Growth response of African catfish,Clarias gariepinus (B.), larvae and fingerlings fed protease‐incorporated diets

African catfish, Clarias gariepinus (B.), is one of the promising freshwater fish species in African aquaculture but the expansion of its farming needs more production of its larvae. The use of live food organisms at first feeding for larvae is still obligatory. That increases the cost of larvae production. Hence, the incorporating of exogenous enzymes especially protease in artificial microdiets may provide affordable alternatives for enhancing the larvae performance. The present study was carried out to evaluate the growth and survival of larvae or fingerlings of African catfish fed artificial diets incorporated with different protease levels. Four artificial diets were formulated and enriched with protease enzyme at levels of 0.0, 750, 1,000, and 1,250 unit/kg diet; after that diets were made into crumbles (100–200 µm diameter). After absorption of the yolk sac, diets were offered to fish larvae (3.6 ± 0.2 mg) in triplicates as a starter feed up to apparent satiation every two hours for 30 days. In another treatment, fish larvae were fed on newly hatched Artemia nauplii (2,500 Artemia/L) as a starter food. In another experiment, African catfish fingerlings (10.1 ± 1.6 g) were fed on the same diets up to satiation twice a day for 2 months. It was noticed that the dietary protease improved larval growth and survival but not as Artemia nauplii did where fish larvae fed on Artemia nauplii showed highest growth and survival followed by those fed a diet enriched with 1,250 unit/kg diet of protease. The mortality of larvae fed protease‐enriched diets as well as the control diet was occurred mostly at the first week reaching its maximum at the third week. The poor growth was observed with fish larvae fed the control diet. Meanwhile, catfish fingerlings fed protease‐enriched diets showed higher growth over those fed the control diet. The larvae survival (11.0%–41.7%) was enhanced by increasing protease levels and it was lower than that of fingerlings (95.6%–100.0%). Furthermore, protein retention and digestibility were significantly improved with protease supplementation over the control diet especially at a level of 1,000 unit/kg diet. As compared with the previous studies, live food should be used in larvae rearing for the first week after that a starter diet enriched with protease at levels of 1,250 unit/kg diet should be used. In case of fish fingerlings, the dry diets should be enriched with 1,100 unit/kg diet to improve diet digestibility and subsequently enhance their growth.     

Effects of polyherbal formulation 'ImmuPlus' on immunity and disease resistance of Indian major carp, Labeo rohita at different stages of growth

A series of experiments were performed to determine the impact of polyherbal immunomodulatory formulation 'ImmuPlus' (AquaImmu) on growth, immunity and disease resistance of rohu (Labeo rohita), one of the Indian major carp at different stages of growth. Rohu larvae were fed on plankton, ImmuPlus-mixed compound feed, and plankton plus ImmuPlus-mixed compound feed (ImmuPlus added at three dose levels of 0.25, 0.50, and 0.75 g/kg feed) from 4th day of hatching to 14th day. ImmuPlus-mixed diets enhanced growth of larvae, survival and disease resistance against Aeromonas hydrophila challenge, compared to only plankton-fed group. In two other experiments, advanced rohu larvae and fingerlings were fed with ImmuPlus-mixed compound feed (at 0, 0.5, 1.0 and 2.0 g/kg) for 15, 30 and 45 days. At the end of 45 days for advanced larvae and 30 days for fingerlings, the fish fed with ImmuPlus at 1.0 g/kg level showed significantly higher growth and disease resistance against A. hydrophila challenge. In a separate experiment, juveniles of rohu were fed with 1 g/kg of ImmuPlus incorporated feed for 15 and 30 days. At the end of the trial, the ImmuPlus fed fish showed enhanced non-specific immunity (as measured through nitroblue tetrazolium reduction assay, serum lysozyme activity, serum haemolysin titre and resistance against A. hydrophila challenge in non-vaccinated fish as well as specific immunity levels (as measured through bacterial agglutination titre against A. hydrophila in vaccinated fish). Incorporation of ImmuPlus at 1 g/kg level in the diet of rohu may be beneficial for enhancing disease resistance.     

