Grey Mullet Research Articles

Production of Flathead Grey Mullet (Mugil cephalus) and Lettuce (Lactuca sativa) in a Coupled Aquaponic System under Suboptimal Water Temperatures

The combined production of three varieties of lettuce (romaine, iceberg, and red leaf) with flathead grey mullet (Mugil cephalus) was tested in triplicate in three independent coupled aquaponic units with no thermal control. For this purpose, a total of 114 fish (2.5 kg/m3) were stocked in each fish tank (2 m3), and 92 lettuces were planted in the hydroponic unit (6 m2). As no thermal control was included in the design of the aquaponic system, water temperatures declined from maximum values of 20.4 °C to minimum values of 5.0 °C, which directly affected fish growth. However, the conditions imposed by the aquaponic system were suitable for promoting lettuce’s growth and external appearance, as no pests or leaf discoloration were noticed. Lettuce survival was similar among the three tested varieties (98.5 ± 1.7%). The yields for the romaine and iceberg varieties were 384 ± 100 g/lettuce and 316 ± 70 g/lettuce, respectively, and that for the red leaf variety was lower, at 176 ± 75 g/lettuce. Yield values ranged between 3.6 and 4.4 kg/m2 depending on the replicate considered (4.0 ± 0.4 kg/m2). According to present results, each aquaponic unit required ca. 2.6–2.7 L of water per unit of lettuce produced.

Dietary co-enzyme Q10 boosted the growth performance, antioxidative capacity, immune responses, and intestinal and hepatic histomorphology of grey mullet (Liza ramada)

The aim of this experiment was to assess the potential benefits of supplementing coenzyme Q10 (CoQ10) in the diet of Liza ramada, with a focus on growth promotion, enhanced feed utilization, improved digestive enzyme activity, bolstered antioxidant defenses, and overall health. Five diets were prepared, maintaining consistent levels of lipids (7%) and protein (32%). These diets featured equivalent raw materials but varied in their CoQ10 content (0, 20, 40, 60, and 80 mg CoQ10/kg diet). Initial fish weight averaged 90.89±0.41 g, and each diet was administered to fish in triplicate tanks over a 60-day feeding period. Surprisingly, the diet with 80 mg/kg of CoQ10 showed the most substantial increases in weight gain (131.23±1.82 g), specific growth rate (1.40±0.01%/day), and a more favorable feed conversion ratio (1.73±0.01), outperforming the 60, 40, and 20 mg/kg CoQ10 diets. Additionally, 40 and 60 mg/kg CoQ10 diets demonstrated substantial improvements in digestive enzyme activity [protease (22.30±0.80 and 21.34±0.77, U/ mg), amylase (19.90±0.65 and 20.15±0.43, U/ mg), and lipase (27.04±0.80 and 27.41±0.87, U/ mg)], antioxidant markers [superoxide dismutase (14.01±0.27 and 14.44±0.62, U/ mg), catalase (1.19±0.04 and 1.20±0.04, U/ mg), and glutathione peroxidase (3.27±0.14 and 3.47±0.16, U/ mg)], and immune responses [lysozyme (302.12±3.18 and 294.25±7.64, U/ ml), bactericidal activity (5.00±0.04 and 6.03±0.14, U/ ml), respiratory burst using nitroblue tetrazolium (0.55±0.01 and 0.55±0.01, U/ ml), and alternative complement pathway activities (58.29±1.01 and 58.74±0.80, U/ ml)] in L. ramada (p < 0.05). Histological evaluations of the liver and intestine indicated structural enhancements, particularly in the 60 and 80 mg/kg CoQ10 groups, suggesting potential benefits for organ health. CoQ10 supplementation did not affect the survival rate and biochemical parameters [albumin, glucose, total protein, globulin, total cholesterol, triglyceride, AST, ALT, urea, and creatinine] (p > 0.05). These findings underscore the potential of CoQ10 as a valuable dietary additive to enhance the growth and overall health of L. ramada, with recommended inclusion levels of CoQ10 falling between 60 and 80 mg/kg.

