Movements in the harlequin fish (Othos dentex), a large predatory serranid from southern Australia: implications for detection and protection

The harlequin fish (Othos dentex) is the largest serranid found in the temperate waters of southern Australia. Acoustic telemetry was used to continuously track the movements and activity patterns of 10 harlequin fish (330–620?mm total length; 0.5–3?kg weight) for a 16-month period at a coastal reef site. Data showed that the harlequin fish is a site-attached, diurnal predator, with a relatively small home range in comparison with other temperate reef fishes from Australia and New Zealand. These characteristics indicate that the harlequin fish is susceptible to localised depletions from fishing, but that it can be protected within no-take marine protected areas and can be detected with appropriate daytime monitoring techniques. Individuals also displayed discrete depth preferences on the reef slope, evidence of a nocturnal home base, and homing ability following disturbance from an extreme storm event.     

东昆仑牦牛山组流纹岩锆石U-Pb年龄及构造意义

东昆仑水泥厂地区造山后火山-沉积盆地内形成的牦牛山组磨拉石建造不整合覆盖在前泥盆系地层之上,其形成时代的研究对限定东昆仑早古生代洋盆关闭的时间具有重要意义。应用激光烧蚀多接收器电感耦合等离子体质谱仪(LAMC-ICPMS)方法,对火山-沉积盆地内牦牛山组不同层位的流纹岩夹层进行了精确的锆石U-Pb定年研究。结果表明,盆地北缘牦牛山组底砾岩之上的流纹岩(B743-2)中岩浆锆石~(206)Pb/~(238)U年龄平均值为423.2±1.8Ma,盆地西缘牦牛山组底砾岩之上的流纹岩(B820-1)中岩浆锆石~(206)Pb/~(238)U年龄平均值为408.2±2.4Ma,盆地西缘和南缘牦牛山组中上部碎屑岩中流纹岩夹层(B705-1和B656-1)的岩浆锆石~(206)Pb/~(238)U年龄平均值分别为404.9±4.8Ma和399.6±2.8Ma。它们代表了牦牛山组不同层位火山岩的形成年龄,由此可以限定水泥厂地区牦牛山组形成时间为400～423Ma。上述年代学结果较为精确地限定了东昆仑早古生代洋盆关闭的构造年代。流纹岩中2486～920Ma元古代继承锆石的发现,说明东昆仑南的变质基底和扬子板块变质基底类似,是晋宁期0.9～1.0Ga罗迪尼亚超大陆形成时发育起来的。