Predicting recruitment density dependence and intrinsic growth rate for all fishes worldwide using a data‐integrated life‐history model

Fisheries scientists use biological models to determine sustainable fishing rates and forecast future dynamics. These models require both life‐history parameters (mortality, maturity, growth) and stock‐recruit parameters (juvenile production). However, there has been little research to simultaneously predict life‐history and stock‐recruit parameters. I develop the first data‐integrated life‐history model, which extends a simple model of evolutionary dynamics to field measurements of life‐history parameters as well as historical records of spawning output and subsequent recruitment. This evolutionary model predicts recruitment productivity (steepness) and variability (variance and autocorrelation in recruitment deviations) as well as mortality, maturity, growth, and size, and uses these to predict intrinsic growth rate (r) for all described fishes. The model confirms previous analysis showing little correlation between steepness and either natural mortality or asymptotic maximum size (). However, it does reveal taxonomic patterns, where family Sebastidae has lower steepness () and Salmonidae has elevated steepness () relative to the prediction for bony fishes (class Actinopterygii, ). Similarly, genus Sebastes has growth rate (0.09) approaching that of several shark families (Lamniformes: 0.02; Carcharhiniformes: 0.02). A cross‐validation experiment confirms that the model is accurate, explains a substantial portion of variance (32%–67%), but generates standard errors that are somewhat too small. Predictive intervals are tighter for species than for higher‐level organizations (e.g. families), and predictions (including intervals) are available for all fishes worldwide in R package FishLife. I conclude by outlining how multivariate predictions of life‐history and stock‐recruit parameters could be useful for stock assessment, decision theory, ensemble modelling and strategic management.     

Reproductive resilience or sweepstakes recruitment? Assessing drivers of lifetime reproductive success in exploited marine fish

Understanding the processes that drive reproductive success in marine fish stocks is critical to effective fisheries management. These processes can be difficult to investigate, especially in age-structured populations, because they occur at transgenerational scales. Reproductive success is often attributed to a small portion of the adult population (<0.01%) and thought to be driven primarily by random external factors, consistent with the concept of sweepstake reproductive success (SRS). A competing concept, the reproductive resilience paradigm, posits that fishes have evolved complex spawner-recruit systems to achieve lifetime reproductive success and maintain population stability within highly variable environments. Here, we examine these two concepts. First, we analyse the popular sport fish red drum (Sciaenops ocellatus, Sciaenidae), drawing on genetic and reproductive data to estimate a plausible range for the ratio of effective population size ($N_e$) to adult abundance ($N_A$) and to infer variance in lifetime reproductive success ($V_k^{*}$). Then, we synthesize available data and infer $V_k^{*}$ for two other fishes that have $N_e/N_A$ ratios reportedly >0.10, the southern bluefin tuna (Thunnus maccoyii, Scombridae) and the silver seabream (Chrysophrys auratus, Sparidae). Although commonly regarded as an SRS species, red drum did not meet the SRS criterion. Overdispersed $V_k^{*}$ values were inferred for all three species, with those for red drum and silver seabream being dependent upon population-closure assumptions. Results are presented within the conceptual framework of reproductive resilience, considering the roles of random extrinsic forces versus evolved traits to achieve lifetime reproductive success and population stability in high and variable mortality environments.     

The ability of clove oil and MS-222 to minimize handling stress in rainbow trout (Oncorhynchus mykiss Walbaum)

The effects of 60‐mg L^?1 clove oil and 60‐mg L^?1 tricaine methanesulphonate (MS‐222) on the blood chemistry of rainbow trout were compared after exposure to handling stress via caudal puncture blood sampling. Fish sampled by caudal puncture and subsequently exposed to anaesthetics showed a typical handling stress response over a 48‐h period. There were no significant differences between the responses of fish exposed to equal concentrations of clove oil and MS‐222, with the following exceptions: the blood glucose at full anaesthesia, and lactate at full recovery increased significantly in the clove oil‐exposed fish. In a subsequent experiment, the stress response observed in fish sampled by caudal puncture and exposed to clove oil and MS‐222 was compared with a non‐anaesthetized control group. The increases in plasma cortisol levels were significantly lower at recovery in fish treated with either anaesthetic compared with the control fish. Fish exposed to MS‐222 had significantly higher cortisol levels at 1 h. These findings show that few differences exist between the anaesthetic effects of clove oil and MS‐222 on the physiological response of fish to stress. However, clove oil is more effective at reducing the short‐term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.     

