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

本数据集为基于渔获物与体长数据构建的衍生数据集。数据按年度采集，用于追踪11个主要湖泊的鱼类群落组成，涉及湖泊包括：Allequash湖、Big Muskellunge湖、Crystal湖、Sparkling湖、Trout湖，沼泽湖27-02号（Crystal Bog，水晶沼泽湖）与12-15号（Trout Bog，鳟鱼沼泽湖），以及Mendota湖、Monona湖、Wingra湖与Fish湖。
Monona湖、Wingra湖及Fish湖的采样工作始于1995年，其余湖泊的采样起始年份为1981年。
每个湖泊设置6个沿岸带（littoral zone）采样点位，采用围网（seine）、小型鱼类陷阱、螯虾陷阱及捕鱼笼（fyke nets）开展采样；同时搭载船载电捕鱼系统，完成3条沿岸样带的采样。此外，在每个湖泊的最深点位布设垂直悬挂刺网（gill nets），采集2份远洋带（pelagic waters）样本；还会在每个湖泊的2个位点跨温跃层（thermocline）布设三层刺网（trammel net）进行采样。仅在沼泽湖中部署捕鱼笼与小型鱼类陷阱。
所有捕获鱼类均完成物种水平鉴定与体长测量，并从部分采样个体中获取鳞片样品与体重数据。衍生数据集涵盖物种丰富度（species richness）、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数据。
各湖泊的优势物种存在差异。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、白斑狗鱼（northern pike）与北美狗鱼（muskellunge）为主要的食鱼性鱼类。西鲱（Cisco）曾在4个湖泊的远洋带水域被记录；外来物种彩虹胡瓜鱼（rainbow smelt）见于2个湖泊。沼泽湖中含有泥鳉（mudminnows）。
采样频率：年度采样。
数据生成方案：刺网数据已标准化为24小时采样周期，标准化所依据的假设可向研究人员获取。1981年曾使用日间围网，现已从本数据集中剔除，以确保不同年份间的采样努力量具有可比性。每个5mm体长区间的渔获数量（0