An assessment of NAFO roughhead grenadier Subarea 2 and 3 stock

Abstract

The aim of this paper is to present the status of NAFO roughhead grenadier Subarea 2 and 3 stock based on different assessments models using all the available information. Different assessment methods have been applied based on the data available: Extended Survivors Analysis, a Stock-Production Model Incorporating Covariates (ASPIC) and a qualitative assessment based on survey and fishery information. XSA results are considered uncertainties due to the low Fishing mortality estimated compare with the natural mortality level assumed and the high number of iterations needed to reach the convergence. ASPIC results make sense with historical data available for this stock despite the uncertainty in the B1/K parameter and the low contrast index value. Although all these problem both models results present a very similar trend in the fishing mortality and biomass values and are comparable to the qualitative assessment base on the surveys information. Biomass presents in all methods a general increased trend in the 1995-2006 period and between 2006 and 2009 is more or less stable at high levels. Between 2009-2012 presents a decreasing trend in the surveys indices and XSA results however remains stable at high levels in the ASPIC results. Trends of the different estimations of F were very similar. F presents a decreasing trend since 1998 till 2006 and since then is more or less stable at very low levels. All recruitment indices analysed show a clear recruitment pick around 2004 and the XSA and survey length abundance show other quite good recruitment in 2012 despite the difficult to follow cohorts strength.