摘要:

Abstract.Semipurified diets containing either 25% or 30% crude protein (CP) from soy isolate (soy) or 30% CP from casein and gelatin (casein) were supplemented with either of two levels of L‐lysine HCI (0 or 0·5% of diet) in a 3 × 2 factorial arrangement and fed to fingerling channel catfish,Ictalurus punctatus(Rafinesque), in aquaria for 8 weeks. Factorial analysis of variance indicated a significant (P<0·001) positive effect of lysine on weight gain, protein conversion efficiency (PCE) and feed efficiency. Fish fed the soy diet containing 25% CP showed increased weight gain of 24% with lysine supplementation while fish fed soy and casein diets containing 30% CP showed increases of 11 % and 3%, respectively. However, supplementing the 25% CP soy diet with 0–5% L‐lysine HCI did not enhance growth performance to the level offish fed the unsupplemented 30% CP soy diet. Significant effects of dietary protein levels and sources on weight gain, PCE, feed efficiency, haematocrit, hepatosomatic index (HSI; % liver weight), intraperitoneal fat (IPF) ratio, dry matter of fillet and whole‐body, as well as lipid and protein content of whole‐body tissue, were also observed. Fish fed the casein diet containing 30% CP had the greatest weight gain, PCE, feed efficiency, haematocrit and whole‐body protein values and lowest IPF ratio and whole‐body lipid values compared with those of fish fed the soy diets. Supplemental lysine did not affect body condition indices or proximate composition of whole‐body and fillet tissues of fish fed the different protein sources. Therefore, based on this study, dietary protein levels and sources significantly influenced performance characteristics of channel catfish and supplemental lysine was most beneficial at

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00711.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Observations of adult Atlantic halibut,Hippoglossus hippoglossus(L.), behaviour in cages were made with underwater camera and video recording equipment. Significantly more fish (P<0·01) were found on the cage bottom than in the water column, fish tending to congregate around the outside rather than in the centre of the cage. During rough weather, the cage bottom was observed to heave violently and proportionately fewer fish remained on the bottom, those which did adopting an arched body posture with heads and tails not in contact with the cage bottom. Around 25% of the caged fish were active at any time, most of the active fish remaining close to the cage surface or bottom, with little use being made of the remaining cage volume. Fish were observed to swim in a circular pattern close to the cage walls (mean velocity 0·53 m/s), maintaining such behaviour for periods of up to 5min with little change in swimming speed. Whilst all food types were ingested, items delivered directly lo the cage bottom were taken only if detected within the first minute or so. The implications for rearing Atlantic halibut in conventional cages are discusse

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00712.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Compounded diets given to juvenile lobsters,Homarus gammarus(L.), during the critical post‐settlement phase of their development induced moulting abnormalities that resulted in limb loss and deformity. These potentially lethal effects were minimized, and in some cases overcome, through the provision of a supplement of natural food given just once or twice each week. The degree to which a poor diet could be improved was proportional to the quality and frequency of supplementation. Both moult increment and frequency were affected by dietary regime. A quantitative index of general health was derived from selected physical attributes exhibited by juvenile lobsters, which was useful in assessing a combination of responses to different diets and supplement

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00713.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Oxidation treatment of sugarmill waste using duckweed (Lemnasp.) as part of the system, to reduce effluent nutrient concentrations and biological oxygen demand (BOD), was evaluated during a 6 month milling season in Negros Oriental, Philippines. Mean ammonia concentration in effluent water was reduced from 0·87 to 0·31 mg/l NH3‐N and orthophosphate from 0·93 to 0·51 mg/l P2O5, while mean BOD was reduced from 611 to 143mg/t BOD5, after treatment. Seasonal mass fish kills in the adjoining bay no longer occurred during the 3 years following introduction of this treatment. The mean duckweed production (dry weight) was 8–8g/m2/day. Duckweed was harvested from a 1·9ha area of the system and transferred to an adjacent milkfish,Chanos chanosForskal, farm. Its fertilization effect, in terms oflablabproduction (lablabis the biological complex of bluegreen algae, diatoms, bacteria and various animals which forms a mat at the bottom or floats in patches), was evaluated in the milkfish ponds. This was compared with ponds fertilized with either inorganic fertilizers or cow manure, in the traditional way.Lablabgrowth was significantly increased using duckweed, with ash‐free dry weight production averaging 32g/m2/day following fertilization with duckweed compared with 4g/m2/day using inorganic fertilizers. Milkfish net production averaged 320 kg/ha/90‐day crop in inorganically fertilized ponds. 545kg/ha/90‐day crop for cow manure and 820kg/ha/90‐day crop in duckweed‐fertilized ponds. The system is described and the benefits of this integrated waste treatment‐fish production fa