The Effects of a Synbiotic Mixture of Galacto-Oligosaccharides and Bacillus Strains in Caspian Salmon,Salmo trutta caspius Fingerlings

The effect of dietary supplementation with a synbiotic mixture of galacto-oligosaccharides (GOS) and Bacillus spp. was examined in Caspian salmon, Salmo trutta caspius (Kessler, 1877) fingerlings. Caspian salmon fed with the synbiotic diet had significantly higher weight gain rate, protein efficiency ratio, and survival rate, as well as lower feed conversion ratio, compared to the control group (P < 0.05). The serum protein, albumin, globulin, and lactate dehydrogenase levels of the fish fed with the synbiotic diet were significantly higher than the control group (P < 0.05), while the serum alkaline phosphatase levels were significantly lower (P < 0.05). The activities of the innate immune response parameters, including lysozyme, superoxide dismutase, and catalase were significantly higher in the Caspian salmon fed with the synbiotic diet (P < 0.05). The gut microbiota of the Caspian salmon fed with the synbiotic diet contained significantly elevated total viable aerobic bacterial counts (TVABCs), lactic acid bacteria (LAB) levels, and LAB/TVABCs ratio (P < 0.05). Additionally, the gut activities of amylase, trypsin, and chymotrypsin in the gut, as well as the trypsin/chymotrypsin ratio, were significantly increased in the fish that received the synbiotic diet (P < 0.05). In conclusion, the combined GOS and Bacillus spp. supplement positively affected the growth, survival rate, immunobiochemical parameters, digestive activity, and beneficial microbial density in the gut of Caspian salmon fingerlings.

     

The effects of diet and stocking density on the growth and behaviour of pond pre-reared pikeperch under intensive conditions

Experiments were carried out between 1999 and 2001 on pikeperch fingerlings using two feeds at four stocking densities to evaluate the success of training 35‐day‐old pond‐reared pikeperch, Stizostedion lucioperca L., to lifeless feed in intensive culture. Training periods of 28 days for each of three cohorts (1999–2001) were applied to introduce pikeperch from zooplankton to minced feed. In a preliminary study (1999), two feeds (live prey and minced fish meat) were compared at two stocking densities. Two higher densities were investigated in 2000 and 2001 and matched with the minced fish diet. Different feeds had significant effects on feed consumption and, as a consequence, on body weight gain; fish fed live prey showed highest growth rates. Unexpectedly, the stocking density had no significant effect on growth, and at the highest density there was a significantly betterfeed conversion rate. Stocking density and feed type significantly influenced the feeding behaviour. Three characteristic foraging techniques are described.     

Use of bacterial lipopolysaccharide (LPS) as an immunostimulant for the control of Aeromonas hydrophila infections in rainbow trout Oncorhynchus mykiss (Walbaum)

Aims: To determine the effect of lipopolysaccharide (LPS) for the prevention of infection by Aeromonas hydrophila in rainbow trout (Oncorhynchus mykiss Walbaum) fingerlings. Methods and Results: Rainbow trout fingerlings were fed with 0 mg (= controls), 1·875 mg, 3·75 mg, 7·5 mg and 15 mg of LPS per 100 g of commercial feed for 14 days before experimental challenge with A. hydrophila. The results revealed a reduction in mortalities to 5% in the two lowest doses and 15% in the group, which received 15 mg LPS per 100 g of feed, compared with 45% mortalities in the control. LPS exerted a powerful oxidative burst effect and was a potent mediator of phagocytic, lysozyme, bactericidal and antiprotease activities and total protein. However, whereas there were increases in specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER) in LPS‐treated fish, the data were not significantly (P > 0·05) different. Conclusions: LPS was effective at preventing disease caused by A. hydrophila and in stimulating the innate immune response of rainbow trout. Significance and Impact of the Study: The results of this study highlight the role of LPS in fish disease control.     

Azadirachta indica (neem) leaf dietary effects on the immunity response and disease resistance of Asian seabass,Lates calcarifer challenged with Vibrio harveyi

The present study was aimed to address the possible evaluation of Azadirachta indica (neem) leaf-supplemented diets on innate immune response in Asian seabass, Lates calcarifer fingerlings against Vibrio harveyi infection. Fish were fed for two weeks diets containing six graded levels of neem leaf at 0 g, 1 g, 2 g, 3 g, 4 g and 5 g per kg feed. Fish fed neem leaf-supplemented diet displayed significant differences (p < 0.05) in weight gain, specific growth rate (SGR) and feed conversion ratio (FCR) compared to the control group fed without neem leaf-supplemented diet. Various innate immune parameters were examined pre-challenge and post-challenge. Fish was injected intraperitoneally with a lethal dose of V. harveyi containing 10⁸ cells mL^?1. Supplementation of neem leaf diet significantly increased phagocytic activity, superoxide anion production, serum lysozyme, serum bactericidal activity, serum anti-protease activity throughout the experimental period when compared with the control group. Dietary doses of neem leaf diet significantly influenced the immune parameters, haematological parameters and blood biochemical indices of treated fish. The results suggested that fish fed neem leaf-supplemented diet improved the immune system and increased survival rate in L. calcarifer fingerlings against V. harveyi infection.     

