共查询到20条相似文献,搜索用时 32 毫秒
1.
Yi Hu Gang Yang Zhaolin Li Yajun Hu Lei Zhong Qiubai Zhou Mo Peng 《Aquaculture Research》2018,49(6):2108-2118
This study was conducted to evaluate the effect of dietary taurine supplementation on growth, immunity and resistant to dry stress of rice field eel (Monopterus albus) fed low fish meal diets. Six isonitrogenous and isolipid diets (32% fish meal) supplemented with six taurine concentrations (0, 0.3, 0.6, 0.9, 1.2 and 1.5 g/kg; designated as T0, T0.03, T0.06, T0.09, T0.12 and T0.15 groups, respectively) were prepared. A diet including 42% fish meal (FM group) was also included as a reference. The results showed that specific growth rate (SGR) in FM group was significantly higher than that in lower fish meal treatments. SGR significantly increased and slowly decreased with the increase in taurine supplementation level. Lipase activity value in intestine of M. albus fed FM diet was maximum, and with the increase in taurine supplementation level, lipase activity significantly increased and slowly decreased. The FM group had relative higher total antioxidant capacity (T‐AOC) content, catalase (CAT), total superoxide dismutase (T‐SOD), and lyzozyme (LZM) activities in serum than the other groups. With the increase in dietary taurine supplementation level, the CAT, T‐SOD, T‐AOC and LZM activities in serum significantly increased and then decreased. In the dry stress experience, the adrenaline (AD), cortisol (COR), glucose (GLU), total cholesterol (CHOL), and malondialdehyde (MDA) concentrations, T‐AOC content, CAT and T‐SOD activities in serum of M. albus in the four groups first increased and reached the peak at 2 hr, and then decreased under air‐exposure stress. Compared to the FM group, T0.15 group had relative higher T‐AOC content, CAT and T‐SOD activities, and lower AD, COR GLU, TC and MDA concentrations. 相似文献
2.
Jinhua Xiang Lu Qin Di Zhao Fan Xiong Guitang Wang Hong Zou Wenxiang Li Ming Li Kaibo Song Shangong Wu 《Aquaculture Nutrition》2020,26(3):693-704
Housefly larvae are widely used in livestock breeding industry as a functional feed additive with immunostimulant properties, but their effects as dietary additive are poorly understood in aquatic animals. We conducted an eight‐week rearing experiment to determine the effects of housefly larvae (complete) on growth performance, immunity and intestinal microbiota in swamp eel (Monopterus albus). Dietary treatments were as follows: BD (control group, fed a basal diet), FL7 (fly larvae supplemented once weekly, i.e., 6‐day basal diet, 1‐day larvae) and FL3 (larvae supplemented every third day, i.e., 2‐day basal diet, 1‐day larvae). The final body weight (FBW) and weight gain (WG) of the FL3 group significantly (p < .05) increased. Hepatosomatic index (HSI) and malondialdehyde (MDA) concentration significantly decreased in FL3 and FL7 groups. The expression of immune‐related genes was also influenced by the fly larvae. Aeromonas hydrophila challenge experiment produced higher survival rates in the FL3 (75%) and FL7 (37.5%) groups. Fly larvae also affected the composition of gut microbiota: the abundance of Bacteroides increased, and Pseudomonas decreased, in the treatment groups. Dietary supplementation of housefly larvae has positive effects on the growth and immunity of swamp eel, and we suggest supplementing housefly larvae every third day. 相似文献
3.
Lihai Xia Panpan Han Xiaoli Cheng Youshen Li Chuwen Zheng Hanwen Yuan Wenbing Zhang Qiaoqing Xu 《Aquaculture Research》2019,50(10):2978-2985
More and more diseases were occurred in the aquaculture of Asian swamp eel. Bacterial isolates were collected from the pathogenic organs of diseased Asian swamp eels. A dominant strain, Aeromonas veronii JL‐01, was isolated and identified from the liver and intestine tissue of diseased Asian swamp eels. The symptoms of fish infected artificially with A. veronii were the same as those observed under natural infection. The mortality rate was 40%–80% and infected Asian swamp eels died 2–3 days after infection. Drug sensitivity tests showed that the isolated bacterium was highly sensitive to seven kinds of antibiotics, including cephalosporins, aminoglycoside, quinolones, tetracyclines (except Tetracycline), pheniclos, nitrofurans and sulfonamides. The bacterium was resistant to penicillins (except Piperacillin), macrolides, polypeptides and lincomycin. The histological changes in Asian Swamp Eel induced by A. veronii infection mainly occurred in the liver, intestines and kidney. A. veronii showed strong pathogenicity towards the Asian swamp eel, causing tissue damage and death. Gentamycin, doxycycline and sulfamethoxazole could be used for preventing and treat this disease. 相似文献
4.
