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H. Migaud R. Mandiki J.N. Gardeur P. Kestemont N. Bromage P. Fontaine 《Fish physiology and biochemistry》2003,28(1-4):395-397
The effects of photoperiod regimes under ambient temperature on gonadal growth and spawning were investigated in Eurasian perch, Perca fluviatilis. This study showed that continuous lighting inhibited reproduction in male and female fish with very low sex steroid levels being measured. Constant LD 16:8 resulted in heterogeneous gonad development and sex steroid levels compared to natural regime, with only 54% of females and <?30% of males maturing. Seasonal variations in daylength also seem to be required to control reproduction. 相似文献
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M.J.R. Porter S.O. Stefansson G. Nyhammer Ø. Karlsen B. Norberg N.R. Bromage 《Fish physiology and biochemistry》2000,23(3):191-200
This study investigated the effects of photoperiod and temperature on plasma melatonin secretion in Atlantic cod (Gadus morhua L.). Initial work confirmed the presence of a diel profile of melatonin synthesis, with elevated levels during the dark phase. Unusually for fish, the peak in plasma melatonin occurred towards the end of the dark phase, which is indicative of a type `A' melatonin profile. When exposed to 60 hours of continuous darkness a clear endogenous rhythm of melatonin synthesis was observed, which continued for 4 cycles with a periodicity which, approximated to 24 h. When acclimated to varying temperatures (4, 8, 12 or 16 °C) no variation in melatonin production was seen, however, body size appeared to be an important influence, with the smallest fish exhibiting significantly higher levels of dark phase melatonin. Finally, the application of additional night-time illumination to cod maintained in sea cages i.e. without blackout, did not significantly reduce dark phase plasma melatonin, suggesting that cod are less sensitive to photoperiod manipulation in cages than salmonids. 相似文献
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B. North M. Porter V. Crampton D. Guerrero-Tortolero N. Bromage 《Fish physiology and biochemistry》2003,28(1-4):513-514
This study identifies the presence of a spring drop of flesh pigmentation that coincided with oocyte atresia in Atlantic salmon and outlines the potential influence that additional lighting and feed management strategies can have on these processes. 相似文献
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Niall Bromage Mike Bruce Ngappa Basavaraja Krishen Rana Robin Shields Carl Young John Dye Peter Smith Malcolm Gillespie John Gamble 《Journal of the World Aquaculture Society》1994,25(1):13-21
Egg quality, those characteristics of the egg that determine its capacity to survive, is a significant problem for many species of fish currently being farmed. Little is known about the determinants of egg quality and there is little agreement regarding reliable methods for its assessment. To be of practical benefit, assessments should be simple to perform and should be carried out as early in development as is possible. Fertilization rates are often used as measures of quality. For the Atlantic halibut Hippoglossus hippoglossus, fertilization rate and assessments of cell symmetry at early cleavage stages provide reasonable indicators of quality. Regardless of assessment method, it is strongly recommended that performance data from all batches of each broodfish be examined when surveying the overall quality of a stock. The misleading effects of pooling such information are demonstrated for a rainbow trout Oncorhynchus mykiss broodstock. Although a large number of factors have been implicated as possible determinants of egg quality, only 1) bacterial colonization of the eggs, 2) nutritional status of the broodfish and, 3) overripening, the process of aging that occurs when eggs are retained within the broodfish after ovulation, have been clearly shown to affect egg quality. The effect of overripening on fish egg quality is discussed in detail. Species-specific differences in the time scale of overripening are pointed out and related to spawning strategy and water temperature. Rainbow trout eggs and those of other salmonids should be fertilized within approximately one week of ovulation. Overripening proceeds much more rapidly in warm water species, e.g., tilapia eggs must be fertilized within an hour or so of ovulation. Egg viability also decreases rapidly for batch spawning species. Fertilization data are presented for Atlantic halibut demonstrating that egg quality decreases 4–6 h after ovulation. The rate of overripening was comparable for eggs held in vitro in ovarian fluid to those retained within the ovarian lumen. These halibut data, combined with information from other marine and freshwater fish, indicate that overripening is a significant determinant of egg quality for many if not all fish. 相似文献
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Objective To investigate wool organophosphorus concentrations resulting from a range of farm pesticide application methods.
Design Random sampling of wool for pesticide residues and on-farm interviews to determine associated treatments.
Procedure Tasmanian fleece wool lots were sampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview.
Results The residue concentrations showed a large variation that was not accounted for by differences in treatments by growers. Organophosphorus concentrations were proportional to the number of treatments applied, and inversely related to the time between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide residue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused larger residues than the use of jetting races.
Conclusions We recommend that plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 months after shearing, provided only one application is administered. 相似文献
Design Random sampling of wool for pesticide residues and on-farm interviews to determine associated treatments.
Procedure Tasmanian fleece wool lots were sampled at random and tested for organophosphorus residues. The grower was identified and the pesticide treatments applied to the sheep were ascertained by on-farm interview.
Results The residue concentrations showed a large variation that was not accounted for by differences in treatments by growers. Organophosphorus concentrations were proportional to the number of treatments applied, and inversely related to the time between pesticide application and the subsequent shearing, and were significantly influenced by the method of application. After allowing for the time of application, plunge dipping resulted in pesticide residue concentrations 2 to 2.5 times greater than shower dipping, using spray races or hand jetting, and the use of these methods caused larger residues than the use of jetting races.
Conclusions We recommend that plunge or shower dipping should not be used more than 7 weeks after shearing, nor at higher concentration than the standard dose rate used for lice control, whereas jetting may be satisfactory for up to 7 months after shearing, provided only one application is administered. 相似文献
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Atlantic cod (Gadus morhua) placed under 24 hour illumination (LL) from 15 months post hatch (MPH), did not spawn at 2 years and only 7.2% were found to be spawning at 3 years. Ultrasound scanning however showed some gonad development from 22–28 MPH in the LL treated group. This data shows that cod reared in enclosed tanks receiving LL from 15 MPH do not spawn at two years, however, they do go through some gonadal development. Cod placed under LL between 6–18 MPH. showed that in order to prevent spawning at 24 MPH, LL must be applied at or before 15 MPH. and after such time not be returned to a SNP. 相似文献