Effects of acute thermal stress on acid–base regulation,haematology, ion‐osmoregulation and aerobic metabolism in Channel Catfish (Ictalurus punctatus)

The Channel Catfish Ictalurus punctatus is an important ecological, recreational and aquaculture species. In both natural and pond culture systems, Channel Catfish are periodically exposed to acute increase in temperature, especially in the summer, which may induce a stress response. With the effects of global climate change, the impact of rising temperatures on aquatic systems is expected to be exacerbated in the future. Hence, there is the need to understand the physiological mechanisms controlling the thermal stress response in fish. Acid–base, haematological, osmotic and metabolic regulations were investigated following acute temperature increase from 28°C to either 32°C or 36°C at a rate of 2°C/hr to assess the physiological response of Channel Catfish to temperature increase. Blood was sampled 1 hr after treatment temperatures were reached. When temperature increased from 28 to 32°C, blood bicarbonate () decreased while cortisol, partial pressure of carbon dioxide (pCO₂) and glucose increased. When temperature increased from 28 to 36°C, blood pH, , chloride, total proteins and mean corpuscular haemoglobin concentration decreased while cortisol, pCO₂, haematocrit, haemoglobin, glucose, lactate, mean corpuscular volume and mean corpuscular haemoglobin all increased. The changes observed are characteristic of acute stress responses in fish and suggest that acute temperature increases to both 32 and 36°C are physiologically stressful to Channel Catfish.     

Survival and serum biochemical responses of spotted sea bass Lateolabrax maculatus during simulated waterless live transportation

Waterless live fish transportation is an alternative and promising transport strategy, which may reduce shipping costs, increase stocking density and improve survival of some species. Spotted sea bass is one of the most economically important marine fish in China. However, waterless transportation has not yet been studied on spotted sea bass. To explore the possibility of waterless transportation of spotted sea bass and its sublethal stress responses, the survival rate and dynamics of blood biochemical parameters were evaluated in the present study by preserving it under no water, less water and water (control) conditions for 9 hr. The serum biochemical parameters including total protein, cortisol, glucose, lactate, alanine aminotransferase (ALT), aspartate aminotransferase (AST), total carbon dioxide (TCO₂), creatinine, blood urea nitrogen (BUN), ammonia, superoxide dismutase (SOD) activity and malonaldehyde (MDA) were investigated. Results showed that the survival rates of fish in all groups gradually declined with time increasing. At the end of transportation, the survival rates in the control group, less‐water group and no‐water group decreased to 49.11%, 15.60% and 23.96% respectively. Significant changes were observed in several selected serum biochemical parameters, including glucose, lactate, ALT, TCO₂, BUN and ammonia during simulated waterless transportation, which might negatively affect the physiological homeostasis of fish, leading to the high mortality in present study. In general, waterless transportation of spotted sea bass was possible, but it might be rather suitable for short time than long time.     

Interactive effects of salinity on oxygen consumption,ammonium excretion,osmoregulation and Na+/K+‐ATPase expression in the bullseye puffer (Sphoeroides annulatus,Jenyns 1842)

A physiological study was performed to explore the effects in Sphoeroides annulatus (Jenyns 1842) juveniles of exposure to different salinities 10, 17, 23, 29, 35 and 41‰ on oxygen consumption rate (OCR), ammonium excretion rate (AER), the oxygen‐nitrogen atomic ratio (O:N), osmoregulation and Na⁺/K⁺‐ATPase expression. The OCR values ranged from 27.9 to 30.9 mg O₂ h^?1 kg^?1, displaying a Type 1 response pattern Kinne (1977). AER ranged from 0.60 to 0.69 mg h^?1 kg^?1, and O:N values were from 53.12 to 59.26, indicating that the puffers use proteins and lipids as an energy‐substrate. Osmoregulation in S. annulatus was hyposmotic in salinities of 23, 29, 35 and 41‰ and hyperosmotic in a salinity of 10‰. The isosmotic point of the bullseye puffer was 356 mmol kg^?1 (10.5‰). The enzyme expression analysis indicates that the fish acclimated to 41‰ had the highest Na⁺/K⁺‐ATPase expression level, whereas, the lowest expression level was found close to the isosmotic point. Na⁺/K⁺‐ATPase expression in the gills was found to have a U‐shaped relationship with environmental salinity. We conclude that the bullseye puffer is strongly euryhaline and can be cultivated in a wide range of environments that has important economic implications.     

Effects of chronic confinement on physiological responses of juvenile gilthead sea bream, Sparus aurata L., to acute handling

Understanding how gilthead sea bream, Sparus aurata L., an important Mediterranean Sea species for aquaculture, respond physiologically to stressors commonly encountered in intensive rearing is important for effective production, as managing for stress is a major factor in maintaining healthy fish stocks. Our objective was to determine whether holding juvenile gilthead sea bream at a high density (HD), as a chronic stressor, would affect their physiological responses to a subsequent acute handling stressor. After acclimation at a low density (LD) of 6 kg m^?3 in 200‐L circular tanks containing 33–36 g L^?1 recirculating seawater at 19°C under a normal photoperiod, juvenile 37‐g gilthead sea bream were confined for 14 days at a HD of 26 kg m^?3 and then subjected to 30‐s aerial emersion in a dipnet. Plasma levels of cortisol, glucose, lactate, osmolality and chloride were determined in fish held in separate lots during LD (control) and HD confinement at 0, 1, 2, 7 and 14 days, and then after handling at 0, 1, 2, 4 and 8 h. Although plasma cortisol levels were similar in LD and HD fish groups after 14 d of confinement (15 and 23 ng mL^?1, respectively), the cortisol response in fish from the HD treatment at 1 and 2 h following acute handling (70 and 37 ng mL^?1, respectively) was only about half of that measured in the control group (139 and 102 ng mL^?1); plasma cortisol was similar in both groups by 4 and 8 h. In contrast, plasma glucose elevations in response to handling were higher at 4 and 8 h in the HD‐held fish (94 and 72 mg dL^?1, respectively) than in those from the LD treatment (59 and 51 mg dL^?1); glucose responses were similar in both groups at 1 and 2 h after handling and throughout confinement. Plasma lactate levels were higher in LD fish than in the HD group at the beginning of the experiment but were similar after 14 d confinement and responses to handling were similar (e.g. 33 and 35 mg dL^?1 at 1 h). Plasma osmolality showed increases during the first 2 h after acute handling but no differences were evident between the two density treatments at any time during confinement or posthandling. Plasma chloride levels did not change throughout the experiment. The reduced plasma cortisol response to acute handling likely resulted from negative feedback of mildly but chronically elevated circulating cortisol caused by the confinement stressor on the hypothalamic–pituitary–interrenal axis. While other post‐handling physiological changes also showed differences between treatment groups, the suppressed cortisol response in the HD‐held fish suggests a reduction in the gilthead sea bream's normal capacity to respond to an acute stressor.     

Harvesting,post‐harvest handling and live‐transport of freshwater prawns in the United States

Freshwater prawn Macrobrachium rosenbergii aquaculture continues to expand in the United States though is still a relatively small industry. Innovations continue to improve efforts in harvesting with novel harvest basin designs and concrete internal pond aprons. Purging and holding strategies are more defined. Some producers are now investing in water re‐use systems to extend holding times for many days, making prawns more readily available for market. The lucrative live‐market, which historically has had many challenges, seems poised for success when following new protocols which address handling and oxygen stress.     

