Grey Mullet Research Articles

Lipid and fatty acid composition of muscle, liver, ovary, and peritoneal fat in wild flathead grey mullet (Mugil cephalus) according to ovarian development

Wild adult females of a low trophic omnivore teleost species, the flathead grey mullet (Mugil cephalus), caught in the western Mediterranean were sampled. The lipid and fatty acid composition of ovaries, liver, muscle, and peritoneal fat were analysed at previtellogenesis, early-vitellogenesis —first observed at mid-summer (early August)—, late-vitellogenesis, and the post-spawning period —from mid-September to mid-October—. During ovarian development, the lipid content of muscle was low and constant (3.85%–4.92%), indicating that the muscle was not used to store lipids for gonadal growth. Although constant, lipid content in the liver was higher (18.46%–22.62%) than in the muscle, and HSI% increased during gonad development, suggesting a dynamism in the mobilization of the hepatic lipids. Total lipids in the gonads significantly increased with maturation (from 4.90% to 34.59%) in parallel with the GSI (from 0.8% to 15.5%) to decrease after spawning. Peritoneal fat was probably transitional fat that could be rapidly metabolized or transferred to other tissues but no specific function could be assigned because its presence in previtellogenic and early-vitellogenic females varied greatly. One of the main sources of lipids accumulated in the ovary was most likely diet. The total percentage of ΣMUFA, mainly 17:1 —previously not identified in high quantities in teleost vitellogenic ovaries and likely of bacterial origin— and 16:1, strongly increased in the ovaries with maturation. The 16:1 might be an important source of lipids for embryo development. High percentages of DHA, EPA, and ARA were found in the ovary during previtellogenesis available to be used during gonadal maturation. Understanding lipid and fatty acid changes in broodstock tissues can increase our knowledge of the nutritional requirements of the fish used in aquaculture breeding programs.

A NEW SPECIES OF PROSOGONOTREMA (SCLERODISTOMIDAE: PROSOGONOTREMATINAE) FROM THE FLATHEAD GREY MULLET, MUGIL CEPHALUS LINNAEUS (MUGILIFORMES: MUGILIDAE), FROM THE ARABIAN GULF OFF IRAQ.

Prosogonotrema iraqiense n. sp. (Sclerodistomidae: Prosogonotrematinae) is described in the flathead grey mullet, Mugil cephalus Linnaeus (Mugiliformes: Mugilidae), collected from the Arabian Gulf off Iraq during June and October 2019. Currently there are 11 species of ProsogonotremaVigueras, 1940 commonly accepted: Prosogonotrema arabicaYadav, 1980; Prosogonotrema bilabiatumVigueras, 1940 (type species); Prosogonotrema caesionisGu and Shen, 1979; Prosogonotrema diacanthiBilqees and Durrani, 1980; Prosogonotrema karachienseBilqees and Durrani, 1980; Prosogonotrema pavasiLokhande, 1990; Prosogonotrema piscicola (Srivastava, 1949) Gibson, 2002 (Syn. Bhaleraoia piscicolaSrivastava, 1949); Prosogonotrema plataxumGu and Shen, 1979; Prosogonotrema posterouterinaYadav, 1980; and Prosogonotrema symmetricumOshmarin, 1965 originally described from marine fishes, and Prosogonotrema nickoliBilqees and Khan, 1992 described from a freshwater cyprinid. Six additional species that have been considered synonyms of P. bilabiatum are also considered. Prosogonotrema diacanthi is considered a junior synonym of P. piscicola and Prosogonotrema carangiHussain and Rao, 1980nec Velasquez, 1961 is determined to be a species distinct from P. bilabiatum and is reassigned herein as Prosogonotrema aluteri nomen novum per the ICZN. Prosogonotrema iraqiense differs from all currently recognized species in the genus by having the width of the ventral sucker approach or exceed the width of the body and from all except P. pavasi (body length/width ratio 1:1.4-1:1.5) by having a distinctive narrower, more elongate body profile with a larger body length/width ratio (1:5.8-1:6.1 vs. 1: 2.0-1:4.1). A key to the 18 species we recognize in Prosogonotrema is included.

