Does fin damage allow discrimination among wild,escaped and farmed Sparus aurata (L.) and Dicentrarchus labrax (L.)?

The present study compares fin damages in gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax) according to their wild, escaped or farmed origins. In addition, the potential applicability of fin condition indices (Fin Erosion Index ‘FEI’ and Fin Splitting Index ‘FSI’) as identification tools is discussed. Farmed seabream fins evidenced more erosion and splitting (FEI ± SD: 2.1 ± 0.3; FSI ± SD: 1.9 ± 0.6) than wild seabream fins (FEI: 0.8 ± 0.6; FSI: 1.2 ± 0.9), a result of farming conditions in open‐sea cages. Escaped seabream fin erosion was between that of farmed and wild seabream (FEI: 1.6 ± 0.4), which could indicate that fins in farmed fish recover over time from farming abrasions once they are in the wild. However, the fins of escaped seabream seem to be weaker than those of the wild fish, and therefore might be more susceptible to suffer other types of erosion such as splitting or nipping (FSI: 2.3 ± 0.7). No significant differences were found in seabass FEI according to their origins, although wild seabass presented significantly more split caudal fins (FSI: 3.3 ± 2.8) than the farmed seabass (FSI: 1.2 ± 1.1) and escapees (FSI: 2.5 ± 1.6). Therefore, FEI for seabream could be used as tools not only to distinguish between wild and farmed fish, but also to identify recent escapees, improving further assessments on the contribution of seabream escapees in fishery landings. However, the healing potential of damaged fins must be considered for the proper identification of escapees. Use of fin condition indices from both species could be helpful for aquaculture management, to assess fish welfare in fish farms stocks, and improve the knowledge of handling, stock densities and open‐sea cage environment conditions.     

Ecogenotoxicological studies for an early toxicity screening and monitoring in Epinephalus chlorostigma and Scamberomorus commerson

The study was planned to investigate DNA fragmentation in fish to screen aquatic toxicity and in Epinephalus chlorostigma and Scamberomorus commerson collected from Red sea near Jizan, Saudi Arabia from three locations “(Corniche North park: “16.92161, 42.54631; Jizan Port: 16.874, 42.54952” N and Jizan Economic City: 17.26589, 42.34738“ ”)“ were used as a case study for the application of comet assay. The study area of the Red Sea is polluted due to anthropogenic activities and the disposal of wastes from multiple sources. Comet and micronucleus assays were used to detect genotoxicity in these fish species harvested from three sites. The concentration of Pb, Cr, Zn, Mn, Cu, Cd, Sn, and Hg was higher in the water samples collected from the polluted site compared to the non-polluted site of the Red sea. Comet assay for S. commerson showed significant (p < 0.05) genetic damage about 44.33 ± 3.03% DNA in comet tail at site S1. It was subsequently reduced to 31.71 ± 3.52% and 22.11 ± 2.52% at sites S2 and S3. E. chlorostigma also showed significant DNA in comet tail as 17.34 ± 2.19%, 11.87 ± 3.01%, and 36.41 ± 3.98% at site S1-S3, respectively. Significant (p < 0.05) DNA damage was observed in the fishes procured from non-polluted locations and upstream locations. The micronucleus induction in E. chlorostigma was recorded as 23.20 ± 4.19 and 2.20 ± 0.58%, respectively, non-polluted and polluted sites. S. commerson exhibited significant differences between polluted and non-polluted sites (44.80 ± 3.73 and 8.20 ± 2.20‰) polluted and upstream (44.80 ± 3.73 and 20.60 ± 4.02‰), respectively. A significant difference was obtained between E. chlorostigma and S. commerson for nuclear abnormalities S. commerson showed higher frequencies for nuclear deformities than E. chlorostigma. S. commerson showed substantial micronucleus induction frequencies collected from an area of low pollution intensity (upstream). This study showed that E. clorostigma and S. commerson could be successfully used as a bioindicator to determine the health of the Red Sea through the most specific assays such as comet and micronucleus tests as an early warning and to devise the monitoring strategies to ensure a safe supply of fish for human consumption.     

