A Review on Roughhead Grenadier (Macrourus berglax) Biology and Population Structure on Flemish Cap (NAFO Division 3M) 1991-2005 Based Upon EU Flemish Cap Bottom Survey Data

• Main Authors: Murua, H. (Hilario), González-Costas, F. (Fernando)
• Format: Report
• Language: English
• Published: Centro Oceanográfico de Vigo 2006
• Subjects: North Atlantic; Northwest Atlantic
• Online Access: http://hdl.handle.net/10508/821

The European Union has conducted since 1988 an annual bottom trawl survey in Flemish Cap (NAFO Division 3M) in the 200-720 m depth range. The information on roughhead grenadier population structure recorded during the last 14 EU surveys (1991-2005) in Flemish Cap is presented. Depth distribution of captures, length/age distribution of captures, growth rates, sex-ratios, catch curves, and abundance/biomass estimated by the swept area method are present ed. In general, the biomass index increased from low levels to a peak of about 3 000 tons in 1993, then decreased in 1994 and remained around 1 500 and 2 000 tons till 2002. It increased again in 2003 to reach the peak of 3 575 tons in 2004. The biomass index in 2005 was 2 387 tons. Age and length composition of the catches showed clear differences between the two sexes. The importance of males in the capture declines in larger fish, disappearing from the capture in largest length classes. Results show that roughhead grenadier has a prolonged li fe cycle and multiaged population structure with differences in growth and mortality between males and females.