摘要:

Abstract.Significant differences were found in allelic frequency distribution among three strains of rainbow trout,Oncorhynchus mykiss(Walbaum). The isocitrate dehydrogenase (IDH‐3, 4* 1.1.1.42) locus was fixed in two of the strains while the superoxide dismutase (SOD‐I* 1.15.1.1) locus was absent in one of the strains.Similarity indices ranged from 0·973 to 0·988 on the scale of 1·000 among pairwise comparisons of the strains while Nei's genetic distance was 0·012 between Mount Lassen and Manx, 0·025 between Mount Lassen and Tagwerker and 0·027 between Manx and Tagwerker. Gene diversity was highest in the Mount Lassen strain, followed by Manx, with Tagwerker having the least. These differences in gene diversity were attributed to breeding and management practices used at the hatchery. The need for characterization of strains of rainbow trout, especially in crossbreeding programmes that aim to increase genetic variation, was emphasized by thes

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00720.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Eight‐day‐old striped bass,Morone saxatilus(Walbaum) larvae, and one‐month‐old juveniles were held in varying salinities and exposed to a range of concentrations of potassium permanganate. Lethal concentrations of potassium permanganate for 50% of the larval fish exposed for96h (96h LC50) were 1middot;02, 2 middot;11, 1 middot;41 and 1 middot;73mg/1 for salinities of 0, 3, 6and 9 g/l, respectively; The 96h LC50S for juveniles were 0 middot;96, 3 middot;26, 1 middot;63 and 1 middot;48 mg/l for salinities of 0, 5, 10 and 15g/l, respectively. There were significant differences in 96h LC50values at different salinities for both life stages. The 96 h LC50values derived for both life stages revealed a decrease in toxicity as salinity increased from 0 to 3–5g/l. Results indicated potassium permanganate to be toxic in fresh water to striped bass larvae and fingerlings at recommended treatment levels (3 midd

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00721.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Laboratory experiments were conducted on larvae or Australian bass,Macquaria novemaculeata(Steindachner), to establish the age at which they can fully osmoregulate in fresh water. The effect of acclimation at two different salinities (15‰ and 28‰) was also examined. It was found that larvae survived transfer to 2‰ salinity at 7 days post hatch, regardless of acclimation. Acclimation was also found to have little effect on the development of full osmoregulation in fresh water, which occurred between 21 and 28 days after hatching. The data obtained extend previous knowledge on the survival of larval Australian bass in low‐salinity water and suggest that early release of suitably acclimated larvae into brackish ponds could reduce the need for intensive hatchery

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00722.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.A method of testing the growth of different genetic groups of common carp,Cyprinus carpioL., over 3 year cycles was demonstrated. In European aquaculture, attaining market weight of common carp usually requires growth periods of 3 years. Typical mean weights at the end of the first year are 20 to 40g. For genetic testing, each progeny is nursed in a separate first‐year pond. Co‐stocking these nursery ponds with samples of a genetically marked group of carp is a convenient method of multiple nursing for second‐ and third‐year testing. This method does not require additional ponds for generating multiply nursed samples.Four successive experiments were carried out using this method of testing. Each experiment was run over a period of 3 years. The modified multiple nursing method generated sufficiently large weight differences only in one experiment. In the others, weight differentiation was small and unreliable, or several multiply nursed groups were lost or unidentifiable. Some improvements of this method are suggested. The genetic groups participating in the test included Ropsha carp, an Estonian strain and a strain of German mirror carp. The results are consistent with a similar study involving Chinese and European races of comm