Home range estimates for squaretail coralgrouper, Plectropomus areolatus (Rüppell 1830)

The aim of the study was to estimate home range areas and distance of movement away from a squaretail coralgrouper (Plectropomus areolatus) spawning aggregation site located within a small-scale 1.5 km² Marine Protected Area (MPA) in Pohnpei, Micronesia. Fifteen P. areolatus were acoustically tagged and re-located within a ca. 50 km² search area over a 4-month period that included reproductive and non-reproductive months. All relocated fish were found in areas of moderate to high coral cover either on the fore reef or inside the lagoon in home ranges of 0.048 ± 0.018 km² (μ ± S.E.). Variability in home range area (0.004–0.12 km²) and distance of movement from aggregation sites following spawning (0.02–23.0 km; 5.3 ± 3.6 km, μ ± S.E.) was observed, but did not appear to be sex specific. Five of the six relocated individuals were found within 0.02–6.1 km of the aggregation. This evidence and that from recent tag-recapture studies of epinephelids suggest that a substantial proportion of individual P. areolatus spawning populations reside within close proximity to their respective aggregation sites. Reproductive populations could be protected by MPAs of moderate scale (10 s of km²) that include aggregation sites, migratory corridors and adjacent home range habitats.     

Evaluation of some heavy metals toxicity in Channa punctatus and riverine water of Kosi in Rampur,Uttar Pradesh,India

This study was aimed to assess the bioaccumulation and concentration level of three heavy metals such as Chromium (Cr), Cadmium (Cd) and Lead (Pb) in the riverine water and edible fish, Channa punctatus obtained from River Kosi, Rampur, Uttar Pradesh, India. These toxic heavy metals are released into the environment because of E-waste, industrial activities, municipal urban runoff, coal burning, fertilizers etc., then paved the way into the aquatic system due to direct input, atmospheric deposition, and erosions caused by rain. There is every apprehension of aquatic animals getting exposed to elevated levels of heavy metals, thus possessing harmful effects both to flora and fauna. The concentrations of Cd, Cr and Pb in water were found to be 0.051 ± 0.026, 1.091 ± 0.408, and 0.019 ± 0.002 whereas in the kidneys of Channa punctatus, as 0.076 ± 0.208, 0.482 ± 0.059, and 0.127 ± 0.705 respectively.     

Cadmium,chromium, and lead accumulation in aquatic plants and animals near a municipal landfill

This research was conducted to assess the contamination of heavy metals in the water, sediment, aquatic plants and animals around a municipal landfill. The heavy metals were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). The concentrations of cadmium (Cd), chromium (Cr), and lead (Pb) in water and sediment were Not detected (ND), 0.05 ± 0.98, and 0.02 ± 0.01 mg/L; and 0.47 ± 0.23, 18.65 ± 11.39, and 5.36 ± 2.08 mg/kg, respectively. A total of 24 aquatic plants from 4 species were collected from the municipal landfill. Cd concentrations in all plant species were within the standard, while Cr and Pb exceeded the standard. Forty-four fish from 4 species, 29 freshwater snails from 3 species, 10 freshwater prawns from 1 species, and 9 freshwater crabs from 1 species were collected. Cd and Cr concentrations in 2 species of fish samples exceeded the standard and Pb concentration in all fish species exceeded the standard. Cd and Pb concentrations in all freshwater snails were within the standard, except Cr. Meanwhile, Cd and Pb in freshwater prawns and snails were within the standard, except Cr. Five species of frogs were collected. Cd and Cr concentrations in 2 species exceeded the standard. Pb concentrations in all frog species exceeded the standard. The pattern of metal accumulation was fish > frogs > freshwater snails > freshwater prawns = freshwater crab (Cd), freshwater prawn > frogs > freshwater crab = freshwater snail > fish (Cr), and freshwater prawn > fish > frogs > freshwater snail > freshwater crab (Pb).     

