Collaborative Research: Radiometric Age Validation of the Patagonian and Antarctic Toothfishes (Dissostichus Eleginoides and D. Mawsoni)

近年来，南极重新建立了人类对海洋资源的大规模利用。与早期的海豹和捕鲸活动不同，现代活动对磷虾和鳍鱼种群的影响是直接的，最明显的是罗斯海的巴塔哥尼亚牙鱼(Dissostichus Eginoides)，但也包括其同源南极牙鱼(Dissostichus Mawsoni)。牙鱼是一种宝贵的资源，很可能继续在世界市场上获得高价。然而，广泛的非法捕捞已引起人们对巴塔哥尼亚牙鱼种群被过度捕捞的严重关切。在世界其他地区，对更大的、有商业价值的物种的过度捕捞导致了海洋食物网的捕捞，留下了贫穷的、价值较低的生态系统。《养护南极海洋生物资源公约》是《南极条约》体系的一部分，其目标是在允许收获的同时避免对南极生态系统的破坏。为了实现这一目标，渔业的可持续管理取决于可靠的年龄数据。年龄数据允许对人口年龄结构进行建模，从而可以估计增长、死亡率和招聘率，并使用这些数据来了解人口动态。年龄数据为确定物种的生活史模式、建立种群动态模型以及确定在特定环境条件下哪些年龄段容易受到过度开发提供了依据。牙鱼目前的年龄和生长信息是基于年龄确定方法的，这些方法未经验证，并取决于具体的实验室和主要研究人员。最近，南极海洋生物资源养护委员会批准了使用耳石的三种制备方法和一套根据耳石微结构估计年龄的共同标准。南极海生委耳石网络也已启动，作为交换样本的媒介，以确保读者和实验室之间的年龄估计具有可比性。然而，需要做大量的工作来确保这三种方法产生的年龄估计是准确的。一项成功的技术是放射性年龄测定，它使用耳石中铅-210和镭-226的不平衡作为自然计时器。这项提议汇集了一个国际合作，以检查这两个牙鱼物种的种群年龄结构，在一个实验设计中，建立在所有三种制备方法产生的年龄数据的放射性验证测试基础上。为了将验证部分纳入整个南极审查牙鱼种群年龄结构的努力，验证工作的子样本将从澳大利亚、新西兰、联合王国和法国以及美国的研究小组为进行种群年龄研究而采集的样本集中抽取。莫斯·兰丁海洋实验室的科学家们将使用放射性年龄测定技术来独立测定巴塔哥尼亚和南极牙鱼的耳石年龄。老道明大学的科学家将使用已经建立的老龄化系统来生成经过验证的年龄数据，从而可以根据地理区域估计生长、死亡率和寿命。该项目将提供经过验证的耳石样本集，作为建立统一和有效的牙鱼年龄估计系统的基础。这项研究将提供信息，向公众、政策制定者和国际社会传播。该项目将为两所大学中代表性不足的学生提供机会。

Recent years have seen the re-establishment of large-scale marine resource utilization by humans in the Antarctic. In contrast to early sealing and whaling activity, the modern impact is directed on krill and finfish populations, most notably of the Patagonian toothfish (Dissostichus eleginoides), but also its congenor the Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea. Toothfish are a valuable resource and are likely to continue to command a high price in world markets. However, extensive illegal fishing has lead to considerable concern that Patagonian toothfish populations are being over-harvested. In other parts of the world, over-harvesting of larger, commercially valuable species has led to fishing down of marine food webs, leaving impoverished, less valuable ecosystems. The goal of the Convention for the Conservation of Antarctic Marine Living Resources, part of the Antarctic Treaty System, is to allow harvest while avoiding disruptions to the Antarctic ecosystem. To achieve this, the sustainable management of the fishery depends on reliable age data. Age data allow population age structure to be modeled, so that growth, mortality and recruitment rates can be estimated and used to understand population dynamics. Age data provides the basis to determine the life history pattern of a species, to model population dynamics, and to determine which age classes are vulnerable to over-exploitation under a particular set of environmental conditions. Current age and growth information for toothfish is based on age determination methodologies which are not validated and depend on the specific laboratory and principal investigator. Recently, the Commission of the Conservation of Antarctic Marine Living Resources has endorsed three preparation methodologies using otoliths and a common set of criteria for estimating age from otolith micro-structure. The CCAMLR Otolith Network has also been initiated as a medium for exchanging samples to ensure that age estimates are comparable between readers and laboratories. However, considerable work is needed to ensure that age estimates generated by the three methodologies are accurate. One technique that has been successful is radiometric age determination, which uses the disequilibria of lead-210 and radium-226 in otoliths as a natural chronometer. This proposal brings together an international collaboration to examine population age structure for both toothfish species, in an experimental design built around radiometric validation tests of age data generated by all three preparation methodologies. To integrate the validation component within an Antarctic-wide effort to examine toothfish population age structure, sub-samples for validation work will be drawn from sample sets taken for population age studies by research teams working in Australia, New Zealand, the United Kingdom and France, as well as the United States. Scientists at Moss Landing Marine Laboratories will use radiometric age determination to independently age otoliths from Patagonian and Antarctic toothfishes. Scientists at Old Dominion University will use a system already established for aging to generate validated age data, allowing growth, mortality, and longevity to be estimated by geographic areas. The project will provide validated otolith sample sets that can be used as a foundation for a unified and validated age estimation system for the toothfishes. This study will provide information which will be disseminated to the public, policy-makers and the international community. The project will provide opportunities for under-represented students at both universities.