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1.
Groupers are economically important for aquaculture in Thailand. A novel hybrid grouper (Epinephelus lanceolatus × Epinephelus fuscoguttatus) has been successful cross‐bred; therefore, the present work aimed to assess the hybrid's traits. The growth performance, strength and tolerance to a pathogenic bacterial infection of this hybrid were compared with its parent species, tiger grouper and giant grouper. The results of all measured growth parameters indicated that the hybrid strain grew fastest followed by giant and tiger grouper respectively. The expressions of the growth‐related genes, insulin‐like growth factor (IGF) I and II, were also analysed in fish muscle and liver which are the main target organs in fish growth regulation. Among tested species, similar expression patterns of IGF‐I and IGF‐II were detected in both organs. The levels of these genes in liver and muscle of hybrid and giant grouper were higher than those of tiger grouper comparable with the growth manner. After challenge with Vibrio vulnificus, the immunological parameters, clearance time of Vibrio in haemolymph and survival was measured to verify the fish immunity. Leucocyte number, lysozyme activity and the ability to eliminate the pathogen were very high in hybrid and giant grouper while these parameters were lower in tiger grouper. Correspondingly, the mortality rate of tiger grouper was higher than others and % survival at the end of observation time (15 days post challenge) was lowest in infected tiger grouper. Altogether, the results suggested that the hybrid grouper has desirable traits that will improve cultured grouper.  相似文献   

2.
Hybridization was used to take advantage of desirable traits in offspring. In the present study, we applied the cryopreserved Epinephelus lanceolatus sperm into interspecific hybridization with E. moara. Successful hybridization between these two species was achieved and cultured in 23–24°C seawater (34‰). There was no difference in survival rate between hybrid (E. moara ♀ × E. lanceolatus ♂) and non‐hybrid (E. moara ♀ × E. moara ♂) at 24 hrs post hatch (HPH), but less hybrid (14.35 ± 8.02%) hatched than non‐hybrid (93.60 ± 1.65%), which might be due to irregularity cell cleavage and skeletal deformities from the formation of embryonic body to the later embryonic development. Similar phenomenon was found in hybrid embryos from fertilization with fresh sperm, indicating that species variations between parents, rather than cryopreserved sperm, resulted in deformities in embryos. Mean hatch time of the hybrid was 1 hr faster than that of E. moara. The hybrid was 1.95 ± 0.06 mm in total length when newly hatched and reached 38.00 mm at 58 days post hatch (DPH), which showed faster growth than E. moara (recorded in the previous study). Considering its faster growth, E. moara × E. lanceolatus hybrid was a potential breeding production in aquaculture. Over 212,000,000 larvae have been produced and launched in the market since 2015. The results of this study also shed some lights on further comparative studies in grouper hybrid performance.  相似文献   

3.
The hybrid grouper, Epinephelus fuscoguttatus (♀) × Epinephelus lanceolatus (♂), is a newly bred cultivated marine fish species of high economic value. However, a skin ulcer disease with high mortality has occurred, and the responsible pathogen remains unknown. In this study, we summarized the epidemic status and external signs of this disease. We screened potential pathogens and finally isolated one bacterial strain ML01 from affected fish. We subjected healthy juvenile hybrid groupers to bacterial challenge tests with the isolate by immersion, immersion after dermal abrasion and intraperitoneal injection, respectively. Within 14 days post‐infection, the isolate ML01 caused mass mortality of juveniles infected via immersion after dermal abrasion or intraperitoneal injection. Diseased juveniles displayed obvious signs of skin ulcers. The median lethal dose of ML01 by intraperitoneal injection was 1.10 × 105 colony‐forming units. ML01 was identified as Vibrio harveyi by bacterial morphology, analytical profile index identification, 16S rDNA sequencing and multilocus sequence analysis. Antibiotic susceptibility tests showed that ML01 was sensitive to ceftriaxone, doxycycline and minocycline. The results of this study suggest that V. harveyi is the causal agent of skin ulcer disease in juvenile hybrid groupers, thus providing a basis for effective control and prevention of this disease.  相似文献   

