Dietary methionine requirement for juvenile rockfish, Sebastes schlegeli

A 65-day growth trial was conducted at 19.5 degrees C to determine the optimal dietary methionine for juvenile rockfish, Sebastes schlegeli. Semipurified diets were formulated to be isonitrogenous and isoenergetic. Fish meal was used as intact protein source and crystal amino acid was used as a part of dietary protein. Six experimental diets were formulated to contain 5.8, 10.8, 15.8, 20.8, 25.8 and 30.8 g kg(-1) dietary methionine. The results showed that dietary methionine significantly affected specific growth rate, weight gain, food conversion ratio, protein productive value (PPV), energy retention efficiency, carcass index and body composition. No significant difference was found in hepatosomatic index. The dietary methionine requirement for maximum growth was 13.7 g kg(-1) dry matter or 28.0 g kg(-1) of dietary protein when cystine content was 1.2 g kg(-1) dry matter.

Rearing of Procypris rabaudi during early life-history stages

The early life-history of Chinese rock carp Procypris rabaudi was investigated during a 56-day rearing period: 318 artificially propagated P. rabaudi larvae were reared throughout metamorphosis in a small-scale recirculation system (345 L water volume, 10 x 18 L rearing tanks, 150 L storage and filter compartment with bioballs, 20-30 larvae L-1) at the Institute of Hydrobiology, Wuhan, Hubei Province, China. The newly hatched larvae had an initial total length of 8.93 +/- 0.35 mm SD (n = 10) at 3 days post-hatch and reached an average total length of 33.29 mm (+/- 1.88 mm SD, n = 10) 56 days after hatching. Length increment averaged 0.45 mm day(-1), resulting in a mean growth of 24.4 mm within the 56-day period. High mortality rates of up to 92% derived from an introduced fungus infection and subsequent treatment stress with malachite green. Our results indicate that Chinese rock carp can be raised successfully from artificially fertilized eggs. We therefore assume this species to be a candidate for commercial aquaculture.

Meat and bone meal replacement in diets for juvenile gibel carp (Carassius auratus gibelio): effects on growth performance, phosphorus and nitrogen loading

A 11-week growth trial was conducted in a flow-through system with juvenile gibel carp Carassius auratus gibelio to evaluate the effects of gradual replacement of fish meal (FM) by meat and bone meal (MBM) on growth performance, phosphorus (P) and nitrogen (N) loading. Six isonitrogenous (crude protein: 410 g kg(-1)) and isoenergetic (gross energy: 18 kJ g(-1)) diets were formulated. FM was used as the control protein. In the other five diets, 20, 40, 60, 80 and 100% FM protein was substituted with MBM20, MBM40, MBM60, MBM80, MBM100, respectively. Total P content in the diets ranged from 16.0 to 28.3 g kg(-1) and the available P was 5.0-6.6 g kg(-1). The results showed that the best growth was achieved with fish fed on the control diet and MBM20. Final body weight, weight gain, feed efficiency, protein retention efficiency and energy retention efficiency decreased with increased dietary MBM. No significant differences were found in the feeding rate and hepatosomatic index between the groups. Apparent digestibility coefficient (ADC) of dry matter, protein and P decreased with increase in dietary MBM, while there were no significant differences in the ADC of energy. P and N retention decreased linearly while P and N loading increased linearly with the increased dietary MBM levels. No significant differences were observed in the activity of alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase, as well as pyruvate kinase in liver or in serum. Total superoxide dismutase activity in MBM20 was significantly higher than that of MBM100.

Zebraflsh z-otu, a novel Otu and Tudor domain-containing gene, is expressed in early stages of oogenesis and embryogenesis

Several studies have suggested that Otu domain had de-ubiquitinating activity and Tudor domain was important for the formation of germ cells. Here, we reported a novel zebrafish ovary-specific gene containing Otu and Tudor domain, z-otu, which was expressed at stages I-III oocytes and embryonic stages from zygotes to early blastula during embryonic cells maintained their totipotency. Therefore, z-otu might link the ubiquitin signaling pathway to early oogenesis and maintaining the totipotency of embryonic cell. (c) 2005 Elsevier B.V. All rights reserved.

Effects of animal-plant protein ratio in extruded and expanded diets on nitrogen and energy budgets of juvenile Chinese soft-shelled turtle (Pelodiscus sinensis Wiegmann)

In this study, we investigated the effects of animal-plant protein ratio in extruded and expanded diets on nutrient digestibility, nitrogen and energy budgets of juvenile soft-shelled turtle (Pelodiscus sinensis). Four extruded and expanded feeds (diets 1-4) were formulated with different animal-plant protein ratios (diet 1, 1.50:1; diet 2, 2.95:1; diet 3, 4.92:1; diet 4, 7.29:1). The apparent digestibility coefficients (ADCs) of dry matter and crude lipid for diet 1 were significantly lower than those for diets 2-4. There was no significant difference in crude protein digestibility among diets 1-4. The ADC of carbohydrate was significantly increased with the increase in animal-plant protein. Although nitrogen intake rate, faecal nitrogen loss rate and excretory nitrogen loss rate of turtles fed diet 1 were significantly higher than those fed diets 2-4, nitrogen retention rate, net protein utilization and biological value of protein in these turtles were significantly lower than those fed diets 2-4. In addition, energy intake rate, excretory energy loss rate and heat production rate of turtles fed diet 1 were also significantly higher than those fed diets 2-4. Faecal energy loss was significantly reduced with the increase in the animal-plant protein ratio. The ADC of energy and assimilation efficiency of energy significantly increased with a higher animal-plant protein ratio. The growth efficiency of energy in the group fed diet 1 was significantly lower than those in the groups fed diets 2-4. Together, our results suggest that the optimum animal-plant protein ratio in extruded and expanded diets is around 3:1.

Effect of feeding frequency on growth, feed utilization, and size variation of juvenile gibel carp (Carassius auratus gibelio)

Juvenile (3.0 +/- 0.2 g) gibel carp (Carassius auratus gibelio ) were fed to satiation for 8 weeks to investigate the effect of feeding frequency on growth, feed utilization and size variation. Five feeding frequencies were tested: two meals per day (M2), three meals per day (M3), four meals per day (M4), 12 meals per day (M12) and 24 meals per day (M24). The results showed that daily food intake increased significantly with the increase in feeding frequency and there was no significant difference between daily food intakes in M12 and M24 treatments. Growth rate, feed efficiency increased significantly with increasing feeding frequencies. Size variation was not affected by feeding frequency. Apparent digestibility of dry matter was not influenced by feeding frequency, while apparent digestibility of protein and energy increased significantly at high feeding frequencies. The feeding frequency had no significant effect on the moisture, lipid, protein, or energy contents of gibel carp, while the ash content decreased with increased feeding frequency. It was recommended that 24 meals per day was the optimal feeding frequency for juvenile gibel carp.

Spawning areas and early development of long spiky-head carp (Luciobrama macrocephalus) in the Yangtze River and Pearl River, China

The spawning areas and early development of long spiky-head carp, Luciobrama macrocephalus (Lacepede), an endemic fish species in China, were investigated in the Yangtze River and Pearl River of central and southeastern China between 1961 and 1993. The potamodromous fish migrated upstream to spawn between May and July as the floodwater began to rise. The water-hardened eggs drifted down the river, and the embryos and larvae developed in the course of drifting. The spawning areas of the fish were widely found in the upper and middle main channels and large tributaries. Two large dams (Gezhouba dam and Danjiangkou dam) did not significantly impact on the reproduction of the fish. Fifty stages of the early development from one cell to the juvenile with fully formed fins were observed and characterized pictorially. The larvae of long spiky-head carp could be distinguished from the larvae of other co-occurring species by counting the number of somites and comparing the proportion of sizes of eye to otic capsule.

The toxic effects of microcystin-LR on embryo-larval and juvenile development of loach, Misguruns mizolepis Gunthe

Microcystin-LR, a specific and potent hepatotoxin, was tested for its effects oil loach embryo-larval and juvenile development, The results of this study showed that loach embryos were more sensitive when exposed to microcystin-LR at a later than at an earlier stage of development, Juveniles were far less sensitive to MC-LR than were embryos and larvae. Mortality and developmental abnormality were proven to be dose-dependent and to be stage-specific sensitive. Among the abnormal changes noted were: pericardial edema and tubular heart, bradycardia, homeostasis, poor yolk resumption. small head, curved body and tail, and abnormal hatching, Liver and heart were the main targets of microcystin-LR toxicity. Ultrastructural analysis documented a complex set of sublethal effects of microcystin-LR on loach hepatocytes, chiefly including morphological alteration in nuclear and RER of loach liver cells. fit addition, microcystin-LR was lethal to loach juvenile in the subacute (7 days) exposure (LC50) = 593.3 mug/l). (C) 2002 Elsevier Science Ltd. All rights reserved.

Food habits and feeding rhythm of the early juvenile Chinese mitten crab (Eriocheir sinensis) in experimental tanks

Gastric mills were examined from 98 early juvenile Chinese mitten crabs (Eriocheir sinensis) from experimental tanks. Recognizable food items were macrophytes, algae, oligochaetes, and detritus; their percent frequencies of occurrence were 94.6%, 86.5%, 10.7%, and 18.3%, respectively. The crabs had a diet feeding rhythm.

Effect of several feeding stimulants on diet preference by juvenile gibel carp (Carassius auratus gibelio), fed diets with or without partial replacement of fish meal by meat and bone meal

The objectives of this work were to study the effects of several feeding stimulants on gibel carp fed diets with or without replacement of fish meal by meat and bone meal (MBM). The feeding stimulants tested were betaine, glycine, L-lysine, L-methionine, L-phenylalanine, and a commercial squid extract. Three inclusion levels were tested for each stimulant (0.18, 0.5%, and 1% for betaine and 0.1, 0.25 and 0.5% for the other stimulants). Two basal diets (40% crude protein) were used. one with 26% fish meal (FM), and the other with 21% fish meal and 6% MBM, Betaine at 0.1% in the fish meal group and at 0.5% in the meat and bone meal group was used in all experiments for comparison among stimulants. In the experiment on each stimulant, six tanks of fish were equally divided into two groups, one fed the FM diet, and the other fed the MBM diet. After 7 days' adaptation to the basal diet, in which the fish were fed to satiation twice a day, the fish were fed for another 7 days an equal mixture of diets containing varying levels of stimulants. Each diet contained a unique rare earth oxide as inert marker (Y2O3, Yb2O3, La2O3, Sm2O3 or Nd2O3). During the last 3 days of the experiment, faeces from each tank were collected. Preference for each diet was estimated based on the relative concentration of each marker in the faeces. Gibel carp fed the FM diet had higher intake than those fed the MBM diet, but the difference was significant only in the experiments on betaine, glycine and L-methionine. None of the feeding stimulants tested showed feeding enhancing effects in FM diets. All feeding stimulants showed feeding enhancing effects in MBM diets. and the optimum inclusion level was 0.5% for betaine, 0.1% for glycine, 0.25% for L-lysine, 0.1% for L-methionine. 0.25% For L-phenylalanine. and 0.1% for squid extract. The squid extract had the strongest stimulating effect among all the stimulants tested. (C) 2001 Elsevier Science B.V. All rights reserved.

The growth patterns of juvenile and precocious Chinese mitten crabs, Eriocheir sinensis (Decapoda, Grapsidae), stocked in freshwater lakes of China

Stocking experiments with Eriocheir sinensis were conducted in two small, shallow lakes to study its growth pattern in 1994-1997. For the initially immature crabs, carapace width (CW) increases from 21.2 +/- 0.4 mm (mean +/- s.e.) for females and 22.3 +/- 0.5 mm for males in January, to 65.4 +/- 0.5 mm for females and 66.9 +/- 0.6 mm for males in October. There is no significant difference in CW and carapace length (CL), although there is a large difference in body weight (BW) between sexes in every month from January to August when crabs are juvenile, however, there are significant differences in CW, CL. and BW between sexes after September when the crabs become sexually mature. The growth curve from January to October fits a logistic equation and may be expressed as CW = 75.7 (1 + exp (0.914 - 0.011t))(-1) for females, and CW = 77.5 (1 + exp (0.889 - 0.011t))-1 for males, where CW is in mm, t in days. For precocious crabs (reaching maturity by the first autumn, CW does not change much from January to July, which indicates that precocious crabs stop growing. Like juveniles, the precocious crabs show no differences in CW and CL, but do show a statistically significant difference in BW between sexes.

