Mugil Cephalus Research Articles

Occurrence and risk assessment of endocrine-disrupting compounds in fish muscle: The case study of the Douro River estuary (North East Atlantic Ocean)

This work was focused on evaluating the occurrence of endocrine-disrupting compounds (EDCs) in fish muscles, such as bisphenol analogues, personal care products, including some UV-filters and musk fragrances, and selected pesticides. A total of 238 muscle samples of three fish species (Platichthys flesus, Mugil cephalus, and Dicentrarchus labrax) of an important estuary ending in the North East Atlantic Ocean (Douro River estuary, Portugal), in different seasons of the year, was analysed. M. cephalus was the species with a greater occurrence of contaminants, mainly in fishes collected during the spring. Bisphenol A was the main bisphenol analogue detected with an average content of 23.1 μg/kg wet weight (w.w.). Among chemicals used in personal care products, galaxolide, tonalide, and 2-ethylhexyl salicylate, were the most often found, being present in 15.9% (2.2–538.4 μg/kg w. w.), 4.6% (1.1–57.8 μg/kg w. w.) and 3.4% (3.9–56.1 μg/kg w. w.) of the samples, respectively. About 14% of the samples contained residues of at least one pesticide, being alachlor, aldrin, p,p’-DDT, permethrin, and prochloraz the main chemicals observed, varying from 0.1 μg/kg w. w. (p,p’-DDT) to 37.8 μg/kg w. w. (prochloraz). The daily intake estimates of the most frequent EDCs found in the fish muscles suggested that there are no health concerns, based on the recommended weekly consumption of fish for adults.

Effect of Seasonal Variations in Hematology, Biochemical, Immunity Constituents in Mugil cephalus, Chano chanos, and Arius arius on Southeast Coast of Tamil Nadu, India

The assessment of the effect of seasonal variations on health, hematology, and serum biochemical components of three marine teleost fishes, Mugil cephalus, Chanos chanos, and Arius arius from Kovalam, East Coast Road, Southeast coast of Tamil Nadu, India. The objectives of the study pointed out the effect of seasonal variation on fish health and immunity. During summer and pre-monsoon, a total of 20 samples were collected from each sample, and hematological, biochemical, immunity parameters, and fish health were considered. M. cephalus (L-23.86±1.03; W-171.22±35.42) C. chanos, (L-22.36±1.17; W-163.03±33.32) and A. arius (L-22.62±1.08; W-168.72±35.04) have different length and weight. The WBC, RBC, Hb, and HCT were higher during summer in M. cephalus, C. chanos, and A. arius likewise, these parameters were lower in the pre-monsoon period (P<0.05). The MCV, MCH, MCHC, and ESR of all three species were higher in the pre-monsoon whereas in the summer they decreased. Likewise, leukocytes such as neutrophils, monocytes, lymphocytes, eosinophils, and thrombocytes show minimum levels in the pre-monsoon and attain maximum levels in the summer. Most importantly, in the summer, serum components protein and glucose were higher, while cholesterol and urea were lower, and vice versa. Although IgM and IgG levels (P<0.05) were higher in the summer and declined in the pre-monsoon season. In the lysozyme assay, respiratory burst activity (NBT) (P<0.05) reveals a higher concentration in the pre-monsoon and was lower in the summer. A total of thirteen hematological parameters, six biochemical, and two immunological parameters, and lysozyme and NBT activities showed a significant relationship with fish health throughout the seasonal changes. Based on the findings, M. cephalus shows maximum variations in length, weight, hematology, biochemical, and immunity levels, whereas C. chanos showed minimum variations. Hence the report indicates the seasons mainly impact the physiological status of the fish species.

Effects of salinity on lipids reserves, survival and growth of flathead grey mullet Mugil cephalus (Linnaeus, 1758)

Salinity is one of the main factors affecting physiological performances of teleost fish. Its influence on survival and growth rate of juvenile (five months old) Mugil cephalus (25.33 ± 1.01 mm length) was tested under hatchery conditions. After acclimation, fish were reared for three months at two salinities: freshwater (FW, 0 ppt) and saltwater (SW, 36 ppt). At the end of the experiment, growth, survival, and lipids deposition in the liver and carcasses were evaluated by histological and biochemical methods. Survival was high and similar between treatments. Fish reared in SW showed a significantly higher specific growth rate for body weight while Condition Index was similar. Lipid accumulation in the liver and total lipids and fatty acid profiles in the whole body were also similar among salinity treatments, while the levels of bioactive metabolite N-acylethanolamines were significantly higher in fish reared in FW. The high survival rate, a similar Condition Index and lipid deposition in both treatments strongly suggest that the transfer of mullet juveniles from SW hatchery conditions to FW is a viable commercial scale production strategy. These results contribute to our understanding of mullet juveniles' performances under different salinities and indicate that FW conditions provide a suitable environment for mullet juveniles.