Individual aerobic performance and anaerobic compensation in a temperate fish during a simulated marine heatwave

Marine heatwaves (MHWs) are becoming more frequent and intense due to climate change and have strong negative effects on ecosystem. Few studies have reproduced the complex nature of temperature changes of a MHW, while it is suggested that ectotherms may be more vulnerable to rapid changes such as during MHWs. Effects of an experimental MHW were investigated in the golden grey mullet Chelon auratus. Juveniles acclimated to 20 °C were exposed to a rapid 5 °C increase in temperature, followed by a five-day period at 25 °C, before quickly returning to 20°C. Metabolic variables (SMR-standard, MMR-maximum rate, AS-aerobic scope, EPOC-excess post‑oxygen consumption) and critical swimming speed (Ucrit) were measured at different phases of this MHW and after a thermally stable recovery phase.Although the pattern was only significant for the SMR, the aerobic three variables describing aerobic metabolism (SMR, MMR and AS) immediately increased in fish exposed to the acute elevation of temperature, and remained elevated when fish stayed at 25 °C for five days. A similar increase of these metabolic variables was observed for fish that were progressively acclimated to 25 °C. This suggests that temperature increases contribute to increases in metabolism; however, the acute nature of the MHW had no influence. At the end of the MHW, the SMR remained elevated, suggesting an additional cost of obligatory activities due to the extreme event. In parallel, Ucrit did not vary regardless of the thermal conditions. Concerning EPOC, it significantly increased only when fish were acutely exposed to 25 °C. This strongly suggests that fish may buffer the effects of acute changes in temperature by shifting to anaerobic metabolism.Globally, this species appears able to cope with this MHW, but that's without taking into consideration future projections describing an increase in both intensity and frequency of such events, as well as other stressors like pollution or hypoxia.

The seasonal assessment of heavy metals pollution in water, sediments, and fish of grey mullet, red seabream, and sardine from the Mediterranean coast, Damietta, North Egypt

The current study investigated the deposit of heavy metals, including copper (Cu), zinc (Zn), cadmium (Cd), manganese (Mn), lead (Pb), chromium (Cr), and iron (Fe) in grey mullet (Mugil cephalus), red seabream (Pagrus pagrus), and sardine (Sardinella aruita) over winter and spring seasons 2022 at the Damietta port, a marine port constructed in 1982 on the north coast of Egypt, and the surrounding region. Water, sediment, and fish samples were collected from four sites near Damietta port throughout the spring and winter of 2022 to evaluate the amount of heavy metal in water, sediment, muscles, and fish liver. Heavy metal concentrations significantly differed across organs; however, their levels in liver tissues exceeded those in muscle tissues. It was noted that M. cephalus had the highest concentrations of heavy metals compared with other fish species. Heavy metals accumulation in fish organs was in the following order: Fe > Zn > Mn > Pb >Cu > Ni > Cd > Cr. During winter season, metals levels in water samples were in the following sequence: Fe > Ni > Zn > Cd > Cr > Pb > Cu > Mn, meanwhile in spring season, the order was as follows: Ni > Pb > Fe > Cr > Zn > Cd > Cu > Mn. During the winter time, the order of metals levels in sediment samples was Zn > Fe > Mn > Cu > Pb > Ni > Cd > Cr, but in the springtime, it was Zn > Fe > Mn > Cu > Ni > Pb > Cd > Cr. Finally, the human risk assessment concluded that grey mullet, red seabream, and sardine in Damietta port and neighboring regions are safe for human feeding and that various wastes may be disposed of securely, avoiding the buildup of heavy metals.

Reproductive management of the mugilid Liza aurata and characterization of proximate and fatty acid composition of broodstock tissues and spawnings

The golden grey mullet (Liza aurata) is a promising species for aquaculture's sustainable expansion. However, the lack of sustainable juvenile provision, mainly related to the lack of reproductive control, is one of the most significant bottlenecks for further expanding the culture of this species. In many cases, mullet broodstock management needs the application of hormone treatments to induce gonadal maturation or spawning. However, no works are directly related to the broodstock collection, acclimation, and reproductive management of Liza aurata. On the other hand, the knowledge of essential fatty acids (EFA) requirements and mobilization patterns by the broodstock is a first step to designing appropriate feeding protocols and formulas, which are crucial for the success of reproduction and larval development.For these reasons, this study aimed 1) to describe for the first time the reproductive management of Liza aurata broodstock under controlled conditions and 2) to offer a first approach to the reproductive lipid metabolism of the former species.A selection of 22 Liza aurata broodstock from wild origin was acclimated in open seawater conditions. Additionally, the proximate and fatty acid composition of body tissues (gonads, liver, and muscle) of the initial wild population were evaluated, to be later compared with the profile of the eggs obtained after one year from the selected broodstock, for the first time described under cultured conditions.The results highlighted the feasibility for the obtention of natural spawnings from broodstock with a mean weight of 787 g and 604 g (females and males, respectively), at a sex ratio of 2:1 (females/males), under natural photoperiod and marine water conditions with temperatures decreasing from 20.4 ± 0.3 °C to 18.8 ± 0.4 °C.On the other hand, it was evidenced the crucial role of HUFA (highly unsaturated fatty acids) precursors for the gonadal development of Liza aurata, primarily for females. Additionally, the wild males' gonads presented a remarkable high content of HUFA, predominantly DHA (docosahexaenoic acid) (34% of the total fatty acids). In the eggs, significant variations appeared under captivity conditions, with lower levels of ARA (arachidonic acid) and EPA (eicosapentaenoic acid) and higher EPA/ARA and DHA/ARA ratios than the wild female gonad. Additionally, it was evidenced the significant role of the liver as a physiological reservoir of HUFA, which seem to be mobilized to the gonad during the maturation process.Present results may help obtain a better insight to adjust broodstock management conditions and feeds, contributing to a more sustainable aquaculture growth.

Using molecular phylogenetic and stable isotopic analysis to identify species, geographical origin and production method of mullet roes

The flathead grey mullet, Mugil cephalus (Mugilidae), is one of the most commercially important fish species in Taiwan since mullet roe is considered as a delicacy with a high economic value. Farmed, wild-caught, and imported mullet roes are often not properly labelled in retail stores and merchants can make unethical profits from selling mislabeled products. Therefore, there is an urgent need to identify the provenance and production method of the mullet roes. In this study, we conducted a molecular phylogenetic analysis so as to identify the species and geographical origin of the mullet roes and we used stable isotopic values as a tool to differentiate between the wild-caught and farmed mullet roes. DNA sequence variations of a mitochondrial COI gene from the sampled mullets and mullet roes of wild-caught and farmed individuals, as well as the roe products sold in retail stores in Taiwan, were analyzed within the phylogenetic framework. The results showed that the samples were from four M. cephalus lineages (or putative Mugil species B, C, I, and H) occurring in the Caribbean Sea, Northwestern Pacific, and Southeastern Australia, and the M. liza in the Western Atlantic, respectively. The M. liza samples were from the salted roe products purchased from two retail stores, in which one claimed that the roes were imported from Brazil, whereas the other claimed that the roes were from locally reared flathead grey mullets. The farmed mullet roes had significantly lower δ13C values and less variation in δ15N values when compared with the wild-caught and imported mullet roes. Quadratic discriminant analysis based on the δ13C and δ15N values successfully discriminated the farmed mullet roes from the wild-caught and imported roes with an approximate error rate of 2%. Our study demonstrated that the combined approach of genetic and stable isotopic analyses can effectively authenticate the mullet roe origin and production methods.

