摘要:

Abstract.Artisanal culture ofMacrobrachium malcolmsonii(Milne Edwards) was studied on two sites in Pakistan. The juvenile prawns ofM. malcolmsoniiwere collected randomly from the lower belt of the river Indus, transported and stocked in ponds at Mirpur Sakro and Chilya, Thatta, Sindh, Pakistan after acclimation. They were fed on supplementary feed containing 15% protein once daily. The stocked prawns grew from a mean weight of 0·5–2·0g to 47·5–83·5g in ponds under the conditions described herein, so a total production of 216·5–1037·5kg/ha w

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00700.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Field‐caught fry of the common wolfish,Anarhichas lupusL., and the spotted wolffish,A. minorOlafsen, were reared on a commercial dry pellet. Both species experienced the same environmental conditions, including an annual fluctuation in temperature from 5·8 to 13·7°C. The spotted wolffish reached 1·58 kg in 2 years from hatching, more than four times the weight of common wolffish (0·37kg). Analysis showed that for both species the specific growth rate decreased with increasing fish size and increasing temperature. Estimates, based upon optimum conditions, indicate that the spotted wolffish would reach a total wet weight of 5 kg (<7°C) in 2 years from hatching, and the common wolffish (7–9°C) a total wet weight of 2·5kg within that same period. Female common wolffish matured at a weight above 0·5kg, whereas those of the spotted wolffish matured at a weight above 2·5kg. The spotted wolffish had a significantly higher fillet proportion (∼50%) than the common wolffish (∼45%) and a significantly lower hepato‐somatic index (3·7%

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00701.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The effects of two synthetic androgens, 17α‐methyltestosterone (5–50mg/kg food), 19‐nor‐ethynyltestosterone (2–50 mg/kg food) and two natural androgens, 11 ketotestosterone (10–60mg/kg food) and androstenedione (20–100mg/kg food) were investigated in the fighting fish,Betta splendensRegan. Androgens were administered for 40 days from the first day of feeding. Masculinization occurred in 100% of individuals fed 8, 15, 60, 90 mg/kg food 19–nor–ET, 17α–MT, 11–KT and AT respectively. Mortality due to treatment of natural steroids was significantly less than that with the synthetic steroids. Sex–reversed males were sexually functional and their genotype was identified by progeny testing. Sex‐reversed males produced 100% female monosex when mated with normal females, indicating that the mechanism of sex determination in this fish is homogametic fe

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00702.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.An examination of biochemical‐genetic variation at seven polymorphic loci was carried out among five year classes of wild Atlanticsalmon, SalarL., in the R. Bush and in a hatchery strain derived from the wild population. Within some of the year classes, gene frequencies at several loci differed significantly between wild and artificially reared salmon. Highly significant temporal variation in gene frequencies was detected among successive year classes of the hatchery strain, while this was less significant among the wild salmon. Samples of wild salmon taken as 0+ and 1 + parr in the river showed no significant temporal variability in allelic frequencies. Heterozygosity levels among the wild and hatchery‐reared salmon were comparable, averaging 0·185 and 0·176 respectively. The genetic variability of the artificially reared salmon is discussed in relation to numbers of broodstock and breeding regime used at the hat

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00703.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Allozyme variation at 32 protein genetic loci was studied in four populations ofMacrobrachium nipponense(de Haan) from two contrasting habitats, wholly freshwater lacustrine sites and brackish water riverine areas from different parts of Asia (Hong Kong, Canton, Wuhan, Japan). The average values of observed heterozygosity were 7·45% for lacustrine and 12·30% for riverine sites, the percentage of polymorphic loci (0·99) was 32·5%. The freshwater/lacustrine populations had lower estimates of genetic variability than the river/brackish water populations. The average genetic similarity and genetic distance (Nei's) were 0·92 and 0·084 respectively. The results were compared with those of the only other study on this species. The implications of these results for this species are disc

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00704.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Effects of low doses of salmon gonadotropin (SG‐G100) and three steroids — 17α,20β‐dihydroxyprogesterone (17α,20β‐diOHprog), deoxycorticosterone (DOC) and progesterone — individually, or combinations of steroid with SG‐G100, on ovulation and hatching inClarias batrachus(L.) were investigated. None of the steroids at any of the three different dose levels (1μg, 1·5μg/g and 2μg/g BW) could induce ovulation when injected alone. SG‐G100 at a dose level of 10 μg/g BW was not effective but at the dose level of 15 μg/g BW it could induce ovulation. All the three steroids at their lowest doses (1μg/g BW) when injected in combination with SG‐G100 (10μg/g BW) were significantly effective in inducing ovulation. When hatching percentage was taken into account, 17α,20β‐diOHprog in combination with SG‐G100 was found to be the most effective combination in