Huamei Yue Xianquan Huang Rui Ruan Huan Ye Zhong Li Chuangju Li 《Aquaculture Research》2020,51(1):400-409
A 12‐week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole‐body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%. 相似文献
5.
Andre P. Seale;Ke Cao;Ryan J. A. Chang;Tyler R. Goodearly;G. H. T. Malintha;Reilly S. Merlo;Taylor L. Peterson;Jasmine R. Reighard; 《Reviews in Aquaculture》2024,16(3):1351-1373
The life history, distribution and diversity of fishes are largely influenced by environmental salinity. Changes in salinity affect a range of physiological processes including metabolism, nutrition, reproduction and growth. Therefore, fish can be conditioned to environmental parameters most suitable for production, where distinct traits are optimised through species-specific manipulation of salinities. The primary purpose of this review is to summarise the existing literature on the salinity tolerance of aquacultured fish. The various experimental approaches for determining salinity tolerance are compared, along with summarised information for key species employed in aquaculture, including their native distributions, life history stage and optimal salinity for survival and growth. The implications for production were assessed by considering the effects of salinity on growth, reproduction, management, disease mitigation and marketability. 相似文献
6.
I. Plaut 《Fish physiology and biochemistry》1998,19(2):181-188
This study compares osmoregulatory capabilities of two closely related blennies inhabiting different habitats: Salaria pavo which inhabits marine rocky coasts in the Mediterranean and the eastern coasts of the Atlantic Ocean, and Salaria fluviatilis which inhabits freshwater habitats around the Mediterranean, both in rivers connected to the sea and in lakes that for a long time have been separated from the sea. Fishes for this study were collected in Lake Kinneret (Sea of Galilee) (S. fluviatilis) and Habonim beach, Israel, East Mediterranean coast (S. pavo). Both species tolerated salinities of 0, 40 and 100% seawater (0, 14.4 and 36 ppt sea salt respectively). Acclimation for a period of three months to freshwater (S. pavo) and seawater (S. fluviatilis) did not affect survival rates. After acclimation, total body water content of S. fluviatilis remained unaffected by experimental salinities but increased in S. pavo as salinity decreased. The hematocrit of both species increased as salinity increased. Plasma osmolality and Na+ concentrations were unaffected by experimental acclimation salinities in S. fluviatilis, but significantly decreased in S. pavo as salinity decreased. The results indicate that S. fluviatilis is able to osmoregulate both in fresh and seawater. S. pavo, living in seawater, while able to tolerate freshwater environment, fails to maintain constant extracellular fluid concentration. It is suggested that S. pavo, or its marine ancestor, has euryhaline capabilities that enabled it to invade freshwater habitats. S. fluviatilis, as the evolutionary result of this invasion, is thus better adapted to freshwater environment, but did not lose its ability to live in seawater. 相似文献
7.
Huamei Yue Xianquan Huang Rui Ruan Huan Ye Zhong Li Chuangju Li 《Aquaculture Nutrition》2021,27(1):63-76
Five isonitrogenous and isocaloric diets containing dietary lipid concentrations from 71.90 to 142.70 g/kg were formulated and fed to Chinese rice field eel Monopterus albus fingerlings (5.00 ± 0.50 g). The highest values of weight gain, specific growth rate (SGR), together with the lowest feed conversion ratio (FCR) were found in fish fed with 89.10 g/kg lipid diet. Fish fed with 71.90 g/kg diet (F1) had higher hepatosomatic index, viscerosomatic index and whole‐body crude lipid than fish in the other four treatments (p < .05). Plasma concentration of triacylglycerol and the activity of alanine aminotransferase were also higher in fish fed with F1 diet. Whole‐body fatty acid profile varied exclusively, but with a stable value of n?3/n?6 ratio. Gas chromatography–mass spectrometry‐based metabolomics identified eighteen differential metabolites (including idose, alanine, glutamic acid, serine and hypotaurine) in liver affected by dietary lipid content using PLS‐DA analysis. The subsequent pathway enrichment revealed ten affected pathways, with the top three pathways being glycine, serine and threonine metabolism; starch and sucrose metabolism; and D‐glutamine and D‐glutamate metabolism. The broken‐line model of SGR suggested that a dietary lipid concentration of 83.50 g/kg was appropriate for M. albus fingerlings. 相似文献
8.
9.
Salinity tolerance and growth of Japanese flounder Paralichthys olivaceus at different developmental stages were evaluated, including newly hatched larvae (nhl), yolk sac larvae (ysl), oil droplet larvae (odl), post oil droplet larvae (podl), premetamorphic larvae (preml) and prometamorphic larvae (proml), at 11 salinities from 5 to 55 g L?1 for 96 h. The ontogenesis during the early life of P. olivaceus was investigated under hatchery salinity 35 g L?1. The results showed that suitable salinities for nhl, ysl, odl, podl, preml and proml larvae were 10 to 25 g L?1, 10 to 30 g L?1, 20 to 30 g L?1, 30 g L?1, 10 to 30 g L?1, 15 g L?1, respectively, demonstrating an ontogenetic variation of salinity tolerance. The salinity tolerance of nhl, ysl, preml was higher than that of odl, podl and proml. The ysl and preml larvae displayed wide salinity tolerances. The present findings demonstrate that the suitable salinity for larviculture of P. olivaceus is 20–25 g L?1 before the depletion of oil droplet; after that, higher salinity (30 g L?1) should be ensured for the post‐oil droplet larvae; the premetamorphic larvae can be cultured at a wide salinity range (10–30 g L?1), and the metamorphosed larvae should be reared at salinity about 15 g L?1. 相似文献
10.
To evaluate environmental impacts of yellowtail culture and to examine the efficiency of the sea cucumber Apostichopus japonicus in reduction of waste loading, surface sediments were sampled and A. japonicus were cultured at a yellowtail farm in Owase Bay, Japan. Waste feed‐ and faeces‐derived organic matter (WOM, FOM) in sedimentary organic matter (SOM) was estimated based on the δ13C and δ15N of the fish feed (?21.7‰, 9.2‰), yellowtail faeces (?20.6‰, 6.2‰) and SOM reference (?24.4‰, 4.4‰). Small WOM (0–22% in SOM) but substantial FOM (28–61%) loadings in the fish farm area and high sulphide concentrations in the sediments (1.0 mg g?1) suggest that reduction in the fish stocks or mitigation of the faeces should be considered. A. japonicus juveniles were cultured in three cages deployed below a pen and growth was assessed after three different periods (62, 107, 181 days). A. japonicus grew well during the first 107 days (daily specific growth rate, 3.7%) and their survivorship was high (80–90%). Growth ceased after 107 days, probably due to fouling on the cages. The δ13C and δ15N of their hypothetical diet (–19.7‰, 5.5‰) were close to the FOM values, suggesting assimilation of FOM. 相似文献
11.
Jade Irisarri Alhambra M Cubillo María José Fernández‐Reiriz Uxío Labarta 《Aquaculture Research》2015,46(8):1988-2002
Fish farming releases extensive amounts of particulate organic waste that can be exploited by bivalves in integrated culture. We tested if mussels Mytilus galloprovincialis cultured at two depths (1 and 6 m) in a raft, moored 170 m from a fish farm had greater growth than bivalves held 550 m from the fish cages. Mussel growth was monitored monthly, covering the second phase of the culture, from thinning‐out to harvest (March to November 2011). We also studied if fish solid and dissolved nutrients increased the organic content of the seston and chlorophyll‐a levels near the fish cages through weekly samples. Results showed no differences in seston, chlorophyll and physiochemical characteristics of the water among rafts. Maximum growth and Condition Index (CI) occurred during spring–summer (April–August), when mussels had access to greater food quality and quantity. Mussels cultivated close to the cages showed similar shell length, weight and CI compared with mussels distant from the fish farm. Average shell length, meat dry weight and CI at harvest were 76.31 mm, 2.51 g and 23%. Bivalves cultured distant from the fish cages displayed 26% higher biomass than the other raft at the end of the experiment. Differences in biomass were explained by the significantly higher recruitment of mussel seed observed at the raft distant from the fish cages from June to November. The lack of a significant enhancement in growth of the bivalves cultured next to finfish is discussed. 相似文献
12.
Ali Al‐Hisnawi Einar Ringø Simon J Davies Paul Waines Graham Bradley Daniel Lee Merrifield 《Aquaculture Research》2015,46(12):2962-2971
A study was conducted to characterize the autochthonous gut microbiota present in the pyloric caeca (PC), anterior mucosa (AM) and posterior mucosa (PM) of brown trout (Salmo trutta). Total viable counts (TVC) bacterial populations were enumerated using tryptone soy agar, lactic acid bacteria (LAB) levels were enumerated on de Man, Rogosa & Sharpe agar and PCR‐DGGE was employed as a culture‐independent method to assess the total communities. No significant differences were observed between the different gut regions for TVC or LAB levels. 16S rRNA sequencing identified all LAB isolates as Carnobacterium maltaromaticum. In contrast, the TVC community was more diverse; Firmicutes and Bacteroidetes were present but all gut regions were dominated by Proteobacteria, accounting for 88.4–92.6% of the communities. Citrobacter freundii was the dominant species and accounted for 51.0–57.8% of the isolates. Complex bacterial communities were observed using PCR‐DGGE and a trend towards the reduction in the number of operational taxonomic units (OTUs), microbial richness and microbial diversity was observed from the PC to the PM. The similarity between regions was low (52–68%) and cluster analysis revealed that the communities grouped into two distinct clusters; one dominated by the PM samples and the other contained the AM and PC samples. OTUs from the DGGE were identified as members of the phyla Proteobacteria and Firmicutes. Many OTUs were detected in all gastrointestinal regions, however, some OTUs showed regional specialization. Further studies are required to elucidate the activity of these genera in situ and how their actions impact the host. 相似文献
13.
Hongyu Liu Beiping Tan Jinfang Yang Shuyan Chi Xiaohui Dong Qihui Yang 《Aquaculture Research》2016,47(2):540-553
The synchronous effects of aqueous Na/K and dietary potassium (K+) on growth and physiological characters was studied on the Pacific white shrimp (Litopenaeus vannamei) reared in low‐salinity well water (4 ppt) for 8 weeks with initial weight of 0.28 ± 0.01 g. Three practical diets were formulated with supplement of 0, 0.3%, 0.6% K+ which contained 1.29 g/100 g, 1.60 g/100 g, 1.93 g/100 g K+ respectively. The supplement of K+ to the low‐salinity well water was 10, 20, 40 mg L?1 which formed Na:K ratios of 42:1, 33:1, 23:1 respectively. Results showed that when the aqueous Na:K ratio was 42 and dietary K+ was 1.93 g/100 g K+, the WGR and PER of L. vannamei were the highest and the FCR was lower than that of others (P < 0.01). Supplement of K+ into well water and diets did not showed significant effects on haemolymph ammonia‐N, uric acid, urea content (P > 0.05), but had a extremely significant effect on arginase activity and Cl? concentration (P < 0.01). Moreover, similar results were observed in alkaline phosphatase (ALP), bacteriolytic activity (LSZ) and respiratory burst activity (O2?) (P < 0.05). These results suggested that aqueous Na/K in the low‐salt well water and dietary K had significant synergistic effect on the growth, osmoregulation and immunity of L. vannamei. Concluded from the growth performance, nitrogen metabolism, osmoregulation and immunity, as the Na/K in the low‐salinity well water descended from 42 to 23, the requirement of dietary K+ was also decreased. 相似文献
14.
C.C. Piccinetti F. Tulli N.E. Tokle G. Cardinaletti I. Olivotto 《Aquaculture Nutrition》2014,20(1):90-100
Considering the well‐known problems arising from the use of rotifers and Artemia as live prey in larval rearing in terms of fatty acid deficiencies, the aim of this study was to evaluate a partial or complete replacement of traditional live prey with preserved copepods during the larviculture of gilthead sea bream (Sparus aurata). Sea bream larvae were randomly divided into 4 experimental groups in triplicates: group A larvae (control) fed rotifers followed by Artemia nauplii; group B fed a combined diet (50%) of rotifers–Artemia and preserved copepods; group C fed rotifers followed by preserved copepods; and group D fed preserved copepods solely. Survival and biometric data were analysed together with major molecular biomarkers involved in growth, lipid metabolism and appetite. Moreover, fatty acid content of prey and larvae was also analysed. At the end of 40 days treatment, a stress test, on the remaining larvae, was performed to evaluate the effects of different diets on stress response. Data obtained evidenced a positive effect of cofeeding preserved copepods during sea bream larviculture. Higher survival and growth were achieved in group B (fed combined diet) larvae respect to control. In addition, preserved copepods cofeeding was able to positively modulate genes involved in fish growth, lipid metabolism, stress response and appetite regulation. 相似文献
15.