4.
Growth‐related traits are the main target of genetic breeding programmes in grouper aquaculture. We constructed genetic linkage maps for tiger grouper (Epinephelus fuscoguttatus) and giant grouper (E. lanceolatus) using 399 simple sequence repeat markers and performed a quantitative trait locus (QTL) analysis to identify the genomic regions responsible for growth‐related traits in F1 hybrid grouper (E. fuscoguttatus × E. lanceolatus). The tiger grouper (female) linkage map contained 330 markers assigned to 24 linkage groups (LGs) and spanned 1,202.0 cM. The giant grouper (male) linkage map contained 231 markers distributed in 24 LGs and spanned 953.7 cM. Six QTLs affecting growth‐related traits with 5% genome‐wide significance were detected on different LGs. Four QTLs were identified for total length and body weight on Efu_LG8, 10, 13 and 19 on the tiger grouper map, which explained 6.6%–12.0% of the phenotypic variance. An epistatic QTL with a reciprocal association was observed between Efu_LG8 and 10. Two QTLs were identified for body weight on Ela_LG3 and 10 on the giant grouper map, which explained 6.9% of the phenotypic variance. Two‐way analysis of variance indicated that the QTL on Efu_LG13 interacts with the QTLs on Ela_LG3 and 10 with large effects on body weight. Furthermore, these six QTLs showed different features among the winter, summer and rainy seasons, suggesting that environmental factors and fish age affected these QTLs. These findings will be useful to understand the genetic structure of growth and conduct genetic breeding in grouper species.  相似文献   

5.
Scale drop and muscle necrosis disease with high mortality widely occurred recently in the hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂), a crucial cultured marine fish species in China. In this study, 30 Harveyi clade isolates of 27 Vibrio harveyi strains were isolated from diseased hybrid groupers in the south‐east and north‐east coastal areas of China. A total of 22 V. harveyi strains were determined to be pathogenic, and most challenged fish died within 2 days of infection; surviving individuals exhibited scale drop and deep dermal lesions as naturally diseased fish. Although five typical virulence genes, including luxR, toxRVh, chiA, serine protease and vhh widely existed in V. harveyi, no obvious correlation was established between virulent strains and virulence genes harboured in them. Furthermore, multiple antibiotic resistance was widely exhibited in Harveyi clade strains, particularly for penicillins, polypeptides, lincomycins, acetylspiramycin, streptomycin, metronidazole and bacitracin. And the multiple antibiotic resistance indices were gradually decreased from southern to northern areas of China. This study demonstrated that the pathogenic V. harveyi with multiple antibiotic resistance is highly prevalent in hybrid grouper in China, which requires particular attention.  相似文献   

6.
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7.
A 56‐day feeding trial was conducted to study the effects of cottonseed protein concentrate (CPC) as fishmeal (FM) replacement on growth, digestive proteinase, intestinal morphology and microflora in pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu). FM of 0% (FM), 12.00% (R12), 24.00% (R24), 36.00% (R36), 48.00% (R48) and 60.00% (R60) was replaced with CPC, to prepare six diets and feed groupers. Weight gain (WG) and specific growth rate (SGR) were highest in the R24 group, and the lowest feed coefficient rate (FCR) was observed in this group compared with the other groups (p < .05). Pepsin activity of the R12 group and chymotrypsin activity of the R36 group reached significant maximum (p < .05). With increasing CPC replacement, the plica height and width and the lamina propria thickness of intestine decreased significantly (p < .05). 16S rDNA amplicon sequencing suggested dominant intestinal microflora of grouper subjected to different treatments was similar. At the phylum level, the abundance of Proteobacteria, Firmicutes, Verrucomicrobia, Bacteroidetes and Actinobacteria was high, while Photobacterium, Pseudoxanthomonas, Romboutsia, Akkermansia, Vibrio and Bifidobacterium were the dominant taxa at the genus level. The abundance of probiotics (Bifidobacterium) decreased, whereas the abundance of opportunistic pathogen (Proteobacteria, Actinobacteria and Vibrio) increased. These results suggested that CPC replacement affected growth, digestive proteinase activity, intestinal morphology and microflora structure in grouper. Under the conditions of this experiment, the fishmeal replacement with CPC (24% level) yielded the most satisfactory results, providing reference for sustainable aquaculture.  相似文献   

