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Proteases secreted by strains of Aeromonas salmonicida 总被引：2，自引：0，他引：2
Abstract. The proteases secreted by four strains (MT004, 1102, 480 and 480P- ) of Aeromonas salmonicida grown in liquid culture have been studied. Strains MT004, 1102 and 480 all show a similar pattern with two types of proteases produced; one of molecular weight 70 000 which is active against casein and gelatin and one (or more) of lower molecular weight (about 20 000) which is (are) active against gelatin but not casein. Strain 480P- produces only the latter type of protease(s). The protease of molecular weight 70 000 is classified as a serine-type protease, but further characterization of the features of its active site has not yet proved possible. The results are discussed in terms of the previously published but often contradictory data on the proteases of A. salmonicida. 相似文献
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This study examines the impact of tax rates and tax rate differentials in a trade area on local sales tax revenues. Sales data for FY 1986 were analyzed for the 75 nonmetropolitan communities in Oklahoma with populations between 2,500 and 50,000. Multiple regression techniques were used to estimate local tax revenues as a function of tax rates, tax rate differential and local community economic and locational attributes. The results indicate that the tax rate differential was not significantly related to local revenue collection in the overall sample, but that the differential was significant for rural communities with relatively higher tax rates. Tax rate, income, service sector employment and a gravity factor were also significant influences on local sales tax revenues. These results imply that, because of the unique characteristics of rural retail markets and the dominance of rural trade centers, these rural trade center cities are able to raise local tax rates and effectively export tax burden to nonresidents without significantly affecting their retail sales when the tax differential is not a large one. 相似文献
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HEIDI DEWAR ERIC D. PRINCE MICHAEL K. MUSYL RICHARD W. BRILL CHUGEY SEPULVEDA JIANGANG LUO DAVID FOLEY ERIC S. ORBESEN DERKE SNODGRASS R. MICHAEL LAURS JOHN P. HOOLIHAN BARBARA A. BLOCK LIANNE M. MCNAUGHTON 《Fisheries Oceanography》2011,20(3):219-241
Swordfish are highly specialized top‐level predators that have been challenging to study. In this paper, data from 31 pop‐up satellite archival tags attached to swordfish from (i) the eastern Pacific, (ii) central Pacific, and (iii) western North Atlantic‐Caribbean were analyzed. Common across locations was a pronounced diel vertical pattern with daytime hours spent primarily below the thermocline and nighttime hours spent in warmer waters, close to the surface. One exception to this pattern was periodic daytime basking events which were most common in cooler waters off California. Maximum daytime depths were significantly correlated with light penetration as measured by the diffuse attenuation coefficient at 490 nm. Temperature did not appear to influence daytime depths, and swordfish tolerated both extremely low temperatures (4°C) and rapid and dramatic temperature changes (>20°C). Temperature did appear to influence the nighttime depths in the Pacific where fish typically remained in the surface mixed layer. In contrast, in the warm tropical Atlantic this was not the case, and nighttime depths were much deeper. In all areas, nighttime depth increased around the full moon. Given the parallels between the vertical movement patterns of swordfish and those of the deep sound scattering layer we suggest that swordfish vertical distribution patterns, especially during daytime, are influenced largely by resource availability. At night, when swordfish are typically targeted by fisheries, both ambient light and temperature influence movements. Understanding vertical movement patterns of swordfish can help evaluate gear vulnerability, improve population assessments, and potentially reduce fisheries bycatch. 相似文献
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E. D. PRINCE D. SNODGRASS E. S. ORBESEN J. P. HOOLIHAN & J. E. SERAFY J. E. SCHRATWIESER 《Fisheries Management and Ecology》2007,14(2):173-182
Abstract This study evaluates the performance of two types of non-offset circle hooks (traditional and non-traditional) and a similar-sized 'J' hook commonly used in the south Florida recreational live-bait fishery for Atlantic sailfish, Istiophorus platypterus (Shaw). A total of 766 sailfish were caught off south Florida (Jupiter to Key West, FL, USA) to assess hook performance and drop-back time, which is the interval between the fish's initial strike and exertion of pressure by the fisher to engage the hook. Four drop-back intervals were examined (0–5, 6–10, 11–15 and >15 s), and hook performance was assessed in terms of proportions of successful catch, undesirable hook locations, bleeding events and undesirable release condition associated with physical hook damage and trauma. In terms of hook performance, the traditionally-shaped circle hook had the greatest conservation benefit for survival after release. In addition, this was the only hook type tested that performed well during each drop-back interval for all performance metrics. Conversely, 'J' hooks resulted in higher proportions of undesirable hook locations (as much as twofold), bleeding and fish released in undesirable condition, particularly during long drop-back intervals. Non-traditional circle hooks had performance results intermediate to the other hook types, but also had the worst performance relative to undesirable release condition during the first two drop-back intervals. Choice of hook type and drop-back interval can significantly change hook wounding, and different models of non-offset circle hooks should not be assumed to perform equivalently. 相似文献
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ERIC D. PRINCE JIANGANG LUO C. PHILLIP GOODYEAR JOHN P. HOOLIHAN DERKE SNODGRASS ERIC S. ORBESEN JOSEPH E. SERAFY MAURICIO ORTIZ MICHAEL J. SCHIRRIPA 《Fisheries Oceanography》2010,19(6):448-462
Oxygen minimum zones (OMZs) below near‐surface optimums in the eastern tropical seas are among the largest contiguous areas of naturally occurring hypoxia in the world oceans, and are predicted to expand and shoal with global warming. In the eastern tropical Pacific (ETP), the surface mixed layer is defined by a shallow thermocline above a barrier of cold hypoxic water, where dissolved oxygen levels are ≤3.5 mL L?1. This thermocline (～25–50 m) constitutes a lower hypoxic habitat boundary for high oxygen demand tropical pelagic billfish and tunas (i.e., habitat compression). To evaluate similar oceanographic conditions found in the eastern tropical Atlantic (ETA), we compared vertical habitat use of 32 sailfish (Istiophorus platypterus) and 47 blue marlin (Makaira nigricans) monitored with pop‐up satellite archival tags in the ETA and western North Atlantic (WNA). Both species spent significantly greater proportions of their time in near‐surface waters when inside the ETA than when in the WNA. We contend that the near‐surface density of billfish and tunas increases as a consequence of the ETA OMZ, therefore increasing their vulnerability to overexploitation by surface gears. Because the ETA OMZ encompasses nearly all Atlantic equatorial waters, the potential impacts of overexploitation are a concern. Considering the obvious differences in catchability inside and outside the compression zones, it seems essential to standardize these catch rates separately to minimize inaccuracies in stock assessments for these species. This is especially true in light of global warming, which will likely exacerbate future compression impacts. 相似文献
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