ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFive groups of Arctic charr,Salvelinus alpinus(L.), were studied, each group consisting of 13 females. The fish in four of the groups received a single intramuscular (IM) injection: three groups were injected with LHRHa in various forms and dosages, and one was injected with saline (control). The females in the fifth group were implanted with controlled‐diffusion implants containing LHRH analogue. Ovulation in two of the treatment groups (30μg/kg D‐Ala6LHRH and 150μg/kg D‐Trp6LHRH) occurred earlier, and was better synchronized, than in the control group. The treatments did not significantly affect (1) the weight of eggs released from each female; (2) egg size, weight, or chemical composition; (3) mortality rates; (4) hatching times or the length of alevins. The fertilization rate in one of the treatment groups (150 μg/kg D‐Trp6) was significantly lower than in the con

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe timing of ovulation and survival of eggs following exposure of 2‐sea‐winter Atlantic salmon,Salmo salarL., to different temperature regimes during the spawning season were investigated. Water temperature was either increased from 10 to 13–14°C (warm water), decreased abruptly from 10 to 5–7°C (cold water), or gradually decreased from 10 to 8°C (ambient control) from 1 November onwards. Median ovulation time was delayed by 5 weeks in the warmwater group compared with ambient controls, with 43% of the females remaining non‐ovulated at the end of the study. Only minor effects were observed on timing of ovulation in the coldwater group compared with ambient controls. Survival of eggs to the eyed stage was significantly higher in the coldwater group (92·1%), compared with both the ambient control group (84·5%) and the warmwater group (76·6%). The results indicate that high water temperature during the spawning season inhibits ovulation and has a detrimental effect on gamete quality in

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractPlasma melatonin levels were measured at hourly intervals in rainbow trout,Oncorhynchus mykiss(Walbaum), maitained under three different skeleton photoperiods: 8L:2D:2L:12D;8L:7D:2L:7D; and 8L:12D:2L:2D. Blood samples were taken before, during and after the 2‐h light pulses. Melatonin levels increased rapidly to mean scotophase (dark period) values of 261 ± 7 pg/ml after the first light‐dark transition and had returned to mean photophase (light period) values of 51 ± 2 pg/ml 30min after the end of the scotophase. Light pulses during the early, mid‐ and late scotophase elicited similar reductions in melatonin levels, followed by rapid increases after the light pulse, reaching previous scotophase values within 90 min. The inability of any of the light pulses to modulate or truncate melatonin secretion under a LD 8:16 photoperiod provides further support for the hypothesis that melatonin secretion in the rainbow trout is a direct response to darkness, and is not under endogenous circadian control as in other vertebrates e

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractBroodstock segregation based on the measurement of maternalRenibacterium salmoninaruminfection levels by the enzyme‐linked immunosorbent assay (ELISA) and the membrane filtration‐fluorescent antibody technique (MF‐FAT) was previously shown to affect the prevalence and levels of bacterial kidney disease (BKD) in progeny of chinook salmon,Oncorhynchus tshawytscha(Walbaum), during hatchery rearing. Subgroups of fish from that study were marked with passive integrated transponder (PIT) tags, and monitored by PIT‐tag detectors during the first 342km of their migration to the Pacific Ocean. Differences in the recovery of tagged fish were significant (P≤ 0·01) at each detection point and became more pronounced as the fish moved downstream. Cumulative recoveries of fish from the low‐BKD group and the high‐BKD group, respectively, were 31% and 28% after 116km, 44% and 37% after 176km, and 51% and 42% after 342km. There were no apparent differences in the migration timing of the two groups to the first detection point. The data suggested that in‐river survival was higher in the progeny group from parents that had lowR. salmoninaruminfection levels or tested negative forR. salmoninarum(low‐BKD group) than in the group female parents with high infection level

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe common sole, Solea solea (L.), readily spawns naturally in captivity. This paper reviews the conditions and procedures used to obtain natural spawning from captive broodstocks and describes the characteristics of egg production. Spawning has been obtained under a wide range of conditions. The time of year has varied, even at the same location, but analysis of published data shows the temperature at which it commenced was related directly to the minimum temperature of the previous winter. Annual relative fecundity has varied from 11 to 141 eggs/g of female with a tendency, although not statistically significant, for the higher values to have occurred following winter temperatures of less than about 12°C. Variations in egg size and fertilization rate have not correlated with larval viability which has been consistently high

