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1.
During culture of grouper, cannibalism is a frequent phenomenon that usually causes economic loss. Grouper culture often requires grading to prevent size‐dependent cannibalism. In comparison with orange‐spotted (Epinephelus coioides) and giant grouper (E. lanceolatus), failure to swallow prey during cannibalism is frequently observed in brown‐marbled grouper (E. fuscoguttatus). The cannibal cannot engulf the entire prey and the two fish ultimately end up dying together. Herein, we attempted to compare morphometric differences among orange‐spotted, giant and brown‐marbled grouper. We established a cannibal–prey total length (TL) relationship for brown‐marbled grouper: TLprey=0.71 TLcannibal−1.75. According to the equation, a difference of approximately 50% in TL is a threshold to use for grading the grouper. This value is much larger than that used (30%) in orange‐spotted and giant grouper, and this size difference results in a higher incidence of failed cannibalism attempts in brown‐marbled grouper. It is our belief that the standard grading method will fail to produce as good an effect in brown‐marbled grouper as is seen in orange‐spotted and giant grouper. Therefore, in addition to grading, other manipulations such as satiation feeding, nutritional supplementation and optimal stocking densities should be applied to reduce cannibalism of brown‐marbled grouper.  相似文献   

2.
To predict the occurrence of cannibalism in the culture of larval black rockfish, Sebastes schlegelii, we developed a regression model based on morphometric measurements. First, 156 black rockfish were measured to obtain a theoretical model, that is LT prey = 0.624 LT cannibal + 0.835. Then, 202 trials of paired fish, together with 31 pairs of cannibalistic fish, were used to revise this model, and the practical model was constructed: LT prey = 0.522 LT cannibal + 4.908 (R² = 0.99). According to this equation, the threshold of size ratio was deduced, that is 1.30–1.69, which could be used to grade black rockfish by size and remove potential cannibals.  相似文献   

3.
Cannibalism has been described in 390 teleost fish species belonging to 104 families. In rearing conditions, intra‐cohort cannibalism is one of the major bottlenecks during the early life stages of pikeperch (Sander lucioperca). This study aims to describe precisely the occurrence and the onset of cannibalism of this species during the first two post‐hatching months. In a first step, the cannibalistic behaviour was analysed through observations in three experiments. In each experiment, the number of cannibalistic cases was similar. From 14 to 48 days post‐hatching (dph), more than 60 % of prey ingestions were realized by tail‐first, but after 48 dph, the number of prey ingestions by head‐first increased. In a second step, the behavioural sequence exhibited to attack and to capture a conspecific was analysed, taking into account the size ratio between the cannibal and its prey. The behavioural sequence to capture was always the same, similar to a predatory sequence and it seems that the cannibal chose its prey about 10 s before attacking. Moreover, prey choice by a cannibal was based more on the size ratio between the cannibal and its prey than the previous activity of the potential prey. These new results could lead to solutions to decrease cannibalism in pikeperch rearing.  相似文献   

4.
In fish culture, cannibalism, which induces critical damage, is separated into two types: type I, which occurs in early larval stages when size heterogeneity is low; and type II, which starts in later larval and/or early juvenile stages following type I when size heterogeneity is high. In type II, the cannibal's maximum prey size is limited by its gape size relative to the prey fish body size. Ratios of prey to cannibal body size changes are associated with allometric factors and feeding behaviour with growth. In a previous study on grouper, the maximal prey size was estimated morphologically (i.e., the relationship between gape size and body height). This method is very simple and useful; however, it does not consider allometric factors and feeding behaviour changes; therefore, it probably causes a large estimation error. To overcome this, we present a new method for estimating maximal prey size to determine the size ranges for size grading of longtooth grouper, Epinephelus bruneus, juveniles using predation experiments. It is shown that grouper type II cannibalism is affected by two factors; in early juvenile stages by morphology and in later (TL over 50 mm) by prey size selectivity.  相似文献   