Growth and survival of tench larvae fed under different feeding strategies

Two feeding experiments were conducted to evaluate the growth and survival rates of tench Tinca tinca L. larvae when initially fed with a combination of three different brands of Artemia nauplii under two conditions: (A) in the laboratory and (B) on a commercial farm. At the same time, a protozoan culture of the freshwater ciliate Colpoda cucullus was additionally tested in one of the experiments to possibly enhance the initial hunting behaviour of the larvae. The larvae were fed every 4 h from the onset of exogenous feeding up to 14 days of age. Three types of commercial Artemia products, mainly differing in size and high unsaturated fatty acid (HUFA) content, were used. One group was fed with C. cucullus as a starter. The different combinations of Artemia nauplii were used to evaluate possible effects on larval growth. The final growth at 26.3 °C, expressed in length and weight, did not show significant differences, suggesting the use of the most economically feasible Artemia strain studied. The experiments confirmed that using smaller prey during the first 2 days of feeding increases their survival rate, although the mean final survival rate was high (89%). In the experiment carried out at the commercial fish farm facilities, experimental groups were also fed with Artemia nauplii, using the EG type either enriched or not enriched with HUFA. Again, one of the groups was offered the ciliate C. cucullus as initial feed. Final growth showed significant differences when using Colpoda culture as a starter feed, although this test resulted in the lowest survival rate (69%), indicating that further studies on the management of its culture should be undertaken to improve the applicability of the technique. The mean final survival rate was 83%.     

Growth and contribution of stocked channel catfish,Ictalurus punctatus (Rafinesque, 1818): the importance of measuring post‐stocking performance

In this study it was sought to quantify post‐stocking growth, survival, and contribution of advanced size (178 mm total length [TL]) channel catfish Ictalurus punctatus fingerlings, something rarely done. Channel catfish populations were evaluated before (May 2010) and after (May to August 2011 and 2012) stocking. Relative abundance, stocking contribution, and growth were different (P < 0.05) in the two study impoundments (lakes Lone Chimney and Greenleaf, Oklahoma). For fish stocked in Lake Lone Chimney, stocking contribution was lower (3–35%), and average length and weight of stocked fish by age‐2 reached 230 mm TL and 85 g, whereas the stocking contribution (84–98%) and growth in length (340 mm TL) and weight (280 g) were higher by age‐2 in Lake Greenleaf. Given these unambiguous differences of post‐stocking performance, benchmark metrics that represent population‐level information such as relative abundance and average length and weight of the sample masked these significant differences, highlighting the importance of marking hatchery‐fish and then following them through time to determine the effectiveness of stocking. These results suggest that stock enhancement programmes would benefit from studies that quantify post‐stocking performance of hatchery fish.     

Biological evaluation of frozen zooplankton as food for milkfish (Cbanoschanos) fry

Milkfish fry with an average standard length and weight of 13.88 mm and 3.95 mg, respectively, were reared for 30 days using live and frozen Moina macrocopa and Brachionusplicatilis at feeding densities of 10–20 individuals per ml. Growth, survival and yield were used as indicators of the overall performances of the various treatment groups. Fry fed live M. macrocopa showed gains (both length and weight), growth and survival rates and yields significantly higher than fry fed with other treatment groups (P < 0.05). However, significant reductions in growth and survival rates resulted when fry were fed frozen M. macrocopa. On the other hand, there were no significant differences in growth and survival rates (P < 0.05) in fry fed live or frozen B. plicatilis. The results of the current study showed that although milkfish fry could be grown successfully using B. plicatilis, feeding with live Moina significantly improved growth, survival rate and yield (P lt; 0.05). Frozen Moina was found to be unsuitable as a feed for rearing milkfish fry because it reduced growth rates and increased mortality. Comparisons between live and frozen rotifers have proven the suitability of frozen rotifers as feed for rearing milkfish fry. By freezing surplus rotifers this would permit short term storage in anticipation of high hatchery demand and overcome any unpredictable failures with live cultures.     

Effectiveness of phytase pre-treatment on growth performance,nutrient digestibility and mineral status of common carp (Cyprinus carpio) juveniles fed Moringa by-product based diet

Several anti-nutritional substances are found in plant derivatives for example phytate, that make the nutrients and minerals unavailable to fish, hence leading to poor growth performance. Presence of the anti-nutrient factor such as phytate is a chelated compound and need enzyme for its breakdown and availability of nutrients to improve fish growth. This research work was performed to check the improvement of overall performance of Cyprinus carpio fingerlings by the help of phytase addition in Moringa oleifera by- products based diet. Combination of Moringa seed meal and Moringa leaf meal was utilized as test ingredient to formulate seven test feeds, containing graded levels of phytase (0, 500, 650, 800, 950, 1100 and 1250 FTU kg⁻¹). In feeding trial of 70 days, fingerlings were given feed two times in a day at the rate of 4% of wet weight of their bodies and faeces were collected. According to current results, it was found that growth performance parameters i.e. weight gain; 25 g, specific growth rate; 1.67 and feed conversion ratio; 1.10 were improved to maximum at 950 FTU kg⁻¹. Digestibility of nutrients (crude protein; 73%, crude fat; 71% and gross energy; 67%) and minerals absorption was also maximum (Ca; 70%, Zn; 66%, K; 74%, Mn; 66% and P; 71%) at 950 FTU kg⁻¹. Lowest growth efficiency, nutrient digestibility and mineral absorption were observed in fingerlings fed at control diet (0 FTU kg⁻¹). Results of the current study, proved that 950 FTU kg⁻¹ is the most optimum level of phytase to formulate economical and ecofriendly feed for improved growth of C. carpio fingerlings as it decreases the discharge of minerals and nutrients in water bodies.     

Effect of Dietary Incorporation of Dry-Powdered Water Hyacinth (<Emphasis Type="Italic">Eichhornia crassipes</Emphasis>) Meal on Growth and Digestibility of <Emphasis Type="Italic">Labeo rohita</Emphasis> Fingerlings

Keeping the importance and search for unconventional feed resources and/or standardizing their level of incorporation in mind, we incorporated dry-powdered water hyacinth (Eichhornia crassipes) meal in feeds and studied its effect on growth and digestibility in Labeo rohita fingerlings. Five feeds with 30 % crude protein level were formulated using Eichhornia meal (EM) at 0 (control), 5 (EMF1), 10 (EMF2), 15 (EMF3) or 20 % (EMF4) of the diet replacing rice bran by equal proportions. Three hundred fingerlings (7.40 ± 0.05 cm; 5.27 ± 0.12 g) were distributed into fifteen tanks (200 l capacity) and fed the experimental diets for 60 days. In the last 30 days, digestibility studies were conducted using 0.5 % chromic oxide as an external marker in feed. At 10 % inclusion of EM, the experimental fish showed the highest weight gain percent (WG%), specific growth rate (SGR), protein efficiency ratio and apparent net protein utilization with lowest feed conversion ratio. Whereas the growth performance at 15 % inclusion level was comparable with the control and further increase to 20 % level of EM showed reduced growth responses but the feed was fairly palatable to the fish. Lower digestibility was also observed in EMF4 group. It is concluded that EM can be included at 15 % level in the feed of L. rohita fingerlings without adversely affecting the growth, dry matter and nutrient digestibility. However, economic feasibility of this feedstuff needs to be analyzed to see whether the reduced cost of diets would compensate for the reduced performance of fish at higher inclusion levels.     

Effect of feeding under-year zander (Sander lucioperca) on size, body mass and body composition before and after wintering

Zander (Sander lucioperca) is one of the most important fish species in the German inland fishery. As a pelagic predator, zander is able to regulate populations of small cyprinids and perch and is therefore used in ‘top‐down’ projects to directly control the food web. At present, natural waters are mainly stocked with one‐summer‐old zander from pond hatcheries; however, such fish are poor stocking material due to low survival rates, presumably because of their small size. Two groups of 50‐day‐old zander fingerlings reared in a recirculation system (T = 23 °C) were used. For 90 days one group (FG 1) was fed with a commercial dry feed (Trouvit Pro Aqua Brut), and the other group (FG 2) was fed with chironomides (Chironomus spp.). The fat content of the dry feed was increased with fish oil supplemented up to 22%. After the rearing period the FG 1 fishes attained the largest size and fat content. A pond with a surface of 667 m² and a mean depth of 0.8 m was stocked with 24‐tagged zander (12 of each feeding group) for wintering. After the winter period of 176 days, survival rate of each feeding group was 83.3%. The fatty acid composition in the membrane lipids of group 2 changed dramatically. In contrast to previous investigations, presented results indicate that the survival rate is not influenced by fish size (weight and length). The crucial factors for high survival rates of zander during wintering are the crude tissue fat content (>5%) and its fatty acid composition.     

Food and feeding habits of Mirogrex fingerlings in Lake Kinneret (Israel)

The food composition of the fingerlings (13–41 mm TL) of Mirogrex terraesanctae terraesanctae was studied on specimen collected at four stations in Lake Kinneret. The fingerling feed mostly on pelagic zooplankters and zoobenthic forms whereas algae were found in the intestines in low biomass. The number of zooplankton organisms in the guts of the fingerling that were sampled during June–August was higher by 234% than in fingerlings that were sampled during March–April. The role of sardines fry in the Kinneret ecosystem is discussed.     

Effect of feeding different protein to energy (P/E) ratios on the growth performance and body composition of Oreochromis niloticus fingerlings

This study evaluated the growth performance and body composition of Oreochromis niloticus fingerlings (average initial weight 16.53 ± 0.44 g) fed 9 experimental diets (A, B, C, D, E, F, G, H and I) containing three different levels of protein (26, 31 and 36 g 100 g^?1) at three different gross energy (GE) levels (16, 19 and 22 MJ kg^?1) for a period of 64 days. Significant differences were observed in the feed consumption, body weight gain, specific growth rate (SGR), condition factor (k), feed conversion ratio (FCR), protein efficiency ratio (PER), net protein retention (NPR) and apparent net energy retention (ANER) values of fish when the energy level of diet was increased at different protein levels. The maximum weight gain, SGR and k were observed on diet F containing 36% protein and an energy level of 19 MJ kg^?1 of dry feed with a protein to energy (P/E) ratio of 18.96 (g protein MJ^?1 GE). A further increase in the energy content of the diet (22 MJ kg^?1) at the same protein level (Diet I) did not produce any improvement in the growth performance. Lowering the energy level at the same protein level significantly affected the growth performance. Fish fed diet B containing 31% protein and a lower energy level of 16 MJ kg^?1 with the same P/E ratio of 18.61 as diet F showed significantly lower weight gain and growth performance than diet F. Diets E and H containing 31% crude protein at all three energy levels produced similar results as diet B. The poorest FCR was observed when the diet contained both lower levels of protein and energy. Fish fed diet G, containing 26% protein at high energy level (22 MJ kg^?1), showed the best PER and NPR values. The PER and NPR were the poorest on diet C containing 36% protein at low energy level (16 MJ kg^?1). The body moisture content at all protein levels decreased (P < 0.05) with the increasing level of dietary energy whereas the body fat content increased (P < 0.05). Similar trends were observed in the body ash and energy content. Increasing the dietary energy content at lower protein levels did not show any difference (P > 0.05) in body protein content. Our results indicated the optimum P/E ratio for O. niloticus as 18.96 g protein per mega joule of gross energy at 36% dietary protein level and a dietary gross energy value of 19 MJ kg^?1.     

Nutritional evaluation of fermented black gram (Phaseolus mungo) seed meal in compound diets for rohu, Labeo rohita (Hamilton), fingerlings

Six isonitrogenous (approximately 35% crude protein) and isocaloric (approximately 4.0 kcal g⁻¹) diets were formulated incorporating raw and fermented black gram, Phaseolus mungo, seed meal at 20%, 30% and 40% levels by weight into a fishmeal‐based control diet fed to rohu, Labeo rohita, fingerlings (mean weight, 1.81 ± 0.21 g) for 80 days for a study of fish performance. A particular bacterial strain (Bacillus sp.) isolated from the intestine of adult common carp (Cyprinus carpio) reared in the wild having significant amylolytic, cellulolytic, lipolytic and proteolytic activities was used for fermentation of seed meal for 15 days at 37 ± 2°C. Fermentation of P. mungo seed meal was effective in significantly reducing the crude fibre content and antinutritional factors such as tannins and phytic acid, and enhancing available free amino acids and fatty acids. In terms of growth, feed conversion ratio and protein efficiency ratio, the 30% fermented black gram seed meal incorporated diet resulted in a significantly (P < 0.05) better performance of rohu fingerlings. In general, growth and feed utilization efficiencies of diets containing fermented seed meal were superior to diets containing raw seed meal. The apparent protein digestibility (APD) values decreased with increasing levels of raw seed meal in the diets. The APD for raw seed meal was lower at all levels of inclusion in comparison to those for the fermented seed meals. The maximum deposition of protein in the carcass was recorded in fish fed the diet containing 40% fermented seed meal. The results indicate that fermented black gram seed meal can be incorporated in carp diets up to the 30% level compared to the 10% level of raw seed meal.     

Food selection by Labeo Rohita (Ham.) and its feeding relationship with other major carps

Selectivity of food byLabeo rohita (Ham.) was studied in a stocking pond (Moat), by calculating an Electivity index (E) for each food organism as described byIvlev (1961). It was found thatL. rohita was definitely selective in its feeding. In case of fingerlings, there was a strong selection for zooplanktonic organisms (Arcella andDifflugia among protozoans,Keratella andBrachionus among rotifer andDaphnia andCyclops among crustaceans) and smaller algae (Cosmarium andClosterium among desmisd,Euglena andVolvox among phytoflagellates and algal spores and zygotes) while most of the phytoplanktonic organisms, belonging to green algae, diatoms and blue green algae, were avoided. In case of adults, a strong negative selection was observed for all zooplanktonic organisms and a strong positive selection for most of the green algae and diatoms (Ankistrodesmus, Zygnema, Spirogyra, Selenastrum, Pediastrum, Scenedesmus, Tetraspora, Stephanodiscus, Naviculla, Diatoma, Synedra andNitzchia). However, all blue green algae were avoided.The feeding relationship ofL. rohita with other major carps,Cirrhina mrigala (Ham.) andCatla catla (Ham.) was studied in two different habitats, pond and river. It was observed that in both habitats all three species were found to feed on almost similar types of food organisms, but the quantity of any food item eaten by adults differed markedly from one species to another and the food items which were dominant in one species, were of secondary importancce for the other two species. The adults ofL. rohita were found to feed mainly on phytoplankton and macrovegetation, the main food of adultC. mrigala was decayed organic matter, sand and mud supplimented by plankton, while the food of adultC. catla was chiefly composed of zooplankton, and some phytoplankton. Hence there was no true identity of feeding habits between the adults of any two species. However, there was an indication of competition for food between the fingerlings of all three species, because all of them feed mainly on zooplankton (Crustaceans, rotifers and protozoans). However, such feeding habits lasted a very short time only and as the fishes grew, their feeding habits diverged.     

不同年龄香果树种子雨和种子库及其更新特征

对宝天曼自然保护区香果树种子雨、土壤种子库进行了观测,并进行不同微生境播种实验,研究其种子萌发及幼苗生长动态。结果表明:(1)不同龄级香果树种子雨持续时间及其高峰期有所不同,种子雨强度存在极显著差异。(2)20~50龄级香果树的种子饱满率、土壤种子库中种子密度均显著低于其他龄级,但其不同类型种子的水平和垂直分布规律一致;大约80%的香果树种子在其萌发前消失,剩余种子中以霉烂种子密度最高(9.81粒·m-2),饱满种子密度最低(1.94粒·m-2)。(3)野外育苗实验表明,不同龄级香果树所产饱满种子的萌发率及幼苗存活率差异不显著,其种子萌发率约为16.93%,但仅有3.86%的幼苗寿命超过5个月;不同微生境对香果树幼苗存活率产生显著影响,林窗是其最适宜微生境。研究认为,人工采集香果树种子,于次年4月份在原生境下播种;清理母树冠下和冠缘的地被物,增加林缘空地地被物覆盖度,以减少香果树种子的损失,改善香果树种子萌发和幼苗生长的光照条件,以利于幼苗根系的生长,促进香果树的自然更新。     

Stocking rate and organic waste type affect development of three Chrysomya species and Lucilia sericata (Diptera: Calliphoridae): Implications for bioconversion