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AhstractHigh resolution ultrasound scanning was tested as a non‐invasive technique for monitoring oocyte maturation and ovulalion in the Atlantic halibutHippoglossus hippoglossus(L.). Female broodstock halibut were examined using a 7.5‐Mhz linear ultrasound transducer, prior to and during spawning. Representative images of halibut ovaries are presented and discussed. Individual oocytes of spawning females were discernible during oocyte final maturation, due to the large increase in volume caused by water uptake. The yolky (vitellogenic) cocytes of pre‐spawning fish were more reflective to ultrasound than hydrating oocytes. The resulting differences in depth of ultrasound penetration permitted easy distinction of pre‐spawning from spawning females. In addition, short‐term changes in the depth of ultrasound penetration were observed during repeated scanning of a spawning female, owing to progressive hydration of the oocyte batch destined for ovulation. Although of similar diameter, hydrating oocytes in the ovarian tissue could be discerned from eggs in the ovarian lumen because of the different acoustic properties of the surrounding media. The findings of the present study are considered promising for the future routine use of ultrasonography in halibut broodstock m

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00539.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe production of viable larvae is critical to any aquaculture venture. Since lipids are important components of fish eggs, the amount and nature of the lipid may be crucial to the survival of the larvae. In this study the lipid content of unfertilized eggs from first‐time and repeat spawning Atlantic halibut females was compared. The egg lipid content for the first‐time spawner ranged from 0·18 to 0·41mg/egg; the range for the repeat spawner was 0·27 to 0·38mg/egg. However, the mean total lipid per egg values were similar for both fish at ca. 0·31mg/egg. The repeat spawner prodticed more eggs than the first‐time spawner, thus allocating more lipid to egg production. In the eggs from the two fish 62–84% of the lipids was

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00540.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEggs of Pacific halibut held in a conical incubator at 6deg;C hatched 422 h post‐fertilization. Levels of moisture, monosaccharides and total carbohydrates in the embryos demonstrated significant linear increases during this period of development. Significant linear declines in levels of total lipid and ash occurred, but polysaccharide and protein contents were virtually unchanged. The ratio of RNA:DNA, signifying rate of protein synthesis, declined during embryogenesis from 9·74 in the egg to 4·49 in the larvae. The slight increase in relative proportions of the essential eicosapentaenoic and docosahexaenoic acids was offset by a decline in palmitic add and indicated catabolism of only the saturated acid as a source of energy. Energy derived from carbohydrate, protein and lipid in the eggs increased, remained constant and decreased, respectively, with embryonic development. Total accountable energy expended during embryogenesis, principally by lipid catabolism, was 88·11 J/g wet weight or a decline of 6·96% of the original energy in the fertilized egg. However, non‐protein nitrogenous constituents may also have contributed considerably to the total energy expended during embryo

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00541.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractFour parameters were examined in order to define sperm quality in turbotScophthalmus maximusL., sperm: (1) sperm motility, measured by direct counts of the number of active spermatozoa, expressed as % of total spermatozoa; (2) retention of motility after activation, measured by direct counts, 0–60min after activation, expressed as a % of the initial level of activity; (3) resistance to thermal stress, measured as change in retention of motility, and (4) adenosine phosphate (ATP) concentration, determined for samples of non‐activated sperm. The proportion of motile spermatozoa at activation ranged from 34·8% to 97·6% (mean 76·3%) for the individual males tested. Turbot sperm retained on average 52% (range 27–90%) of its initial activity one hour after activation. Sperm samples which were stressed by cooling to –27°C retained only 8·6% (range 0–25%) of initial activity, compared to control samples which retained 49% (range 38–63%) of initial activity. The retention of motility after activation was not significantly related to the initial motility or the levels of ATP. Concentrations of ATP in turbot sperm (mean 0·46mg ATP/106spermatozoa, equivalent to 9·2nmol ATP/108spermatozoa) were comparable to those m

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1993.tb00542.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY