Gill morphometry of the red drum,Sciaenops ocellatus

The structure and morphometry of the gills of the marine teleost, red drum, have been studied. The present analysis of gas exchange area of fish gills is one of the most intensive and the results are compared to less intense averaging methods. Based on the gill area estimates, red drum falls into the category of a fish of intermediate activity. Its gill clearly has an exchange area less than that of the tunas, but is slightly greater than that of trout or bass. The three components that contribute to total exchange area (filament length, lamellar density, and area of individual lamellae) are not all greater in species with a greater total exchange area. The best correlate is total filament length.     

Effects of dietary thyroid hormones on the red drum (Sciaenops ocellatus)

Four separate 8-week feeding trials were conducted to assess the effects of supplementing semipurified diets with either triiodothyronine (T₃) or thyroxine (T₄) at 0, 2, 10, and 50 mg/kg on growth and body composition of juvenile red drum (Sciaenops ocellatus) held in artificial brackish water (6‰) and artificial seawater (32‰). At both levels of salinity, increasing doses of T₃ resulted in fish with reduced weight gain, feed efficiency, condition factor (weight × 100/length³), and muscle ratio (muscle weight × 100/body weight), as well as a lighter body color. Significant (p < 0.05) effects of T₃ on the proximate composition of whole body, liver, and muscle were variable, generally reflecting decreased lipid and protein storage in liver and muscle, respectively. The two highest doses of T₃ given to seawater adapted fish increased survival. Dietary T₄ supplementation had no distinctive effects on appearance, growth or proximate body composition. These results indicate that whereas T₃ may function to regulate protein and lipid metabolism in red drum, dietary supplementation with T₃ leads to a hyperthyroidism-induced catabolic state. The elevated endogenous thyroid hormone levels found in fish fed optimal diets may thus adequately supply tissue needs during juvenile growth.     

Dietary vitamin E requirement of the red drum Sciaenops ocellatus

A 12-week feeding trial was conducted to establish the minimum dietary vitamin E requirement of juvenile red drum by broken-line regression analysis. The semi-purified basal diet was supplemented with 10, 20, 30, 40, 60 or 80 IU vitamin E kg⁻¹ as all-rac -α-tocopheryl acetate. Juvenile red drum were conditioned by feeding the basal diet for 8 weeks prior to the feeding trial to reduce whole-body vitamin E levels. Then, fish initially averaging 12.2 ± 0.4 g fish⁻¹ (mean ± SD) were fed the experimental diets at a rate approaching apparent satiation for 12 weeks. Weight gain and feed efficiency responses of fish fed diets were significantly ( P  < 0.01) altered by the level of vitamin E supplementation but not strictly in a dose-dependent manner. Vitamin E concentrations in liver and plasma also were significantly ( P  < 0.001) influenced by dietary vitamin E level. Plasma ascorbic acid in fish fed the basal diet tended ( P  = 0.066) to be lower than in fish fed diets containing the various levels of vitamin E. In addition, fish fed the basal diet showed edema in the heart, while fish fed all other diets were normal. Fish fed 60 or 80 IU all-rac -α-tocopheryl acetate kg⁻¹ diet had significantly higher respiratory burst of head kidney macrophages than fish fed all other diets, although dietary effects on hematocrit and neutrophil oxidative radical production were not significant. The minimum dietary vitamin E requirement of juvenile red drum was established based on broken-line regression of liver thiobarbituric acid reactive substances to be 31 mg all-rac -α-tocopheryl acetate kg⁻¹ diet.     

Ontogeny of pancreatic enzymes in larval red drum Sciaenops ocellatus

The growth, survival and trypsin, lipase and amylase activities of red drum larvae were measured in two experiments. For the first trial, a group was fed live prey only (L) and another group was fed a combination of a microparticulate diet (MPD) and live food (L-MP). For the second growth trial a group fed the MPD only (MP) and a starvation group (ST) were examined in addition to the L and L-MP treatments. Enzyme activities of live prey were measured to estimate their possible contribution to larval digestion. No significant ( P  > 0.05) differences in final size and survival were observed between treatments L and L-MP. Larvae subjected to starvation or fed the MPD diet alone were smaller than treatments fed live prey and did not survive past days 5 and 14, respectively. Trypsin, lipase and amylase activities were detectable at hatching. No significant differences ( P  > 0.05) in total enzyme activities among treatments were observed before day 14. Specific activity of trypsin, lipase and amylase peaked on day 3 (prior to first feeding) and subsequently decreased. For trypsin, the percentage of enzyme activity potentially attributable to ingested prey increased with age to a maximum of 17%. For lipase and amylase this fraction was less than 5% throughout the study, except on day 8 (12% and 24%, respectively). The lack of significant differences observed in the activity of digestive enzymes among treatments suggests that dietary regime, availability of prey and possible effects of exogenous enzymes did not significantly influence enzyme activity. Therefore, the lower growth rate observed in the L-MP, MP and starved treatments cannot be attributed to low digestive enzyme production of the enzymes measured. It is more likely that the MPD failed to supply the required nutrients for adequate development.     

Dietary effects on thyroid hormones in the red drum,Sciaenops ocellatus

Juvenile red drum (Sciaenops ocellatus) were cultured at 25°C on a variety of diets and blood sampled over eight weeks to examine the relationship between growth and plasma thyroid hormone levels. Maximum growth rates were achieved on formulated experimental diets and a simulated natural shrimp diet. Associated with these maximal rates was a significant increase in triidothyronine (T₃), but no consistent change in thyroxine (T₄). Reduced rations of diets resulted in low growth rates associated with significantly lowered levels of T₃ but not T₄. To determine whether weight gain could be increased by application of exogeneous hormone, diets were supplemented with T₃ or T₄ at 2, 10, and 50 mg hormone/kg diet. Significantly elevated T₃ was induced by supplementation with 10 and 50 mg T₃/kg diet, although there were no indications of an anabolic effect of T₃ incorporation, and 50 mg T₃/kg diet was in fact associated with decreased weight gain. Incorporation of T₄ into diets had no effect on growth or T₃, and had effects on T₄ which were small and inconsistent, indicating that T₄ may not be effectively absorbed from the gut. No difference was found in response to hormone feeding between low (6 ppt) or high (35 ppt) water salinity. T₃ levels thus appear to closely parallel growth in fish on unsupplemented diets, whereas T₄ which were small and manipulation. Supplementation with T₃ is not an effective means of stimulating growth in red drum fed optimum diets. Whereas thyroid hormones may function to regulate intermediary metabolism in red drum, elevated endogenous thyroid hormone levels appear adequate to supply tissue needs during juvenile growth in culture.     

Role of sensory mechanisms in predatory feeding behaviorof juvenile red drum Sciaenops ocellatus

ABSTRACT:   The red drum Sciaenops ocellatus Linnaeus is an exoticaquaculture species in Taiwan. As a carnivore it preys on a varietyof food organisms, including fishes and invertebrates. Isolatingthe sensory mechanisms that govern its predatory behavior wouldhelp clarify its feeding habit. The present study focused on predationresponses influenced by vision, olfaction and lateral line in captivejuvenile red drum. Results showed that the lateral line had themost significant influence on predatory behavior of the fish. Blockingmechanoreception of the lateral line system resulted in completeloss of ability to catch prey. Ablation of olfaction, in contrast,caused a booster effect on the predation rate. Experimental fishwith scorched olfactory rosettes showed active predatory behavior. Nearor complete darkness had insignificant influence on the predationrate. When the lateral line system was blocked, the fish could notprey normally, even when vision and olfaction were left intact. Itwas concluded that mechanoreception plays the primary role and visionthe secondary role in predatory behavior of the red drum.     

Heritability of juvenile growth traits in red drum (Sciaenops ocellatus L.)

Heritability of juvenile growth rate was estimated for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐eight families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring were individually tagged with Passive Integrated Transponder (PIT) tags and mixed for grow‐out in replicate ‘common‐garden’ tanks. Juvenile growth was followed from 166.4±18.6 to 254.0±27.0 mm (total length). Offspring were assigned a posteriori to individual brood fish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability (h²) of a thermal growth coefficient was estimated using an animal‐additive model and a restricted maximum‐likelihood algorithm. Estimates of h² were 0.33±0.08 and 0.31±0.08 for thermal growth coefficient based on length and weight respectively. These results indicate a significant genetic component in juvenile growth rate in red drum. Estimates of h² for condition coefficient (K) at various measurement dates averaged 0.38, suggesting a genetic component to shape in juvenile red drum.     

Evaluation of dietary creatine and guanidinoacetic acid supplementation in juvenile red drum Sciaenops ocellatus

Two separate comparative feeding trials were conducted to evaluate if supplemental dietary guanidinoacetic acid (GDA), either singly or in combination with creatine, could enhance growth performance of red drum. The basal diet for both trials was formulated with practical ingredients but was not supplemented with creatine or GDA. For the experimental diets, creatine (0 or 20 g/kg) and GDA (0, 5 or 10 g/kg) were added to the basal diet in a 2 × 3 factorial arrangement for trial 1. Another 2 × 3 experimental design was adopted in trial 2 to further evaluate creatine (0 or 20 g/kg) and GDA (0, 10 or 20 g/kg) supplementation. Each diet was fed to juvenile red drum in either quadruplicate (trial 1) or triplicate (trial 2) aquaria twice daily for a total of 8 weeks. After each feeding trial, fish were sampled for body condition indices and whole‐body composition analysis, as well as determination of plasma, liver and muscle creatine concentrations. In trial 1, dietary creatine supplementation alone significantly (p < .05) improved weight gain and feed efficiency of red drum. An interaction between creatine and GDA was seen in whole‐body protein and lipid in the two trials. In trial 1, the highest levels of whole‐body protein and lipid were observed in fish fed 10 g GDA/kg, and in trial 2, supplementation of the diet with 10 g GDA/kg increased muscle protein and muscle lipid although there was a trending decline in fish fed the 20 g/kg GDA‐supplemented diet. In both trials of the present study, dietary GDA significantly (p < .05) enhanced liver creatine content. Dietary creatine also significantly (p < .05) enhanced plasma and muscle creatine content of red drum. Based on the results of this study, creatine was effective in enhancing weight gain and feed efficiency of red drum as seen in previous studies; however, GDA was not effective in influencing growth performance but limited synthesis of creatine from dietary GDA was apparent.     

Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus

This study was conducted to evaluate the effects of different concentrations of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Diets were formulated to contain 40% crude protein from solvent-extracted menhaden fish meal and 0, 7, 14 or 21% lipid from menhaden fish oil. The basal diet, without supplemental fish oil, contained lipid at 0.4% of dry weight. The diets were fed to groups of 25 juvenile red drum initially averaging 7.3 ± 0.18 g fish^–1 in a recirculating culture system for 8 weeks and weight gain was recorded. After an additional 8 weeks, 16 fish from each treatment were sacrificed and the following measurements were recorded: hepatosomatic index (HSI), intraperitoneal fat (IPF) ratio, and liver -tocopherol, malondialdehyde (MDA) formation, and cytochrome P-4501A activity (measured as 7-ethoxyresorufin O-deethylase (EROD) activity). The activity of alanine and aspartate aminotransferases and concentrations of -tocopherol also were measured in plasma.Weight gain was significantly (p<0.05) affected by dietary lipid concentration, with values ranging from 361% of initial weight for fish fed the basal diet to 527% of initial weight for fish fed the diet containing 7% lipid. The HSI and IPF ratio values also were significantly affected by lipid with the lowest values recorded for fish fed the basal diet and the highest values observed in fish fed the diet containing 21% lipid. Increasing dietary lipid significantly increased oxidative stress as reflected in reduced -tocopherol in liver and plasma and increased MDA formation in the liver, although no overt pathological signs were observed. These findings suggest that lipid concentrations between 7 and 14%, when the diet contains 60 IU vitamin E kg^–1, are likely to limit oxidative stress and result in normal physiological responses of red drum.     

浙江自然海区逃逸美国红鱼食性研究

通过对浙江自然海区逃逸美国红鱼胃含物的分析,从食料生物组成、食性类型、摄食强度及营养级4个方面对浙江自然海区逃逸美国红鱼的食性进行了探讨。结果表明,美国红鱼属游泳动物食性。主要摄食鱼类、长尾类、短尾类和头足类,兼食口足类和多毛类。其食料生物组成和食性类型与原栖息地有较大差异。逃逸美国红鱼的摄食率为80.28%,最高饱满度系数达60.93‰,平均10.26‰。根据计算,其饵料的生境宽度为4.09,营养级为3.43级。浙江自然海区美国红鱼是一种凶猛的中级肉食性鱼类。     

Nutrition of red drum,Sciaenops ocellatus L.: An additional evaluation of the effects of soya‐based diets and supplemental prebiotic

We assessed the effects of a fishmeal (FM)‐ and two soya‐based diets [without or with prebiotic (GroBiotic^® ‐A; GBA) supplementation] on the production performance, non‐specific immunity, blood parameters and gut microbiota diversity of red drum, Sciaenops ocellatus. All diets were formulated to contain 450 g/kg crude protein (CP) and 120 g/kg lipid. A combination of soya bean meal and soya protein concentrate (SP) was used to replace 88% of the FM in the FM‐based diet (REF) originating the first soya‐based diet (SOY). The second soya‐based diet (SOY + GBA) was designed identically to SOY except for the supplementation of GBA (20 g/kg) substituting for wheat flour. After feeding the experimental diets to triplicate groups of 25 (~3.4 g/fish) and 90 (~4.1 g/fish) red drum juveniles for 9 (Trial I) and 16 weeks (Trial II), our results showed that (i) red drum was highly sensitive to the soya‐based diets in the first week of feeding; (ii) replacing 88% of FM with SP reduced the production performance of red drum without affecting intestinal micromorphology; (iii) whole‐blood leucocyte oxidative radical production was unaffected while lower haematocrit and higher plasma lysozyme activity were found in fish fed REF; (iv) plasma osmolality was unaffected while lower glucose and higher lactate levels were observed in fish fed SOY and SOY + GBA; (v) 16S rRNA gene‐based diversity of fish gut microbiota was affected both by SP and by GBA. This study expands the information on red drum responses to soya‐based diets and prebiotic supplementation.     

Sensory characteristics and nutritional value of red drum Sciaenops ocellatus reared in freshwater and seawater conditions

This study compares sensory attributes, chemical composition, fatty acid profiles, and the taste of raw and cooked red drum Sciaenops ocellatus fillets, reared in seawater (SW) and in freshwater (FW) aquaculture systems. Significant nutritional differences were found in the raw fillets. The total lipid was higher (5.31%) in FW fish than the SW (2.60%). The ratio n‐3/n‐6 and EPA/DHA was higher in SW than FW fillets. The eicosenoic acid was only present in FW fillets. DHA was dominant in SW specimens, contrary to the arachidonic acid level, which was dominant in FW fillets. The assessors perceived a significant difference in the firmness and colour of raw fillets, but its odour intensity was not affected. Fillets from SW fish have higher acceptability (33.3%) than FW fillets (26.4%). Sensory differences in raw fillet were not correlated with consumer perceptions, as cooked fish was considered to have similar flavour, independent of its origin.     

逃逸美国红鱼在浙江海域生长特性的初步研究

根据2004~2006年采集的浙江海域156尾美国红鱼的生物学测定资料,分析了该鱼种可量性状间关系,回归得出全长-体长、体重-纯重、体长-体重关系,并比较分析了其他研究者的结果。采用美国红鱼矢耳石磨片法鉴定年龄,并用FiSATⅡ软件拟合得出von-Bertalanffy生长方程,其中:BL∞=951·09mm,k=0·27,t0=0·57;TL∞=1144·61mm,k=0·26,t0=0·52;WB∞=14468·07g,结合生长拐点(tx=4·514)、生长特征指数(Φ′BL=5·388)及肥满度指标(Q=1·82)。比较分析不同生态环境下美国红鱼的生长情况,表明浙江海域美国红鱼生长特性最接近于美国自然海区,浙江海域适合其生长,一旦形成种群可能会对本地种造成威胁。     

Sex differences in circulating steroid hormone levels in the red drum, Sciaenops ocellatus L.

Steroid profiles of cultured and captive red drum (Sciaenops ocellatus L.) were investigated to evaluate the potential use of circulating sex steroid levels as a tool for gender identification in this species. Cultured 18‐month‐old fish were maintained on a 120‐day shortened photothermal cycle to induce precocious maturation. Additionally, wild‐caught fish were maintained in captivity under simulated natural photothermal conditions from late spring to early fall. Circulating 11‐ketotestosterone (11‐KT) levels were significantly higher in males compared with females during the early stages of gonadal growth in both cultured and captive fish. Plasma testosterone (T) levels showed a similar trend; however, the differences were significant only when males were already producing sperm. 17β‐estradiol (E₂) concentrations were low in males and females before gonadal recrudescence but increased significantly with the progression of vitellogenesis in females. These results show that a test using a minimum concentration of circulating 11‐KT could be developed to differentiate between sexes in the early stages of gonadal maturation in red drum. Moreover, plasma E₂ concentrations could be used to identify vitellogenic females. The two steroids considered together could help avoid possible error in gender identification due to unusually high levels of certain steroids encountered in some individuals.     

Evaluation of fisheries by-catch and by-product meals in diets for red drum Sciaenops ocellatus L.

This study evaluated various by‐catch and by‐product meals of marine origin with red drum (Sciaenops ocellatus L.). Four different kinds of by‐catch or by‐product meals [shrimp by‐catch meal from shrimp trawling, Pacific white shrimp (Litopenaeus vannamei (Boone)) processing waste meal, red salmon (Oncorhynchus nerka (Walbaum)) head meal, and Pacific whiting (Merluccius productus (Ayres)) meal] were substituted for Special Select? menhaden fish meal at 33% or 67% of crude protein in diets formulated to contain 40% crude protein, 12% lipid, and 14.6 kJ digestible energy g^?1. Each of these diets and three additional diets consisting of shrimp processing waste meal formulated on a digestible‐protein basis and two Pacific whiting diets containing reduced levels of ash were also evaluated in two 6‐week feeding trials with juvenile red drum (initial weight of 4–5 and 1–2 g fish^?1 in trials 1 and 2). Red drum fed by‐catch meal at either level of substitution performed as well as fish fed the control diet; whereas, fish fed shrimp processing waste meal diets had significantly (P≤0.05) reduced weight gain and feed efficiency ratio values compared with the controls, even when fed on a digestible‐protein basis. The diets containing Pacific whiting at either levels of substitution and regardless of ash level supported similar performance of red drum as those fed the control diet. Fish fed the red salmon head meal diet fared poorly, probably owing to an excessive amount of lipid in the diet that became rancid. Overall, by‐catch meal associated with shrimp trawling and Pacific whiting appear to be suitable protein feedstuffs for red drum.     

Tests of Mendelian segregation and linkage-group relationships among 31 microsatellite loci in red drum, Sciaenops ocellatus

Two families (parents and full-sibling progeny) of red drum (Sciaenops ocellatus) were assayed for genotypes at 31 nuclear-encoded microsatellites. Tests of expected Mendelian segregation at 29 of the microsatellites were non-significant following Bonferroni correction; occurrence of null alleles was inferred at the remaining two microsatellites. Nine of the 24 possible linkage groups (range 2–5 microsatellites per linkage group) were identified. Significant differences in recombination rates were found both between sexes and between families. The microsatellite linkage groups generated in this study represent the beginning of a genetic map for red drum, an economically important marine fish in the southeastern region of the United States of America.     

美国红鱼继饥饿后的补偿生长及其机制

对两种不同规格 (8.2 5± 0 .5 0g ,4 0 .4 1± 2 .4 5g)的美国红鱼分别在 18～ 2 0℃和 2 0～ 2 4℃条件下进行了不同饥饿时间处理后再恢复投喂实验。在实验的 30d内 ,两次实验结果均表现为饥饿 5d组的美国红鱼生长略快于对照组 ,而饥饿 10d和 15d的鱼在相同的时间内 ,体重的增加量未能赶上对照组。各组间生长虽有差别 ,但都未达到显著水平。饥饿使鱼体水分、灰分含量增加 ,脂肪含量下降 ,蛋白质含量变化不大 ,但各成分从恢复投喂到实验结束时又恢复到对照组水平。各组间摄食量随饥饿时间延长而逐步下降 ,而饵料转换效率逐步上升。随着饥饿时间的延长 ,标准代谢率下降 ,而在恢复投喂之后又逐步回升至对照组水平。结果表明 ,美国红鱼的补偿生长效应主要是由降低标准代谢和提高食物转化率实现的     

Dietary requirements for leucine,isoleucine and valine (branched‐chain amino acids) by juvenile red drum Sciaenops ocellatus

The objective of this study was to determine the minimum dietary requirements of the branched‐chain amino acids (BCAAs: leucine [Leu], isoleucine [Ile] and valine [Val]) for juvenile red drum, Sciaenops ocellatus. This was accomplished by conducting three independent 49‐day feeding trials with juvenile red drum. Experimental diets were prepared by supplementing a basal diet containing 370 g/kg crude protein from red drum muscle and crystalline amino acids with incremental levels of Leu (9.0, 13.0, 17.0, 21.0, 25.0 and 29.0 g/kg of dry diet), Ile (5.0, 8.0, 11.0, 14.0, 17.0 and 20.0 g/kg of dry diet) and Val (6.8, 8.0, 9.2, 10.4, 11.6, 12.8 and 14.0 g/kg of dry diet). Fish were fed to apparent satiation twice daily in each trial, after which growth performance parameters were calculated and body composition and concentrations of BCAAs in plasma were analysed. Incremental levels of dietary Leu, Ile and Val significantly affected weight gain, feed efficiency and protein retention. Analyses of the weight gain data using a broken‐line regression model estimated the minimum Leu, Ile and Val requirements for maximum growth of juvenile red drum to be 15.7 ± 1.7 g/kg (±95% confidence interval), 11.1 ± 2.3 g/kg and 12.4 ± 0.6 g/kg of dry diet, respectively.     

Effects of inorganic and organic dietary copper supplementation on growth performance and tissue composition for juvenile red drum (Sciaenops ocellatus L.)

A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO₄) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.