGS AND LARVAE

BIOTESTING OF THE ANTHROPOGENIC IMPACT ON AREAS OF THE R. ROS AND R. PROTOKA ON THE VIABILITY OF CARP FISH EGGS AND LARVAE