Fly larvae can be used effectively to reduce various organic waste types and produce value-added products, including protein as an ingredient in livestock feeds and oil for biodiesel production. However, fly development on different waste types may cause differences in growth rate and the body composition, which can further be influenced by fly species and their stocking rate. This study explored the impact of different waste types (kitchen waste, abattoir waste and swine manure) and larval stocking rate on growth and body composition of four blowfly species, Chrysomya chloropyga (Wiedemann), Chrysomya megacephala (Fabricius), Chrysomya putoria (Wiedemann) and Lucilia sericata (Meigen). First-instar larvae (20, 50 or 100), less than 3 hr old, were placed on 100 g of each waste type. Pre-pupal mass at commencement of post-feeding larval dispersal, time to onset of dispersal, survival and nutrient reserves were determined for each species, stocking rate and waste type. Our results revealed that larvae fed kitchen and abattoir waste had significantly higher dry mass, crude protein and lipid content compared with those fed swine manure. Higher survival rate was observed with increasing larval stocking rate. We provide important information to guide the mass production of high-quality nutrient-rich larvae and recommend C. putoria, which is versatile and effective on a range of waste products, as well as high in protein and lipids. The implications for waste management are discussed.     

Dietary protein requirement of fingerling sterlet sturgeon (Acipenser ruthenus)

Although sterlet sturgeon is a valuable candidate for aquaculture development, information regarding the nutrient requirements of this species is limited. Therefore, in this study, we aimed to determine the optimum protein level required by sterlet sturgeon fingerlings. Groups of fingerlings (mean initial body weight ± SD: 7.02 ± 0.02 g; N = 3) were assigned to one of the six dietary protein levels at 29.1%, 39.1%, 46.8%, 49.2%, 53.7%, and 57.6% on a dry matter basis. Isocaloric (18.3 ± 0.2 kJ GE/g diet) semi-purified diets were prepared using white fish meal and casein as the major sources of protein. After the 8-week feeding trial, the fingerlings fed the 49.2% protein diet exhibited the best results in terms of weight gain, feed efficiency, and whole-body nutrient composition (crude protein, crude lipid, gross energy, and amino acid contents), whereas those fed the 53.7% and 57.6% protein diets showed poor performance. Application of the two-slope straight broken-line and quadratic models on the dataset of weight gain revealed the optimum protein level to be 45.9% and 44.1%, respectively. Based on the model selection criteria, including the adjusted coefficient of correlation and corrected Akaike information criterion, the protein level (44.1%) estimated using the quadratic model was more accurate than that obtained using another model (45.9%). Taken together, 44.1% protein level (18.3 kJ GE/g diet on dry matter basis) resulted in the optimal growth of the sterlet sturgeon fingerlings (initial body weight: approximately 7 g).     

不同人工饲料对刀鲚幼鱼生长、血清生化指标及脂质代谢酶活性的影响

试验选择体长、体质量基本一致的6月龄刀鲚,分别投喂日粮1(人工配合软颗粒饲料)、日粮2(人工配合饲料与鱼油混合的软颗粒饲料)及日粮3(人工配合缓沉硬颗粒料)3种配合饲料60 d,探讨不同人工饲料对刀鲚幼鱼生长性能、血清生化指标及脂质代谢酶活性的影响.结果表明: 日粮2组和日粮3组的幼鱼体质量、体质量增长率、特定生长率和肥满度显著高于日粮1组;日粮3组的饵料系数显著低于日粮1组和日粮2组;各组间体长、体长/体高、体长/体厚、肝体比及脏体比等生长指标及总蛋白、白蛋白、血糖、胆固醇和甘油三酯等血清生化指标均无显著差异;日粮1组的肉碱软脂酰基转移酶-Ⅰ(CPT-Ⅰ)含量显著高于日粮2组和日粮3组;日粮2组的肉碱软脂酰基转移酶-Ⅱ(CPT-Ⅱ)含量显著低于日粮1组和日粮3组;各组间淀粉酶、胃蛋白酶、脂肪酶活性及脂蛋白脂酶(LPL)和乙酰辅酶A羧化酶(ACC)含量均值无显著差异.表明日粮中添加多不饱和脂肪酸有利于刀鲚幼鱼的生长,缓沉饲料的利用效率最高,适合于刀鲚幼鱼驯养阶段使用.