Marius Takvam;Kristina Sundell;Henrik Sundh;Naouel Gharbi;Harald Kryvi;Tom Ole Nilsen; 《Reviews in Aquaculture》2024,16(3):1087-1098
The Na+, K+ ATPase (NKA) enzyme is important to generate the transmembrane ion gradient in the gills, intestine, and kidneys, hence, is vital for secondary transport of fluids and different solutes in teleosts. Gill NKA enzyme activity is often used as a proxy for parr–smolt transformation (PST) during which anadromous salmonids prepare for seawater (SW). Increased intensification and production of larger smolts in modern salmonid aquaculture has resulted in reports of gill NKA activity being less reliable as a proxy for smolt quality. Consequently, changes in mRNA nka-α1b/α1a ratios in gills are increasingly used as indicators of PST. However, nka isoform mRNA abundance may not reflect translation into the functional protein, nor the activity of the mature enzyme. This may limit the predictive power of molecular markers under certain environmental conditions, rearing regimes and biological scenarios. During PST, the osmoregulatory transformations necessary for SW tolerance and survival does not only occur in the gills. Equally important are the changes in ion transporting activities, including NKA activity, in the intestine and kidneys. However, to our knowledge, there are no previous studies addressing the timing and concurrent changes in NKA activity in the three osmoregulatory tissue during PST. Here we present modifications and optimization of the NKA enzyme activity protocols for gill, intestinal and kidney tissue and outline how to best utilize NKA activity measurements as part of a more holistic approach to evaluate overall smolt quality in modern aquaculture. 相似文献
16.
X.D. Wang E.C. Li S.F. Wang J.G. Qin X.F. Chen Q.M. Lai K. Chen C. Xu L. Gan N. Yu Z.Y. Du L.Q. Chen 《Aquaculture Nutrition》2015,21(6):904-912
Juvenile Litopenaeus vannamei were fed for 8 weeks with diets containing four ratios of protein to carbohydrate (CBH) at P26 : C30, P30 : C25, P34 : C19 and P38 : C14, respectively, at 3.0 g L?1 salinity. Shrimp weight gain of P34 : C19 group was the highest and differed from the shrimp fed the P26 : C30 or P30 : C25 diet. Shrimp fed the P26 : C30 diet obtained higher survival than those fed other diets. Shrimp fed the P34 : C19 diet contained the highest body protein and lipid, which were significantly higher than those fed the P38 : C14 diet. Shrimp fed the P30 : C25 diet had the highest haemolymph glucose content, which was significantly higher than those fed the P26 : C30 or P38 : C14 diet. Shrimp muscle glycogen of the P26 : C30 group was the highest. Hepatopancreas B‐cell number of shrimp fed the P26 : C30 diet was lower than those fed other diets, and the R cell number was the highest in the shrimp fed the P30 : C25 diet. This study indicates that the protein‐sparing effect by CBH occurred in the P30 : C25 and P34 : C19 groups because these proteins to CBH ratios can support normal growth. Within the range of basic energy demand, the high dietary CBH to protein ratio can improve L. vannamei survival at low salinity. 相似文献
17.
《Reviews in Aquaculture》2018,10(1):153-167
Farmed fish that escape and mix with wild fish populations can have significant ecological and genetic consequences. To reduce the number of escaped fish in the wild, recapture is often attempted. Here, we review the behaviours of escapees post‐escape, and how recapture success varies with escaped fish size, the size of the initial escape event and recapture methods. Success rates of fishing gears varied among species, with gill‐nets and coastal barrier nets most effective for recapture of salmonids. Recapture success was strongly negatively correlated with both fish size and the number of fish escaped, regardless of species. Recapture success was universally low across all studied species (8%). Numerous tracking studies of escaped fish indicate that recapture efforts should be initiated within 24 h of an escape incident for highest recapture success. However, most large escape events are due to storms, which mean recapture efforts rarely start within this timeframe. Recapture of escaped fish is broadly ineffective in marine habitats, with rare exception. High bycatch rates during ineffective recapture attempts imply that large‐scale recapture efforts should be weighed against the possibility of affecting wild fish populations negatively. We suggest three alternative approaches to reduce escapee numbers in wild habitats: (i) protect populations of predatory fish around sea‐cage farms from fishing, as they prey upon smaller escapees; (ii) construct impact offset programmes to target recapture in habitats where escapees can be efficiently caught; and (iii) ensure technical standards are legislated so that fish farmers invest in preventative technologies to minimize escapes. 相似文献
18.
