Update of thorny skate (Amblyraja radiata) commercial and survey data

The 7 species in the Northeast Region (Maine to Virginia) skate complex are: little skate (Leucoraja erinacea), winter skate (L. ocellata), barndoor skate (Dipturus laevis), thorny skate (Amblyraja radiata), smooth skate (Malacoraja senta), clearnose skate (Raja eglanteria), and rosette skate (L. garmani). Landings have generally been increasing since 2000, and the 2007 reported commercial landings of 20,342 metric tons (mt) were the highest on record. The principal commercial fishing method in the directed skate fishery is otter trawling. Skates are frequently taken as bycatch during groundfish trawling and scallop dredge operations and discarded. Discard estimates from the Data Poor Stocks Working Group were revised in this assessment based on new data and new imputation according to the Standardized Bycatch Reporting Methodology (NEFSC 2009). Differences were generally minor and mostly caused by the imputation. Recreational and foreign landings are currently insignificant. Landings and discard estimates were disaggregated to skate species by using several methods, all of which showed a decline for thorny skate over the time series. Northeast Fisheries Science Center (NEFSC) indices of thorny skate abundance have declined steadily since the late 1970s, reaching historically low values in 2012 and 2013 that are less than 5% of the peak observed in the 1970s. The minimum swept area abundance and biomass in 2015 are 628,000 individuals and 843 mt in the fall and 867,000 skates and 1,264 mt in the spring. Survey indices from other surveys are generally in agreement with either a decline since the 80s or a flat survey during the 2000s. In 2014 a new cooperative bottom longline survey was implemented that is able to cover rough bottom that the regular bottom trawl cannot survey. This survey, while currently only 2 years in duration, indicates that more thorny skate are caught on rough bottom than on smooth. [doi:10.7289/V5/RD-NEFSC-16-08(https://doi.org/10.7289/V5/RD-NEFSC-16-08)] by Katherine Sosebee, Alicia Miller, Loretta O'Brien, Dave McElroy, Sally Sherman. "November 2016." System requirements: Adobe Acrobat Reader. Includes bibliographical references. 2016 NMFS (National Marine Fisheries Service) NEFSC (Northeast Fisheries Science Center) Library http://doi.org/10.7289/V5/RD-NEFSC-16-08 Public Domain 1862

美国东北海域（缅因州至弗吉尼亚州）的鳐类复合群包含7个物种，分别为：小鳐（little skate, Leucoraja erinacea）、冬鳐（winter skate, L. ocellata）、平背鳐（barndoor skate, Dipturus laevis）、棘鳐（thorny skate, Amblyraja radiata）、光鳐（smooth skate, Malacoraja senta）、钝吻鳐（clearnose skate, Raja eglanteria）以及玫瑰鳐（rosette skate, L. garmani）。自2000年以来，商业捕捞量总体呈上升趋势，2007年报告的商业捕捞量达20342公吨（mt），为有记录以来的最高值。定向鳐类捕捞的主要商业作业方式为翼网拖网捕捞（otter trawling）。在底层鱼类拖网捕捞及扇贝耙网作业中，鳐类常作为兼捕渔获物被捕获后丢弃。本次评估中，基于新数据及标准化兼捕报告方法（Standardized Bycatch Reporting Methodology, NEFSC 2009）下的新插补方法，对数据匮乏种群工作组（Data Poor Stocks Working Group）的兼捕丢弃量估算值进行了修订。修订后的估算值与原估算值间的差异总体较小，该差异主要源于插补方法的调整。目前休闲捕捞及境外捕捞的渔获量可忽略不计。研究人员通过多种方法将总渔获量及丢弃量估算值按鳐类物种进行拆分，所有拆分方法均显示，棘鳐在整个时间序列内的种群数量呈下降趋势。东北渔业科学中心（Northeast Fisheries Science Center, NEFSC）的棘鳐种群丰度指数自20世纪70年代末以来持续下降，2012年及2013年达到历史最低值，仅为20世纪70年代观测峰值的5%以下。2015年扫海面积法估算的最低种群丰度及生物量为：秋季62.8万尾、843公吨（mt），春季86.7万尾、1264公吨（mt）。其他调查的种群丰度指数结果总体一致，要么显示自20世纪80年代以来种群数量下降，要么显示2000年代的调查结果趋于平稳。2014年，一项新型合作性底层延绳钓调查正式启动，该调查可覆盖常规底拖网无法涉足的崎岖海底区域。尽管该调查目前仅开展了2年，但结果显示，崎岖海底区域捕获的棘鳐数量多于平坦海底区域。[DOI:10.7289/V5/RD-NEFSC-16-08(https://doi.org/10.7289/V5/RD-NEFSC-16-08)] 作者：Katherine Sosebee、Alicia Miller、Loretta O'Brien、Dave McElroy、Sally Sherman。"2016年11月"。系统要求：Adobe Acrobat Reader。包含参考文献列表。2016年 美国国家海洋渔业服务局（National Marine Fisheries Service, NMFS）东北渔业科学中心（Northeast Fisheries Science Center, NEFSC）图书馆 http://doi.org/10.7289/V5/RD-NEFSC-16-08 公有领域 1862