Evaluation of copper and vanadium concentration in the soft tissue of Tylosurus crocodilus in Bahregan region,Persian Gulf

Abstract

The present study has been carried out to evaluate the concentration of copper (Cu) and vanadium (V) elements in the muscle, skin, and gill tissues of Tylosurus crocodilus (Belonidae), an edible fish, in the Bahregan region which is located in the northern part of the Persian Gulf. For this purpose, 18 fish samples in three different length groups (small, medium, and large) were randomly collected in Bahregan region. Tissues were separated and concentration of the heavy metals was determined by atomic absorption. The results showed that mean concentration of Cu and V were 0.2851 ± 0.10036 and 1.1368 ± 0.12405, 0.1117 ± 0.02322 and 2.5091 ± 1.14201 and 0.1803 ± 0.03204 and 3.3133 ± 1.05995 μg g^-1 dry weight, in skin, muscle and gill tissues, respectively. Also, the results revealed a significant positive correlation between the standard length and Cu concentration in the muscle and gill tissues (P ≤ 0.05), as well as between the standard length and V concentration in all the tissues (P ≤0.05). The results indicated that the concentration of V was higher than the World Health Organization (WHO) standard but the concentration of Cu was lower. It is therefore highly recommended that usage of this carnivore species in the studied area is limited because of the high accumulation of V in its muscle tissue.     

Histopathology and helminth parasites of African catfish Clarias gariepinus (Burchell, 1822) in relation to heavy metal pollution in a subtropical river system

In a study aimed to determine the histopathology, component parasite communities and level of selected heavy metals, African catfish Clarias gariepinus from three rivers in Zimbabwe (Gwebi, Manyame and Mukuvisi) were analysed for heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) in the gills, liver, kidney and muscles. The histopathology of these tissues was assessed by microscopic examination of stained thin sections. Metazoan parasite diversity and species composition in fish along different sites of the rivers were determined and compared. Levels of Cd, Fe, Pb and Zn were lowest in the Gwebi, Cr and Cu in the Manyame, and Ni in the Mukuvisi River. There were significant differences (P < 0.5) in concentration of iron and nickel in the gill and liver tissues of fish among the three rivers while significant differences in concentration of iron and lead were observed in muscle tissue. Gill chronic inflammation and ossification were significantly different (P < 0.5) in fish from among the three rivers. Chronic inflammation, hemosiderin deposits and bile accumulation in the liver were also significantly different (P < 0.5) among the three rivers and so was the extent of chronic inflammation in the kidney tissue. Lamellar fusion was slightly more present in gills of catfish from the Mukuvisi than the Gwebi River. The parasite community of C. gariepinus comprised three monogenean, two cestode and three nematode species. The least polluted Gwebi River had the highest parasite community diversity while the most polluted Mukuvisi River had the lowest diversity. Fish parasite community structure is thus a potential indicator of river pollution, while heavy metal pollution is a potential threat to fish and human health in the system.     

Spatial,temporal, and environmental dynamics of a multi-species epinephelid spawning aggregation in Pohnpei,Micronesia

Long-term and short-term underwater visual censuses using SCUBA, technical Nitrox, and closed circuit rebreathers (CCR) were carried out in Pohnpei, Micronesia, to define spatial and temporal dynamics within a semi-protected multi-species epinephelid (fish) spawning aggregation (FSA) of brown-marbled grouper, Epinephelus fuscoguttatus, camouflage grouper, Epinephelus polyphekadion, and squaretail coralgrouper, Plectropomus areolatus. Results identified species-specific patterns of habitat use, abundance, residency, and dispersal of FSAs. Fish spawning aggregations formed and dispersed monthly within a 21–160-d period after winter solstice within adjacent yet distinct outer reef habitats. The reproductive season coincided with periods of seasonally low sub-surface seawater temperature. Peaks in density varied among species both within the calendar year and relative to the winter solstice. Significant long-term declines in FSA density were observed for all three species, suggesting population-level fishery-induced impacts, similar to those previously reported for E. polyphekadion. Differences in density estimates were also observed between dive gear, with a threefold difference in densities measured by CCR for E. polyphekadion versus SCUBA that suggest a disturbance effect from exhaled SCUBA bubbles for this species. CCR also allowed surveys to be conducted over a larger area in a single dive, thereby improving the potential to gauge actual abundance and density within FSAs. Based on these findings, a combination of long-term and intensive short-term monitoring strategies is recommended to fully characterize trends in seasonal abundance and habitat use for aggregating species at single or multi-species FSA sites. Inherent variations in the timing and distribution of species within FSA make fine-scale temporal management protocols less effective than blanket protective coverage of these species at (e.g., marine protected areas covering FSAs and adjacent migratory corridors) and away from (i.e., temporal sales and catch restrictions) FSA sites.     

Effects of dietary katuk (Sauropus androgynus L. Merr.) on growth,non-specific immune and diseases resistance against Vibrio alginolyticus infection in grouper Epinephelus coioides

This study was conducted to investigate the effect of katuk (Sauropus androgynus L. Merr) on growth, non-specific immune and diseases resistance against Vibrio alginolyticus in grouper (Epinephelus coioides). Grouper juveniles (mean weight 10.97 ± 1.99 g, and length 9.67 ± 0.33 cm) were separated into four groups and cultivated in 100-L tank. Each group was fed with diets containing 0, 1.0, 2.5 and 5.0 g/kg herbs diet twice daily. Fish were sampled for non-specific immune parameters at 0, 1, 2, 4, 7, 14 and 30 days. Results showed that fish received S. androgynus at 1.0 and 2.5 g/kg diets affected the growth and non-specific immune responses. Weight gain, specific growth rate, respiratory burst activity, phagocytosis and reactive oxygen species significantly increased in fish administered with 1.0 and 2.5 g/kg S. androgynus diets. The mortality rate after V. alginolyticus challenge decreased in fish fed with 1.0 g/kg S. androgynus extract. Thus, this study indicated that administration of grouper with S. androgynus supplemented diets can affect the growth performances, diseases resistance and enhances non-specific immune responses.     

Thermal tolerance and standard metabolic rate of juvenile gilthead seabream (Sparus aurata) acclimated to four temperatures

Temperature variation affects the growth, maturation and distribution of fish species due to increasing constraints on physiological functions therefore, the aim of the present study is to evaluate effect of temperature on thermal tolerance and standard metabolic rate (SMR) of gilthead seabream (Sparus aurata). For this purpose, tolerable temperature ranges of juvenile gilthead seabream acclimated at 15, 20, 25, and 30 °C for 30 days were estimated using dynamic and static thermal methodologies. The SMRs of the fish were also determined based on oxygen consumption rate (OCR). The dynamic and static thermal tolerance zones of gilthead seabream were calculated as 737 °C² and 500 °C², respectively, with a resistance zone area of 155.5 °C². The SMR of the fish at the above acclimation temperatures (AT) was determined as 138, 257, 510, and 797 mg O₂ h⁻¹ kg⁻¹, respectively and were significantly different (P < 0.01, n = 10). The temperature quotient (Q₁₀) in relation to the SMR of the fish was calculated as 3.45, 3.91, and 2.44 for acclimation temperature ranges of 15–20, 20–25, and 25–30 °C, respectively. The fact that the SMR increased with rising temperatures and then decreased gradually after 25 °C indicates that the temperature preference of juvenile gilthead seabream lies between 25 and 30 °C. This study shows that gilthead seabream tolerates a relatively narrow temperature range, and consequently, a low capacity for acclimatisation to survive in aquatic systems characterised by temperature variations.     