Omega-3 long chain highly unsaturated fatty acid content in tissue correlates with escape response efficiency in golden gray mullet

Omega-3 long-chain highly unsaturated fatty acids (n-3 HUFA) are poorly synthesized de novo by marine fish, but are necessary to maintain their metabolic and physiological performance. Consequently, fish must find them in their diet. However, the availability of these lipid compounds is predicted to decrease in relation to global changes in ocean waters. The aim of this study was to experimentally determine the effects of an n-3 HUFA-deficient diet on the escape performance of Chelon auratus, a microphytobenthos grazer of high ecological importance. Fish were fed either a standard n-3 HUFA diet or an n-3 HUFA-deficient diet for 2 months. At the end of this conditioning period, several variables (latency, responsiveness, initial direction of escape, response duration, distance covered, maximum acceleration and velocity, and turning rate) related to escape performance were characterized in the tested fish. The results showed that a lower dietary n-3 HUFA content caused a significant reduction in the proportion of these fatty acids in fish muscle, both in membranes and in reserves. While the FA composition of the brain also reflected that of the diet in reserves, the membrane fatty acid composition of the brain remained similar between the two dietary groups, suggesting the preservation of neural and cognitive functions of the fish. Neither growth rate nor escape response variables were significantly different between the two diets. However, some escape response variables (e.g., latency, duration, maximum velocity and acceleration, and turning rate) were highly correlated with fish n-3 HUFA content in brain or muscle, and these correlations were tissue specific. While response duration and latency seemed to be more correlated with n-3 HUFA content in the brain membrane, other escape response variables such as turning rate, maximum velocity, cumulative distance, and maximum acceleration seemed to be correlated with n-3 HUFA content in the lipid reserve, both in the brain and in the muscle. Our results indicate that the reduction of n-3 HUFA in the dietary sources of marine fish appears to reduce the performance of the escape response, suggesting some impact of n-3 HUFA dietary changes with global change on predator-prey relationships within the marine ecosystem.

Relationship between otolith morphometry and fish total length of Chelon auratus from two localities (Mediterranean Sea and Ain Ziana Lake) in Libyan waters

ABSTRACT The relationship between fish total length and otolith length, width, and weight were inspected in the golden grey mullet, Chelon auratus, collected from the Mediterranean Sea coast of Libya and Ain Ziana, an inland lagoon located northeast of the Libyan coast. Chelon auratus is considered a valuable marketable fish in Libya. The main aim of the study was to estimate the statistical relationship between fish total length and the otolith length, width, and weight. This information will be noteworthy in the upcoming analyses on the biology of this species, which will provide critical information about feeding, age and growth of this species. Linear and non-linear regression models were used. The regression equations for each locality were significantly different, with exception of the right and left weight of individuals collected from the Mediterranean Sea coast as well as for the Ain Ziana Lagoon. The regression relationships were more homogeneous in Ain Ziana Lagoon than in the Mediterranean Sea, where there was greater variation in total length and otolith characteristics. The results obtained from this investigation were the first to address the relationship between otolith morphometric and total length for golden grey mullets collected from two localities in the Libyan waters.

Carcinogenic and non-carcinogenic health risks associated with the consumption of fishes contaminated with heavy metals from Manzala Lake, Egypt

Manzala Lake was sampled to assess the concentrations and possible ecological risks of heavy metals. The mean heavy metal levels in the muscles of Nile tilapia, Flathead grey mullets and African catfish were 0.01, 0.15 and 0.29 mg/kg, respectively, for mercury; 3.16, 4.25 and 4.74 mg/kg for arsenic; 1.01, 0.87 and 0.95 mg/kg for lead; and 0.05, 0.12 and 0.06 mg/kg for cadmium. The levels of heavy metals exceeded their maximum permissible limits in most samples. The EDIs of some metals were higher than their PTDIs or BMDLs. The THQs and TTHQs from metal intake were >1 for Hg and Cd. In addition, the TCR values of As in all fish species were higher than 1.0 × 10−4 indicating a potential health risks from consumption of fish species which need strict hygienic procedures to prevent fish contamination with heavy metals and ensure that their levels did not exceed the maximum permissible limits.