Characterization of potential probiotic in digestive tract of Mugil cephalus (Linnaeus, 1758)

Probiotics are beneficial microbes in living things that are useful for improving the balance of microbes in the digestive tract and have a positive influence on the physiology and healthiness of the host. This study aimed to obtain bacterial isolates that could be used as probiotics from striped mullet (Mugil cephalus) and to characterize it macroscopically, microscopically, and biochemically. Isolation of probiotic bacteria was carried out using the spread plate method. The medium used to isolate probiotic bacteria was MRSA (De Man Rogose Sharpe Agar) medium. The probiotic test was carried out by hydrolysis of starch and casein. The diversity of bacterial morphology was observed based on macroscopic, microscopic, and biochemical tests. A total of 2 probiotic bacteria (PIB 1 and PIB 2) were obtained. The characterization results showed that the two probiotic bacteria belonged to the Gram-positive bacteria, in the form of bacilli which had different colony morphology. The results of morphological and biochemical tests indicated that one bacterial isolate belonged to the genus Bacillus (PIB 1) and the other isolate belonged to the genus Lactobacillus (PIB 2).

Hazard index of microplastics contamination in various fishes collected off Parangipettai, Southeast coast of India

The authors of the present research aimed to assess microplastics (MPs) contamination in the gills and gut of selected fishes from various aquatic zones and also to bring out the risks of the identified polymers. Accordingly, about 200 fish specimens of 10 different species were collected from the landing center at Parangipettai, southeast coast of India. The fishes were dissected to investigate MPs contamination in their gills and gut. The dissected tissues were acid digested and filtered to observe its microplastic contamination using a stereozoom microscope. In gills, Cynoglossus arel had the least contamination (0.4 ± 0.01 particles/ind) and Mugil cephalus had highest microplastic contamination (1.7 ± 0.01 particles/ind). In gut, C. arel had the minimum contamination (0.7 ± 0.09 particles/ind) and Rastrelliger kanagurta had maximum contamination (2.3 ± 0.26 particles/ind). The size of microplastics isolated from the present study ranged from 100 to 1000 μm. Among microplastic shapes, fibers (97%) and pellets (3%) were observed. About eight colours of microplastics were observed in the fishes among which black was dominant. Three polymers such as LDPE, PP and PS were identified by μFTIR, among which LDPE (57%) was dominant. Polymer Hazard Index denotes that LDPE (6.27), PP (3.4) and PS (2.7) have a PHI score of 1–10 classifying them in the hazard category II which has a medium risk. These polymers may directly enter the human body when consumed and cause health implications which require further investigation.

Understanding common dolphin and Australasian gannet feeding associations from nutritional and ethological perspectives

Abstract Prey detection and subsequent capture is considered a major hypothesis to explain feeding associations between common dolphins and Australasian gannets. However, a current lack of insight on nutritional strategies with respect to foraging behaviours of both species has until now, prevented any detailed understanding of this conspecific relationship. Here we combine stomach content analysis (SCA), nutritional composition of prey, a multidimensional nutritional niche framework (MNNF) and videography to provide a holistic dietary, nutritional, and behavioural assessment of the feeding association between dolphins and gannets in the Hauraki Gulf, New Zealand. Dolphins consumed ten prey species, including grey mullet (Mugil cephalus) as the most representative by wet mass (33.4%). Gannets preyed upon six species, with pilchards (Sardinops pilchardus) contributing most of the diet by wet mass (32.4%) to their diet. Both predators jointly preyed upon pilchard, jack mackerel (Trachurus spp.), arrow squid (genus Nototodarus), and anchovy (Engraulis australis). Accordingly, the MNNF revealed a moderate overlap in the prey composition niche (0.42) and realized nutritional niche (0.52) between dolphins and gannets. This suggests that both predators coexist in a similar nutritional space, while simultaneously reducing interspecific competition and maximizing the success of both encountering and exploiting patchily distributed prey. Behavioural analysis further indicated that dolphin and gannets feeding associations are likely to be mutually beneficial, with a carouselling foraging strategy and larger pod sizes of dolphins, influencing the diving altitude of gannets. Our approach provides a new, more holistic understanding of this iconic foraging relationship, which until now has been poorly understood.