Study on release kinetics of nitrogen and phosphorus from fish feed

Nitrogen and Phosphorus are the major end products of fish feed loading and affect the water environment as a whole. A magnetic stirrer was used to simulate the intensity of water flow by using different stirring strengths (0, 600, 1,200 rpm), and kinetic experiments on nutrients release from different fish feed (0.2500 and 0.5000 g) were performed. Results have shown that total phosphorus (TP) increase rapidly and become stable in about 96 hr, while orthophosphate ( ), total nitrogen (TN) and ammonia nitrogen ( ) increase relatively slowly and gradually reach stable from 200, 300 and 300 hr respectively. Both released contents of unit weight fish feed (i.e. released nutrients contents) and released nutrients concentrations in the condition of stirring were higher than those in the static condition. All of the pseudo‐first‐order, pseudo‐second‐order and Elovich kinetic models can be used to describe variations of released TP, , TN and contents with time, while the pseudo‐first‐order kinetic and Elovich kinetic models give better results with R² = .66–.99 and R² = .57–.99 respectively. Variance analysis showed that both stirring strength and fish feed type have significant effects on released TP, TN and contents (p < .05), while fish feed dosage has no significant effects (p > .05). In addition, only the fish feed type does have significant effects on contents (p < .05). In sum, the release kinetics and the factors related to the release of nutrients from fish feed are essential in planning strategies of nutrient management and pollution control.     

Effects of Temperature Reduction and MS‐222 on Water Quality and Blood Biochemistry in Simulated Transport Experiment of Largemouth Bronze Gudgeon,Coreius guichenoti

The effects of temperature reduction, MS‐222 (3‐aminobenzoic acid ethyl ester methanesulfonate) anesthesia and the combination of these factors on water quality and the blood biochemistry of the largemouth bronze gudgeon, Coreius guichenoti, a rare, endangered, and valuable fish in the upper Yangtze River, were investigated before and after simulated long‐term transport. The results showed that transport caused deterioration of water quality and elevated the concentrations of plasma cortisol (2–3.5 times) and plasma lactate (1.33–2.5 times) in C. guichenoti. Temperature reduction was found to play a major role in improving the water quality by reducing total ammonia nitrogen and oxygen consumption, while MS‐222 anesthesia mainly inhibited the activity of transported C. guichenoti and suppressed the increases in plasma lactate and alanine aminotransferase. Some interactions were observed between anesthesia and temperature reduction during C. guichenoti transportation regarding improving the water quality and reducing the physiological stress. The results suggest that during the long‐term transportation of C. guichenoti, the combined use of temperature reduction and MS‐222 is most preferable, followed by the use of temperature reduction alone or MS‐222 at a relatively high temperature. These data provide useful information regarding the transport and physiological response of C. guichenoti as well as other related stresses in this fish.     

Time‐series response of immune enzymes and catecholamines in juvenile sea cucumber Apostichopus japonicus during long‐term live transport

Sea cucumbers are free of protective exoskeleton and capable of autolysis under stress conditions. The live transport of small‐size juveniles to grown‐out sites induces hypoxia and congesting stress. The transport process is essential to production of outdoor healthy seedlings. Here, we evaluated the effects of damp transport and water transport on Apostichopus japonicus, an economic species inhabiting along the Asian coast. The survival after transport and immune performance of small‐size juveniles (0.05–0.1 g of immersed weight) were monitored during distinct duration of transport (1, 3, 5, 8 and 12 hr). The results revealed that there were no significant differences between the two transport systems within 5 hr. Given the survival for recovery of 48 hr and responses of immune enzymes and catecholamines during transport, water transport was less detrimental to sea cucumbers than damp transport when the transport duration was less than 8 hr. Once the duration prolonged to 12 hr, these immune parameters changed irregularly and the survival declined drastically. Water transport with a notably higher survival for juveniles was the more appropriate manner for long‐time transport. These findings provide insights into long‐term transport of small‐size A.  japonicus juveniles and might be beneficial for production of ecologically healthy seedlings.     

Properties and activities of blood‐ or seawater‐contaminated wild‐caught Striped Jewfish (Stereolepis doederleini) sperm

Understanding the effects of environmental factors in sperm qualities will be helpful in the development of optimal artificial reproduction methods and contributes towards the knowledge base of better short‐ and long‐term fish semen preservation conditions The objectives of this study were to determine properties and activities of wild‐caught striped jewfish Stereolepis doederleini sperm contaminated with blood or seawater and compare them with data reported in the literature on other freshwater and marine fish species, for effective short‐ and long‐term storage of fish semen. Overall, we observed that the sodium, chloride, glucose, total protein concentrations of normal sperm were not significantly different from blood‐ or seawater‐contaminated sperm. The salinity and osmolality concentration of sperm contaminated with blood were lower than sperm contaminated with seawater and were not significantly different from normal sperm. In addition, the spermatozoa motility (SM) and duration of spermatozoa motility (DSM) in blood‐contaminated sperm were higher than seawater‐contaminated sperm and also not significantly different from normal sperm. The best condition for SM and DSM in normal sperm was dilution rate of 1:50. Sperm was immotile in distilled water, and cationic factors were shown to stimulate the initiation of spermatozoa activation. The maximum SM and DSM were observed in solution containing 0.4 M NaCl, 0.6 M KCl, 0.6 M CaCl₂ and 0.4 M MgCl₂. This study provides some basic and important knowledge about striped jewfish sperm sensitivity to a cationic condition. In this regard, Na⁺ is the major inhibitory factor of spermatozoa motility in this fish species.     

Curcuma longa supplementation in the diet of Astyanax aff. bimaculatus in preparation for transport

The physiological state of fish before transportation is an important aspect to be observed when reduction in losses due to mortality is aimed. Various preparative procedures for transport are reported, but little is known about the use of additives in fish diet. In this study, we aimed to evaluate the effect of dietary turmeric (Curcuma longa) supplementation on the tolerance of juvenile Astyanax aff. bimaculatus to transportation stress. The experimental design consisted of six treatments: 0, 20, 40, 60, 80 and 100.0 g kg^?1 turmeric. Fish weighing 0.83 ± 0.04 g were distributed in 24 80‐L aquaria at a density of 0.5 fish L^?1 and were fed to satiation three times a day for 60 days. After this period, fish were transported for 24 h in plastic bags (15 fish per bag). Using a discontinuous linear response plateau (LRP) model, the lowest estimated concentration of turmeric that maximized the survival rate was 16.67 g kg^?1. Quadratic effects of turmeric on blood lactate levels were observed, and the estimated concentration of turmeric required to minimize blood lactate levels was 64.7 g kg^?1. We observed quadratic effects of turmeric on superoxide dismutase activity and the concentration of malondialdehyde in fish gills and the turmeric concentrations required to minimize the transport stress effects on these variables were 42.50 and 83.33 g kg^?1, respectively. Thus, dietary supplementation with turmeric enhanced the tolerance of juvenile A. aff. bimaculatus to transportation stress.     

Survival of captive milkfish Chanos chanos Forsskal broodstock subjected to handling and transport

The survival of milkfish broodstock (body weight range 1–11 kg) was determined until 30 days after handling and transport in open tanks or in sealed oxygenated bags containing chilled sea water (20–25 °C). Maintenance of cool sea water was achieved by the gradual addition of ice chunks or frozen gel packs. A survival rate of 50% after transporting fish at a loading density of 45 kg m^?3 for 4 h in open tanks was not significantly different from those that were handled but not transported (86%). Similarly, survival rates (67–83%) among broodstock confined for 8 h in chilled sea water at 40 and 60 kg m^?3 were not significantly different from each other or from a group not subjected to confinement. Nevertheless, low dissolved oxygen (DO) and accumulation of total ammonia–nitrogen beginning 1 h after transport and confinement may be responsible for low survival rates of milkfish in open tanks. In contrast, all milkfish survived 10 h of overland transport in sealed bags with chilled and diluted (28 g L^?1) sea water. Likewise, all milkfish survived after being bagged and immediately transferred to a communal rearing tank, or bagged and placed in a styrofoam box for 10 h. Except for total ammonia–nitrogen levels, which increased slightly (0.7–0.8 mg L^?1) above background, seawater temperature (20–24 °C), salinity (28 g L^?1) and DO (6 to > 20 mg mL^?1) titres in transport bags were maintained during the 10‐h test. The effectiveness of handling and transporting milkfish broodstock in sealed bags containing chilled sea water was verified in actual field trials. Spawning of sexually mature milkfish subjected to these stressors was not impaired. These results demonstrate that mortalities of large milkfish broodstock can be minimized when fish are handled and transported in sealed oxygenated bags containing chilled sea water.     