Transcriptome analysis of flathead grey mullet (Mugil cephalus) ovarian development induced by recombinant gonadotropin hormones.

Background: Treatment with recombinant gonadotropin hormones (rGths), follicle-stimulating hormone (rFsh) and luteinizing hormone (rLh), was shown to induce and complete vitellogenesis to finally obtain viable eggs and larvae in the flathead grey mullet (Mugil cephalus), a teleost arrested at early stages of gametogenesis in intensive captivity conditions. This study aimed to investigate the transcriptomic changes that occur in the ovary of females during the rGths-induced vitellogenesis. Methods: Ovarian samples were collected through biopsies from the same five females at four stages of ovarian development. RNASeq libraries were constructed for all stages studied, sequenced on an Illumina HiSeq4000, and a de novo transcriptome was constructed. Differentially expressed genes (DEGs) were identified between stages and the functional properties of DEGs were characterized by comparison with the gene ontology and Kyoto Encyclopedia. An enrichment analysis of molecular pathways was performed. Results: The de novo transcriptome comprised 287,089 transcripts after filtering. As vitellogenesis progressed, more genes were significantly upregulated than downregulated. The rFsh application induced ovarian development from previtellogenesis to early-to-mid-vitellogenesis with associated pathways enriched from upregulated DEGs related to ovarian steroidogenesis and reproductive development, cholesterol metabolism, ovarian growth and differentiation, lipid accumulation, and cell-to-cell adhesion pathways. The application of rFsh and rLh at early-to-mid-vitellogenesis induced the growth of oocytes to late-vitellogenesis and, with it, the enrichment of pathways from upregulated DEGs related to the production of energy, such as the lysosomes activity. The application of rLh at late-vitellogenesis induced the completion of vitellogenesis with the enrichment of pathways linked with the switch from vitellogenesis to oocyte maturation. Conclusion: The DEGs and enriched molecular pathways described during the induced vitellogenesis of flathead grey mullet with rGths were typical of natural oogenesis reported for other fish species. Present results add new knowledge to the rGths action to further raise the possibility of using rGths in species that present similar reproductive disorders in aquaculture, the aquarium industry as well as the conservation of endangered species.

Improvement of the shelf life of grey mullet (Mugil cephalus) fish steaks using edible coatings containing chitosan, nanochitosan, and clove oil during refrigerated storage

The effects of edible coatings made of chitosan, or chitosan nanoparticles, and their combinations with clove oil on the physical, chemical, microbiological, and sensory properties of grey mullet (Mugil cephalus) steaks during refrigerated storage (4 °C) for 24 days were evaluated. The data indicated that metrics for all of these characteristics were improved significantly (P ≤ 0.05) in coated fish steak samples compared to the control sample. The coated steaks texture values were higher than those of control sample through storage time with nanochitosan coating containing clove oil having best value 2.51 kg/cm2 among tested samples at the end of storage period. However, pH values of coated samples were lower, a good indicator, than corresponding one of the control (6.46) with nanochitosan coatings with or without clove oil showed low mean values (6.11–6.13). Similar trend regarding chemical indices, i.e. total volatile basic-nitrogen, trimethylamine, peroxide, and thiobarbituric acid reactive substances values for samples coated with nanochitosan with or without clove oil giving better lower values than control or other treatments. Also, the coating delayed microbial (aerobic plate count, psychrotrophic bacteria, yeasts and molds, and total coliform bacteria) growth during the refrigeration storage period, and coated samples produced better results compared to the control sample. Sensory evaluations showed that the treatment enhanced the scores of fish steak samples compared to the control. The results showed that a nanochitosan coating with clove oil was the best treatment prolonged the shelf life of mullet steaks and efficiently maintained the quality attributes to an acceptable level during refrigerated storage for 24 days. Thus, these findings can be bases for producer to provide consumers with fresh fish steaks with good shelf life at refrigerated temperature for up to 24 days.Graphical

Determination of heavy metals from Aloe vera by- product in golden mullet (Liza aurata); A consumer health risk assessment.