5.
A novel marine origin Bacillus subtilis strain H1 isolated from a shrimp culture pond effectively removed NH4+‐N, ‐N and ‐N, with a maximum ammonium, nitrite and nitrate removal rate of 2.35 mg NH4+‐N L?1 hr?1 per OD, 9.64 mg ‐N L?1 hr?1 per OD and 0.75 mg ‐N L?1 hr?1 respectively. The gas chromatography–isotope ratio mass spectrometry results indicated that N2O was emitted when 15NH4Cl, Na15NO2 or Na15NO3 was used. Additionally, N2 was also produced when Na15NO2 was used. Single‐factor experiments suggested that the optimal conditions for NH4+‐N and ‐N removal were glucose as a carbon source, C/N 15, initial pH 7.5, 30 g/L NaCl, 28°C and a shaking speed of 160 rpm. Orthogonal tests showed that the optimal conditions for NH4+‐N removal were C/N 15, pH 9, 10 g/L NaCl and shaking speed 160 rpm when ammonium chloride was used as the substrate. The optimal conditions for ‐N removal were C/N 10, pH 6, 10 g/L NaCl and a shaking speed of 160 rpm when sodium nitrite was used as the substrate. In summary, B. subtilis strain H1 had highly efficient aerobic nitrifying–denitrifying ability and high adaptability, suggesting that it is potentially valuable to marine aquaculture.  相似文献   

6.
Dynamics of intracohort cannibalism in cultured fish   总被引：1，自引：1，他引：1  
Abstract Cannibalism is a frequent phenomenon in fish, especially in culture environments where fish are unable to escape predation via habitat segregation or migration. Not all cultured fish species start to exhibit cannibalism at the same age or size, nor is cannibalism equally intense in different species or life stages. Predator to prey size ratios vary substantially between species and life stages, chiefly because cannibalism is governed by gape size limitations and allometric growth of mouthparts. The development of sense organs, hard body parts, swimming and escape capacities in both the predator and the prey also influence prey size selectivity. The dynamics of cannibalism are influenced by these, as well as by environmental, factors that have effects on feed intake, growth depensation and facilitate or complicate the displaying of cannibalistic behaviour. Knowledge about cannibalistic behaviour and the logistics of cannibalism along with environmental enhancement are prerequisites for the mitigation of cannibalism in aquaculture. Also, within the context of strain selection, it is of importance to determine whether cannibals are natural‐born killers or just lottery winners. These factors are discussed, chiefly as they apply to intracohort cannibalism. In addition, guidelines are suggested for cannibalistic risk assessment, and methods for mitigation of cannibalism are discussed.  相似文献   

7.
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.  相似文献   

8.
Studies on chronic or acute toxicity of nitrogen species on fish in recirculating aquaculture systems (RAS) usually focused on adverse effects of total ammonia nitrogen (TAN: sum of NH3 + NH4+) and nitrite (), while underestimating the potential effects of high nitrate accumulation on growth and health status of fish. In our study, Nile tilapia (Oreochromis niloticus) were exposed to five different nitrate concentrations (0, 10, 100, 500 and 1000 mg L?1 ‐N) over 30 days. Growth parameters (feed conversion ratio (FCR), specific growth rate (SGR), hepatosomatic index (HSI)), blood samples (concentrations of haemoglobin, methaemoglobin, plasma /) and the histology of the gills were studied to evaluate growth and health status of the fish. At the highest nitrate concentration, the fish showed significantly reduced growth and impaired health status (SGR, FCR, plasma /, haemoglobin and methaemoglobin concentration), demonstrating that too high nitrate concentrations can negatively influence tilapia production in RAS. Here, we recommend not exceeding concentrations of 500 mg L?1 ‐N in juvenile tilapia culture to ensure an optimal health and growth status of the fish, as below that concentration no effects on the tilapia have been observed.  相似文献   

9.
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 (λz) 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 λz, , mean absorption time (MAT), absorption half‐life (t1/2ka) 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 AUC0–24 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.  相似文献   

10.
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.  相似文献   

11.
The present study investigated the growth performance of juvenile barramundi Lates calcarifer (Bloch) fed conspecific prey (CP), formulated diet (FD) and a mix of both (MIX) using a bioenergetics approach. Fish in the MIX treatment ingested significantly more CP than FD by dry mass. However, prey mass ingestion and cannibalism rate in the MIX treatment were significantly lower than in the CP treatment. This indicates that the provision of alternative food does not complete mitigate cannibalism, but it can significantly reduce cannibalism in barramundi. Fish in the FD treatment showed a significantly higher daily food intake than fish in the CP or MIX treatments. However, fish fed conspecifics showed significantly better feed conversion efficiencies, apparent digestibility rates and growth performances. Exclusive cannibalistic barramundi assimilated significantly more energy consumed, with 1.5% of energy lost in faeces comparing with 7.3% of siblings feeding exclusively on FD. Consequently, exclusive cannibals channelized more energy consumption into growth (57.1%) than those fed solely on FD (43.9%). Therefore, high energy allocation into growth promoted better feed conversion efficiency and growth performance of cannibalistic barramundi than siblings fed solely on FDs. This study implies that fast‐growing cannibals may continuously prey on slow‐growing conspecifics due to growth advantage through cannibalism. Therefore, size heterogeneity should be reduced at initial stocking and controlled as fish grow to avoid the emergence of new cannibals.  相似文献   