Non-uniform metamorphosis underlies different development trajectories in hatchery-reared flathead grey mullet (Mugil cephalus)

The flathead grey mullet (Mugil cephalus) is at the focus of an intense domestication effort. However, despite significant advances, aquaculture of grey mullets is still based on capture of wild fingerlings in estuaries and stocking them into ponds. Such reliance on wild seed limits aquaculture production since it is highly seasonal, unpredictable, hinders genetic improvement programs and may negatively affect local capture fisheries. As captive breeding has been optimized for the species, to date, larval rearing remains the main challenge hindering the commercial production of captive-bred mullets. Here we set out to characterize larval development of grey mullets under captive conditions and to identify key developmental bottlenecks. By analyzing four larval batches from a commercial hatchery, we defined ten distinct developmental stages from hatching to the end of metamorphosis based on macroscopically observable morphological features. Using this developmental atlas to study development dynamics, we found that mullet larvae exhibit a biphasic growth profile with a 17-fold increase in growth rates at the onset of metamorphosis. Moreover, we found that within rearing batches, size variation almost doubles at metamorphosis, suggesting that the onset of metamorphosis is a critical step that increases variation by dictating different growth trajectories to early and late-metamorphosing larvae. By plotting the developmental stages against different morphometric parameters, we show here that age is a poor predictor of larval development due to large variations in development rates both within and between batches. We found that mullet larvae begin metamorphosis at a set size threshold of ~4.5 mm, however age at this threshold varies greatly even within batches. This age and size variance is further amplified by the aforementioned enhanced growth rates at metamorphosis and results in highly non-uniform fry, which complicate the rearing and weaning procedures. Understanding and treating the underlying causes for delayed metamorphosis are therefore considered important steps for the full domestication of the grey mullet.

Periphyton: A natural fish food item for replacement of feed at optimized substrate surface area for cost-effective production in brackishwater polyculture

Periphyton community grown on submerged substrate in water could serve as a preferred natural food item to herbivorous and omnivorous fish and crustacean species. To determine the optimum substrate area for the growth of periphyton biomass serving as natural food and to reduce the requirement of pellet feed quantity, a 150-day pond experiment was conducted with four treatments of brackishwater polyculture: total feeding and no periphyton substrate (P0), and partial feeding with periphyton grown on nylon net substrate equivalent to 50 (P50), 75 (P75) and 100 (P100) % of pond surface area. Each treatment had three randomly assigned replicate ponds (50 m2). After 15 days of substrate fixation in the surface layer of ponds up to 50 cm water depth, stocking was made with seeds of Mugil cephalus Linnaeus, 1758, Planiliza parsia (Hamilton, 1822), Chanos chanos (Forsskål, 1775) and Penaeus monodon Fabricius, 1798 at 1800, 18000, 2000 and 30,000 number ha−1, respectively. A low-cost pellet feed (30.76% crude protein) was provided at 6–3% of fish biomass per day. Dry matter (DM) of periphyton biomass was estimated from each replicate pond under P50, P75 and P100 from 15 × 15 cm2 net substrate, and then total periphyton DM was calculated according to the substrate surface area at 15-day intervals. Then, the total periphyton biomass was divided to find out daily DM availability. The feed amount in P50, P75 and P100 ponds was reduced proportionately to the equivalent daily periphyton DM availability and the feeding at this reduced quantity was continued for 15 days. The experiment revealed significantly lower levels of nitrogenous and phosphorus compounds, and dissolved organic carbon content in water of P75 and P100, compared to that of P0 and P50 (P < 0.05) and there were interaction effects of experimental period and periphyton substrate area on these parameters. All the species had an increasing growth pattern with experimental period and there was an interaction effect of experimental period and periphyton substrate area on growth of these species, indicating periphyton had positive effects. The highest specific growth rate was recorded in P. monodon and the lowest was in M. cephalus. Pooled survival of fishes and shrimp, and total productivity did not differ among treatments (P > 0.05). Although, the highest level of feed reduction (42%) by the utilization of periphyton biomass was in P100, P75 performed better in terms of productivity and economic return with 30% feed reduction in polyculture. Similarly, there was 26–41% reduction in feed conversion ratio with the highest level being in P100 (41%), followed by P75 (40%) in comparison to P0. Moreover, carcass composition of cultured fishes and shrimp indicated that periphyton based systems with partial feeding could meet up the nutrient requirement of the animals with no negative effects in comparison to the feed-based system. Therefore, this study suggests that provision of periphyton substrate equivalent to 75% of pond surface area along with partial feeding is the most appropriate approach for achieving higher return with environmental sustainability in brackishwater polyculture.