Bioaccumulation of heavy metals in the different tissues of Mackerel scad,Decapterus macarellus (Cuvier, 1833) collected from Karachi and Gwadar Coasts of Pakistan

IntroductionAmong other aquatic animals, fish can also accumulate a large number of toxic metals in their various body organs, which may enter in the human body and cause serious health issues. Therefore, the basic aim of this study was to observe the level of some heavy metals (i.e., Pb, Fe, Cu, Cd, Cr) found in the different tissues of Decapterus macarellus collected from the Karachi and Gwadar coasts of Pakistan.MethodsAbout 200 fish samples of five different size groups of Decapterus macarellus were collected from Gwadar and Karachi fish harbors during April to September 2020. Total 10 samples of each size group i.e., S1, S2, S3, S4 & S5 were collected from each coast. Heavy metals were analyzed in fish samples by using the atomic absorption spectrophotometer (AAS).ResultsThe overall results revealed that some metals like Cu, Pb, Cd & Cr contents were high in the stomach, while less in the muscles. Whereas, the concentration of Fe was found to be high in the liver, while low in skin of fish. The average values of bioaccumulation of these heavy metals (BAF) were found in decreasing order of Cu > Cd > Fe > Cr > Pb. In this study, except Cd and Cr, all metals were found within the permissible limits. Both sediment and water from the selected site areas were also analyzed to observe their pollution levels in the order of; sediment > water > fish tissues.ConclusionThus, it was concluded that the Karachi environment was much more polluted than the Gwadar environment because it is in an industrial unit and a busy sea site for trade. Moreover, consuming muscles from this species is safe for human health except for iron toxicity, but the use of the liver is not beneficial for all selected metals. Thus, the present work will also be helpful to monitor these toxic metals in a food chain and maintain a healthy life, and reduce all kinds of health risks associated with them.     

Ecological risk assessment of heavy metal contamination in mangrove habitats,using biochemical markers and pollution indices: A case study of Avicennia marina L. in the Rabigh lagoon,Red Sea

Contamination of mangrove ecosystems, including those of the Red Sea area, has caused serious concern globally. Spatial distribution of heavy metals and their bioaccumulation in one of the common mangrove plants of Saudi Arabia, Avicennia marina L., was evaluated in 8 stations at the Rabigh lagoon to assess the ecological risks due to heavy metal contamination. Among all the heavy metals, Fe concentration was recorded highest (8939.38 ± 312.63 mg/kg) at station S4. Contamination factor (CF) values for all heavy metals determined in this study were recorded in ascending order as Cu < Cr < Mn < Zn < Fe < Ni < Pb < Cd, with the pollution load index pattern recorded in descending order as S6 > S4 > S3 > S5 > S7 > S1 > S8 > S2. Bio-concentration factor (BCF) was <1 for all the heavy metals and there was a positive correlation between the antioxidants and lead (Pb), which can be a result of the ability of A. marina to exclude or detoxify this metal by its mechanism of exclusion or detoxification. A significant correlation existed between the heavy metals concentration in sediment and A. marina leaves at one combination or the other, except for Cu and Cd, which do not correlate with any other metal concentration. The information provided in the present study can be used in the monitoring and measurement of heavy metal pollution in marine ecosystems or other aquatic environments, to prevent several ecological risks to the mangrove ecosystem.     

Hybridization of tiger grouper (Epinephelus fuscoguttatus ♀) x giant grouper (Epinephelus lanceolatus ♂) using cryopreserved sperm

