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Since 1995, a stratified random spring bottom trawl survey in the NAFO Regulatory Area of Div. 3NO was conducted by Spain. In 2001, the trawl vessel was replaced; so, the time series indices was transformed. The transformed entire series of mean catches, abundance and biomass for Thorny skate are presented for the period 1995-2000, and the length distribution for the period 1997-2000, and the no-transformed data for the years 2001-2003. The standard deviation are shown for abundance and biomass. The summed abundance and biomass based on conversion of the length frequencies are presented and compared to the estimates from the method used to convert the CPUE. A decreasing in Thorny skate abundance and biomass is observed in last years (2001-2003)