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00723.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The effects of the frequency of manure application (twice weekly, weekly and fortnightly) on prawn production and pond dynamics in culture ofMacrobrachium rosenbergii(de Man) were assessed. Juvenile freshwater prawns were cultured for 100 days using pelleted feed and organic fertilizer. Results showed that the greatest (but not significantly different) marketable prawn yield was achieved with fortnightly manuring, but the most stable pond environment as based on oxygen dynamics, developed with weekly fertilization. The highest concentrations of chlorophyll, nitrogen and phosphorus occurred with fortnightly applications, but so too did the lowest ratio of gross primary production: respiration. System dynamics are discussed.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00724.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17‐α methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT‐treated tilapia was evaluated during consecutive treatment, nursery, and grow‐out phases under conditions approximating commercial, semi‐intensive tilapia farms in Central America.Oreochromis niloticus(L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT‐treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0·1 g/fry for both treatments. Fry were subsequently stocked into 0·2‐ha nursery ponds for 94 days growth. Slopes of control and MT‐treated fish growth curves were not significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate significantly from the1:1 male: female ratio, but MT‐treated fish were 97% males. Control male and MT‐treated male fingerlings were stocked for grow‐out into 0·1‐ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT‐treated fish. Mean gross yields after 150 days and mean final individual weights were

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00725.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The adherent aerobic bacterial flora present in the gastrointestinal tract and faeces of free‐living Arctic charr,Salvelinus alpinus(L.), from Lake Takvatn, Northern Norway, were identified both qualitatively and quantitatively. Approximately 105bacteria g−1were found in both the small and large intestines. The predominant bacterial species were identified asAeromonas, Enterobacteriaceae,MicrococcusandLactobacillus.Other microorganisms isolated includedAcinetobacter, Cytophaga, Flavobacterium, Moraxella, Pseudomonas, Vibrio, Coryneforms andStreptococcus.The intestinal microflora of free‐living fish was dominated byAeromonasandLactobacillus, but the intestinal bacterial flora of wild fish transferred to hatchery was affected by feeding them either a capelin roe diet or a commercial feed in fresh and sea water. Approximately 55% of the bacterial flora in intestinal contents from fish fed the capelin roe diet was Enterobacteriaceae when the fish were held in fresh and sea water. However, when the wild‐caught charr were fed a commercial diet in fresh water,AeromonasandPseudomonasdominated in faeces, whileVibrioandPseudomonaswere predominant in the diet group held in se

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00726.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.A feeding experiment was conducted to evaluate the growth of tiger guapote,Cichlasoma managuense(Günther), fed on isocaloric diets with varying protein: energy ratios. The relative metabolic growth rate increased with the protein: energy ratio up to 110–120 mg protein/kcal (P<0·05). The protein efficiency ratio was optimal at 110mg protein/kcal. The body composition was clearly influenced by diet composition. Results indicate that juvenileC managuenseobtains near optimal growth rates when fed 35–40% protein diets with 110–120mg protein/kcal. Higher ratios will not be cost ef

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00727.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The aim of this research was lo evaluate the effect of density and feeding level (initially 8 or 16kg/m3and 1·3% or 2% of present biomass respectively) on productive traits, meat composition and water quality output in farmed rainbow trout,Oncorhynchus mykiss(Walbaum). Individual fish growth shows significant differences in relation to density and feeding level; feed conversion rate is positively Influenced by the lower feeding level and low rearing density. At low density, specific growth rate, protein efficiency ratio and coefficient of variation of individual final weights are more favourable than at high density. Dry matter and lipid composition of meat are positively affected by feeding level; whereas no differences are recorded on the amino acid and fatty acid profiles. Water quality shows differences due to density (NO3and NH4+) and feeding level (NO2, NH4+and P)

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00728.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Young rainbow trout,Oncorhynchus mykiss(Walbaum), with a mean weight of 100g were used in a 42‐day study designed to investigate the influence on several haematological characteristics of two different diets containing 32·5% and 47% protein and 41·4% and 20·0% carbohydrate, respectively. The observed overall mean values of the different blood parameters were similar to those reported in literature. Leucocrit, percentage of periodic‐amino‐Schiff positive granulocytes, percentage of mature lymphocytes and the percentage of the fourth plasma protein fraction were significantly affected by

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00729.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY