排序方式： 共有2条查询结果，搜索用时 0 毫秒
1
1.
Do by‐catch reduction devices in longline fisheries reduce capture of sharks and rays? A global meta‐analysis 
下载免费PDF全文
下载免费PDF全文 By‐catch in marine fisheries, particularly those using pelagic and demersal longlines, is a major driver of declines in abundance of sharks and rays around the world. A wide variety of by‐catch reduction devices (BRDs), that is, modified gears designed to reduce incidental captures of a variety of marine species while maintaining target catch rates, have been proposed, but the extent to which BRDs actually reduce the risk of catching sharks and rays remains unclear. We performed a meta‐analysis of 27 publications that reported the capture of sharks and rays and, in some cases, of targeted teleosts in longline gear deployed with and without BRDs. The risk of shark and ray capture differed between types of BRDs, but only one BRD type, longlines raised off the bottom, reduced by‐catch significantly. Circle hooks did not reduce the risk of capturing sharks and rays but might improve discard survival and are inexpensive, which might make them effective in reducing the detrimental effects of longlining on these species. In addition to being generally ineffective, some devices, such as electropositive and magnetic repellents, are expensive and have inherent construction drawbacks that are likely to make them unsuitable for commercial use. Overall, most BRDs did not affect the likelihood of catching targeted teleosts, but a substantial number of studies did not adequately assess target catch. We identified two poorly studied classes of BRD gear (i.e. raised demersal longlines, and monofilament nylon leaders), which represent promising directions for future research. 相似文献
2.
将240只7日龄AA肉鸡随机分成4组,各组在玉米-豆粕型基础日粮中,分别添加0(对照)、12.5、37.5、62.5mg/kg的大蒜素,饲养期42天。结果表明:各组间肉鸡的免疫器官相对重量相比,添加大蒜素三个处理组35日龄法氏囊均比对照组(0mg/kg)显著增加(p<0.05),其中,37.5、62.5mg/kg两处理组21日龄胸腺和62.5mg/kg处理组35日龄脾脏均比对照组显著增加(p<0.05);T淋巴细胞阳性率结果显示,37.5mg/kg、62.5mg/kg两处理组明显高于对照组(p<0.05)。 相似文献
1