Comparison of compensatory growth responses of juvenile three-spined stickleback and minnow following similar food deprivation protocols

The compensatory growth responses of individual juveniles of two co-existing species were compared after identical periods of starvation to determine inter-specific similarities and differences. The carnivorous stickleback Gasterosteus aculeatus was compared with the omnivorous minnow Phoxinus phoxinus. Both species experienced 1 or 2 weeks of starvation before being re-fed ad libitum. The two species differed in their response to the starvation periods, with minnows showing a lower weight-specific loss. Both species showed compensatory responses in appetite, growth and to a lesser extent, growth efficiency. Minnows wholly compensated for 1 and 2 weeks of starvation. At the end of the experiment, sticklebacks starved For 2 weeks were still showing a compensatory response and had nut achieved full compensation. The compensatory responses of the sticklebacks showed a lag of a week before developing in the re-feeding phase, whereas the response of the minnows was immediate. Analysis of lipid and dry matter concentrations suggested that the compensatory response restored reserve lipids while also bringing the fish back to the growth trajectory of continuously fed fish. (C) 2001 The Fisheries Society of the British Isles.

Long-term toxic impact of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the reproduction, sexual differentiation, and development of different life stages of Gobiocypris rarus and Daphnia magna

The sexual ratio of Gobiocypris rarus exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 17 beta -estradiol from embryo to sexually mature revealed feminization and overdevelopment of connective tissue in male fish gonad in 2-30 pg/L TCDD concentration range. Daphnia magna was not sensitive to the high dose of TCDD (0.1-1000 ng/ml), but the reproduction of D. magna treated with TCDD decreased after the 8th day. 7-Ethoxyresorufin-O-deethylase (EROD) activities in newly fertilized eggs of G. rarus exposed to TCDD dosage groups (1000-100,000 pg/L) were significantly induced and increased with TCDD concentrations at the early life stage, while no difference was found between low TCDD dosage groups (<100 pg/L), but a good relationship between the EROD activity and the TCDD concentration was observed during a long-term developmental stage. There was a pericardial edema formed in a 2-week yolk-sac at the concentration of 1000 pg/L TCDD. But in the exposure group (2 pg/L TCDD for 120 days), the cell nuclei of hepatocytes was far from the center and packed toward the cell membrane; the cristae of most mitochondria in the cell dropped and collapsed; the rough endoplasmic reticulum broke into fragments; and numerous lipid droplets formed in the cell. (C) 2001 Academic Press.

Growth of juvenile Chinese sturgeon Acipenser sinensis fed live and formulated diets

Triplicate groups of 3.8-g juvenile Chinese sturgeon Acipenser sinensis were reared for 8 weeks in indoor flow-through systems on one of four diets: a natural diet consisting solely of live tubificid worms, a semimoist practical diet, a dry practical diet, and a purified diet. The formulated diets were prepared in the laboratory and had protein contents of 47-50%. Except for the group fed the purified diet, fish showed high survival (94-96%) and growth (final weight, 41-45 g). Survival and specific growth rate did not differ significantly between groups fed the natural, semimoist, and dry practical diets, but were significantly (P < 0.05) lower in fish fed the purified diet. Proximate analysis showed that fish fed purified diet had lower protein and lipid levels but a higher moisture content than fish fed other diets. Our results demonstrated that growth and survival of cultured juvenile Chinese sturgeon fed practical diets were comparable with those fed live tubificid worms. However, Chinese sturgeon fed a purified diet showed inferior growth and survival.