Distribution Patterns of Grey Mullet in the Taiwan Strait in Relation to Oceanographic Conditions

The depletion of the grey mullet population in the Taiwan Strait has generated interest in conservation initiatives and to enhance the effectiveness of restoration initiatives, it is essential to comprehend the specific habitat preferences of the species in question, particularly in relation to environmental changes. In this study, habitat suitability modelling was used to investigate the distribution patterns of grey mullet. Sea surface height (SSH) was the most significant predictor of the grey mullet standardized catch per unit effort (S.CPUE). Furthermore, sea surface temperature (SST) was the second most important oceanographic parameter, followed by mixed-layer depth (MLD). The grey mullet S.CPUE peaked in regions with the summed SST, Chla, salinity, SSH, MLD and current values being 20 °C, 0.9 mg/m3, 34.5 psu, 0.45 m, 18–38 m, and 0.25 m2/s2, respectively. From late October, HSI levels in the northern Taiwan ocean increased, with a consistent upward trend. The distribution expanded in November and December, focusing on the northern and mid-ocean regions west of Taiwan. HSI levels peak in January and February, especially in Taiwan’s coastal region. High HSI distribution shifts away from coastlines and diminishes in April. The findings of this study will contribute to the understanding of this specific species and the approach used in this study may be applicable to other fisheries stocks also.

Do catadromous thinlip grey mullet benefit from shifting to freshwater? A perspective from fatty acid signature analysis

To investigate the potential benefits of the catadromous thinlip grey mullet (Chelon ramada Risso, 1827) migration to freshwater, the total lipid content and fatty acid (FA) profile of female’s muscle and gonads caught in both the estuary and river were analyzed. The freshwater contingent presented a higher body condition, greater muscle gross energy, and larger gonads with higher lipid reserves. These animals showed a muscle profile rich in C16:1n-7 and lower LC-PUFA that contrast with the higher relative amount of C18:1n-9, n-3 FA, and unsaturated LC-PUFA, such as C18 and C20 FA found in the estuarine contingent. The gonads of both contingents showed a constant and high relative amount of polyunsaturated FAs (PUFA, 37%). However, in terms of essential fatty acids (EFAs), the estuarine contingent had a higher relative amount of C18:2n-6, C20:4n-6, C20:5n-3, and C22:6n-3. On the other hand, the freshwater contingent showed a higher relative amount of n-3 FA precursors, namely C18:3n-3, and a still low relative amount of C22:6n-3. This suggests a mismatch between the metabolic omega-3 pathway and the physiological maturity stages, similar to a phenomenon of dormancy. In this sense, not all these individuals may reproduce annually, and the later stages of gonad development will require supplementary energy derived from feeding at the estuary. Thus, freshwater migration may promote a reproductive strategy enabling adults to take advantage of the warm and food-rich summer/autumn period, adjust spawning and juvenile appearance, and reduce the population’s exposure to habitat changes and/or stochastic events.

Effect of cryopreservation on motility, DNA integrity and gene expression in grey mullet, Mugil cephalus sperm

This study documents the effect of cryopreservation on motility, DNA integrity, and gene expression in Mugil cephalus sperm. Fresh sperm were cryopreserved using V2 extender (V2E) or 0.3 M glucose, each in combination with one of three cryoprotective agents (CPAs), i.e., 10 % of dimethylsulfoxide, ethylene glycol, or glycerol, all at once. After two different storage (7- vs 60- day) periods in liquid nitrogen, sperm samples were thawed. Single-cell gel electrophoresis was used to detect the DNA integrity. Heat shock proteins (HSPs), HSP70, HSP90 and glutathione peroxidase (GPx2) genes mRNA expression levels was documented using qRT-PCR. The results demonstrated that among 0.3 M glucose + CPAs combinations, EG recorded higher frozen-thawed motility 69 % (7- day) and 59 % (60- day). Similarly, in V2E + CPAs combinations, EG recorded higher frozen-thawed motility 31 % (7- day) and 26 % (60- day). The DNA integrity of all thawed sperm (both periods) did not differ from that of fresh sperm. The qRT-PCR results revealed that in the combination of 0.3 M glucose + CPAs, the level of HSP90 and GPx2 gene expression was found to be upregulated in frozen-thawed sperm on both periods. Whereas, the expression level of the HSP70 gene was down-regulated. On the contrary, in the combination of V2E + CPAs, the expression levels of HSP70, HSP90 and GPx2 genes could not be detected on both periods. Overall, the findings of this study demonstrate that the cryomedium (extender + cryoprotectant) has a more influential role in the motility and levels of gene expression in the frozen-thawed sperm of M. cephalus.

СЦЕНАРНЫЙ ПРОГНОЗ РАЗВИТИЯ СЫРЬЕВОЙ БАЗЫ РЫБОЛОВСТВА И УЛОВОВ РЫБ В АЗОВСКОМ МОРЕ В УСЛОВИЯХ СОКРАЩЕНИЯ ОБЪЕМОВ ПРЕСНОВОДНОГО СТОКА И РОСТА СОЛЕНОСТИ

Background. The reduction in freshwater runoff and the increase in the Azov Sea salinity are accompanied by a drastic transformation of aquatic biocenoses, as well as restructuring of various ecological groups of the ichthyofauna. Abrupt changes in the composition and abundance of fishing targets render traditional approaches to fishing ineffective and dictate the need to develop new kinds of fishery. Relevance. Identification of possible scenarios of the fishery resource development for the next 5–10 years is necessary to ensure the fisheries sustainability in the Azov Sea Basin. The aim of this work is to analyze the dynamics of the composition of commercial fish catches in the Azov Sea in the modern period of the sea salinization and to develop possible status scenarios for the stocks and catches of fishing targets for the next 3–10 years to substantiate fisheries management and regulation. Methods. In the course of developing such scenarios, the data on the actual dynamics and trends in the fishery resource changes during the comparable periods have been used, as well as the data on the ecological valence of the representatives of various ecological groups of fish at different stages of their ontogenesis in terms of their salinity tolerance. Results. 3 main unequally probable scenarios of changes in the abundance and biomass of various ecological groups of fish — primary industrial-scale fishing targets in the Azov Sea — have been developed; the recommendations for adapting the existing fishing practices to the changes in the fishery resources have been given. Conclusion. A further decrease in the commercial importance is predicted for the freshwater fish species, freshwater-spawning anadromous and semi-anadromous fish species, as well as for gobies and Black and Caspian Sea sprat (tyulka). The role of Black Sea migrants — European anchovy, grey mullets, red mullet, Mediterranean horse mackerel, garfish — will be reduced. Marine fish species — acclimatized so-iuy mullet and Black Sea turbot (kalkan) — will become the main fishing targets.

Morphometric characteristics and meristic counts of greenback grey mullet(Liza subviridis)population from the Khulna district

Morphometric characteristics and meristic counts of greenback grey mullet(Liza subviridis)population from the Khulna district

Comparative Gene Expression Level of Reproductive Genes Along the Brain-Pituitary-Gonad Axis in the Ripe Female of the Wild and Captive Grey Mullets; Mugil cephalus

Comparative Gene Expression Level of Reproductive Genes Along the Brain-Pituitary-Gonad Axis in the Ripe Female of the Wild and Captive Grey Mullets; Mugil cephalus

Influence of the host sex, size, and season on Ergasilus lizae infestation of Thicklip Grey Mullet (Chelon labrosus, L., 1758) in Beymelek Lagoon Lake (Antalya, Türkiye)