Effect of Frying on the Quality and Protein Degradation in Mugil cephalus: A Comparative Study of Vacuum and Atmospheric Frying

ABSTRACT Fried Mugil cephalus was investigated under optimal vacuum and atmospheric conditions. The water distribution, texture, and color properties of vacuum-fried samples were enhanced compared with atmospheric-fried samples. Meanwhile, vacuum frying (VF) reduced the total oil content, protein oxidation, and degradation. The molecular weight and amino acid content suggested that protein was well-preserved during VF. In addition, the total carbonyl, free thiol groups, thiobarbituric acid reactive substances (TBARS), and Schiff base values were all significantly improved by the VF method compared to atmospheric frying (AF). VF inhibited the shift of amide bands to a higher frequency and the disordering of protein secondary structure. The sample surface morphology shrank under vacuum conditions, likely resulting in the lower fat content of vacuum-fried M. cephalus. Thus, VF improved the quality, water distribution, and microstructure and decreased the protein oxidation and degradation of M. cephalus and was considered a potential method for frying processing.

Fish-Waste-Derived Gelatin and Carbon Dots for Biobased UV-Blocking Films.

The fish industry produces every year huge amounts of waste that represent an underutilized source of chemical richness. In this contribution, type I collagen was extracted from the scales of Mugil cephalus and carbon dots (CDs) were synthesized from the scales of Dicentrarchus labrax. These materials were combined to make hybrid films with UV-blocking ability, by casting a mixture of gelatin, glycerol (15%), and CDs (0, 1, 3, and 5%). The films were fully characterized from the mechanical, morphological, and optical point of view. Here, 40 μm thick films were obtained, characterized by a high water solubility (70%); moreover, the presence of CDs improved the film mechanical properties, in particular increasing the tensile strength (TS) up to 17 MPa and elongation at break (EAB) up to 40%. The CDs also modulated water vapor permeability and the thermal stability of the films. From the optical point of view, with just 5% loading of CDs the films blocked almost 70% of the UV radiation with negligible change in transparency (88.6% for the nonloaded vs 84.4% for 5% CDs) and opacity (1.32 for nonloaded vs 1.61 for 5% CDs). These types of hybrid biobased films hold promise for the production of sustainable UV-shields both for human health and for prolonging the shelf life of food.

Fish Diversity in Relation to Salinity Gradient in the Meghna River Estuary, Bangladesh

Variation in salinity is one of the major environmental factors influencing the species diversity of fish in an estuary. Therefore, evaluating the relationship between salinity and species diversity is important. In this study, fish diversity was assessed by fish sampling and visiting local fish markets from February to November 2021. Mean salinity was 10.59 psu (Practical Salinity Unit) and 0.46 psu during the dry and wet seasons, respectively. Harpadon nehereus, Odontamblyopus rubicundus and Pseudapocryptes elongatus species were found as polyhaline (0.06~18.1 psu) species. Anguilla japonica and Arius gagora were abundant in brackish water conditions (0.35~14.2 psu). However, Acanthopagrus latus and Setipinna phasa were found in freshwater conditions (0.06~0.11 psu). The suitability index indicates that commercially important fish species such as Liza parsia, Macrobrachium rosenbergii, Mugil cephalus, Penaeus monodon and Scylla serrata can be used for mariculture during the dry season, and Acanthopagrus latus, Pethia canius and Setipinna phasa during the wet season. Overall, these findings suggest that salinity, water temperature, and chlorophyll-a had a significant (p &lt; 0.05) effect on the fish distribution and assemblage composition in the study area. This finding will be helpful in developing policies for the conservation and management of the aquatic resources in the coastal zone to enrich the blue economy.