12.
This study established a pilot‐scale recirculating treatment system that coupled an ecological process with a biological process to achieve adequate water quality and to minimize the water consumption for intensive marine culture. The recirculating treatment system consisted of a settling cell, a biofilter tank, a bivalve tank and gravel beds. The toxic pollutants, threatening the growth of bivalves, were reduced by the settling cell and the biofilter tank, so that the polyculture of shrimp and bivalves could be achieved. The living bivalve tank could function well as a remover of remaining small suspended solids (SS), and other pollutants. As the SS was reduced to a very low level by bivalve tank before the water flowing into the gravel beds, the risk of clogging was prevented. The studies suggested that the system maintained high removal efficiencies of SS, ammonium nitrogen () and nitrite nitrogen () and could contribute to the increase in shrimp yield.  相似文献   

13.
The effects of body and meals sizes on gastric evacuation (GE) of the endangered Siberian sturgeon (Acipenser baerii) were parameterized (at temperatures ranging from 16.8 to 17.6°C) using radiography technique. GE experiments were performed using different body sizes A. baerii ranged from 1.5 kg to 5 kg fed on meal sizes of 4.6 g to 47.6 g composed of either commercial pellets or live food (fish prey, whiting). The commercial pellets used in these experiments had barium sulphate at concentrations of 20%, while the same amount was injected into the body of live food for radiography technique monitoring. The course of GE in A. baerii was best described by the square root model independently of meal size. The effects of body mass and temperature on GE rates were described by power model and simple exponential model respectively. GE rates of A. baerii fed on live food could be summarized by (g/hr), while for commercial pellets, where St is the stomach contents mass (g), W is fish wet weight (cm), T is temperature (°C), and t is time (hr). These summarized models could estimate the time required for a meal to be evacuated from the stomach of A. baerii or determine the stomach fullness at postprandial time t. These results will assess the planning of feeding regime for A. baerii to avoid their overfeeding and underfeeding.  相似文献   

14.
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.  相似文献   

15.
Laboratory and in‐stream enclosure experiments were used to determine whether rainbow trout Oncorhynchus mykiss influence survival of longnose dace Rhinichthys cataractae. In the laboratory, adult rainbow trout preyed on longnose dace in 42% of trials and juvenile rainbow trout did not prey on longnose dace during the first 6 h after rainbow trout introduction. Survival of longnose dace did not differ in the presence of adult rainbow trout previously exposed to active prey and those not previously exposed to active prey ( = 0.28, P = 0.60). In field enclosures, the number of longnose dace decreased at a faster rate in the presence of rainbow trout relative to controls within the first 72 h, but did not differ between moderate and high densities of rainbow trout (F2,258.9 = 3.73, P = 0.03). Additionally, longnose dace were found in 7% of rainbow trout stomachs after 72 h in enclosures. Rainbow trout acclimated to the stream for longer periods had a greater initial influence on the number of longnose dace remaining in enclosures relative to those acclimated for shorter periods regardless of rainbow trout density treatment (F4,148.5 = 2.50, P = 0.04). More research is needed to determine how predation rates will change in natural environments, under differing amounts of habitat and food resources and in the context of whole assemblages. However, if rainbow trout are introduced into the habitat of longnose dace, some predation on longnose dace is expected, even when rainbow trout have no previous experience with active prey.  相似文献   

16.
This study assessed the effect of cyclical feeding on compensatory growth, nitrogen (N) and phosphorus (P) budgets of juvenile Litopenaeus vannamei. A 36‐day growth trial was performed with four different feeding protocols. The control group (S0) was fed to satiation twice every day during the whole experimental period; treatment groups S1, S2 and S3 were fed by the 9, 5 and 3 cycles of 1:3, 2:5 and 3:9 (fasting days:feeding days) respectively. Fasting in S1, S2 and S3 groups did not change the specific growth rate in wet weight (SGRw), but the feed conversion efficiency (FCE) and protein efficiency ratio (PER) were significantly increased (P < 0.05) in comparison with control. The N and P consumed per unit wet weight gain of shrimp in S1, S2, S3 groups were significantly lower (P < 0.05) than control group by 15.39%, 15.96%, 19.33% for N, and 15.16%, 15.98%, 19.26% for P respectively. The total discharge of N and P (including N and P discharged by faeces (FN/P), non‐faecal excretions (UN/P) and exuviations (EN/P); ) was significantly lower (P < 0.05) in the experiment groups by 19.91–22.07% for N and 18.68–26.37% for P respectively. Overall, the results suggest that the L. vannamei can reach completely compensatory growth, and the total discharge of N and P per unit wet weight gain of L. vannamei significantly decreased by cyclical feeding, which could have a positive effect on the reduced of environmental N and P loading due to the cultured of L. vannamei.  相似文献   

17.
This study was carried out in order to determine the effect of stocking density and size distribution on growth, survival and cannibalism of fat snook (Centropomus parallelus Poey) juveniles. Three stocking densities (1.5, 3 and 6 fish L−1) were tested in two groups of fish: homogeneous [total length (TL)=22.1 mm; coefficient of variation of length (CV)=8%] and heterogeneous (TL=22.7 mm; CV=15%). The experimental design was factorial (3 × 2) using triplicates. Fish were reared for 30 days in 80‐L circular tanks with an open flow‐through system. There was no significant interaction between the two factors (density and size distribution). The highest cannibalism rate (14.2%) was observed in the heterogeneous group, which also had a significantly higher growth rate (TL=45.6 mm) than the homogeneous group (3.2% and TL=40.9 mm). Significant differences were found between the two lowest densities and the highest density (6.2%, 6.3% and 13.4% respectively). Growth was not affected by fish density. Cannibalism was the main cause of mortality. In 90% of the occurrences, whole prey ingestion was observed. According to the results obtained, cannibalism was positively correlated to density, although size grading of fat snook juveniles is recommended to control cannibalism in all the densities tested.  相似文献   

18.
In Arctic and alpine lakes, Arctic char [Salvelinus alpinus (L.)] often form two distinct morphs: invertebrate feeders (‘dwarfs’) and piscivores (‘giant or cannibals’). Here, we test for early life history growth variation in dimorphic Arctic char as a proximate explanation for the observed life history variation between the two forms. Char were sampled in 11 alpine and Arctic Norwegian lakes. Dwarfs (defined as sexually mature char less than 15 cm long; N = 304) had a mean total length of 105 mm, whereas the typical cannibal (body length above 20 cm; N = 153) was 388 mm long. A positive correlation between egg size and otolith hatching ring were ascertained in a separate hatching experiment with brown trout (Salmo trutta) and it is assumed that this relationship also is valid for Arctic char, and otolith size was used as a proxy for length. Otolith hatching ring from Arctic char cannibals was larger (mean ± SD; 187 ± 24 μm) than those from dwarfs (mean ± SD; 164 ± 23 μm). There were only minor size differences between dwarfs and cannibals during the next three years, after which dwarfs usually matured. Two mutually nonexclusive, proximate explanations for the differentiation into separate morphs (dwarfs and cannibals) are therefore maternal effects and/or genetic based differentiation. The high catchability of large piscivorous char and low production in alpine and Arctic lake ecosystems may make these stocks particularly vulnerable to overexploitation.  相似文献   

19.
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.  相似文献   

20.
The effect of temperature (10, 13, 16, 19 and 22°C) on hatching, development and survival of yolk‐sac larvae of European hake, Merluccius merluccius, was studied. At 22°C the experiment was suspended because all eggs died a few hours after incubation. Five morphological indicators of larval development (standard length – SL, yolk‐sac volume – YSV, oil globule diameter – OD, body height – BH and body wet weight – BW) were analysed. SL, YSV, OD and BW of newly hatched larvae were biggest in size and weight at low temperatures (P < 0.05). Throughout the experiments, the rates of changes in SL, YSV and OD varied with temperature (P < 0.05). By contrast, BH and BW remained constant and did not show significant relationship with the effect of temperature (P > 0.05). The potential model showed that the SL growth rate varied from 0.05 to 0.08 mm day?1 from 10.5 to 19.5°C respectively. However, at all temperatures two growth phases were identified: a rapid growth phase followed by a slow one. Rapid growth rate in length and depletion in yolk‐sac and oil globule occurred at high temperatures. After total YSV and OD consumption (death by starvation), larvae died between 8 and 14 days at 19.5 and 10.5°C respectively, reaching a maximum length of 4.3 mm at 10.5°C. Metabolic indices such as: lowest threshold temperature (T0); effective larval development (); cumulative thermal units (TC) to complete larval development; the temperature coefficient on growth rate in length (Q10) and the condition factor (K) were also studied.  相似文献   

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