Nephrops Underwater TV Survey FU22 The "Smalls" North East Atlantic Ocean 2006 - Present

Nephrops norvegicus are common around the Irish coast, occurring in geographically distinct sandy or muddy areas where the sediment is suitable for construction of their burrow dwellings. The Marine Institute carries out Underwater TV surveys annually of commercially important Nephrops stocks. This dataset provides quality assured estimates of Nephrops burrow densities over the known spatial and bathymetric distribution of the FU (functional unit) 22: the “Smalls” Nephrops ground. From 2006 to 2011 (UWTV) stations set at 3.0 nautical mile spacing over the known distribution. From 2012 onwards a randomised isometric grid of underwater television (UWTV) stations set at 4.5 nautical mile spacing. Underwater TV Survey reports for this Nephrops stock are available at: http://hdl.handle.net/10793/1428 Also available is the ICES Cooperative Research Reports which details use of UWTV surveys to assess Nephrops stock:https://tinyurl.com/ices-nephrops GIS shapefiles of FU22 and the “Smalls” Nephrops grounds are provided. This dataset covers the period of 2006 and is ongoing. One hundred percent of the survey grid was covered in all years except in 2015, where 83 percent of the grid was covered. These 7 stations in 2015 could not be completed due to very poor or nil visibility conditions encountered at seabed. For these stations density estimates were filled-in using and average of historic values within 2nmi (buffer2estimated). Dataset fields are Nephrops Functional Unit Number; Survey Code; Year; UWTV station number; Date-Start of UWTV track; Time_Start of UWTV track; Date-End of UWTV track; Time_End of UWTV track; Decimalised longitude and latitude midpoint of the UWTV station track; Adjusted density (Nephrops burrows/m²) ;Length in metres of the UWTV station track; Field of View of camera system in metres; Total Nephrops burrow count; Nephrops Fishing Ground Name; Source of positional data to calculate UWTV station track (USBL sled GPS, SHIP GPS, Layback, estimated GPS, buffer2estimated); Camera system used (SD = standard analogue system, HD = high definition system); Data Extraction method (SQL, MSAccess); Data Status (Final for analysis); Research Vessel Name; Correction Factor (Density / Correction Factor = Adjusted Density) and Depth (metres). Entries with NA means data is not available.

挪威海螯虾（Nephrops norvegicus）在爱尔兰海岸周边分布广泛，栖息于地理分隔的沙质或泥质底质区域，这类底质适宜其挖掘洞穴居所。爱尔兰海洋研究所（Marine Institute）每年针对具有商业价值的挪威海螯虾种群开展水下电视（Underwater TV, UWTV）调查。本数据集提供了经过质量验证的功能单元（functional unit, FU）22——即“斯莫尔斯”挪威海螯虾渔场——已知空间与水深分布范围内的挪威海螯虾洞穴密度估算值。2006至2011年间，调查站点以3.0海里的间距布设于已知分布区域内；2012年起，改用间距为4.5海里的随机等距网格布设水下电视调查站点。该挪威海螯虾种群的水下电视调查报告可访问：http://hdl.handle.net/10793/1428。另有详细阐述水下电视调查用于挪威海螯虾种群评估的ICES合作研究报告（ICES Cooperative Research Reports），其链接为：https://tinyurl.com/ices-nephrops。本数据集同时提供了FU22及“斯莫尔斯”挪威海螯虾渔场的GIS形状文件（GIS shapefiles）。本数据集覆盖2006年至今，目前仍在持续更新。除2015年仅完成83%的调查网格外，其余年份均完成了100%的调查网格覆盖。2015年未完成的7个站点因海底能见度极差或完全无能见度而无法开展作业。针对这些站点的密度估算值，采用2海里缓冲区内（buffer2estimated）的历史数据平均值进行填充。数据集包含以下字段：挪威海螯虾功能单元编号；调查代码；调查年份；水下电视调查站点编号；水下电视测线起始日期；水下电视测线起始时间；水下电视测线结束日期；水下电视测线结束时间；水下电视测线中点的十进制格式经纬度；校正后密度（单位：个/平方米）；水下电视测线长度（米）；摄像系统视场范围（米）；挪威海螯虾洞穴总计数；挪威海螯虾渔场名称；用于计算水下电视测线位置数据的来源（包括USBL船载声学定位系统GPS、船舶GPS、滞后校正、估算GPS、buffer2估算）；所用摄像系统（SD为标准模拟系统，HD为高清系统）；数据提取方式（SQL、Microsoft Access）；数据状态（供分析使用的最终版）；研究船名称；校正因子（密度/校正因子=校正后密度）以及水深（米）。字段值为NA表示数据不可用。