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Trawling for cephalopods off the Portuguese coast—Fleet dynamics and landings composition 总被引：1，自引：0，他引：1
Tereza Fonseca Aida Campos Manuel Afonso-Dias Paulo Fonseca Joo Pereira 《Fisheries Research》2008,92(2-3):180-188
Fleet dynamics was addressed for three cephalopod taxa of commercial interest, the squid Loligo vulgaris, the octopuses Octopus vulgaris and Eledone cirrhosa, and the cuttlefish Sepia officinalis, for 48 trawlers of the fish trawling fleet. Landing profiles (LP) were identified based on the species composition of the landings using hierarchical cluster analysis. Four out of a total of 12 different LP were related to cephalopods and other species associated with them.The effects on the landing proportions of a number of variables, year, season and vessel, are analysed for each of the species studied using generalized linear models (GLM). The factor “vessel”, including an ensemble of technical characteristics as well as the abilities of individual skippers, explained most of the model deviance, strongly reinforcing the existence of a fleet component dedicated to catch cephalopods. However, time also explains much of the variation found in the data.Seasonal alternation between landings of octopodidae and cuttlefish was observed within a small group of old trawlers operating mainly off the south coast, following the abundance cycles of these species. For a larger group of more modern trawlers, operating off the western coast, inter-annual shift between octopus and squid was found, together with a well marked seasonal pattern between the catches of cephalopods and horse mackerel.Spatial patterns of activity were identified using vessel monitoring system (VMS) data available for trawlers in Portugal, demonstrating the existence of cephalopod targeting strategies in Portuguese fish trawling activities. 相似文献
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This study was designed as a comparative study with the intention to accumulate fundamental data on a wide variety of farriery methods. Twenty-five warmblood/crossbred horses, allocated into five groups (n = 5), underwent radiological and kinetic examination of the barefoot hoof, the shod hoof with a standard horseshoe, and finally a modified horseshoe. For radiographic measurements, a special podoblock with embedded reference points and changeable ground surfaces was used. Kinetic examinations were performed by placing one sensor between the shoe and the hoof and the second sensor between the shoe and the ground and then walking the horses on four different ground surfaces. When wedges were applied, the palmar angle increased by approximately 5° on all surfaces. However, this effect was only seen on firm surfaces combined with studs. Using a rocker shoe, the palmar angle increased on a firm surface (0.6 ± 0.3°) and decreased on a deformable surface (0.8 ± 0.3°). No consistent data were noted for the orientation of the proximal and middle phalanx in relation to the palmar angle. Pressure distribution showed wedges and studs to cause an increased pressure load on both the toe and the heels on a firm surface. Rocker shoes led to pressure peaks at the inner section of the toe, and high pressure was exerted on the quarters. In conclusion, all modified horseshoes showed unintended side effects and their influence on biomechanical parameters varied depending on the ground surface. 相似文献
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利用内蒙古植保站2009年开展的草地螟(Loxostege sticticalis)越冬代成虫标记放飞、捕获试验结果,对试验期间草地螟迁飞的气象条件进行综合分析.结果表明,草地螟的迁飞过程均对应冷锋的影响过程,850hPa高空图上(低层)具有长距离的暖湿气流,地面冷锋前部的上升气流和850hPa高空图上长距离的西南暖湿输送气流,是草地螟迁飞的主要环流背景条件.迁飞路径上低层气流、适宜的温度及气流的垂直上升运动,均有利于草地螟的飞行运转;回收区产生较大范围和量级的降雨,使其后部强劲的西北下沉气流更为显著,这一时期捕获的草地螟最多.研究结果对了解草地螟的迁飞习性,明确草地螟迁飞的气象条件,并进行早期预警具有重要意义. 相似文献
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