Genetic analysis of the Pacific white shrimp (Litopenaeus vannamei): heterosis and heritability for harvest body weight

The aim of this study was to estimate heterosis and heritability for harvest body weight of the Pacific white shrimp (Litopenaeus vannamei) measured at commercial farm conditions. Heterosis and heritability were estimated using a base population from diallel crosses of eight introduced strains. The base population included 9936 shrimp from 207 families that were produced with 188 sires and 172 dams using a nested mating design by artificial insemination. Heterosis was calculated basing on the least squares means (LSM) of harvest body weight. The results showed that most of the hybrids (75%) have positive heterosis for harvest body weight, which ranged from ?13.36% (UA2 × UA5) to 13.80% (UA6 × UA5) with a mean of 2.41%. The high amount of heterosis manifested in the hybrids indicated the usefulness of these hybrids for improving the growth. Variance components and heritability for harvest body weight were estimated using an animal model. The heritability estimate for harvest body weight was 0.092 ± 0.082 (h²) when genetic groups were excluded from the pedigree, but it was decreased when genetic groups were included in the pedigree ( = 0.066 ± 0.050), implying that there are strain additive genetic effect and heterosis in the base population. However, the heritability estimates for harvest body weight were significantly different from zero (P < 0.05) and there was no significant difference between h² and (P > 0.05). The results from this study indicated that significant improvement for growth is possible through cross‐breeding and selective breeding in L. vannamei.     

Observation of three‐dimensional flow structures and effluent transport around fish cages using a towed ADCP and free‐fall multi‐parameter profiler

A field campaign was conducted around salmon cages, using a combination of a towed ADCP and a free‐fall multi‐parameter profiler, in order to investigate flow structures and the possible distribution of effluent materials. Two transect observations showed that hydrographic conditions changed dramatically within 5 days, from highly stratified open water conditions to weak stratification. Three‐dimensional observation revealed that flow was blocked behind the cages and that the blockage was reduced as the distance from the cages increased. The flow speed was positively correlated with the intensity of the backscattering signal. The R² value was high immediately behind the cages and decreased with distance from the cages. The flow time series behind the cages exhibited a k^–2 power law spectrum that was consistent with a typical internal wave spectrum. This suggests that eddies shed from the cages were highly influenced by stratification. We estimated the rate of kinetic energy dissipation, , from YODA Profiler data based on the Thorpe scale approach. We also estimated the eddy diffusivity coefficient, . Both and followed a lognormal probability density function. The mean was consistent with a one‐dimensional diffusion model assessed from the R² values of flow speed and backscatter intensity.     

The response of coral trout (Plectropomus leopardus) to capture, handling and transport and shallow water stress

The stress response of coral trout (Plectropomus leopardus ) to wild capture or controlled shallow water stressors was investigated. Stress associated with capture from the wild, handling and transport and shallow water evoked significant changes in circulating levels of cortisol, glucose, lactate, haemoglobin (Hb) and haematocrit (Hct) in coral trout. Plasma glucose, Hb and Hct increased over 30 to 60 min in response to the controlled stressor and then returned toward unstressed levels, even if the stressor persisted. Cortisol increased to maximum levels over the 60 min following the onset of the stressor and remained elevated for 4 h in the case of a single 30 min shallow water event or 3 d in response to the capture, handling and transport. The difference between the responses of blood glucose and cortisol suggests that cortisol does not maintain blood glucose during stress in coral trout. The concentrations of circulating thrombocytes, lymphocytes and granulocytes were also significantly affected by shallow water stress. As lymphocytes and granulocytes are important immune components, reduced concentrations of these cells may explain the increases in disease susceptibility, commonly observed in stressed fish during live transport.     