Using Ringer solution as extender, the present study examined the protective effect of dimethyl sulphoxide (Me₂SO; 8-12%, v/v) on the cryopreservation of giant grouper (Epinephelus lanceolatus) sperm. The cryopreserved sperm was then successfully applied in interspecific hybridization with tiger grouper (E. fuscoguttatus). Higher motility (90.56 ± 6.58%) and fertilization rate (69.61 ± 4.83%) was achieved in 10% Me₂SO with Ringer solution as extender (dilution ratio 1:1), which should no significant difference in comparison with fresh sperm (95.88 ± 1.64% and 73.10 ± 1.28%). There were no statistical differences in both fertilization and hatching rates between hybrid and non-hybrid tiger grouper by using cryopreserved sperm for fertilization, but malformation rate of the hybrid was higher than non-hybrid (17%) (P < 0.05). Survival rate of the hybrid was lower than that of the controls at 15 days post hatching (23% vs 48%). However, hybrids showed survival rate equal to the controls at the end of the 60-day study period. Hybridization of E. fuscoguttatus x E. lanceolatus was successfully achieved using cryopreserved sperm from giant grouper. The cryopreservation of giant grouper sperm and its application in hybridization provided a technical support for further grouper breeding work.     

Water quality index,Labeo rohita,and Eichhornia crassipes: Suitable bio-indicators of river water pollution

The present study investigated the water quality index (WQI) of the Kshipra river at Dewas, Madhya Pradesh, India, using native fish Labeo rohita, and plant Eichhornia crassipes. The temperature, pH, dissolved oxygen, alkalinity, turbidity, and dissolved solids were found to be within the prescribed limits. However, heavy metals concentration exceeded the limit except for Cu and Zn. Their occurrence in river water was as follows: Ni > Fe > Cd > Cr > Mn > Zn > Cu. Among these heavy metals, Cd was found to be highly bioavailable, whereas Zn was the least bioavailable metal. Based on WQI, the water was found to be unfit for drinking, and the high WQI value was due to the presence of Cr and Cd. In fish tissues (muscle, liver, gut, gills, and kidney), the highest and lowest metal pollution index was found in gills (45.03) and kidneys (12.21), respectively. Bioaccumulation of these metals resulted in significant depletion of energy reserves (protein, glucose, and glycogen) and also altered hematological parameters. Moreover, liver function tests showed hepatic damage in the exposed fish. In-plant, both the bioaccumulation and mobility factor exceeded 1 for all these metals. On the other hand, the translocation factor was found to be beyond 1 for Fe, Ni, and Zn. These high values make this plant fit for phytoextraction of Mn, Fe, Cu, Zn, and Cd and phytostabilization of Cr in water. Moreover, consumption of L. rohita from the Kshipra River does not pose a non-cancer risk as the target hazard quotient was below 1, but it may pose cancer risk because of the presence of Cr in the range of 1.402 × 10^?3 to 1.599 × 10^?3.     

Light colour influences the behaviour and stress physiology of captive tench (<Emphasis Type="Italic">Tinca tinca</Emphasis>)

Groups of juvenile tench (7.02 ± 0.28 g) were reared under four different light regimes; blue light, red light (80 Wm⁻² 12L:12D photoperiod) white light (912 ± 210 lux, 80 Wm⁻², 12L:12D photoperiod) and no light (0 lux) (0L:24D). Visibility of fish out of shelters was used as an indicator of activity and was monitored by video recording. Blood plasma cortisol concentrations were also measured. Fish under blue or white light were significantly less active during the photophase than those under red or no light (P < 0.01). Red light produced similar activity patterns to fish receiving 24 h darkness. Plasma cortisol concentrations were also significantly influenced (P < 0.05) with the fish under white light having the highest plasma cortisol concentration (317 ± 62 ng cm⁻³) compared to fish in the dark treatment (106 ± 36 ng cm⁻³). Thus, the provision of coloured light filters increases activity in juvenile tench and may reduce their intrinsic stress level.     