8.
The marine leech, Zeylanicobdella arugamensis, is a major threat to aquaculture in grouper-producing countries including Indonesia. This study aimed at investigating prevalence, intensity and histopathology of the ectoparasite in humpback and hybrid groupers cultured in different rearing systems. A total of 260 groupers (60 humpback groupers and 200 hybrid groupers) were used for samples. The marine leech was observed on skin, fins, gills and mouth, followed by histopathological assay on the skin tissue. The results showed that prevalence of the leech in both groupers was higher when they were cultured in the floating net cages compared with the hatchery, p < .05. Furthermore, humpback grouper had a higher prevalence than hybrid grouper when they were cultured in a similar system, p < .05. Meanwhile, there was no significant difference in intensity between the two groupers, p > .05. Within the hybrid groupers, the highest prevalence was obtained from hybrid groupers reared in the earthen ponds. Histopathological studies showed that the infected groupers exhibited inflammation, congestion and erosion of the epidermis layer. Hybrid grouper had more severe histopathological lesions in the skin tissues. These results suggested that species and type of aquaculture system had significantly determined the prevalence, intensity and severity of lesion in Z. arugamensis infestation.  相似文献   

9.
An 8‐week feeding trial was conducted to determine the requirement of protein for large‐size grouper Epinephelus coioides (initial body weight: 275.07 ± 1.56 g). Six iso‐lipidic (124 g/kg) diets were formulated containing graded levels of protein (350, 400, 450, 500, 550 and 600 g/kg). Grouper was hand‐fed twice daily to apparent satiation with triplicate. The results showed that significantly high weight gain, specific growth rate and significantly low feed conversion ratio were observed in fish fed 450 g/kg protein group. High‐protein level diets significantly increased protein content and significantly decreased lipid content of fish body and muscle. Total protein and cholesterol content in serum of 600 g/kg group were significantly higher than those of 350 g/kg group. However, serum glucose and triglyceride contents of fish fed low‐protein diets were significantly higher than those of fish fed high‐protein diets. Meanwhile, liver glutamic‐pyruvic transaminase and glutamic‐oxaloacetic transaminase in high‐protein diet groups were significantly higher than those of low‐protein diet groups. The intestinal protease activity in high‐protein diet groups was significantly higher that of low‐protein diet groups, but lipase and amylase showed opposite trend. With the increasing of dietary protein level, the activities of alkaline phosphatase, superoxide dismutase and lysozyme in liver of grouper increased significantly compared with 350 g/kg group, while the activities of acid phosphatase decreased significantly. With specific growth rate as the evaluation index, the optimum dietary protein level of large‐size grouper Epinephelus coioides was 438.39 g/kg by fitting the broken‐line regression analysis.  相似文献   

10.
An 8‐week feeding trial was conducted to investigate the effects of dietary carbohydrate‐to‐lipid (CHO:L) ratios on growth, liver and muscle glycogen content, haematological indices, and liver and intestinal enzyme activity of juvenile grouper (Epinephelus coioides). Five isonitrogenous (496.0 g/kg protein) and isoenergetic (21.6 KJ/g gross energy) diets with varying CHO:L ratios of 0.65 (D1), 1.31 (D2), 2.33 (D3), 4.24 (D4) and 8.51 (D5), respectively, were fed to triplicate groups of 20 fish (average 10.02 ± 0.1 g) for 8 weeks. Results showed that the weight gain rate, specific growth rate and protein efficiency ratio (PER) of juvenile grouper increased first and then decreased with the increase in CHO:L ratio, reaching a maximum value in the D4 (CHO:L = 4.24) diet. The trend for the feed conversion ratio was opposite to the PER. Along with the diet CHO:L ratios, the apparent digestibility coefficients (ADC) of crude lipid and energy for the juvenile groupers decreased gradually, while the ADC of dry matter, liver and muscle glycogen level increased gradually. Total protein, triglycerides and cholesterol in serum were all maximized in the D4 diet and glucose in the D5 (CHO:L = 8.51) diet. Digestive enzyme activity in the intestine was significantly affected by dietary CHO:L ratio. Liver hexokinase, phosphofructokinase and glucose‐6‐phosphate dehydrogenase activity increased significantly as CHO:L ratio increased. Liver lysozyme and acid phosphatase activity in the groupers fed the D3 (CHO:L = 2.33) diet was significantly higher than that of other diets. Liver fructose‐1,6‐bisphosphatase and alkaline phosphatase activity reached a maximum value in the D4 diet and was significantly higher than that in the D1 diet. Taking the above results together, it can be concluded that an optimal dietary CHO:L ratio of 2.33 is suitable for grouper culture concerning growth performance and health.  相似文献   

11.
A six‐week growth trial was conducted to evaluate the optimum dietary isoleucine requirement of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Seven isoenergetic (3,400 kcal/kg of dry matter), isoproteic (496 g/kg of dry matter) and isolipidic (70 g/kg of dry matter) diets were formulated to contain graded Ile levels (7.3, 11.3, 15.7, 19.6, 23.5, 26.8 and 30.8 g/kg, dry‐matter basis). Each experimental diet was fed to triplicate groups of 12 hybrid grouper juveniles (average initial body weight: 6.00 ± 0.01 g/fish). Experimental fish were randomly distributed into 21 glass tanks (L 60 × W 45 × H 50 cm) connected to mechanical and biological water filters as a recycling system. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. After the sampling of the growth trial, the remaining fish in each group were fed their corresponding diets for 2 d and then exposed to 4 mg Cu2+ · L?1 water for 24 hr. Results showed that growth performance and feed utilization were significantly affected by different dietary Ile levels (p < .05). Weight gain percentage (WG%), protein productive value (PPV), protein efficiency ratio (PER) and feed efficiency (FE) were increased as dietary Ile level increased, reaching a peak value at 19.6 g/kg dietary Ile, and thereafter, these four parameters declined as dietary Ile level continued to increase. Daily feed intake (DFI) showed an opposite tendency of variations as FE. The quadratic regression analysis of WG%, PPV, PER and FE against dietary Ile levels indicated that the optimum dietary Ile requirement for hybrid grouper was estimated to be 19.8, 20.8, 19.4 and 19.1 g/kg dry matter, respectively. Among all experimental treatments, fish fed 19.6 g/kg dietary Ile had the highest expression of growth and protein synthesis‐related genes, including growth hormone (GH) in pituitary, insulin‐like growth factor 1 (IGF‐1), growth hormone receptor 1 (GHR1), target of rapamycin (TOR) and S6‐kinase 1 (S6K1) in liver. Gut micromorphology was significantly influenced by dietary Ile levels. After the exposure to 4 mg Cu2+ · L?1 water for 24 hr, fish fed 19.6 g/kg dietary Ile had the highest survival and the best immunologic manifestation among all experimental treatments. Generally, the optimum dietary Ile requirement for maximum growth of hybrid grouper was estimated to be 19.8 g/kg dry matter, corresponding to 39.9 g/kg dietary protein.  相似文献   

12.
The present study was conducted to investigate the protein requirement of grouper Epinephelus coioides at grow‐out stage (initial weight of 102.8 ± 1.02 g). Six iso‐lipidic diets were formulated using white fish meal and casein as protein sources with graded levels of protein (350, 400, 450, 500, 550 and 600 g/kg). Grouper was hand‐fed twice daily to apparent satiation in triplicates for 8 weeks. The results showed that lack of protein will lead to the declined of weight gain and specific growth rate and suitable protein not only improved growth, but also reduced feed coefficient rate. In addition, high‐protein level diet significantly decreased the morphological index of grouper. For the body proximate composition analysis, the high‐protein diets (500, 550, 600 g/kg) significantly increased the protein contents in the whole body and muscle which was contrary to as observed for the lipid content. High‐protein diets significantly improved the total protein levels of plasma which were contrast to as observed in triglyceride contents. Moreso, the cholesterol content was observed to be significantly decreased after high‐protein diet supplementation. The intestinal protease activity was observed to increase significantly with increasing protein supplementation whereas a decreasing trend was observed for the lipase and amylase activity with the highest going for the groups fed diets containing 350 g/kg protein as compared to the others. The liver alkaline phosphatase, superoxide dismutase and lysozyme activity increased with increasing protein level which later decreased. On the other hand, the acid phosphatase activity showed a significant downward trend. Based on SGR, the broken‐line regression analysis showed that the optimum dietary protein level and digestible protein level of the grouper Epinephelus coioides at grow‐out stage were 466.65 and 395.79 g/kg, respectively.  相似文献   

