ABSTRACT

The snoek, Thyrsites atun, is a pelagic fish of the family Gempylidae that inhabits cold waters of the southern hemisphere. It is an important fishing resource species (e.g. Chile, Namibia, New Zealand) linked mainly to the artisanal fisheries, however, its phylogeographic and population aspects are largely unknown. In this study we provide the first detailed analysis of the phylogeographic patterns and demographic processes of the snoek for the southern hemisphere using mitochondrial data of the Cytochrome c Oxidase subunit I gene. Our results indicate two lineages: (i) Australia-New Zealand, and (ii) Chile-South Africa-Namibia. The Australia-New Zealand clade shows partial isolation between populations associated with distinct biogeographic regions, likely driven by the region’s oceanography. The divergence between the lineages happened ∼800,000 years ago. On the other hand, analysis of the fish caught in the South-eastern Pacific (Chile) showed that the genetic diversity among localities (hT = 0.657) was lower than within localities (hS = 0.664), which was consistent with the pairwise comparisons results, suggesting the absence of phylogeographic structure. Based on our estimations, population expansion in T. atun would have occurred ∼7.5 ka (after LGM) under the Bayesian skyline plots approximation. We discuss the scope that this study could have in fisheries management of this important species.

摘要

The snoek, Thyrsites atun, 是一种生活在南半球寒冷水域的 Gempylidae 科的远洋鱼类。它是一种重要的渔业资源物种（例如智利、纳米比亚、新西兰），主要与手工渔业有关，然而，其系统地理学和种群方面在很大程度上是未知的。在这项研究中，我们使用细胞色素 c 氧化酶亚基 I 基因的线粒体数据，首次详细分析了南半球 snoek 的系统地理学模式和人口统计过程。我们的结果表明有两个谱系：(i) 澳大利亚-新西兰，和 (ii) 智利-南非-纳米比亚。澳大利亚-新西兰分支显示出与不同生物地理区域相关的种群之间的部分隔离，这可能是由该地区的海洋学驱动的。谱系之间的分歧发生在大约 80 万年前。h T = 0.657) 低于区域内 ( h S = 0.664)，这与成对比较结果一致，表明缺乏系统地理学结构。根据我们的估计，在贝叶斯天际线图近似下，T. atun 的人口扩张将发生 ~7.5 ka（LGM 之后）。我们讨论了这项研究在这一重要物种的渔业管理中可能具有的范围。