North Temperate Lakes LTER: Fish Length Frequency 1981 - current

This data set is a derived data set based on fish catch and length data. Data are collected annually to enable us to track the fish assemblages of eleven primary lakes (Allequash, Big Muskellunge, Crystal, Sparkling, Trout, bog lakes 27-02 [Crystal Bog] and 12-15 [Trout Bog], Mendota, Monona, Wingra and Fish). Sampling on Lakes Monona, Wingra, and Fish started in 1995; sampling on other lakes started in 1981. Sampling is done at six littoral zone sites per lake with seine, minnow or crayfish traps, and fyke nets; a boat-mounted electrofishing system samples three littoral transects. Vertically hung gill nets are used to obtain two pelagic samples per lake from the deepest point. A trammel net samples across the thermocline at two sites per lake. In the bog lakes only fyke nets and minnow traps are deployed. Parameters measured include species-level identification and lengths for all fish caught, and scale samples and weight from a subset. Derived data sets include species richness, catch per unit effort, and size distribution by species, lake, and year. Dominant species vary from lake to lake. Perch, rockbass, and bluegill are common, with walleye, large and small mouth basses, northern pike and muskellunge as major piscivores. Cisco have been present in the pelagic waters of four lakes, and the exotic species, rainbow smelt, is present in two. The bog lakes contain mudminnows. Sampling Frequency: annually Protocol used to generate data : Gill net data have been standardized to a 24-hour sampling period. Assumptions used in the standardization are available from the investigators. Day seines were only used in 1981 and have been eliminated from this data set to make sampling effort across years comparable. The number of fish caught in each five mm length interval (0<length<5, 5<=length<10, etc.) have been summed over gear. In cases in which only a random subsample of fish were measured, the unmeasured fish have been assigned to the length categories based on the proportions in length categories for the measured fish of the subsample Number of sites: 11

本数据集为基于渔获物与体长数据构建的衍生数据集。该数据集按年度收集数据，旨在追踪11个核心湖泊的鱼类群落组成，涉及湖泊包括：Allequash湖（Allequash）、Big Muskellunge湖（Big Muskellunge）、Crystal湖（Crystal）、Sparkling湖（Sparkling）、Trout湖（Trout）、两座编号分别为27-02[又名Crystal Bog（水晶沼泽）]与12-15[又名Trout Bog（鳟鱼沼泽）]的沼泽湖，以及Mendota湖（Mendota）、Monona湖（Monona）、Wingra湖（Wingra）与Fish湖（Fish）。
其中，Monona湖、Wingra湖与Fish湖的采样工作始于1995年，其余湖泊的采样则自1981年起开展。
每个湖泊设置6个沿岸带采样站点，采用围网、幼鱼笼、螯虾笼与翼网（fyke net）进行采样；同时借助船载电捕鱼系统对3条沿岸样带开展采样。垂直悬挂的刺网（gill net）在每个湖泊的最深处采集2份远洋带样本。三层刺网（trammel net）则在每个湖泊的2个站点跨越温跃层完成采样。仅在沼泽湖中部署翼网与幼鱼笼。
本次测量的参数包括：所有渔获鱼类的物种鉴定结果与体长数据，以及部分样本的鳞片样品与体重数据。
衍生数据集涵盖以下内容：物种丰富度、单位捕捞努力量渔获量（catch per unit effort），以及按物种、湖泊与年份划分的体长分布特征。
各湖泊的优势物种存在显著差异：鲈鱼（perch）、岩钝鲈（rockbass）与蓝鳃太阳鱼（bluegill）为常见物种；大眼梭鲈（walleye）、大口黑鲈、小口黑鲈、北美狗鱼（northern pike）与北美大梭鱼（muskellunge）为主要的食鱼性鱼类。
西斯科白鲑（Cisco）在4个湖泊的远洋带中均有分布；外来物种彩虹胡瓜鱼（rainbow smelt）见于2个湖泊中。沼泽湖内均分布有泥鳉（mudminnow）。
采样频率：年度采样。
数据生成规范：刺网数据已标准化为24小时采样周期，该标准化所采用的假设可向研究人员索取。日间围网仅在1981年使用过，为保证不同年份间采样努力量的可比性，此类数据已从本数据集中剔除。将各5mm体长区间（0<体长<5mm、5≤体长<10mm等）内的渔获数量按渔具类型汇总。若仅对随机抽取的部分鱼类进行体长测量，则未测量个体的体长区间将根据该子样本中已测量个体的体长区间占比进行分配。
站点总数：11个