Effects of chitosan‐oligosaccharides on growth performance,digestive enzyme and intestinal bacterial flora of tiger puffer (Takifugu rubripes Temminck et Schlegel, 1850)

The present study was conducted to evaluate the effects of different dietary chitosan oligosaccharide (COS) levels on digestive enzyme activity, intestinal bacteria flora, and growth performance of the tiger puffer (Takifugu rubripes). Some 600 fish (initial body weight 129.2 ± 3.1 g) were randomly allocated into twelve 2,000‐L blue cylinder aquaria with 1,500‐L of sea water and divided into four groups (n = 3 aquaria/diet). The fish were fed experimental diets supplemented with different levels of COS (0% [control, L1], 0.05% [LC1], 0.1% [LC2], and 0.2% [LC3]) for 8 weeks. During the experiment, the water temperature was 18 ± 1°C, salinity 28 ± 0.1, pH 8.0 ± 0.1 (mean ± SD, n = 672); airstones were positioned at the bottom of the tank, dissolved oxygen content was above 7.0 mg/L, with a photoperiod of 12 hr light: 12 hr dark. The results showed that dietary COS significantly increased growth performance, intestinal‐somatic index (ISI), and intestinal protease as well as lipase activity (p < .05). However, dietary COS did not have a significant effect on the condition factor (CF), hepatosomatic index (HSI), viscerosomatic index (VSI), survival, or muscle proximate composition of tiger puffers (p > .05). High‐throughput sequencing analysis showed that COS affected the richness and diversity of intestinal microbial species. The Shannon index of intestinal bacterial flora was significantly higher in the control group than in other groups (p < .05). However, dietary COS supplementation did not alter the phyla species of intestinal bacterial flora. There were significantly more Aliivibrio and Bacillus in LC3 than in other groups, and there were significantly fewer Faecalibacterium, Escherichia, and Bacteroides than in other groups at the genus level (p < .05). It can be concluded that dietary COS can improve the growth performance and intestinal digestive enzyme activity and alter the intestinal bacterial flora in the tiger puffer, Takifugu rubripes.     

Global warming may disproportionately affect larger adults in a predatory coral reef fish

Global warming is expected to reduce body sizes of ectothermic animals. Although the underlying mechanisms of size reductions remain poorly understood, effects appear stronger at latitudinal extremes (poles and tropics) and in aquatic rather than terrestrial systems. To shed light on this phenomenon, we examined the size dependence of critical thermal maxima (CTmax) and aerobic metabolism in a commercially important tropical reef fish, the leopard coral grouper (Plectropomus leopardus) following acclimation to current‐day (28.5 °C) vs. projected end‐of‐century (33 °C) summer temperatures for the northern Great Barrier Reef (GBR). CTmax declined from 38.3 to 37.5 °C with increasing body mass in adult fish (0.45–2.82 kg), indicating that larger individuals are more thermally sensitive than smaller conspecifics. This may be explained by a restricted capacity for large fish to increase mass‐specific maximum metabolic rate (MMR) at 33 °C compared with 28.5 °C. Indeed, temperature influenced the relationship between metabolism and body mass (0.02–2.38 kg), whereby the scaling exponent for MMR increased from 0.74 ± 0.02 at 28.5 °C to 0.79 ± 0.01 at 33 °C, and the corresponding exponents for standard metabolic rate (SMR) were 0.75 ± 0.04 and 0.80 ± 0.03. The increase in metabolic scaling exponents at higher temperatures suggests that energy budgets may be disproportionately impacted in larger fish and contribute to reduced maximum adult size. Such climate‐induced reductions in body size would have important ramifications for fisheries productivity, but are also likely to have knock‐on effects for trophodynamics and functioning of ecosystems.     

Effects of temperature change on the innate cellular and humoral immune responses of orange-spotted grouper Epinephelus coioides and its susceptibility to Vibrio alginolyticus