13.
ABSTRACT

In this study, the cryopreserved spermatozoa of Epinephelus lanceolatus were transported using a novel method involving dry ice as the medium of preservation and a Styrofoam box. Five conditions were investigated for the cryopreserved sperm under different dry ice exposure times of (24, 48, and 72) h corresponding to treatment 1 (T1), 3 (T3), and 5 (T5), respectively. Meanwhile, the remaining treatments (T2 and T4) involved the same exposure to dry ice for (24 and 48) h followed by re-immersion into liquid nitrogen (LN). The performance of the cryopreserved spermatozoa of the hybrid grouper (E. fuscoguttatus ♀ × E. lanceolatus ♂) was evaluated through fertilization and hatching trials. The results showed no significant difference in fertilization for all five treatments. However, significantly poorer hatching rates than the fresh sperm were observed for spermatozoa exposed to dry ice after 48 h. This study recommends the use of the proposed method to successfully transport E. lanceolatus spermatozoa for the production of hybrid groupers via artificial insemination.  相似文献   

14.
Effects of rhythmic temperature change on the growth, body composition and energy budget of hybrid grouper (Epinephelus lanceolatus ♂ × E. fuscoguttatus ♀) were investigated. Nine groups of fish received repeating cycles of low‐temperature manipulation (22°C) for 1, 2 and 4 days followed by recovery temperature (28°C) for (3, 7 and 11 days), (6, 14 and 22 days) and (12, 28 and 44 days) respectively, designated as L1R3, L1R7, L1R11, L2R6, L2R14, L2R22, L4R12, L4R28 and L4R44 respectively. In the control group (C), fish were reared at 28°C throughout the whole experiment. After 96‐day feeding trail, the final weight, relative weight gain rate, specific growth rate, food conversion efficiency and apparent digestibility coefficient of fish in L4R28 were significantly higher than those of control (p < .05). The crude protein contents of fish in L2R14, L2R22, L4R12, L4R28 and L4R44 were significantly higher compared to the control (p < .05). According to energy budget, fish in L4R28 exhibited significantly higher proportion of food energy assimilated into growth and lower proportion consumed for excretion than the control fish (p < .05). These results indicated the occurrence of complete or over growth compensation in hybrid grouper, and the use of repeated cycles of low temperature (22°C) for 4 days followed by recovery temperature (28°C) for 28 days could obtain enhanced growth, that is overcompensation, with improved apparent digestibility coefficient, food conversion efficiency and energetic efficiency into growth. This technique would be more practically applicable in indoor culture for this species.  相似文献   

15.
Effects of Bacillus cereus BC‐01, Lactobacillus acidophilus LAG01, Clostridium butyricum CBG01 and their combinations as supplementation on the growth performance, digestive enzyme activities and serum non‐specific immunity of hybrid grouper (Epinephelus lanceolatus ♂×E. fuscoguttatus ♀) were assessed. Seven different diets, that is one control diet (basal feed without any probiotics, CT) and six treatment diets containing single B. cereus (Bs), L. acidophilus (Ls) and C. butyricum (Cs) at 1.0 × 109 cfu/kg feed, and also their combinations in equal proportion at 1.0, 2.0 and 3.0 × 109 cfu/kg feed (BLC1, BLC2 and BLC3) were prepared respectively. After 60‐day feeding trial, the final weight, specific growth rate,food consumption, food conversion efficiency and apparent digestibility coefficient of fish in Ls and BLC3 were significantly higher compared with the control (p < .05). The activities of pepsin and trypsin in the intestine of fish for Ls and BLC3 were significantly higher relative to the control (p < .05). Relative to controls, significantly enhanced amylase and lipase activities in proximal intestine except for Cs and BLC1 and lipase activities in distal intestine except for Cs were observed (p < .05). Meanwhile, activities of superoxide dismutase in the serum of fish for all treatments, lysozyme and catalase in Ls and BLC3, and glutathione peroxidase except for Cs were significantly enhanced (p < .05). Based on the above, dietary supplementation of single L. acidophilus at 1.0 × 109 cfu/kg or combination of three strains at 3.0 × 109 cfu/kg for hybrid grouper is recommended.  相似文献   

16.
The study evaluated effects of cholesterol supplementation in a diet with high soybean meal (SBM) on the growth and cholesterol metabolism of giant grouper (Epinephelus lanceolatus). All‐fish‐meal diet was used as control. The diet including SBM (replaced 50% of the fish meal protein, SBM diet) and the SBM diet supplemented with 10 g/kg cholesterol (SBM + cholesterol) were used as experimental diets. Three diets were each fed to triplicate groups of juvenile grouper (initial body weight: 12.39 ± 0.36 g) in a recirculating aquaculture system for 8 weeks. Grouper fed the control diet showed higher (p < .05) weight gain, feed intake, feed efficiency and protein efficiency ratio than the other two dietary treatments. Hepatic cholesterol concentrations and 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase gene expressions were higher in fish fed the control diet than fish fed the control diet and SBM + cholesterol diet. Hepatic cholesterol 7α‐hydroxylase gene expression was higher in fish fed the SBM + cholesterol diet than that in fish fed the control diet. Results indicate that giant grouper on a diet low in cholesterol can regulate cholesterol synthesis, suggesting that the reduced dietary cholesterol intake in the fish fed diet containing SBM is sufficiently compensated by increased cholesterol synthesis.  相似文献   

17.
This study investigated the effects of coconut oil as a dietary supplement on the growth, lipid metabolism and related gene expressions of juvenile orange‐spotted grouper Epinephelus coioides. Coconut oil at concentrations of 0, 10, 30 and 50 g/kg was used to replace dietary lipids in a basal diet containing 150 g/kg lipids. The four experimental diets were, respectively, fed to triplicate groups of juvenile groupers (initial weight: 8.53 ± 0.13 g) in a recirculating system for 8 weeks. Fish fed the diet containing 50 g/kg coconut oil exhibited lower (p < .05) weight gain than did fish fed the diet containing 30 g/kg coconut oil; however, no significant differences in weight gain were observed between fish fed diets containing 0 and 10 g/kg coconut oil. Hepatic carnitine palmitoyltransferase‐1, fatty acid synthase, fatty acid elongase, fatty acid desaturase and peroxisome proliferator‐activated receptor gamma gene expressions were all the highest in fish fed the diet containing 10 g/kg coconut oil. Fish fed the coconut oil‐free basal diet demonstrated upregulated gene expression of neuropeptide Y. The results suggest that dietary supplementation with 10 g/kg coconut oil exerted beneficial effects on lipid metabolism by E. coioides.  相似文献   

18.
Since 2007, 96 wild Queensland groupers, Epinephelus lanceolatus, (Bloch), have been found dead in NE Australia. In some cases, Streptococcus agalactiae (Group B Streptococcus, GBS) was isolated. At present, a GBS isolate from a wild grouper case was employed in experimental challenge trials in hatchery‐reared Queensland grouper by different routes of exposure. Injection resulted in rapid development of clinical signs including bilateral exophthalmia, hyperaemic skin or fins and abnormal swimming. Death occurred in, and GBS was re‐isolated from, 98% fish injected and was detected by PCR in brain, head kidney and spleen from all fish, regardless of challenge dose. Challenge by immersion resulted in lower morbidity with a clear dose response. Whilst infection was established via oral challenge by admixture with feed, no mortality occurred. Histology showed pathology consistent with GBS infection in organs examined from all injected fish, from fish challenged with medium and high doses by immersion, and from high‐dose oral challenge. These experimental challenges demonstrated that GBS isolated from wild Queensland grouper reproduced disease in experimentally challenged fish and resulted in pathology that was consistent with that seen in wild Queensland grouper infected with S. agalactiae.  相似文献   

19.
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   

20.
Diploid and triploid hybrids of large yellow croaker (Pseudosciaena crocea, Pc) and Miiuy croaker (Miichthys miiuy, Mm) were produced by interspecific hybridization. The result showed that Pc (♀) and Mm (♂) can be successfully crossed and hybrid offspring of normal hatch rate were produced. In contrast, a lower fertilize and hatch rate were produced for hybrids of Pc (♂) and Mm (♀), and the offspring died day 19 after hatching. To confirm the ploidy of hybrid offspring, we examined the karyotypes of offspring. The result of DNA relative content investigation and genetic relationship analysis demonstrated that the major hybrid offspring were hybrid diploid. In addition, a small number of hybrid were triploid and gynogenesis diploid. Morphological analysis based on the measurable traits data indicated the success of the interspecific crosses. The natural gynogenetic diploid large yellow croaker (PP), diploid hybrids (PM) and triploid hybrids (PPM) were closer to maternal parent (Pc) than paternal parent (Mm). This study provided genetic evidences of the chromosome, DNA content and morphological levels to support the successful establishment of the polyploidy hybrids of Pc (♀) and Mm (♂).  相似文献   

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