The aim of the study was investigation of the changes in infestation levels of Ergasilus lizae on economically important fish species, thicklip grey mullet (Chelon labrossus) from Beymelek Lagoon Lake located on the western Mediterranean coast (Antalya, Türkiye). In this context, the infestation levels of E. lizae with respect to fish sexes, fish sizes and season were evaluated statistically. The research was conducted seasonally between May 2008 to April 2009, and the gills which belong to 103 fish samples were examined. The overall infection prevalence and mean intensity values were 60.2% and 15.95, respectively. The prevalence and mean intensity of E. lizae for thicklip grey mullet male and sexually unidentified fish samples were higher than that for females. Prevalence and mean intensity were determined the highest in size class I with 69.6% and 26.3, and almost the same values in size groups II and III. E. lizae on host fish were observed in every season. The highest prevalence and mean intensity of E. lizae was recorded in spring with 100%, 24.88. The lowest prevalence of E. lizae was recorded in summer at 12% and the lowest mean intensity of E. lizae was in the summer and the winter with 9, 8.67 respectively. The infestation level of E. lizae was statistically significant with host sex and season, but there was no effect on the fish size groups.

Effects of Chlorella fusca-supplemented diet on intestinal microbiota and gene expression related to metabolism, stress, and immune response in Chelon labrosus

Microalgae are emerging as promising alternatives to traditional fishmeal and crop ingredients in aquaculture diets. In this study, we aimed to characterize the intestinal microbiota and evaluate the transcription of genes related to metabolism, stress, and the immune system in various tissues of thick-lipped grey mullet (Chelon labrosus) fed a diet containing 15 % of microalga Chlorella fusca against a microalgae-free control diet for 90 days. After this period, the fish were challenged with Aeromonas hydrophila and polyinosinic–polycytidylic acid (poly I:C) to assess their immune response during 72 h. Microbiota analysis revealed that dietary inclusion of microalgae did not produce significant differences in intestine diversity compared to the control group. The dominant genera differed between the groups, with Pseudomonas and Mycoplasma most abundant in the fish fed with C. fusca, and Brevinema, Cetobacterium, and Pseudomonas predominant in the control group. Gene expression analysis indicated significant changes in hif3α, mhcII, ferritin, and mx genes in different organs of fish fed the microalgae-supplemented diet. Gene expression in the head kidney showed variations after A. hydrophila or poly I:C challenges, and higher peak values were observed in poly I:C-injected fish. Furthermore, c3 mRNA levels were significantly up-regulated in the fish fed with C. fusca at 24 h following A. hydrophila challenge. In conclusion, the inclusion of C. fusca in the fish diet modifies the composition of microbial species in the intestine but does not seem to affect its functionality. Regarding the influence on gene expression, the microalgae-supplemented diet effectively modulates the transcription of stress and immune-related genes, which may potentially enhance the fish resistance to stress and infections.

Microbiome study of a coupled aquaponic system: unveiling the independency of bacterial communities and their beneficial influences among different compartments

To understand the microbiome composition and interplay among bacterial communities in different compartments of a coupled freshwater aquaponics system growing flathead grey mullet (Mugil cephalus) and lettuces (Lactuca sativa), 16S rRNA gene amplicon sequencing of the V3–V4 region was analysed from each compartment (fish intestine, water from the sedimentation tank, bioballs from the biological filter, water and biofilm from the hydroponic unit, and lettuce roots). The bacterial communities of each sample group showed a stable diversity during all the trial, except for the fish gut microbiota, which displayed lower alpha diversity values. Regarding beta diversity, the structure of bacterial communities belonging to the biofilm adhering to the hydroponic tank walls, bioballs, and lettuce roots resembled each other (weighted and unweighted UniFrac distances), while bacteria from water samples also clustered together. However, both of the above-mentioned bacterial communities did not resemble those of fish gut. We found a low or almost null number of shared Amplicon Sequence Variants (ASVs) among sampled groups which indicated that each compartment worked as an independent microbiome. Regarding fish health and food safety, the microbiome profile did not reveal neither fish pathogens nor bacterial species potentially pathogenic for food health, highlighting the safety of this sustainable food production system.

Combined Dietary Administration of Chlorella fusca and Ethanol-Inactivated Vibrio proteolyticus Modulates Intestinal Microbiota and Gene Expression in Chelon labrosus

The use of functional feeds in aquaculture is currently increasing. This study aimed to assess the combined impact of dietary green microalgae Chlorella fusca and ethanol-inactivated Vibrio proteolyticus DCF12.2 (CVP diet) on thick-lipped grey mullet (Chelon labrosus) juvenile fish. The effects on intestinal microbiota and the transcription of genes related to metabolism, stress, and the immune system were investigated after 90 days of feeding. Additionally, the fish were challenged with Aeromonas hydrophila and polyinosinic–polycytidylic acid (poly I:C) to evaluate the immune response. Microbiota analysis revealed no significant differences in alpha and beta diversity between the anterior and posterior intestinal sections of fish fed the control (CT) and CVP diets. The dominant genera varied between the groups; Pseudomonas and Brevinema were most abundant in the CVP group, whereas Brevinema, Cetobacterium, and Pseudomonas were predominant in the CT group. However, microbial functionality remained unaltered. Gene expression analysis indicated notable changes in hif3α, mhcII, abcb1, mx, and tnfα genes in different fish organs on the CVP diet. In the head kidney, gene expression variations were observed following challenges with A. hydrophila or poly I:C, with higher peak values seen in fish injected with poly I:C. Moreover, c3 mRNA levels were significantly up-regulated in the CVP group 72 h post-A. hydrophila challenge. To conclude, incorporating C. fusca with V. proteolyticus in C. labrosus diet affected the microbial species composition in the intestine while preserving its functionality. In terms of gene expression, the combined diet effectively regulated the transcription of stress and immune-related genes, suggesting potential enhancement of fish resistance against stress and infections.

Distribution and Abundance of Fry and Juveniles of A Few Cultivable Fishes in and Around Cochin Backwater, Kerala, India

The investigation was carried out at four selected stations in Cochin Backwater and intertidal water of the sea representing different ecological conditions at fortnightly intervals from February to September 1989. As per the observations, among the five species of fry recorded, the grey mullet Liza parsia was dominating throughout the study period with maximum abundance during the south-west monsoon. The fry of the milk fish Chanos chanos and the Indian tarpon Megalops cyprinoides were noted only during the pre-monsoon months when the salinity and temperature of water were considerably high, whereas the fry of the grey mullet Mugil cephalus were recorded during lower temperature and salinity conditions from June to August. Among the environmental parameters, salinity, temperature and distribution of phyto- and zooplankton were found to have profound influence on the distribution of different species directly or indirectly. Hydrogen ion concentration and dissolved oxygen were not found to influence the distribution. Among the eight species of juveniles recorded during the study, those of L. parsia were dominating followed by L. macrolepis. The juveniles of C. chanos, M. cyprinoides and Valamugil cunnesius were observed only after the onset of the monsoon indicating their preference of low salinity and temperature, and higher concentration of food materials.

Comparison of physical properties and fishing performance between biodegradable PLA and conventional PA trammel nets in grey mullet (Mugil cephalus) and red-lip mullet (Liza haematocheila) fishery

Marine plastic pollution and continuous capture of marine animals, so-called “ghost fishing”, by abandoned, lost, or otherwise discarded fishing gear (ALDFG) are global concerns. This study investigated whether biodegradable polylactic acid (PLA) monofilaments can be used to replace conventionally used non-biodegradable polyamide (PA) in trammel net fishery for limiting ALDFG associated effects. It evaluated the physical properties of PLA and PA monofilaments and compared fishing performance of PLA and PA trammel nets in a commercial mullet fishery in the Yellow Sea, China. Although PA monofilament exhibited superior physical properties, no significant differences in catch efficiency between PA and PLA trammel nets were observed. Fish of both species were mainly captured by pocketing which can further explain observed similar catch efficiency. These initial results suggest a potential for applying biodegradable materials in trammel net fisheries. Therefore, further long-term testing is encouraged to investigate whether this promising performance is persistent over long-term.

