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Field experiments were conducted to ascertain if trawling utilizing electrical currents was an effective method of harvesting crawfish.Results suggest that catch efficiency relative to vegetation density is more dependent upon trawl mechanical ability than on relative crawfish abundance. Catch is also dependent upon trawling speed, water depth and time of trawling. Trawling consistently yielded higher catches per area than did conventional traps. Unmarketable individuals and mortality were no different for the two gear types.Trawling could be an effective supplemental harvesting method, but additional work needs to be performed to alleviate electrical and mechanical problems before economic efficiency can be realistic. 相似文献
54.
Joshua D. Gamble Gregg Johnson Craig C. Sheaffer Dean A. Current Donald L. Wyse 《Agroforestry Systems》2014,88(1):75-85
In May 2010, alley cropping systems consisting of switchgrass (Panicum virgatum L.), prairie cordgrass (Spartina pectinata Bosc ex Link), an alfalfa (Medicago sativa L.) and intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey) mixture, and a native tallgrass-forb-legume polyculture, planted between multi-row strips of poplar hybrid ‘NM6’ (Populus maximowiczii x P. nigra) and willow cultivar ‘Fish Creek’ (Salix purpurea) were established at Empire and Granada, Minnesota, USA. Crop establishment and productivity were characterized for each species over two growing seasons and at two distances from the tree-crop interface. Prairie cordgrass and the native polyculture were among the most productive herbaceous crops at both sites, averaging between 7.1 and 11.9 Mg DM ha?1, and have shown no evidence of competition for resources along the tree-crop interface thus far. Basal area (BA) was similar at Empire for NM6 (1,744 mm2 tree?1) and Fish Creek (1,609 mm2 tree?1), but was greater for NM6 (1,045 mm2 tree?1) than Fish Creek (770 mm2 tree?1) at Granada. Despite this, stand basal area (SBA) was greater for Fish Creek at both sites due to greater planting density. Across species, BA and SBA were greater for trees along the alley than those in center rows at Empire, whereas no difference was observed at Granada. Results suggest that alley cropping provides suitable conditions for establishment of short-rotation woody and certain herbaceous biomass crops, and that some of these crops may be well suited to the alley cropping environment. However, continued research is needed to evaluate crop persistence and productivity as crops and trees mature and the potential for interspecies competition increases. 相似文献
55.
Jerom R. Stocks Sam Davis Marti J. Anderson Martin W. Asmus Katherine J.M. Cheshire Dylan E. van der Meulen Chris T. Walsh Dean M. Gilligan 《水产资源保护:海洋与淡水生态系统》2021,31(11):3228-3247
- Fish assemblages in dryland rivers have life-history strategies that have evolved in response to environmental conditions and triggers, particularly water temperatures and flow regimes. The regulation of rivers through the construction of dams, weirs and other water diversion structures has altered natural flow regimes and the associated ecological processes of river systems worldwide.
- Over a 3-year period, using standardized fish sampling and daily otolith ageing, the recruitment of eight freshwater fish species was monitored in response to various abiotic drivers, including hydrology and water temperatures, throughout the Macquarie River, a large regulated river system of the Australian Murray-Darling Basin.
- A data-driven statistical classification system is provided that groups species into reproductive guilds, based on their recruitment response to hydrology and water temperature, specifically designed for use in environmental flow management.
- The eight species were grouped into three distinct reproductive guilds that showed similar recruitment responses to the abiotic drivers. Murray-Darling rainbowfish, Murray cod, and eel-tailed catfish were considered as a single guild, characterized by seasonal recruitment during a relatively narrow thermal window under low to moderate stable discharges. The second group included common carp, bony herring, and golden perch, which recruited primarily in association with larger flow events. Un-specked hardyhead and Australian smelt formed a more differentiated guild, recruiting over a broad range of temperatures and discharges. Limitations associated with using a reproductive guild approach to simplify water management are discussed.
- This study highlighted important relationships among hydrology, water temperatures, and successful recruitment that can, in turn, be used to inform development of adaptive flow management plans and effective use of environmental water for the conservation management of native fish communities. Important considerations in the design of studies that aim to examine relationships between recruitment and abiotic drivers are also discussed.
56.
Effects of age and prosthesis material on in vitro cartilage retention of laryngoplasty prostheses in horses 总被引:1,自引:0,他引:1
Cartilage retention strengths of laryngoplasty prostheses were compared in larynges of 2-, 3-, and 4-year-old horses, using doubled polyester and expanded polytetrafluoroethylene prostheses. Bilateral laryngoplasties were performed on each of 15 (seven 2-year-old, two 3-year-old, and six 4-year-old) larynges, which were collected at an abbatoir. Prostheses were secured to a mechanical testing machine, and tension causing arytenoid cartilage abduction was applied, until total failure of the cartilage or prosthesis resulted. Tension caused cricoid cartilage failure in 1 specimen, and muscular process cartilage failure in the remainder. There was no significant effect of age, prosthetic material, or side of prosthesis placement on cartilage retention of the prostheses. Additionally, frequency of multiple load-displacement peaks, indicating partial muscular process failure, was not affected by age or prosthetic material variables. 相似文献
57.
Lisa S Baller Dean A Hendrickson 《Veterinary Clinics of North America: Equine Practice》2002,18(1):117-31, vii
Pain management is an extremely vital part of equine orthopedic surgery. Providing optimum analgesia for the patient will decrease recovery time, decrease physiologic stress on the animal, and provide maximum comfort during the post-operative period. The major analgesic drug categories and routes covered are nonsteroidal anti-inflammatory drugs, local anesthetics, intra-articular drugs, and epidurals. 相似文献
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59.
Muhammad Iqbal Alireza Navabi Donald F. Salmon Rong-Cai Yang Brenda M. Murdoch Steve S. Moore Dean Spaner 《Euphytica》2007,154(1-2):207-218
Due to the short growing season in the high northern latitudes, the development of early maturing spring wheat (Triticum aestivum L.) cultivars is important to avoid frost damage which can lower production and quality. We investigated earliness of flowering and maturity, and some associated agronomic traits, using a set of randomly selected high northern latitude adapted spring wheat cultivars (differing in maturity) and their F1 and F2 crosses made in a one-way diallel mating design. The parents, and their F1 and F2 crosses were evaluated under field conditions over 2 years. Anthesis and maturity times were controlled by both vernalization response and earliness per se genes, mainly acting additively. Non-additive genetic effects were more important in controlling grain fill duration, grain yield and plant height. Additive × additive epistatic effects were detected for all traits studied except time to anthesis. Segregation analyses of the F2 populations for time to anthesis indicated the presence of different vernalization response genes. Molecular genetic analyses revealed the presence of Vrn-A1 and Vrn-B1 genes in the parental cultivars. Narrow-sense heritability was medium to high (60–86%) for anthesis and maturity times but low to medium (13–55%) for grain fill duration, plant height and grain yield. Selection for early flowering/maturity in early segregating generations would be expected to result in genetic improvement towards earliness in high latitude spring wheats. Incorporation of the vernalization responsive gene Vrn-B1 in combination with vernalization non-responsive gene Vrn-A1 into spring wheats would aid in the development of early maturing cultivars with high grain yield potential for the high latitude wheat growing regions of the northern hemisphere. 相似文献
60.
Inheritance of fiber quality and lint yield in a chemically mutated population of cotton 总被引:2,自引:0,他引:2
Andy D. Herring Dick L. Auld M. Dean Ethridge Eric F. Hequet E. Bechere Cary J. Green Roy G. Cantrell 《Euphytica》2004,136(3):333-339
The narrow germplasm base of the upland cotton (Gossypium hirsutum L.), grown on the Texas high plains historically, has limited improvement of fiber quality. Chemical mutagenesis and subsequent selection have helped the development of lines with improved fiber quality in cultivars adapted to this region. This study was conducted to determine the inheritance of improvements in fiber quality. M3 lines with divergent fiber properties of micronaire, length, and strength were selected from a population of Paymaster HS 200 treated with 3% v/v ethyl methanesulfonate (EMS) for two hours. The 115 selected lines of M4 and M5 generation were evaluated for fiber quality and lint yield. Regression of the M4 and M5 on the M3 generation, as well as the M5 on the M4 was used to generate narrow sense heritability coefficients. Significant variations were observed between the mutant lines in all generations except for lint yield in the M5 (1997). The highest heritability estimates were found in fiber length (h
2= 0.29** to 0.46**). Micronaire and strength showed intermediate heritability estimates of h
2= 0.14 to 0.19, while lint yield had a very low heritability estimate of h
2= 0.03. Fiber length and strength were correlated (r= 0.58** to 0.46**) in all the three generations. The mutants identified in these studies have the potential to improve fiber quality of upland cotton without introducing alien genes that may reduce adaptation to short growing season production regions. 相似文献