An analytical assessment of NAFO roughhead grenadier Subareas 2 and 3 stock.

Abstract

Catch and research survey data from 1992-2005 on the roughhead grenadier stock in NAFO Subareas 2 and 3 are fitted to the eXtended Survivors Analysis (XSA) model. The model results indicated that the stock biomass has been increasing from 1996 to 2005. The biomass estimated for the beginning of 2005 was around 70.000 tonnes, the highest in the time series. Fishing mortality has declined since 1999 and showed the lowest value in the time series in 2005. Over the last few years, there have been two years with very good recruitment at age 3, which may increase the exploitable biomass in the future. The assessment results showed that the current roughhead grenadier Subarea 2 and 3 stock status is healthy. While the analysis indicated that there was a clear retrospective pattern in the model estimates (i.e., fishing mortality being underestimated and total biomass overestimated), the sensitivity analysis showed that the results were robust to the model set up. Although the short time series available, in addition to the wide age composition of this species, the low fishing mortality level estimate by XSA and the lack of convergence in the retrospective analyses, the results showed that the XSA model adequately fitted the data and that the XSA estimated trends are similar to those observed by research surveys. Therefore, it could be concluded that this assessment model may be an appropriate tool to be used in the quantitative assessment of the roughhead grenadier stock in NAFO Subareas 2 and 3.