Fishery-based adaption to climate change: the case of migratory species flathead grey mullet (Mugil cephalus L.) in Taiwan Strait, Northwestern Pacific.

The flathead gray mullet (Mugil cephalus L.) is a cosmopolitan fish that lives in warm and temperate zones over 42°N-42°S. It is a key fish species for industrial fishing off coastal Taiwan. Gray mullets enter the coastal waters of the southeastern Taiwan Strait (22°N-25°N) to spawn in winter and feed in the coastal and tidal waters of China (25°N-30°N). From 1986 to 2010, the annual catch of gray mullet decreased substantially and remained low. Although the Pacific Decadal Oscillation and El Niño-Southern Oscillation are recognized to affect gray mullet migration, the increase in sea surface temperature may be the main cause of the aforementioned decrease. We explored how weather changes affect fishing conditions and patterns at the gray mullet fishing grounds in Taiwan's coastal areas. Because of the decrease in gray mullet catches, the most common method for catching gray mullet in Taiwan's coastal areas between 1990 and 2010 was the use of drift or trawl nets instead of two-boat purse-seiner fleets. Since 2012, purse-seiner fleets have become the most common method for catching gray mullet. This trend indicates that the local fishing industry is adapting to changing environmental conditions.

Quality and stability of different seafood products treated with high hydrostatic pressure (HPP) intended for raw consumption

The consumption of raw fish has rapidly increased in recent years, but being a highly perishable product, it is characterised by a very short microbiological shelf life. High hydrostatic pressure (HPP) processing is a non-thermal technology has emerged recently as a promising alternative to thermal processing for food pasteurization capable of maintaining fresh-like characteristics and nutritional value. However, the induced changes in product quality should be assessed carefully. The present research aimed to investigate the effect of HPP on different seafood products, namely grey mullet, tiger prawn and rose shrimp, intended for raw consumption. Three pressure levels (400, 500 and 600 MPa) were applied for 10 min. During refrigerated storage, microbiological quality, chemical parameters, colour and texture and fat oxidation were analysed. Results showed that the application of lower pressure was able to inactivate E. coli, pseudomonas and/or positive coagulase staphylococci; however, they were able to recover during storage. In addition, the application of 600-MPa pressure extended the microbiological shelf life by up to 30 days. For all samples, general whitening occurred while the texture was affected in a different way for the three considered species. Fat oxidation was only minimally affected and remained quite low during storage.

Flathead grey mullet (Mugil cephalus) juveniles exhibit consistent proactive and reactive stress coping styles

Stress coping styles (SCS) are defined as a coherent set of individual physiological and behavioural differences in stress responses that are consistent across context and over time. Nowadays, an increased attention has been paid to fish welfare in aquaculture production and to consistent behavioural response to stress in captivity, since these aspects present direct implications on fish health, quality and farming productivity. Therefore, the present study aimed to evaluate the differences between proactive and reactive stress coping styles and their consistency over time and across contexts in flathead grey mullet Mugil cephalus juveniles reared in captivity. Fish were submitted to two runs of a set of behavioural tests, with a four-months interval: one group test (risk-taking test) and three individual tests (restraining, predator and confinement tests), followed by the quantification of blood cortisol and glucose concentrations (control and post-stress). Results confirmed the existence of proactive and reactive SCS in mullet juveniles and demostrated that behavioural responses in most of the tests were consistent over time (between runs) and across contexts (among tests). Fish that crossed from the safe to the risky area in the risk-taking test also displayed higher activity and escape attempts and lower basal levels of cortisol and glucose than fish than did not cross. This work reported for the first time the consistency of stress coping styles over time and across contexts in M. cephalus juveniles. Due to the increased interest in understanding adaptive mechanisms underlying consistent individual behaviours in response to stressful situations, are of interest for the aquaculture industry to improve productive performance of this fish species. Further studies are required to investigate how different selective pressures might influence the expression and consistency of SCS over time and across contexts.