Orange-spotted grouper Epinephelus coioides held at 27 °C were then further cultured at 19, 27 (control), and 35 °C, and were examined for innate cellular and humoral responses after 3–96 h. The total leucocyte count, respiratory burst, and phagocytic activity significantly decreased 3, 48, and 96 h after fish were transferred to 19 and 35 °C. Both the alternative complement pathway (ACH₅₀) and the lysozyme activity significantly decreased at 3–96 h after fish were transferred to 19 and 35 °C. In another experiment, groupers reared at 27 °C at 34‰ salinity were injected with Vibrio alginolyticus grown in tryptic soy broth (TSB) at a dose of 2.3 × 10⁹ colony-forming units (cfu) fish^?1, and then further reared in water temperatures of 19, 27 (control), and 35 °C. The cumulative mortalities of V. alginolyticus-injected fish held in 19 and 35 °C were significantly higher than that of injected fish held in 27 °C. Resistance had decreased after 12 h for the challenged grouper held at 35 °C. All injected fish held in 19 °C had died after 72 h. It was concluded that at 12 h after transfer of grouper from 27 to 19 and 35 °C, immunity was suppressed and resistance against V. alginolyticus had decreased.     

Seasonal variations in the body composition and bioaccumulation of heavy metals in Nile tilapia collected from drainage canals in Al-Ahsa,Saudi Arabia

The body composition of Nile tilapia (Oreochromis niloticus) collected from drainage canals in Al-Ahsa, Saudi Arabia and the concentration of four heavy metals; zinc (Zn), cadmium (Cd), cobalt (Co) and lead (Pb) in both fish muscles and the water collected from this environment were assessed across the four seasons. The body composition was found to change with the seasons, with the best body composition being recorded in autumn and winter, where higher levels of protein (17.24, 17.65%), and fat (0.58, 0.71%) and lower water content (80.15, 79.86%) respectively were noted. The concentration of heavy metals in both fish muscles and the water body also varied significantly with the seasons. In the fish muscles, the highest content of Zn (0.409 mg/kg dry weight) and Cd (4.140 mg/kg dry weight) was recorded in winter, however, the highest concentration of Co (0.318 mg/kg dry weight) and Pb (1.96 mg/kg dry weight) was observed in spring and summer respectively. On the other hand, the water samples collected in autumn showed the maximum concentration of Cd (1.385 mg/L), Co (0.762 mg/L) and Pb (0.18 mg/L) however, the maximum concentration of Zn (0.0041 mg/L) was recorded in winter. With the exception of Cd, the accumulation of the studied heavy metals in fish muscles was within the safe limits for seafood recommended by various organizations.     

Successful sperm cryopreservation of the brown-marbled grouper,Epinephelus fuscoguttatus using propylene glycol as cryoprotectant

This study developed the cryopreservation of brown-marbled grouper spermatozoa for practical application. We examined 32 cryodiluents, developed from four types of cryoprotectants [propylene glycol (PG), dimethyl-sulphoxide (Me₂SO), dimethyl-acetamide (DMA) and ethylene glycol (EG)] at four concentrations of 5, 10, 15 and 20% in combination with two extenders [Fetal bovine serum (FBS) and artificial seminal plasma (ASP). Cooling rates were examined by adjusting the height of straws (2.5–12.5 cm) from the liquid nitrogen (LN) vapor and cooled for 5 min before immersion into LN. DNA laddering was used to detect DNA damage in cryopreserved sperm. In fertilization trials, 0.5 g of eggs was mixed with cryopreserved sperm stored for 30 days in LN. The best motility of post-thaw sperm was achieved using 15% PG + 85% FBS (76.7 ± 8.8%); 10% PG + 90% FBS was also effective as cryodiluent. Generally, FBS gave better post-thaw motility compared to ASP. The optimum cooling rate was at 17.6 °C min⁻¹ obtained by freezing at the height of 7.5 cm surface of LN. The results obtained showed that cryopreserved sperm of brown-marbled grouper suffered slight DNA fragmentation, which resulted in significantly lower motility. However, the fertilization (90.9 ± 0.5%), hatching (64.5 ± 4.1%) and deformity rates (3.8 ± 0.2%) obtained from cryopreserved sperm showed no significant difference with fresh sperm. These findings show that the developed protocol for cryopreservation of brown-marbled grouper sperm was viable and will be useful for successful breeding and seed production of brown-marbled grouper.