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A stripspawning methodology was evaluated for tilapia (oreochromid) species. This technique achieved an average hatching success of 68.6 ± 3.6% (N= 31). Female fecundity and spawning frequency were dependant on both genetical and husbandry factors. Egg yields for Oreochromis niloticus, O. mossambicus, and O. niloticus±O. mossambicus hybrids averaged 4.54, 10.86 and 10.36 eggs/g female/spawn, respectively. Female broodstock that were adapted to an intensive spawning regime exhibited a significant increase in fecundity. Additionally, egg survival was not affected by hydration for up to 15 minutes prior to fertilization. Results suggest that the strip spawning of tilapia species may be an efficient method of providing viable gametes for hatchery purposes. 相似文献
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James M. Myers William K. Hershberger Robert N. Iwamoto 《Journal of the World Aquaculture Society》1986,17(1-4):1-7
The induction of tetraploidy was attempted in three intraspecies crosses (autotetraploid) of sal-monid: chinook salmon ( Oncorhynchus tshawytscha ), coho salmon ( O. kisutch ) and rainbow trout ( Salmo gairdneri ), and in the interspecies hybrid (allotetraploid) coho × Atlantic salmon ( Salmo salar ).
Pressure treatments of 6.2 × 104 kPa (9,000 psi) were applied for six minutes at intervals from 50% of the time to cleavage to beyond first cleavage. Analysis of eyed stage embryos via flow cytometry indicated two periods of tetraploid induction existed corresponding to 55–75% and 100–110% of the first cleavage interval (FCI).
The effects of different pressures and the times of application were analyzed in a study with rainbow trout. Treatments of 4.8 × 104 kPa (7,000 psi) for eight minutes, and 5.5 and 6.2 × 104 kPa (8,000 and 9,000 psi) for four minutes, were applied at 65, 78, and 100% FCI. Tetraploids were found in the 5.5 and 6.2 × 104 kPa group treatments only when applied at 65% FCI.
The results indicate that, while tetraploidy is inducible in salmonids, further experimentation is necessary to discern the appropriate time and treatment for optimal tetraploid induction in each species. 相似文献
Pressure treatments of 6.2 × 10
The effects of different pressures and the times of application were analyzed in a study with rainbow trout. Treatments of 4.8 × 10
The results indicate that, while tetraploidy is inducible in salmonids, further experimentation is necessary to discern the appropriate time and treatment for optimal tetraploid induction in each species. 相似文献
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Procedures for a viral replication in excised fin tissue (VREFT) assay were adapted to Pacific herring, Clupea pallasii, and optimized both to reduce processing time and to provide the greatest resolution between naïve herring and those previously exposed to viral haemorrhagic septicaemia virus (VHSV), Genogroup IVa. The optimized procedures included removal of the left pectoral fin from a euthanized fish, inoculation of the fin with >105 plaque‐forming units (PFU) mL?1 VHSV for 1 h, rinsing the fin in fresh medium six times to remove unadsorbed virions, incubation of the fin in fresh medium for 4 days and enumeration of the viral titre in a sample of the incubation medium by plaque assay. The optimized VREFT assay was effective at identifying the prior exposure history of laboratory‐reared Pacific herring to VHSV. The geometric mean VREFT value was significantly greater (P < 0.01) among naïve herring (1.2 × 103 PFU mL?1) than among groups that survived exposure to VHSV (1.0–2.9 × 102 PFU mL?1); additionally, the proportion of cultures with no detectable virus was significantly greater (P = 0.0002) among fish that survived exposure to VHSV (39–47%) than among naïve fish (3.3%). The optimized VREFT assay demonstrates promise for identifying VHSV exposure history and forecasting disease potential in populations of wild Pacific herring. 相似文献
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Two genetically distinct populations of chinook salmon, Oncorhynchus tshawytscha (Walbaum), were simultaneously sampled at the confluence of the Yukon and Tanana rivers in 2003. Upper Yukon-Canadian fish had significantly higher infection prevalence as well as more severe infections (higher parasite density in heart tissue) than the lower Yukon-Tanana River fish. Both populations had migrated the same distance from the mouth of the Yukon River at the time of sampling but had significantly different distances remaining to swim before reaching their respective spawning grounds. Multiple working hypotheses are proposed to explain the differences between the two stocks: (1) the two genetically distinct populations have different inherent resistance to infection, (2) genetically influenced differences in feeding behaviour resulted in temporal and/or spatial differences in exposure, (3) physiological differences resulting from different degrees of sexual maturity influenced the course of disease, and (4) the most severely infected Tanana River fish either died en route or fatigued and were unable to complete their migration to the Tanana River, thus leaving a population of apparently healthier fish. 相似文献
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Coal bed natural gas (CBNG) extraction in the Powder River (PR) Basin of Wyoming and Montana produces modestly saline-sodic
wastewater, which may have electrical conductivity (EC) and sodium adsorption ratios (SAR) exceeding accepted thresholds for
irrigation (EC = 3 dS m−1, SAR = 12 (mmolc l−1)1/2. As an approach to managing large volumes of CBNG-produced water, treatment processes have been developed to adjust produced
water salinity and sodicity to published irrigation guidelines and legislated in-stream standards. The objective of this laboratory
study was to assess acute and chronic soil solution EC and SAR responses to various wetting regimes simulating repeated flood
irrigation with treated CBNG product water, followed by single rainfall events. Fifty-four soil samples from irrigated fields
in southeast Montana were subjected to simulated PR water or CBNG water treated to EC and SAR values accepted as thresholds
for designation of saline × sodic water, in a single wetting event, five wetting–drying events, or five wetting–drying events,
followed by leaching with distilled water. Resultant saturated paste extract EC (ECe) and SAR of soils having <33% clay did
not differ from one another, but resulting ECe and SAR were all less than those for soil having >33% clay. Repeated wetting
with PR water having EC of 1.56 dS m−1 and SAR of 4.54 led to SAR <12, but brought ECe near 3 dS m−1. Repeated wetting with water having salinity = 3.12 dS m−1 and SAR = 13.09 led to ECe >3 dS m−1 and SAR near 12. Subsequent inundation and drainage with distilled water, simulating rainfall-quality leaching, reduced ECe
and SAR more often in coarse-textured, high salt content soils than in finer-textured, lower salt content soils. Decreases
in ECe upon leaching with distilled water were of greater magnitude than corresponding decreases in SAR, reinforcing supposition
of sodium-induced dispersion of fine-textured soils as a consequence of rainfall following irrigation with water having salinity
and sodicity levels equal to previously published thresholds. 相似文献
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Persistence of external signs in Pacific herring Clupea pallasii Valenciennes with ichthyophoniasis 
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下载免费PDF全文 The progression of external signs of Ichthyophonus infection in Pacific herring Clupea pallasii Valenciennes was highly variable and asynchronous after intraperitoneal injection with pure parasite preparations; however, external signs generally persisted through the end of the study (429 days post‐exposure). Observed signs included papules, erosions and ulcers. The prevalence of external signs plateaued 35 days post‐exposure and persisted in 73–79% of exposed individuals through the end of the first experiment (147 days post‐exposure). Among a second group of infected herring, external signs completely resolved in only 10% of the fish after 429 days. The onset of mortality preceded the appearance of external signs. Histological examination of infected skin and skeletal muscle tissues indicated an apparent affinity of the parasite for host red muscle. Host responses consisted primarily of granulomatous inflammation, fibrosis and necrosis in the skeletal muscle and other tissues. The persistence and asynchrony of external signs and host response indicated that they were neither a precursor to host mortality nor did they provide reliable metrics for hindcasting on the date of exposure. However, the long‐term persistence of clinical signs in Pacific herring may be useful in ascertaining the population‐level impacts of ichthyophoniasis in regularly observed populations. 相似文献