Effects of replacing fish meal with soya protein concentrate on growth,feed efficiency and digestibility in diets for snakehead,Channa striata

Soya bean meal‐based formulated feeds have recently become available for snakehead culture in Vietnam. This study was conducted to determine the appropriate replacement of fish meal (FM) protein by another soya product, soya protein concentrate (SPC), in snakehead (Channa striata) diets. Five iso‐nitrogenous (45% crude protein) and iso‐caloric (19 KJ g^?1) practical diets were formulated to replace 0% (control), 40%, 60%, 80% and 100% of protein FM by protein SPC (100% FM, 40% SPC, 60% SPC, 80% SPC and 100% SPC respectively). A digestibility experiment was also conducted with the same formulated diets with addition of 1% chromic oxide. Fish fed 100% FM and 40% SPC diets had significantly better growth and survival compared with other treatments. Feed intake, feed conversion ratio, protein efficiency ratio and net protein utilization, trypsin and chymotrypsin activities of experimental fish fed 100% FM and 40% SPC diets were significantly higher than those fed other diets. The apparent digestibility coefficient (ADC) of the diet and diet components, ADC_diet, ADC_protein and ADC_lipid, of fish fed diet 40% SPC and 100% FM treatment were significantly higher than those of other treatments. The cost/kg fish produced in diets 100% FM and 40% SPC was much lower compared with other treatments. Dietary inclusion levels of SPC in diet above 40% significantly affected fish survival, growth, digestibility and trypsin and chymotrypsin activities, although fish chemical composition was not greatly affected.     

Salinization intensifies the effects of elevated temperatures on Channa striata,a common tropical freshwater aquaculture fish in the Mekong Delta,Vietnam

Fisheries Science - Increasing water temperatures and salinity intrusion due to climate change are serious challenges for freshwater aquaculture. In this study, we assessed the combined effects of...     

Effects of larger fish and size grading on growth and size variation in fingerling silver perch

This study presents two experiments addressing growth and size variation in fingerling silver perch (Bidyanus bidyanus. In the first experiment, fish close to mean population size were raised either in the presence or absence of five larger fish for 60 days. Mean specific growth rate (SGR) and increases in the coefficient of variation and skewness were lower in the presence of larger fish, indicating a negative effect of large fish on the growth of smaller ones. In the second experiment, fingerlings were graded into groups smaller and larger than the median size of the population and raised in size-sorted groups of 60 large or small fish and mixed groups of 30 fish of each size category, for 60 days. There was no difference in mean SGR among groups, nor between the mixed group ad the weighted mean of the small and large groups. Biomass gain was higher in the mixed groups than in the weighted small-and-large groups, probably due to a slightly lower survival in the groups comprised of large fish. The fact that the effect of large fingerlings on the growth of smaller ones was evident in the first, but not the second, experiment may be attributed to higher size disparity between large and small fingerlings in the first experiment.     

Gill morphometry of the facultative air-breathing loricariid fish,Hypostomus plecostomus (Walbaum) with,special emphasis on aquatic respiration

Gill respiratory surface area and oxygen consumption during aquatic respiration were measured in the facultative air-breathing loricariid fish,Hypostomus plecostomus. The fish did not surface to breathe atmospheric air in normoxic water; air-breathing was evoked by environmental hypoxia (water oxygen tension=35±2, mmHg) and did not show size-related threshold differences for air breathing.During gradual hypoxia, without access to atmospheric, air,H. plecostomus was found to be an oxyregulator and showed a reduced range of water oxygen tension in which the oxygen consumption remained constant in smaller fish. The critical oxygen tensions were 55 and 33 mmHg at 25°C for fish of 14–30 g and 31–80g body weight, respectively.The gill respiratory surface area (total lamellae area) is reduced, however, the lamellar frequency per mm of gill filament is high which facilitates the gas exchange. Moreover, the increase of gill respiratory surface area (b=0.666) is higher than the increase in routine VO₂ (b=0.338) showing a positive relationship between the gill respiratory surface area /VO₂ ratio and body mass (b=0.328); this indicates that the fish have greater gill respiratory surface area per unit of routine VO₂ as they grow.     

Effect of varying levels of dietary protein on the growth performance and feed conversion efficiency of snakehead Channa striata fry

Six isocaloric test diets, based on fishmeal-groundnut oil cake and containing 350–600 g kg^?1 protein at 50 g kg^?1 incremental levels were fed to snakehead, Channa Striata (Bloch), fry at a rate of 10% of body weight per day under laboratory conditions to determine the effect of varying level of dietary protein on the growth response. On the basis of percentage weight gain, daily weight gain, specific growth rate and daily tissue protein deposition, the dietary protein requirement of fry was found to be 550 g kg^?1 when fish meal was used as the major source of protein. There was a significant increase in carcass protein and a significant decrease in ash content with progressive dietary protein substitution. Fry fed with high protein diets tended to have lower carcass lipid contents and higher moisture contents.     

Air-breathing behavior and physiological responses to hypoxia and air exposure in the air-breathing loricariid fish, Pterygoplichthys anisitsi

Hypoxic water and episodic air exposure are potentially life-threatening conditions that fish in tropical regions can face during the dry season. This study investigated the air-breathing behavior, oxygen consumption, and respiratory responses of the air-breathing (AB) armored catfish Pterygoplichthys anisitsi. The hematological parameters and oxygen-binding characteristics of whole blood and stripped hemoglobin and the intermediate metabolism of selected tissue in normoxia, different hypoxic conditions, and after air exposure were also examined. In normoxia, this species exhibited high activity at night and AB behavior (2–5 AB h^?1). The exposure to acute severe hypoxia elicited the AB behavior (4 AB h^?1) during the day. Under progressive hypoxia without access to the water surface, the fish were oxyregulators with a critical O₂ tension, calculated as the inspired water O₂ pressure, as 47 ± 2 mmHg. At water O₂ tensions lower than 40 mmHg, the fish exhibited continuous apnea behavior. The blood exhibited high capacity for transporting O₂, having a cathodic hemoglobin component with a high Hb–O₂ affinity. Under severe hypoxia, the fish used anaerobic metabolism to maintain metabolic rate. Air exposure revealed physiological and biochemical traits similar to those observed under normoxic conditions.     

Tolerance of juvenile black sea bass Centropristis striata to acute ammonia and nitrite exposure at various salinities

ABSTRACT:   Experiments were conducted to determine the acute tolerance of juvenile (mean weight ± standard error, 9.9 ± 0.9 g) black sea bass Centropristis striata to environmental un-ionized ammonia-nitrogen (NH₃-N) and nitrite-nitrogen (NO₂-N) exposure at various salinities. Specifically, median lethal concentrations (LC50 values) of NH₃-N and NO₂-N at 24, 48 and 96 h of exposure were determined at salinities of 10, 20 and 30 g/L at 22°C. With the exception of LC50 values determined at 48 h, median lethal concentrations of NH₃-N to black sea bass were not influenced by environmental salinity; 24, 48, and 96 h LC50 values ranged from 0.81 to 0.85, 0.65–0.77, and 0.46–0.54 mg-NH₃-N/L, respectively. In contrast, tolerance of black sea bass to environmental NO₂-N was compromised at reduced salinities. Median lethal concentrations of NO₂-N to fish at 24, 48 and 96 h of exposure ranged from 288.3 to 429.0, 258.4 to 358.8 and 190.0 to 241.9 mg-NO₂-N/L, respectively. Results indicate that while juvenile black sea bass are relatively sensitive to acute NH₃-N exposure, they are highly resistant to NO₂-N exposure.     

Relationship between oxygen consumption,growth and survival of larval fish

This work aimed to evaluate the relationship between morphological development, oxygen consumption and reduced mortality in larval fish. We measured the resting metabolic rate (RM), specific metabolic rate (SMR) and the change in the total length during the larval stage of four fish species. Resting metabolism decreased from hatching to mouth opening, and then increased after mouth opening. The changes in the SMR were variable during the larval stage. After hatching, there was no increase in SMR in yolk‐sac larvae. However, SMR increased between mouth opening and the onset of notochord flexion and then decreased during notochord flexion before finally stabilizing. We observed two peaks in mortality during the larval period of all species: between mouth opening to the onset of notochord flexion and from the completion of notochord flexion to the juvenile stage based on the per cent mortality and the number of dead fish collected from the bottom of the rearing tank. Interestingly, the changes in SMR coincided with these periods of mortality. We hypothesize that larvae require more energy during these periods of larval development and are thus more susceptible to mortality when energy is insufficient. Thus, it is important to supply enough nutrition to larvae in during early development to prevent mass larval mortality.     

溶解氧、非离子氨和亚硝酸氮对大菱鲆幼鱼生长代谢的影响研究

以大菱鲆(Scophthalmus maximus)幼鱼为试验对象,在室内进行为期60 d的生长、代谢试验.采用正交设计,设定不同浓度的溶解氧、非离子氨和亚硝酸氮,研究在三者作用下大菱鲆幼鱼的生长和代谢情况.结果表明,溶解氧和氨氮对大菱鲆幼鱼的生长和代谢有显著影响,而亚硝酸氮对其影响不显著.提高溶解氧的浓度能显著降低非离子氨和亚硝酸氮对大菱鲆幼鱼的毒性,改善其生长环境,并能有效的提高大菱鲆幼鱼的生长和代谢.研究表明,在循环水养殖过程中,可以通过增加溶解氧的浓度来降低有毒物质对大菱鲆的毒性,以此减小生物处理的压力,从而在循环水养殖系统设计过程中减少生物过滤装置的成本投入,提高经济效益.     

Effects of chromium yeast,tributyrin and bile acid on growth performance,digestion and metabolism of Channa argus

A 60‐day feeding trial was carried out to evaluate the effects of chromium yeast (CY), tributyrin (TB) and bile acid (BA) on the snakehead (Channa argus). The control (CT) group was fed the basal diet, and the experimental groups were fed 200 mg/kg CY (concentration: 1,000 mg/kg), 2.5 g/kg TB (purity: 45%) or 1 g/kg BA (purity: 30%) in addition to the basal diet. The addition of CY, TB and BA statistically increased the weight gain rate, and specific growth rate, whereas the feeding rate and feed conversion ratio were significantly reduced (p < 0.05). When compared with the CT group, TB elevated the serum glutathion peroxidase (GSH‐Px) activity; and BA reduced low density lipoprotein cholesterol (LDL‐C) contents significantly (p < 0.05). The three feed additives reduced intestinal malonaldehyde (MDA) levels dramatically. Tributyrin significantly enhanced intestinal trypsin and pepsin activities (p < 0.05). The activity of fructose‐1,6‐bisphosphatase and pyruvate carboxylase in the group fed CY was significantly lower than in the CT group. In conclusion, dietary inclusion of the three additives enhanced growth performance of C. argus. Dietary supplementation of CY affected protein, glucose and lipid metabolism. Diets with TB levels improved intestinal digestive enzyme activity and antioxidant capacity. The addition of BA improved glycolipid metabolism.     

Effects of rearing technique and fish size on post-stocking feeding, growth and survival of European grayling, Thymallus thymallus (L.)

European grayling, Thymallus thymallus (L.), were reared by four different techniques: (A) in a natural pond without a supply of artificial diet; (B) in a net pen fed artificial dry diet; (C) in tanks fed artificial dry diet; (D) in tanks, and for 16 days before stocking, transferred to a diet based on mixed frozen natural food exclusively. Fish within groups C and D were also split into subgroups of large and small fish. Feeding, growth and survival of fish in the different groups were compared after stocking into three different stocking sites during the spring of 1994. The stocking sites consisted of a barren lake (Lake L), a second lake (Lake N) containing an allopatric perch, Perca fluviatilis L., population, and a barren man-made pond. In Lake L, higher recapture rates and mean weights of stomach contents were obtained in fish reared in the natural pond and in the net pen. There were no differences in total recapture rate, or mean condition factor between small and large fish within groups C and D. In Lake N only five (0.5%) stocked grayling from rearing groups A and B were recaptured during the experiment and more fish from categories C and D were recaptured. This was probably related to size-selective predation. In the pond, there were no differences in recapture rates or in mean weight of stomach contents between fish from any of the groups. In sample 1 (Lake N, 22 days after stocking), mean weight of stomach contents was higher in the larger fish within categories C and D but there was no difference in condition factor between the groups. In sample 1, mean condition factor of fish from the different groups varied markedly, being highest in Lake L followed by Lake N and the Pond. Fourteen out of 26 dead fish in the pond showed clinical symptoms of the bacterial disease ASA. Mortality was related to low initial condition factor at the time of stocking. No stocked grayling were recaptured from the two lakes in the last sample (June 1995).     

月鳢年龄与生长的研究↑（*）

月鳢鳞片可作为年龄鉴定的依据,其年轮形成时期在4～6月。鳞长与体长呈直线关系,体长和体重呈幂函数关系。月鳢2龄以前生长较快,2龄以后生长逐渐减慢,其生长适合于VonBertalanffy生长方程。为有效保护月鳢资源,应限制捕捞体重在200g以下的个体。     

Studies on the effect of air exposure on gill Na+/K+-ATPase of the marble goby,Oxyeleotris marmorata,a facultative air-breathing fish

Gill and liver microsomal Na⁺/K⁺-adenosine triphosphatase (ATPase) activities, body weight, and several blood parameters were measured in marble gobies held in freshwater, in air on wet filter paper for 7 days and three days after return to freshwater following 7 days in air. During the 7 days in air, body weight, and blood Na⁺ and K⁺ concentrations remained unchanged. During the same period, however, mean specific activity of the gill ATPase fell 79% while liver ATPase specific activity was unchanged. When these fish were returned to water the specific activity of the gill ATPase returned to values seen in freshwater gobies within 3 days. Several changes were also noted in the characteristics of the ATPase in the fish held in air.     

pH对乌鳢胃、肠、肝胰脏蛋白酶活性的影响

设定胃蛋白酶活性在pH2.2~4.6、肠及肝胰脏蛋白酶活性在pH6.4~8.8范围内测定。pH各5个梯度,梯幅0.6。乌鳢胃、肠、肝胰脏蛋白酶的活性最适pH值为别为2.8、8.2、8.2。在最适pH值时酶活性的大小顺序为胃>肠>肝胰脏。pH对胃蛋白酶的影响大于对肠和肝胰脏蛋白酶的影响。     

Effects of delayed feeding on growth and survival of Channa striatus (Bloch) larvae

Abstract. Newly hatched Channa striatus (Bloch) were tested for survival and growth under various delayed feeding regimes. Channa striatus larvae were found to be extremely tolerant to the delay in initial feeding. About 9% of the larvae died when initial feeding was delayed by 2 days after yolk absorption. However, mortality progressively increased with further delays in first feeding. Only 26% of larvae took food when it was offered 11 days after yolk absorption.'Point of no Return'was reached only on the 14th day of starvation.     

光照、氧气、pH和盐度对沼泽红假单胞菌2-8菌株生长和亚硝酸盐消除的影响

以1株具有亚硝酸盐消除能力的沼泽红假单胞菌（Rhodopseudomonas palustris）2-8菌株（简称2-8菌株）为材料,研究了不同光照和氧组合、pH、盐度对菌株生长和亚硝酸盐消除能力的影响。结果发现,光照厌氧条件最利于2-8菌株的生长,该条件下菌株亚硝酸盐消除能力最强,25h消除率达（91.33±1.27）%;菌株在pH7.0时生长和亚硝酸盐消除能力最强,25h亚硝酸盐消除率达到（95.58±4.34）%,在pH9.0以上和5.0以下时基本不生长;菌株在w（NaCl）为0和0.4%的培养基中生长和亚硝酸盐消除能力最强,在w（NaCl）为0.8%～2.0%的培养基中,生长和亚硝酸盐消除能力随w（NaCl）增高而减弱。测定的4个环境因子主要通过影响菌株的生长来影响其对亚硝酸盐的消除能力。     

Effects of shelter on growth and survival in age-0 black sea bass, Centropristis striata (L.)

Black sea bass Centropristis striata (L.) juveniles were reared in aquaria containing either shelter or no shelter to investigate the effects of shelter on growth and survival. The specific growth rates of juveniles were significantly higher in the sheltered aquaria. With shelter present, the average mortality of juveniles caused by agonistic behaviour was 44% compared with no mortality in the unsheltered aquaria. The results provide evidence that shelter is advantageous for growth, but not survival of black sea bass juveniles under culture conditions.