Reproduction and growth of Mugil cephalus (Linnaeus, 1758) in Moroccan South Atlantic

Reproduction and growth of Mugil cephalus (Linnaeus, 1758) in Moroccan South Atlantic

Greenwater Technology for Controlling Vibriosis and Achieving Higher Shrimp Production - A Case Study

Disease due to luminous Vibrio has been a major problem in the shrimp industry. Brackishwater shrimp Penaeus monodon is susceptible to fatal effects of luminous vibriosis adversely affecting the shrimp production and creating economic losses in India. Different technologies have been introduced to control the disease. One of the techniques reported to work against luminous bacteria is greenwater culture system (or finfish–shrimp integrated culture system). The greenwater culture system has been proven the most functional and innovative technique, wherein euryhaline finfish are propagated as bioremediators in an isolated net pens/cages inside the shrimp growing ponds or shrimp are cultured in fish produced greenwater. This paper reports a case study on the successful demonstration of greenwater technology based on the integration of milkfish, Chanos chanos and grey mullet, Mugil cephalus in pens for environmental and health management of brackishwater aquaculture with the result of higher production of shrimp, Penaeus monodon. The greenwater technology has been found to be effective as biomanipulators in controlling the luminous bacteria disease and can be a good alternative to expensive microbial products/probiotics in the aqua-farming ponds throughout the culture period.

Feeding habits and the influence of pellet diameter on the feeding responses of the flathead grey mullet (Mugil cephalus) in captivity

The feeding habits and effect of the diameter of pelleted feeds on the feeding responses of wild juvenile and adult flathead grey mullet (Mugil cephalus) in captivity were examined. Optimal pellet size for feeding was defined according to the behavioural responses and ingestion of pellets with different diameters (2, 4, 6, 8 mm) that were dropped into the tank in a random sequence. Larger pellets (6 and 8 mm) were more attractive (lower reaction time, high percentage of capture), but the small to medium-sized pellets (2 and 4 mm) were consumed the most. The optimal size was the 2- and 4-mm pellet diameter for juvenile individuals (365.50 ± 36.90 g; 28.8 ± 0.84 cm) and the 4-mm diameter pellet for adults (937.49 ± 146.54 g; 40 ± 1.12 cm). The preferred feeding area of adult mullet was also studied to estimate preference in relation to pellet characteristics such as floating or sink. Two pellet types, floating or sinking, were offered simultaneously in the water column: at the surface, mid-water column and bottom of the tank. The flathead grey mullet had a preference to feed in the mid-water column and the bottom of the tanks indicating that sinking or slow-sinking pellets would be the optimal feed type in relation to mullet feeding behaviour.

Myxozoan infection in thinlip mullet Chelon ramada (Mugiliformes: Mugilidae) in the Sea of Galilee

Mullets (Mugilidae) are economically important fish in Israel. Two species of mugilids (i.e., the thinlip mullet Chelon ramada and the flathead grey mullet Mugil cephalus) have been stocked in the Sea of Galilee (Lake Kinneret) in order to increase fishermen’s income and lake water quality. These catadromous species do not reproduce in the lake, consequently, fingerlings have been introduced every year since 1958. Few additional mugilid species have been introduced unintentionally together with these two species, including C. labrosus. Following a survey of myxozoan infections in the Sea of Galilee, we described Myxobolus pupkoi n. sp. infecting the gill arches of C. labrosus, and reported Myxobolus exiguus from visceral peritoneum and gall bladder of C. ramada. Our study indicates that the parasites infecting C. ramada and C. labrosus belong to a lineage of myxozoans infecting mugilids. This result suggests that the infection took place in the Mediterranean Sea, where the fingerlings were caught, before their introduction into the Sea of Galilee. Since 2018 only farm-raised fingerlings have been introduced. We thus recommend to closely monitor the presence of these parasites in the future to determine if the presence of parasites disappear with the introduction of farm-raised fingerlings.

First description of Vibrio harveyi as the causative agent of morbidity and mortality in farmed flathead grey mullet Mugil cephalus

Flathead grey mullet Mugil cephalus is an important species in the aquaculture industry in the Mediterranean basin and throughout the world. During the last 10 yr, M. cephalus breeding stocks, larvae, and juveniles cultured in Eilat (Israel) have shown neurological signs such as uncoordinated circular swimming, while also presenting oral hemorrhages. Death follows days after the onset of the clinical signs, and mortality rates may reach 80% in some cases, causing high economical losses. Bacteriology isolations from different organs, including the brain, and a Koch’s postulate experiment, confirmed Vibrio harveyi as the causative agent. Histological analyses showed the presence of the bacterium in different organs. However, in the brain, the bacterium was observed only within blood vessels and meninges. In some samples, mild to severe brain tissue damage was seen. In order to understand the virulence and lethality of V. harveyi, a median lethal dose was calculated, and the result was 106 colony-forming units fish-1. To the best of our knowledge, this is the first report that describes V. harveyi isolated from the brain of M. cephalus and validates it as an etiological agent causing neurological signs in this fish species.

A β-defensin isoform from the Flathead grey mullet, Mugil cephalus (Linnaeus 1758): Structural and functional characterisation in silico

Defensins are an important class of AMPs, rich in cysteine with antibacterial, antifungal and antiviral functions. The present study identified and functionally characterised a β-defensin gene from Grey mullet, Mugil cephalus, termed as Mc-Def. A 192 base pair complementary DNA with an open reading frame encoding 63 amino acids comprising 20 amino acid signal and 43 amino acid mature peptide region was obtained. Mc-Def has a net charge of 3.9 and a molecular weight of 7.27 kDa with an isoelectric point of 8.88. It possessed six cysteines forming 3 disulphide bonds between C1–C5, C2–C4 and C3–C6. Three dimensional structure identified a short N-terminal α helix followed by β sheet strands stabilized by disulfide bonds. The mRNA structure was predicted by Biomodel server with significant MEF score. Multiple sequence alignment and phylogeny revealed the sequence similarity of Mc-Def with fish β-defensin 2 type of AMPs. Molecular diversity and evolution of β-defensin provided immunity to host system against various infections. In silico analysis identified its potential as antibacterial, antifungal, anticancer, antioxidant and non-hemolytic peptide activity. These intriguing results firmly suggest that the Mc-Def can be used as a potent drug molecule in fish health management.

Comparative Transcriptomic Immune Responses of Mullet (Mugil cephalus) Infected by Planktonic and Biofilm Lactococcus Garvieae.

Lactococcus garvieae is an important pathogen of fish, associated with high rates of mortality and infection recurrence in summer or stressful conditions. Chronic infection and disease recurrence have also been reported to be associated with biofilms. However, the impact of biofilm and planktonic bacterial infection on fish immune responses remains unclear. In this study, de novo sequencing was used to compare differences of the spleen transcriptome in planktonic- and biofilm-infected mullets. Among the 181,024 unigenes obtained, 3,392 unigenes were associated with immune response genes. Comparative analysis of the gene expression between infection with the L. garvieae planktonic type and biofilm type identified a total of 3,120 and 3,489 differentially expressed genes in response to planktonic and biofilm infection, respectively, of which 1,366 and 1,458 genes were upregulated, and 1,754 and 1,458 genes were downregulated, respectively. Gene ontology enrichment analysis of immune genes identified genes involved in the complement system, toll-like receptor signaling, and antigen processing, which were further verified by qPCR. Additionally, genes encoding TLR2, IL-1β, TNF-α, C7, and MHC class II peptides were downregulated in response to biofilm infection. Importantly, the results show that biofilm infection induces a different immune pathway response compared with planktonic bacterial infection and, furthermore, illustrates that the prevention of biofilm formation may be a necessary and new strategy for controlling bacterial infection in aquaculture.