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00705.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.A new means ofin vivodrug administration was developed in order to reach the direct environment of the pituitary gland of common carp,Cyprinus carpioL., without any surgery. This permits decreased dosage of rhe drugs and (heir possible side effects. Injections‘on the pituitary'(o.pit.) were done with a 20G × 23/16 inch needle attached to a microsyringe. The needle, introduced under the eyeball, followed the route of thenervus opticus.The effects of different doses of D‐Ala6LHRH (GnRH‐A) injected o.pit. were compared with those of intraperitoneal (i.p) injection. It was found that a dose of 4mu;g/kg of GnRH‐A injected i.p. significantly stimulated GtH2 release starting at 15min post injection, whereas o.pit. injection had no effect. A ten times lower dose of GnRH‐A (0.4mu;g/kg) injected o.pit. provoked a significant increase of GtH2 secretion in comparison with i.p. injection at 10 and 15min post injection. Starting from 25min after injection no differences were found between these two groups, however GtH2 levels in these two groups were still significantly higher than in their controls. I.p. injection of 0·04pmu; g/kg of GnRH‐A caused no significant rise in GtH2 secretion at any sampling time, whereas o.pit. injection evoked a significant rise in GtH2 secretion in comparison with all the other groups at 10 and 15 min post injection. Our results show that using this new method, the dosage of injected drugs can be highly decreased, down to the level which is ineffective after classic i.p. administration. This is also of economic importance because of the cost of

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00706.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The effect of two GnRH‐As – des Gly10(D‐Ala)6LHRH and des Gly10(D‐Tle)6GnRH in total doses 10–249mu;g/kg – and four neuroleptics – pimozide, sulpiride, metoclopramide and isofloxythepin in total doses 1–50mg/kg ‐ and environmental temperatures on the development of final stages of Pacific mullet oogenesis was investigated. The best technique of those used by us for spawning stimulation of Pacific mullet,Mugil so‐iuyBas., females is shown to be administration of neuroleptics in doses of l‐8mg/kg with posterior injections on GnRH‐A in doses of 25 and 50mu; g/kg applied 4 and 28h respectively after the neuroleptic injection. At water temperatures below 17°C, ovulation does not occur unless the optima

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00707.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.Protein and energy maintenance and optimum feed requirements are reported in the catfish,Clarias batrachus(L.), fed a purified diet (40% CP; 1487·1kJ/100g) at 0 to 8% (BW/day) ration levels. Linear (r = 0·985) increase was observed in daily average growth increment up to a ration level of 4% (BW/day), corresponding to 6·03g protein/(kg0·8BW/day) and 224·26 kJ energy/(kg0·8BW/day). Maintenance requirements, obtained by regressing daily average growth increment to zero, were 0·942 g/(kg0·8BW/day) for protein and 36·02 kJ/(kg0·8BW/day) for energy. Net gains in muscle protein and energy also depicted linear increase (r = 0·975) with feeding levels up to 6·03g protein/(kg0·8BW/day) and 224·26kJ energy/(kg0·8BW/day). On fitting the above data to regression equations, giving the amount of dietary protein and energy required to maintain a constant amount of body protein and energy, values of 1·005g/(kg0·8BW/day) and 42·11 kJ/(kg0·8BW/day) were obtained for protein and energy respectively. The optimum feeding rate for this species, as evident from specific growth rate and conversion efficiencies, appears to be 3% (BW/day) at 30 ± 2°C. Moisture and lipid contents in muscle were found to be significantly (P<0·05) affected

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00708.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract.The spatial distribution of Atlantic salmon,Salmo salarL., in sea cages was observed by echo integration, which measured fish density at seven in depth intervals. At start of feeding the fish swam towards the surface and into the centre of the cage with a subsequent movement downwards and towards the periphery as hunger was reduced. These changes were more rapid at high than at low feeding intensities. The downward migration during feeding was primarily observed as a reduction in fish density in the 0–1 m depth layer and an increase in the 2–3 m depth layer. For a given feeding intensity, the change in fish density in these depth layers was largely explained by time from the start of feeding and initial hunger level, measured as food intake to satiation. The feeding regime also influenced vertical distribution outside feeding periods. Fish that were fed at low intensity swam generally closer to the surface, and this tendency was even stronger when a restricted food ration kept hunger level constantly high. While fish density peaked at a single depth interval at full ration, a bimodal vertical distribution was observed at restricted ration, suggesting that different subgroups of fish had different feeding motivations. The results suggest that the vertical distribution of salmon in sea cages is based on a trade‐off between attraction to food and avoidance of the surface. This tendency has been exploited in a new method of demand feeding in commercial farming of Atlantic s

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1994.tb00709.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY