Data from: Applying the multistate capture-recapture robust design to characterize metapopulation structure

1. Population structure must be considered when developing mark-recapture (MR) study designs as the sampling of individuals from multiple populations (or subpopulations) may increase heterogeneity in individual capture probability. Conversely, the use of an appropriate MR study design which accommodates heterogeneity associated with capture-occasion varying covariates due to animals moving between ‘states’ (i.e. geographic sites) can provide insight into how animals are distributed in a particular environment and the status and connectivity of subpopulations.
2. The Multistate Closed Robust Design was chosen to investigate: 1) the demographic parameters of Indo-Pacific bottlenose dolphins (Tursiops aduncus) subpopulations in coastal and estuarine waters of Perth, Western Australia; and 2) how they are related to each other in a metapopulation. Using four years of year-round photo-identification surveys across three geographic sites, we accounted for heterogeneity of capture probability based on how individuals distributed themselves across geographic sites and characterized the status of subpopulations based on their abundance, survival and interconnection.
3. MSCRD models highlighted high heterogeneity in capture probabilities and demographic parameters between sites. High capture probabilities, high survival and constant abundances described a subpopulation with high fidelity in an estuary. In contrast, low captures, permanent and temporary emigration and fluctuating abundances suggested transient use and low fidelity in an open coastline site.
4. Estimates of transition probabilities also varied between sites, with estuarine dolphins visiting sheltered coastal embayments more regularly than coastal dolphins visited the estuary, highlighting some dynamics within the metapopulation.
6. Synthesis and applications. To date, bottlenose dolphin studies using mark-recapture approach have focussed on investigating single subpopulations. Here, in a heterogeneous coastal-estuarine environment, we demonstrated that spatially structured bottlenose dolphin subpopulations contained distinct suites of individuals and differed in size, demographics and connectivity. Such insights into the dynamics of a metapopulation can assist in local-scale species conservation. The MSCRD approach is applicable to species/populations consisting of recognizable individuals and is particularly useful for characterizing wildlife subpopulations that vary in their vulnerability to human activities, climate change or invasive species.

1. 在制定标记重捕（mark-recapture, MR）研究方案时，必须考量种群结构——从多个种群（或亚种群）中抽取个体，可能会加剧个体捕获概率的异质性。反之，采用适配因动物在不同“状态”（即地理位点）间移动所导致的、与随捕获时段变化的协变量相关的异质性的恰当标记重捕研究设计，可帮助解析动物在特定环境中的分布模式，以及亚种群的现状与连通性。
2. 本研究选用多状态闭合稳健设计（Multistate Closed Robust Design, MSCRD），旨在探究两大核心内容：其一，西澳大利亚州珀斯沿岸与河口水域中印太瓶鼻海豚（Indo-Pacific bottlenose dolphins, Tursiops aduncus）亚种群的种群统计参数；其二，它们在集合种群（metapopulation）中的相互关联模式。研究依托覆盖三个地理位点、为期四年的全年度照片识别调查，基于个体在各地理位点间的分布情况校正了捕获概率的异质性，并依据种群丰度、存活率与连通性特征，刻画了各亚种群的现状。
3. MSCRD模型结果显示，不同地理位点间的捕获概率与种群统计参数均存在显著异质性。河口水域的亚种群呈现高捕获概率、高存活率与稳定的种群丰度，体现出极高的栖息地保真度。与之形成鲜明对比的是，开放海岸线位点的亚种群捕获率较低，存在永久性与临时性迁出，且种群丰度波动显著，表明该类群仅临时利用该生境，栖息地保真度较低。
4. 转移概率的估算结果同样存在位点间差异：河口水域的海豚会更频繁地前往受庇护的沿岸海湾，而沿岸海豚则较少进入河口区域，这反映出该集合种群内部存在一定的动态变化。
6. 综合与应用
迄今为止，采用标记重捕法开展的瓶鼻海豚研究多聚焦于单一亚种群的探究。本研究在异质性较强的沿岸-河口水域环境中证实，空间结构化的瓶鼻海豚亚种群拥有独特的个体组成，且在种群规模、种群动态与连通性方面存在显著差异。这类关于集合种群动态的研究成果，可为局域尺度的物种保护工作提供有效助力。MSCRD方法适用于包含可识别个体的物种种群，尤其适用于刻画那些受人类活动、气候变化或入侵物种威胁程度存在差异的野生生物亚种群特征。