Biomass and length distribution for roughhead grenadier, thorny skate and white hake from the surveys conducted by Spain in NAFO 3NO

Abstract

Data for roughhead grenadier (Macrourus berglax), thorny skate (Amblyraja radiata) and white hake (Urophycis tenuis) from the Spanish Spring survey are presented. Abundance and biomass were estimated for roughhead grenadier and thorny skate for the period 1997-2011 and for white hake for the period 2001-2011. The length distribution is presented as numbers per haul stratified mean catches. The indices of roughhead grenadier show no trend until 2003, increasing in years 2004-2006 but mainly in 2004. Biomass in 2007 declined to 2003 levels, increased slightly afterwards. The values obtained in 2010-2011 are similar to those in 2003 and 2007. The thorny skate indices increased to a historical maximum in 2000 and after which it has followed an oscillating trend until 2011. White hake biomass shows a decline since the great maximum in 2001, with a small peak in 2005. Values in 2011 were slightly higher than in previous year but nevertheless represented one fifth of the 2001 maximum. Individuals within the length range 16 - 26 cm can only be seen in 2001 and 2004.