Heavy metals have become subject of concern in the recent years because of its potency to cause cardiovascular diseases and other toxic health effects. Therefore, this research was assumed to investigate the level of toxicity in terms of heavy metals accumulation in the fish samples and its benefits and risk for human consumers health and also evaluate the partial replacement of plant sources by canarian Aloe vera diets as a pure product or like a by-product on toxicological effects on the golden mullet (Liza aurata) fillet and whole body. In this study risks arising from fish metal content has been measured using various parameters as Estimated Daily Intake (EDI), Maximum Safe Consumption (MSCA), Target Hazard quotient (THQ), Hazard Index (HI) Carcinogenic risk of As (As- CR), the Value Selenium Health Benefit (Se HBV) and also the Nutritional Values has been evaluated. The results showed that all heavy metal levels in the fish tissue and diets were below the confirmed safe limits for consumption. In case of diets, it is obvious that with the exception of As, Hg, and Se, the presence of heavy or essential metals in both whole fish and raw fillet in golden grey mullet given experimental diets revealed that the whole fish had the highest concentration. Thus, it can be concluded that Aloe vera product and byproduct were in safety limits for fish and also for humans through food chain. Various risk and benefit assessment measures established by national and international authorities concluded that Liza aurata use was mostly safe.

Characterization of the different behaviours exhibited by juvenile flathead grey mullet (Mugil cephalus Linnaeus, 1758) under rearing conditions

Aim of study: To describe the common behaviour of flathead grey mullet (Mugil cephalus) under rearing conditions.
 Area of study: Tepic, Mexico.
 Material and methods: Behaviours exhibited by mullets were videorecorded with submersible cameras installed inside of three tanks. A total of 690 min per day (07:30 - 18:30 h) were recorded per tank during a week. Afterwards, the different behaviours exhibited by juvenile M. cephalus were described, identified and characterized in an ethogram and grouped into two categories: a) locomotion, including three different observed behaviours (resting, swimming and fast swimming) and b) feeding, including three behaviours (surface feeding, bottom feeding and rubbing). Each of the behavioural variables were quantified.
 Main results: M. cephalus is a species with a constant locomotion associated to feeding, since fish showed continuous movement during most of day light period. On the contrary, fish exhibited reduced movement during dark periods. Mullets were observed to be a non-aggressive fish species under conditions of the present study, since the absence of dominance and aggression towards conspecifics was observed, which suggested a high predisposition for adaptation to captivity. Finally, behavioural frequencies of grey mullet juveniles were similar among the three tanks for most of the behavioural variables analysed (p>0.05) except for the variable bottom feeding (p=0.02).
 Research highlights: Results from this study could be of interest for the aquaculture industry to optimize rearing techniques and welfare for the production of grey mullet.

Spawning induction and larval rearing in the thinlip gray mullet (Chelon ramada): The use of the slow release gonadotropin releasing hormone analog (GnRHa) preparation, leuprorelin acetate

The thinlip gray mullet (Chelon ramada) belongs to the Mugilidae family, it is a low-trophic, euryhaline species adapted to a wide range of environmental conditions. As such, it represent a candidate to diversify aquaculture production toward more sustainable species. Nonetheless, several bottlenecks have to be overcome before production is undertaken at commercial scale. Indeed, C. ramada mature females do not spawn without hormonal treatments in captivity. This report describes the use of the gonadotropin releasing hormone analog (GnRHa), leuprorelin acetate as an effective single-dose inducer of spawning in this species. Wild mature females (n = 10; 29 ± 1 cm total length, TL and 199 ± 20 g body weight, BW) exhibiting protruded papilla and bulging abdomen, presenting vitellogenic oocytes (diameters higher than 657 µm) and fluent males (n = 21; 28 ± 1 cm TL and 181 ± 80 g BW) were treated with a single injection of leuprorelin acetate. Breeders spawned more than 500,000 eggs with a mean fertilization and hatching rate of 92 ± 3 and 91.4 ± 0.4 %, respectively. Larvae grew according to the equation y = 2.6841e0.044x, mean survival rate at 19 dph was 13.8 ± 1.5 %. Mean SGR% day−1 slightly decreased concomitantly with tail flexion, probably for a greater investment on ontogenic development rather than growth. Present results suggest that mature C. ramada presents easily recognizable reproductive traits, adapts without difficulty to captive conditions, and can be easily induced to spawn administrating a single dose of leuprorelin acetate. The protocol used in our study resulted in high fertilization and hatching rates, as well as promising larval survival minimizing broodstock stress.

Effect of Cooking and Freezing on Levels of pesticides residues in Local Fresh Fish

Pesticides are an important part of pests controlling strategies. Misuse of such chemicals has been linked to pollution of various environments and toxicities that lead to various health conditions and diseases. Importance of healthy and non-contaminated fish for human diet is essentially required. Samples of 14 local fresh fish (tilapia, grey mullet, and cat fish) were analyzed for seven pesticides (endosulfan, heptachlor, malathion, chlorpyrifos, bifenthrin, deltamethrin, and fenoxycarb) using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Heat processing applied for positive samples by two different cooking method (roasting at 79 °C for 10 min and frying at 210 °C for 40 min) have influenced the levels of studied pesticides and significantly reduced their levels by 53-95%. Freezing preservation of contaminated fish at -70 °C for one month only reduced the level of the pesticides by 6-30%, however, final reduced levels were not below recommended maximum residue limit values.

Integrated assessment of hydrocarbon and sodium dioctylsulfosuccinate (DOSS) bioaccumulation and biomarker responses in grey mullet (Mugil liza) after exposure to oil, dispersants and chemically dispersed oil

Integrated assessment of hydrocarbon and sodium dioctylsulfosuccinate (DOSS) bioaccumulation and biomarker responses in grey mullet (Mugil liza) after exposure to oil, dispersants and chemically dispersed oil

First Evaluation of Associated Gut Microbiota in Wild Thick-Lipped Grey Mullets (Chelon labrosus, Risso 1827)

This study aimed to characterize the intestinal microbiota of wild thick-lipped grey mullets (Chelon labrosus) and explore its potential functionality on the host. Intestinal contents of anterior and posterior sections from wild fish were collected and DNA was extracted. Subsequently, the V3–V4 regions of 16S rRNA were sequenced using the Illumina technology and results were analyzed by bioinformatics pipeline. The functional profile of the microbial community was analyzed using PICRUSt software. Shannon and Simpson diversity indices were significantly higher in the posterior section of wild specimens. The overall taxonomic composition suggests a certain homogeneity in the anterior section of the intestine and heterogeneity in the posterior section. Due to this, no statistical differences were detected at any level among both intestinal sections. Predicted functions of intestinal microbiota showed the most abundant were those related to amino acid metabolism, carbohydrate metabolism, energy metabolism, membrane transport, and cell replication and repair. Furthermore, the analysis revealed microbial functional genes related to the elimination of environmental toxins.

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.

Comparative Evaluations to Enhance Chemical and Microbial Quality of Salted Grey Mullet Fish

Salted fish preparations are popular and widely eaten across the world. Salting is a preservation strategy to enhance shelf life by decreasing water activity in fish muscles. Salted fish demand increases with less regard for preservation characteristics, and novel strategies are required for healthy production. Lysozyme, EDTA, their mixture, and black cumin oil nanoemulsion (BCN) were used for dipping treatments to make preservative films before salting. A medium-sized mullet were classified into six groups: fresh, commercial salted mullet, and four treatments. Stored salted mullet groups were evaluated for chemical composition changes, lipid profile changes, nitrogen profile changes, and microbial contamination. The results were reflected by nonsignificant changes in protein content (21.08 ± 1.05%) of the BCN compared to the fresh (22.41 ± 1.41%), with the lowest salt penetration to the flesh (11.11 ± 0.74%). The lowest value recorded was the BCN for the pH (5.53 ± 0.06) and water activity (0.447 ± 0.019). The changes in lipid profile compared to the fresh were very low, which does not happen in a commercial salted sample. The changes in total volatile and non-protein nitrogen represented very low for the BCN compared to the commercial salted one. Coliform, E. coli, Staphylococcus aureus, Salmonella, and Clostridium were not detected in the BCN salted mullet. The overall acceptability for the BCN mullet was the best in the test panel list evaluation, followed by the mixture treatment. This research indicated that the BCN treatment before mullet fish salting was optimal, with greater food safety properties and no consumer acceptance alterations.

Prerequisites for the expansion of the range of golden grey mullet Chelon auratus (Risso, 1810) in the conditions of inconstancy of the salt regime of the northern part of the Caspian Sea

In the Caspian Sea, as in any natural body of water, the distribution and dynamics of the number of fish, including mullet, is due to the combined influence of environmental factors. In the present period of regression of the sea and changes in the level of runoff of the Volga River, salinity plays an important role in the life cycle of all representatives of the ichthyofauna. The article is devoted to the topical issue of the impact of the salt regime on the spatial and quantitative characteristics of the mullet population. The distribution and its relative abundance in 2016 and 2019 observations are presented. The distribution areas are mapped with a detailed description of the features of the formation of concentrations during two contrasting periods: desalination and salinization of the sea. Analyzing the data of trawl catches, it was found that in 2016, when the powerful Volga runoff led to the expansion of desalination zones, the average catch of mullet was 7 copies/an hour of trawling. It is noteworthy that this indicator has grown to 11 copies/an hour of trawling, during the salinization of the Northern Caspian in low-water 2019 Graphical data confirming the presence of a direct correlation between the relative abundance of mullet and increasing salinity gradients are presented. It is shown that for two years the value of the correlation coefficient was 0.74–0.76. Mullet was caught in areas with salinity from 2 to 17%. It was found that the majority of concentrations (68–74%) were formed in marine waters from 8%. In conclusion, it is concluded that the increase in salinity indicators of the northern part of the Caspian Sea has a positive effect on the expansion of the range of mullet.

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.

Life-history traits of grey mullet, Liza parsia in the Passur River of Southern Bangladesh: Implications for effective management

The study of life-history features of least-concerned fishes like Liza parsia is critical for developing long-term management and conservation methods for this species. The current study delivers the very first detailed clarification of life-history traits (LHT), containing length-frequency distribution (LFD), length-weight and length-length relationships (LWR and LLR), form factor (a3.0), condition factors, length at first sexual maturity (Lm), natural mortality (Mw) and optimum catchable length (Lopt) of L. parsia from the Passur River in southern Bangladesh. Fish samples (n =150) were randomly collected from May to August 2021, using gill nets. Each individual fish's total length (TL), fork length (FL), standard length (SL), and bodyweight (BW) were recorded. The size classes of TL were 15–17cmleadingmaximum sizes among the fish population. Length-Weight relations (LWR) from exponential b values (TL vs. BW) revealed a negative allometric growth trend (b = 2.6174). The b value based on the LLR similarly specifies the identical growth configuration. The a3.0 score was determined to be 0.01, demonstrating that the fish has extended body morphology. KF is the finest method for measuring the well-being of L. parsia in the Passur River among the four types of condition parameters. Moreover, WR also showed a significant deviation from 100 (p < 0.05) signifying an unstable habitat for L. parsia. The calculated Lm, Mw and Lopt values were 11.20 cm in TL, 0.76/year and 12.64 cm in TL respectively. As a consequence, the findings of this research could be conducted in the future to effectively manage this species in the Passur River, and its interconnecting environments.