Temperature and size range for the transport of juvenile donkey's ear abalone Haliotis asinina Linne

Live transport of hatchery‐produced juvenile donkey's ear abalone Haliotis asinina Linne was examined to evaluate the effect of transportation on the survival of juvenile abalone. Simulated transport experiments were conducted to determine the appropriate temperature using 5, 10 and 20 g L^?1 of ice to air volume for 8 h and the appropriate size using two size groups (Size A, 15–20 mm, 0.5–1.3 g, and Size B, 30–35 mm, 5.3–8.5 g) up to 24‐h out‐of‐water live transport. Survival was significantly higher (P<0.001) when 10 g L^?1 of ice was used to decrease the temperature to the range of 17–23 °C. At this temperature, both size groups subjected to simulated transport for 8 and 10 h had 100% survival after 48 h, while mortality occurred in abalones subjected to 16 and 24 h of simulated transport. The Size B abalone subjected to 24 h of transport had significantly higher survival (64.4 ± 2.9%) (P<0.001) than the Size A abalone (5.5 ± 1.6%) after 48 h. Live juvenile abalone were successfully transported to the field applying the protocols developed in the lab experiment. This study serves as a guide for handling and shipping live juvenile abalone.     

Water quality and physiological response of F1 hybrid seabream (Pagrus major♀ × Acanthopagrus schlegelii♂) to transport stress at different densities

Hybrid seabream (Pagrus major♀ × Acanthopagrus schlegelii♂) grow quickly, with retarded gonadal growth and enhanced muscle nutritional composition. This F₁ hybrid seabream is a new marine aquaculture fish in China. However, the response of hybrid seabream to transport is severe, which seriously restricts its promotion and development. Water quality and the physiological response of hybrid sea bream were studied at three fish transport densities (5, 10 and 20 g/L) during 8 hr of transport in a light van (60 km hr^?1 and 25°C water temperature). We found that total ammonia–nitrogen and nitrite–nitrogen levels in the water of the highest density group increased sharply after 4 and 8 hr of transport. Cumulative survival of the fish in the 10 and 20 g/L groups (86.7% and 75% respectively) was significantly lower than in the 5 g/L group (100%) after 8 hr of transport (p < .05). Serum cortisol and lactate levels were significantly higher after transport than pre‐stress levels, whereas the glucose level decreased significantly (p < .05). Hepatic triglyceride and glycogen levels and superoxide dismutase and catalase activities were significantly lower in the 20 g/L group than in the 5 g/L group (p < .05). The results show that high‐density transport increased ammonia–nitrogen and nitrite–nitrogen levels in the water as well as cortisol secretion and anaerobic metabolism in the F₁ hybrid seabream, suggesting that total cholesterol and glycogen may be used to supply the energy demand and increased oxidative stress. These results will help to optimize the transport conditions for cultured hybrid seabream.     

Pharmacokinetics of minocycline in crucian carp (Carassius auratus) after intravenous and oral administration

The pharmacokinetic of minocycline was studied after a single intravenous as well as oral dose (5 mg/kg body weight) in crucian carp (Carassius auratus) reared in freshwater at 10°C. Plasma samples were randomly collected from six fish at each sampling time. Plasma concentrations were determined by high‐performance liquid chromatography and further subjected to noncompartmental analysis. Initial concentration of minocycline just after intravenous administration was calculated as 7.320 μg/ml, while the other parameters after intravenous injection were determined as flows: apparent elimination rate constant (λ_z) of 0.064 per hr, apparent elimination half‐life () of 10.82 hr, total body clearance (Cl) of 142.72 ml/hr/kg, volume of distribution (Vz) of 2,227.38 ml/kg and volume of distribution at steady‐state (Vss) of 1,937.08 ml/kg. While after oral administration, the λ_z, , mean absorption time (MAT), absorption half‐life (t_1/2ka) and bioavailability were determined as 0.059 per hr, 11.74, 5.55, 3.84 hr, and 81.98%, respectively, and the peak concentration was observed as 1.474 ± 0.362 μg/ml at 8 hr. It was shown that minocycline was slowly but relatively completely absorbed, extensively distributed, and slowly eliminated in crucian carp. Based on the ratios of AUC_0–24 hr/MIC90, a minocycline dosage of 5 mg/kg body weight administered intravenously or orally would be only effective to successfully treat crucian carp infected by bacterium with MIC values ≤0.25 μg/ml.