Nickel and cadmium tissue bioaccumulation and blood parameters in Chelon auratus and Mugil cephalus from Anzali free zone in the south Caspian Sea (Iran) and Faro Lake (Italy): A comparative analysis

BackgroundAnalysis of heavy metal concentrations in fish blood is a valuable tool in environmental pollution monitoring. Among different type of fish, detritivorous fish are a very good indicator for monitoring pollution and environmental stress, along with hematological studies, which are an important indicator in eco-toxicological and biological studies. AimThe aim of this study was to evaluate the influence of environment on bioaccumulation of Ni and Cd and on blood parameters in Chelon auratus and Mugil cephalus (a detritivorous fish which is widely distributed in the world) captured in Caspian Sea and Faro Lake. MethodsFor the research blood and tissues samples were collected from 40 mullets (20 Mugil cephalus from Italy and 20 Chelon auratus from Iran) in 2019. The hematological (white blood cell, WBC; red blood cell, RBC; thrombocyte count, TC; hematocrit, Hct; hemoglobin concentration, Hb; mean corpuscular volume, MCV; mean corpuscular hemoglobin, MCH and mean corpuscular hemoglobin concentration, MCHC) and biochemical parameters (aspartate aminotransferase, AST; alanine aminotransferase, ALT; alkaline phosphatase, ALP; lactate dehydrogenase, LDH and creatine phosphokinase, CPK were assessed. ResultsAlthough the concentration of Ni and Cd in the muscle of fish have no significant health risks and were low in both regions, the most elevated concentration was found in the liver of Caspian Sea mullet. In all cases, the results obtained for all biochemical and most hematological parameters of individual Faro Lake, were considerably lower than the Caspian Sea, demonstrating that habitats and environmental conditions affect the blood metabolites. ConclusionsThe results of this study show that these measurements can be used as criteria for the quantitative evaluation of fish /health and provide information on the extent of potential poisoning and the risks posed to the populations and fisheries.

Effects of short-term exposure to the heavy metal, nickel chloride (Nicl2) on gill histology and osmoregulation components of the gray mullet, Mugil cephalus

The gray mullet, Mugil cephalus is an inshore and bottom-feeding fish species of Oman sea. Therefore, the gray mullet may be more exposed to heavy metal contamination, as the toxic impacts of heavy metals mullet has been reported in various studies. This study was conducted to evaluate the toxic effects of the heavy metal, nickel (as NiCl2) on osmoregulation of the gray mullet by measuring blood biochemicals, hormones, minerals and gill histology. Fish (10 fish/tank) were experimentally exposed to NiCl2 at three environmentally relevant concentrations of 5, 10 and 15 μg/l for 96 h. Then, fish were challenged with seawater (35 mg/l) for a period of 120 min. The samples (blood and gill tissue) were collected After 96 exposure to NiCl2 and during salinity challenge (30, 60 and 120 min post challenge). The plasma levels of cortisol and glucose significantly increased in NiCl2−exposed fish. In addition, cortisol increased in all experimental groups 30 min after salinity challenge and then returned gradually to the same levels as the control at 120 min post salinity challenge (PSC). The triiodothyronine (T3) and thyroxine (T4) levels significantly decreased in response to 10 and 15 μg/l NiCl2. In all groups, the thyroid hormones significantly elevated at 30 min PSC. After 30 min PSC, T3 levels in all NiCl2−exposed fish and T4 in the treatment, 10 μg/l NiCl2 remained unchanged throughout the salinity challenge. In the treatment, 5 μg/l NiCl2, T4 levels were recovered at 120 min PSC and reached the same levels as the control. Exposure of fish to high concentrations of NiCl2 and salinity stress increased the lactate levels. However, lactate levels in 5 and 10 μg/l NiCl2 groups were recovered at 120 min PSC and reached the same levels as the control. Furthermore, plasma protein increased in response to 10 and 15 μg/l NiCl2. At 30 PSC, the protein levels decreased in control and 5 μg/l NiCl2 group, while it remained unchanged in fish exposed to 10 and 15 μg/l NiCl2 throughout the salinity challenge. Exposure of fish to NiCl2 disrupted the electrolyte (Na+, Cl−) balance both before and after salinity challenge, which may be due to gill lesions induced by the heavy metal and following alternations in gill permeability. However, fish in 5 μg/l NiCl2 re-established the ionic balance in the blood at the end of salinity challenge period. The malondialdehyde (MDA) levels significantly increased in response to 10 and 15 μg/l NiCl2. The MDA levels returned to the same levels as the control group at 120 min PSC. The results of the present study showed that nickel-induced toxicity (especially at high concentrations) can reduce the osmoregulation capabilities of mullet. However, fish are able to recover from the toxic effects over time, if contamination be eliminated.