Capture history data for: Sub-seasonal correlation between growth and survival in three sympatric aquatic ectotherms

Animals experience seasonally changing conditions in temperate regions, thus population vital rates change seasonally. However, knowledge is lacking on patterns of seasonal correlation between growth and survival in sympatric ectotherms, and this knowledge gap limits our understanding of environmental change impacts on animal populations and communities. Here, we investigated sub-seasonal (2-month intervals) correlation between growth and survival in three stream fishes (bluehead chub Nocomis leptocephalus, creek chub Semotilus atromaculatus, and mottled sculpin Cottus bairdii) in South Carolina, USA, via a mark-recapture survey over 28 months. 

We found that the patterns of temporal correlation between growth and survival differed among the sympatric species. Growth increased and survival decreased with water temperature in two eurythermal species (bluehead chub and creek chub), resulting in a negative correlation between growth and survival. Growth peaked in sub-seasons with an intermediate water temperature range in a third stenothermal species (mottled sculpin), while survival decreased with water temperature for this species too. Consequently, there was no significant negative or positive correlation between sub-seasonal growth and survival in the stenothermal species. 

Negative correlation among population vital rates stabilizes population size over time and buffers animal populations from environmental change because the vital rates are not affected simultaneously in the same direction, indicating some degree of resiliency in the face of climate changes in the two eurythermal species. However, such a demographic mechanism of resiliency could be maintained so long as climate warming does not exceed optimal growth temperature, above which a negative correlation between growth and survival may no longer be maintained.

Methods
We conducted mark-recapture sampling in the 740m study area of Indian Creek, South Carolina, USA, between November 2015 and March 2018 at an interval of two months (mean = 61 days [range = 48-70]). An average window of 4 days was required for each sampling occasion (range = 1-10 days). The study area was divided into 20-m sections, which were sampled in an upstream direction on each sampling occasion by backpack electrofishing units (Smith Root Model LR-24; and Halltech Aquatic Research Inc. Model HT-2000) using a two-pass depletion approach. 

We marked all captured fish ≥ 60 mm in total length (TL) for bluehead chub and creek chub and ≥ 50 mm TL for mottled sculpin with 8-mm passive integrated transponder (PIT) tags (Oregon RFID; Biomark). We measured TL (mm) of all marked and recaptured fish before they were returned to the section of capture alive. Across 15 sampling occasions between November 2015 and March 2018, we uniquely tagged a total of 429 individuals of bluehead chub, 664 individuals of creek chub, and 928 individuals of mottled sculpin. 

Our data set includes a capture histority of 2,201 individuals of the three fish species used in Cormack-Jolly-Seber models.

温带地区的动物会遭遇随季节波动的环境条件，因此种群生命率（population vital rates）呈现季节性变化。然而，目前学界对同域分布的变温动物（sympatric ectotherms）的生长与存活间的季节相关性模式仍缺乏认知，这一知识缺口限制了我们理解环境变化对动物种群及群落的影响。本研究于美国南卡罗来纳州开展了为期28个月的标记重捕（mark-recapture）调查，针对3种溪流鱼类——蓝头雅罗鱼（bluehead chub，*Nocomis leptocephalus*）、溪雅罗鱼（creek chub，*Semotilus atromaculatus*）与斑鳍杜父鱼（mottled sculpin，*Cottus bairdii*），探究了其亚季节尺度（2个月间隔）下的生长与存活相关性。

研究结果显示，3种同域鱼类的生长与存活的时间相关性模式存在显著差异。对于两种广温性物种（eurythermal species）——蓝头雅罗鱼与溪雅罗鱼，其生长随水温升高而增加，而存活则随水温升高而下降，由此形成生长与存活间的负相关关系。第三种狭温性物种（stenothermal species）斑鳍杜父鱼的生长峰值出现在水温处于中等区间的亚季节时段，但其存活同样随水温升高而下降，因此该物种的亚季节生长与存活间未呈现显著的正负相关关系。

种群生命率间的负相关关系能够在长期内稳定种群规模，并帮助动物种群抵御环境变化——因为各生命率不会同时受到同向影响，这表明两种广温性物种在气候变化面前具备一定的恢复力。不过，这种恢复力的种群动态机制（demographic mechanism）仅在气候变暖未超过物种最适生长温度时得以维持；一旦超过该阈值，生长与存活间的负相关关系可能不复存在。

研究方法
本研究于美国南卡罗来纳州印第安溪（Indian Creek）的740米研究样地内开展标记重捕采样，采样时段为2015年11月至2018年3月，间隔2个月开展一次（平均间隔61天，区间为48-70天）。每次采样的平均耗时窗口为4天（区间为1-10天）。研究样地被划分为20米的分段，每次采样均采用逆流采样的方式，借助背包式电鱼设备（backpack electrofishing units）——Smith Root LR-24型、Halltech Aquatic Research Inc. HT-2000型开展两轮耗尽式采样法（two-pass depletion approach）。

针对蓝头雅罗鱼与溪雅罗鱼，研究人员对总长度（total length, TL）≥60毫米的捕获个体，以及总长度≥50毫米的斑鳍杜父鱼个体，使用8毫米无源集成式射频识别标签（passive integrated transponder, PIT）进行标记。所有被标记及重捕的个体均测量其总长度（毫米），随后被放归至捕获所在的样地分段。在2015年11月至2018年3月的15次采样中，研究人员共为429尾蓝头雅罗鱼、664尾溪雅罗鱼与928尾斑鳍杜父鱼完成了唯一标识标签的植入。

本数据集包含3种鱼类共计2201个个体的捕获历史数据，用于构建科马克-乔利-西尔伯模型（Cormack-Jolly-Seber models）。