Harsha S.C. Galkanda‐Arachchige Luke A. Roy Donald Allen Davis 《Aquaculture Research》2020,51(9):3540-3550
Pacific white shrimp, Litopenaeus vannamei, exhibit a remarkable ability to tolerate low‐salinity environments, facilitating its culture far from coastal areas using various production systems at salinities less than 15 g/L. Recirculating aquaculture systems (RAS) and biofloc systems are usually operated using reconstituted sea salt (RSS), which is a considerable financial burden to commercial producers due to its higher price. Current study was carried out with the objective of testing the efficacy of a low‐cost salt solution to replace expensive RSS to grow shrimp under laboratory conditions. Low‐cost salt mixture (LCSM) was formulated to yield sodium, potassium, calcium and magnesium concentrations closely comparable to that of diluted seawater using agriculture grade sodium chloride, magnesium chloride, magnesium sulphate, potassium oxide, calcium chloride and sodium bicarbonate. Growth trials were conducted at three different salinities of 3, 6 and 15 g/L, incrementally replacing RSS with LCSM (0, 2.5, 25, 50, 75 and 100%) at four replicates per treatment. Twenty juvenile shrimp were reared for 42 days in 150 L polyethylene tanks. Ionic profile of water, ionic profile and osmolality of shrimp haemolymph were determined to justify growth and survival data through analysing ionic variations and osmoregulatory capacity of shrimp. At the conclusion, no significant differences were observed in survival, growth, osmoregulation and levels of cations in shrimp haemolymph between RSS and LCSM treatments at all salinities examined. Results reflect the potential use of LCSM to replace RSS which could be an excellent solution to bring down the cost of production in inland shrimp aquaculture. 相似文献
19.
Majbritt Bolton‐Warberg Damien O'Keeffe Richard D. FitzGerald 《Aquaculture Research》2015,46(3):698-706
Four size groups of juvenile farmed Celtic Sea cod (2.7–41.8 g) were reared at a range of constant temperatures (8–19°C). The optimum temperature for growth (Topt.G) decreased from 15.1°C for ~3 g fish to 12.5°C for ~42 g fish. A comparison of these results with those published for a more northerly population (Icelandic) suggests that there is no significant difference in the optimal temperature for growth of cod stocks within the size range studied. In contrast, the growth rates of Celtic Sea cod were lower than those derived from these established models (for a northerly stock) for small juveniles (<5 g), but similar for larger fish (>40 g). Thus, while Topt.G appears fixed across the range, there may be high plasticity in local growth performance throughout the Holarctic distribution. Some possible explanations for these differences are considered. 相似文献
20.
Nile tilapia (Oreochromis niloticus) is currently one of the most farmed freshwater fish and contributes significantly to total global aquaculture production. The genetically improved strain of O. niloticus (GIFT) was introduced to Papua New Guinea (PNG) in 1999 to improve food and income security. The high cost and low availability of commercial fish feed hinder the growth of GIFT farming in PNG. Stable carbon and nitrogen isotopes were used to determine the role of supplementary and natural food sources in the diet of GIFT in pond‐based aquaculture. Two treatments were used: treatment 1 was daily feeding, and treatment 2 was weekly feeding, each with three replicates. Isotopic analysis of muscle tissue and all potential food sources showed that pellet feed contributed 7% to the growth of GIFT in daily‐fed ponds and 33% in the weekly‐fed ponds. Highly enriched δ15N values for chicken manure, compared to depleted values for GIFT and other natural food sources in both treatments, clearly indicate insignificant contributions of this input to production. After 90 days of cultivation, the average final body weight of GIFT receiving daily feed inputs was 134 g (average 19 cm), while for weekly‐fed it was 92 g (17 cm). The feed conversion ratio (FCR) was poor (6.4:1) in the daily‐fed GIFT ponds compared to a better, and preferable, FCR (1:1) in the weekly‐fed ponds. The findings of this study show that pelleted feed was not the major contributor to the growth of GIFT. Genetically improved farmed tilapia aquaculture should focus on enhancing natural food availability for fish production. 相似文献