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00714.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Atlantic salmon,Salmo salarL., brown trout,S. truttaL. and their hybrids are normally identified in the field by empirical differences in maxilla length, thickness of the caudal peduncle, degree of forking of the tail and overall body conformation. This study quantifies these characters and analyses their variations in electrophoretically identified hatchery‐reared individuals. Means and variances of the various measures are presented for salmon, trout and hybrids separately. The morphometric characters do not satisfactorily distinguish hybrids from the pure species, and even within samples of the pure species, some individuals will be misclassified as hybrids, or as members of the opposite species, if single characters are used on their own. Hybrids often resemble one or other parent species in one or more characters and are less often intermediate in phenotype. Triploidized hybrids are more like salmon than diploid hybrids are, and triploidized salmon are not different from diploid salmon. The results confirm that frequencies of hybrids of these species cannot be reliably assessed by morphological characters alone, and even for individuals of the pure parental species, independent confirmation of species status is advisable. Early reports of hybrid frequencies in wild stocks should be treated with caution, and apparently higher levels of hybridization in more recent studies compared with older, traditional surveys may simply reflect the greater precision of electrophoretic identificatio

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00715.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The influence of macro‐economic factors on production and consumption of aquatic products in the world was evaluated. World aquaculture production and its growth were analysed in terms of commodities, species, countries and regions. Special attention was given to interpreting the consequences of the results obtained on policy and planning of future aquaculture development.The consumption of both aquafood and meat increased significantly with income on a per caput basis in the world. The ratio aquafood:meat decreased with increasing per caput income, stressing the relative importance of aquafood in low‐income countries. A significant correlation between the consumption of aquafood and aquaculture production was found for Asia, Europe and on a world‐wide scale and it is therefore argued that fisheries pave the way for aquaculture development. Growth of finfish culture tends to correlate with agricultural growth. Africa and Latin America have low aquaculture productions compared with their aquafood consumption. These regions offer the highest probability for rapid growth in aquaculture production in the near f

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00716.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.In an attempt to limit the consumption of live prey by marine fish larvae, and in order to overcome the problem of weaning, five feeding regimes comprising live prey, alone or in association with microparticles were tested in parallel intensive‐rearing experiments withDicentrarchus labrax(L.) larvae. These experiments are based on manipulation of feeding behaviour of the larvae and involve suppressing the mobility of the live prey. Under these conditions, the larvae are no longer stimulated by the movements of the prey and do not become conditioned to this type of stimulus. Accordingly they ingest immobilized live rotifers and microparticles alike. This method has permitted the weaning of the larvae on to microparticles at the age of 20 days with less than 10% mortality. In addition, the quantity of live prey used is reduced by a factor of 2

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00717.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Biomass productivity, photosynthetic efficiency and fatty acid profiles of the marine microalgaTetraselmissp. in a turbidostat culture system using an outdoor photobioreactor are described. The maximum productivity depended on the units in which it was expressed; it reached 5·41 × 10−3g/l/h in volumetric units, and 7·26g/m2/day in surface units, the former at the smallest culture depth (0·12m) and the latter at the greatest culture depth (0·25 m). Data from the experiments were adjusted to an equation for light limitation. The comparison of fatty acid composition at both depths showed that biosynthesis of polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA), was favoured when available light was low (0·17 m). Moreover, fatty acid 16:0 seemed to be an indicator of the type of limitation in the culture, i.e. nutrient or light lim

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00718.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00719.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY