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1.
In connection with a case of epidemic disease with high morbidity and mortality in a flock of sheep, a pestivirus infection could be diagnosed. Pathological-anatomical abnormalities were very similar to the character of BVD/MD. Scientific findings on pestivirus infections in sheep are discussed. 相似文献
2.
Michael H. Meeuwig Christopher S. Guy Wade A. Fredenberg 《Ecology of Freshwater Fish》2011,20(2):315-325
Abstract – Bull trout, a species of char listed as threatened under the US Endangered Species Act, have been displaced from portions of their historic range following the introduction of nonnative lake trout. It has been suggested that competitive exclusion as a result of trophic overlap between bull trout and lake trout may be the causal mechanism associated with displacement of bull trout. This study used stable isotope data to evaluate trophic relationships among native bull trout, nonnative lake trout and other fishes in seven lakes in Glacier National Park (GNP), Montana. Bull trout and lake trout had greater δ15N values relative to other fishes among lakes (δ15N ≥ 3.0‰). Lake trout had greater δ15N values relative to bull trout (δ15N = +1.0‰). Bull trout had greater δ13C values relative to lake trout in six of the seven lakes examined. Although both bull trout and lake trout had greater δ15N values relative to other fishes within lakes in GNP, differences in δ15N and δ13C between bull trout and lake trout suggest that they are consuming different prey species or similar prey species in different proportions. Therefore, displacement of bull trout as a direct result of complete overlap in food resource use is not anticipated unless diet shifts occur or food resources become limiting. Additionally, future studies should evaluate food habits to identify important prey species and sources of partial dietary overlap between bull trout and lake trout. 相似文献
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Yukihiro Kitade Michiko Nakamura Hirotoshi Endo Satoru Fukuda Kazuyoshi Kuwano Naotsune Saga 《Fisheries Science》2006,72(3):639-645
ABSTRACT: A cDNA ( PyARP4 ) containing an open reading frame for a protein of 573 amino acids was identified in the marine red alga Porphyra yezoensis . The conceptual PyARP4 protein exhibits significant similarity to actin-related protein (ARP) 4 in the terrestrial plant Arabidopsis . Comparison of the deduced amino acid sequence showed moderate sequence identity (30%) to a conventional actin in P. yezoensis , as seen in comparisons between ARP and conventional actins of other organisms. A putative bipartite nuclear localization signal and an actin motif were found within the PyARP4 amino acid sequence. In a phylogenetic analysis, the PyARP4 was found to cluster with the ARP4 of other organisms. The expression level of PyARP4 did not change significantly among four developmental stages of life cycle and was lower than that of a conventional actin. This cDNA therefore may serve as a useful internal standard in gene expression analyses of differentially expressed genes in P. yezoensis . 相似文献
5.
We address the importance of the isoelectric point (IEP) of proteins and membrane components such as phospholipids for our
understanding and interpretation of isoforms and opposite charge interactions in the formation of complexes. Five examples
drawn from the literature are newly approached from the IEP point of view to clarify general principles. 相似文献
6.
Seeding of new biological filters with nitrifying bacteria is effective in reducing activation time of the new filters. In a series of tests, seeded filters were activated in an average of 10.7 days, compared with 22.2 days for the unseeded controls. The shorter activation period results from the reduced time required for the nitrifying organisms to increase in numbers to their environmental equilibrium in the system tested. 相似文献
7.
Sarah C. F. Hawkshaw Michael P. Gillingham J. Mark Shrimpton 《Ecology of Freshwater Fish》2014,23(3):383-394
Flooding river valleys following construction of dams restrict fluvial environments to reaches that were formerly headwaters. Whether remaining habitat is suitable for all life stages of fluvial species is poorly understood. A fluvial species, Arctic grayling Thymallus arcticus, showed a dramatic decline following flooding of the Upper Peace River and the formation of the Williston Reservoir. We related landscape and field site‐specific features with occurrence of juvenile Arctic grayling using an information theoretic approach. For the landscape model, an association was identified between stream order and Arctic grayling occurrence although stream order alone was a poor predictor. A positive association between juvenile Arctic grayling occurrence and distance from the Williston reservoir and stream order, as well as a negative association with water temperature and temperature variance, was deemed important for the field site model. Both modelling approaches indicated size of stream system to be an important influence on occurrence of juvenile grayling in the Williston watershed. River length required for suitable river habitat for salmonids has not previously been identified, but should be factored into future management plans when evaluating the impact of proposed hydroelectric dams and subsequent flooding of river systems. 相似文献
8.
Abstract This study aimed to develop and test an electrode array for a resistivity fish counter that could be easily installed in a small river without a weir. An electrode array consisting of three steel cables laid in parallel across the stream channel and connected to a microprocessor-based counter was tested in an Atlantic salmon, Salmo salar L., spawning tributary. The accuracy of the counter was assessed by observing fish movements with closed-circuit television. Most salmon moving upstream were registered correctly (90% overall). Detection of downstream movement was less reliable (60% overall), as a consequence of downstream swimming behaviour. The accuracy of the downstream count was improved by tensioning the cable electrodes, but remained lower than that of the upstream count. Since salmon swam repeatedly up- and downstream, this discrepancy resulted in an overestimate of the net upstream count. The accuracy of the downstream count needs to be improved before a bed-mounted electrode array could be used for routine salmon counting. 相似文献
9.
Water quality and waste production in a recirculating trout-culture system with feeding of a higher-energy or a lower-energy diet 总被引：2，自引：0，他引：2
Higher-energy fish feeds can reduce waste discharges and might also improve water quality in recirculating fish-culture systems. A higher-energy diet, Zeigler Salmon High Energy feed (HE; 45% protein, 20% fat, 17.4 MJ digestible energy kg-1) and a lower-energy diet, Zeigler Hi-Fat Trout Grower (LE; 38% protein, 12% fat, 14.6 MJ digestible energy kg -1) were fed ad libitum at different times to rainbow trout, Oncorhynchus mykiss (Walbaum), in a semi-closed recirculating culture system by means of demand feeders. The system contained two 10-m3 fish-culture tanks, each with a downstream microscreen (80 μn) filter. Feeding rates per day and per unit biomass were not significantly different between diets. In general, use of HE was associated with higher levels of total ammonia nitrogen (TAN) and NO2-N, lower BOD5 and total suspended solids (TSS), and lower effluent releases of suspended solids per unit feed, NO3-N per unit feed, and dissolved phosphorus per unit feed. Although total effluent P per unit feed or P fed did not differ significantly between diets, HE had significantly more of the total effluent P in the settleable solids, 85% vs. 76%. Differences in water quality in the system were probably not of great importance with respect to fish health. 相似文献
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11.
Nitrification performance of a propeller-washed bead clarifier supporting a fluidized sand biofilter in a recirculating warmwater fish system 总被引：1，自引：0，他引：1
A propeller-wash bead filter (PWBF) and a fluidized sand filter (FSF) on a 28 m3 recirculating system stocked with tilapia maintained favorable water quality at five different feed rates, ranging from 0.9 to 4.5 kg feed per day. TAN removal rates ranged up to about 200 g TAN/m3 of media per day for each of the units. Peak rates of 244 g TAN/m3 of media per day were observed when the recirculating flow was boosted by 20%. Roughly 75% of the removal was accomplished by the fluidized sand filter an observation that is consistent with the difference between the fluidized sand filter volume (0.92 m3) and the bead filter media volume (0.28 m3). The bead filter's primary function was clarification. At the highest daily feed load, over 570 g dry weight of solids were removed during each daily bead filter backwashing event. A 20% increase in flow, at the same daily feed rate, improved solids removal to over 670 g dry weight per bead filter backwash event. The PWBF and FSF combination provided suitable water quality for fish production; however, further increases in feed loading were limited by carbon dioxide buildup and oxygen limitations. 相似文献
12.
A. J. Blank M. J. Hamel J. J. Spurgeon M. A. Pegg 《Fisheries Management and Ecology》2017,24(6):460-468
Estimates of dynamic rate functions for riverine channel catfish, Ictalurus punctatus (Rafinesque), populations are limited. The open nature and inherent difficulty in sampling riverine environments and the propensity for dispersal of channel catfish impede estimation of population variables. However, contemporary population models (i.e. robust design models) can incorporate the open nature of these systems. The purpose of this study was to determine channel catfish population abundance, survival and size structure and to characterise growth in the lower Platte River, Nebraska, USA. Annual survival estimates of adult channel catfish were 13%–49%, and channel catfish abundance estimates ranged from 8,281 to 24,261 fish within a 10‐km sampling reach. Channel catfish were predominantly (90%) <age 5 and <400 mm total length, and adult growth was similar to other populations across the species’ range. The channel catfish population characteristics in the lower Platte River are likely a result of a combination of factors including recreational harvest and potential shifts in habitat during different life stages. A multifaceted sampling and analytical approach provided additional information such as movement and abundance estimates and may also help to decipher abiotic and biotic factors that interact when managing fish populations in riverine environments. 相似文献
13.
Recently, the increasing population of giant jellyfish Nemopilema nomurai has negatively affected coastal fisheries in Korea. As a result, the fishing industry has begun developing devices to prevent
jellyfish capture. In this study, we assessed the performance of a conical jellyfish exclusion device in the coastal areas
of Yokji Island in southern Korea during 2009. After hauling, we measured the length, diameter, and weight of the jellyfish
and fish that were captured by the cod end and cover net. We found that the captured species included N. nomurai, silver croakers Pennahia argentata, yellow croakers Larimichthys polyactics, shotted halibut Eopsetta grigorjewi, largehead hairtails Trichiurus lepturus, and melon seeds Psenopsis anomala. The catch ratios of the giant jellyfish that entered the cod end in terms of weight ranged from 0.005 to 0.027. In contrast,
the catch ratios of total fish in terms of weight and number were 0.793 and 0.835, respectively. On selectivity analysis of
a conical separator for individual fish species, their exclusion ratios were independent of their length, and were similar
to their observed exclusion ratios in terms of number. These results indicated that the conical jellyfish exclusion device
performs well; however, some improvements are needed to minimize the escape of fish from the net. 相似文献
14.
Spawning period of a southern brown trout population in a highly unpredictable stream 总被引：1，自引：1，他引：0
J. Gortázar D. García de Jalón C. Alonso-González P. Vizcaíno D. Baeza M. Marchamalo 《Ecology of Freshwater Fish》2007,16(4):515-527
Abstract – The spawning period of brown trout ( Salmo trutta L.) was studied in the river Castril, southern Spain, by means of redd counts. This mountain stream is located near to the southern limit of the species' natural distribution range and it shows a highly unpredictable flow regime. The spawning period extended from December to mid-April and the maximum reproductive activity was in February. These results represent the latest reproduction date and the longest spawning period reported in the literature along the natural distribution range of the species. However, belated spawning in the Castril is congruent with the known latitudinal cline: the lower the latitude, the later the spawning period. Our results, along with a review of the literature on natural populations, also showed that the duration of reproduction is the longer, the lower the latitude. Spawning lasted twice as long in the main stem of the river, which is connected with a reservoir, than in the isolated reaches. These differences may be linked to the influence of the reservoir and to habitat fragmentation. We discuss and support the hypothesis that a long spawning period is an advantage for survival in unpredictable habitats. The belated and protracted spawning period found in river Castril has important implications in fisheries management. A strong research effort is needed in order to fill the critical lack of data on southern brown trout populations. 相似文献
15.
The unusual incidence of a pedunculated fibrosarcoma in the uterus of a donkey is reported. The tumor caused colic-like symptoms and blood tinged vaginal discharge. The diagnosis was made by ultrasound and rectal examination. The patient was successfully treated surgically, by ovariohysterectomy. 相似文献
16.
The inland fisheries of Sri Lanka are essentially artisanal on most of the reservoirs in the country. The annual inland fish production declined dramatically after 1990, when state patronage for the development of the inland fisheries was discontinued for 4 years. This decline was shown to be a result of growth overfishing of the two dominant cichlid species which accounted for over 90% of landings. This was a result of using small mesh ( < 6.9 cm) gillnets in the absence of the State-sponsored monitoring procedure in the fishery after 1990. This indicates that it is necessary to monitor inland fisheries management in Sri Lanka through a centralized authority in the current situation. However, in some Sri Lankan reservoirs, fishing communities can be categorized as 'organized' because they collectively make decisions to define procedures for the rational exploitation of the fishery resources. In reservoirs with 'organized' fishing, the communities themselves have developed mechanisms to regulate the landing sizes of dominant cichlid fish species through community-based fisheries management strategies. In such reservoirs, over-exploitation of fish stocks was not evident, even after 1990, when state-sponsored monitoring procedures were suspended. Based on these observations, an alternative approach is recommended for the management of Sri Lankan reservoir capture fisheries in which the Government and resource-users have equal responsibilities in the management of the resources. 相似文献
17.
丙三醇是生物柴油生产的副产物,具有能量利用的饲用价值。本文用丙三醇或甘油的名称讨论了它的营养价值和在不同畜禽种类中的利用情况,提出了有价值的研究方向。 相似文献
18.
The legislation permitting control of phosphorus inputs into the aquatic environment From point and diffuse sources is complex and incomplete. River Purification Authorities in Scotland are responsible for the implementation of this legislation, and additionally, have adopted policies aimed at protecting waters from the effects of eutrophication. This paper describes the implementation of the legislation and the policies adopted by the Forth River Purification Board for the control of freshwater eutrophication by reference to the Lake of Menteith. in Central Scotland. The Lake of Menteith is described, the results of a detailed monitoring exercise are presented and the control measures applied are discussed. The Lake of Menteith is classified as mesotrophic. it has a high conservation and amenity value, and is operated as a commercial sport fishery by the Lake of Menteith Fishery Company. The Company operate a fish cage rearing unit on the Lake and two land-based rearing units on tributary streams. The phosphorus budget for the Lake is described and the implications for future controls discussed. 相似文献
19.
An experiment designed to measure the volume variation of a bag-net within a set-net was conducted in Jaran Bay, Kosung, Korea. Three radio-acoustic-linked positioning (RAP) buoys, a time controller with a personal computer and seven pingers were used to measure the volumes of the bags. During the April neap tide, the minimum and maximum volumes of the bag-net were 4173 m3 (at 17.00 h) and 4757 m3 (12.00 h), respectively. The average current directions and speeds were 99.9°, 12.9 cm/s and 104.0°, 2.4 cm/s, respectively. During the spring tide, the minimum and maximum volumes of the bag-net were 2016 m3 (18.30 h) and 4454 m3 (15.00 h), respectively. The average current directions and speeds were 315.6°, 16.1 cm/s and 289.0°, 5.7 cm/s, respectively. The minimum (2016 m3) and maximum (5568 m3) volumes of the bag-net were observed during the period when the spring tide changed to the neap tide. 相似文献
20.
A case of parakeratosis in pigs due to secondary zinc deficiency (zinc/calcium ratio 0.4 g/100 g; 68.7 mg zinc, 17.1 g calcium per kg food) is reported. Morbidity and symptoms were much more marked in growing boars than in female animals of the same age. In sows the disorder appeared ten days after the first symptoms were seen in the boars. Adult breeding pigs developed no signs of parakeratosis. 相似文献