Fish community and species distribution predictions for streams and rivers of the Chesapeake Bay Watershed

This data release contains predictions of selected fish community metrics and fish species occurrence using Random Forest models with landscape data for inland reaches across the Chesapeake Bay Watershed (CBW). Predictions were made at four time intervals (2001, 2006, 2011, and 2016) according to changes in landcover using the National Land Cover Database (NLCD). The fish sampling data used to compute these metrics were compiled from various fish sampling programs conducted by state and federal agencies, county governments, universities, and river basin commissions across the watershed. Community metrics describe composition, tolerances, habitat preferences, and functional traits of fish communities (and were derived from Krause and Maloney, 2021). Community analyses were developed for four aggregated Level III ecoregions: Northern Appalachians (NAP), Southern Appalachians [split into two sub-regions; the SAP-Piedmont (Piedmont and Northern Piedmont Ecoregions; SAPPIED] and other ecoregions [SAPNW]) and the Coastal Plains (CPL), and a final index was calculated for each ecoregion as the average of selected metric deciles with higher scores inferring less biologically altered (i.e., better) conditions. Species distribution models were created for key sensitive and gamefish species (including Brook Trout, Northern Hog Sucker, Smallmouth Bass, and Torrent Sucker) to predict species occurrence. Uncertainty was calculated for both approaches using model prediction intervals. For complete data descriptions and data interpretation see associated publication (Maloney et al., 2022).

本数据集发布内容包含针对切萨皮克湾流域（Chesapeake Bay Watershed, CBW）内陆河段，基于景观数据与随机森林（Random Forest）模型生成的选定鱼类群落指标预测结果，以及鱼类物种出现情况的预测结果。本次预测依据美国国家土地覆盖数据库（National Land Cover Database, NLCD）的土地覆盖变化数据，设置2001、2006、2011、2016四个时间节点开展。

用于计算上述指标的鱼类采样数据，采集自流域内各州、联邦机构、县级政府、高校以及流域委员会开展的多类鱼类采样项目，并经整合汇总而成。鱼类群落指标用于描述群落的组成、耐受特性、栖息地偏好以及功能性状，相关指标体系源自Krause与Maloney于2021年的研究成果。

本研究针对四类聚合后的三级生态区开展鱼类群落分析：阿巴拉契亚北部（Northern Appalachians, NAP）、阿巴拉契亚南部（拆分为两个子区域：SAP-皮埃蒙特（Piedmont与北皮埃蒙特生态区，缩写SAPPIED）及其他阿巴拉契亚南部子区域（SAPNW））与海岸平原（Coastal Plains, CPL）；随后针对每个生态区计算综合指数，以选定指标的十分位数平均值作为指数得分，得分越高代表该区域受生物干扰程度越低（即生态状况越好）。

针对关键敏感物种与游钓鱼类（包括溪红点鲑、北方猪吸口鱼、小口黑鲈与急流吸口鱼）构建物种分布模型，以预测其物种出现情况。两种分析路径均通过模型预测区间计算了结果的不确定性。如需获取完整的数据说明与解读方法，请参阅相关文献（Maloney等人，2022）。