An Analytical Assessment of the Roughhead Grenadier Stock in NAFO Subareas 2 and 3
Fernando González-Costas and Hilario Murua
Abstract.—Catch and research survey data for 1992–2005 on the roughhead grenadier Macrourus berglax stock in the Northwest Atlantic Fisheries Organization (NAFO) Subareas 2 and 3 are fitted using the Extended Survivors Analysis (XSA) model. Despite the short time series available, the wide age range of this species, the low fishing mortality level as estimated by XSA, and the lack of convergence in the retrospective analyses, the results showed that the XSA model provides an adequate fit to the data and the XSA estimated trends are similar to those observed in research surveys. Therefore, we conclude that this assessment model could be an appropriate tool to be used in the quantitative assessment of the roughhead grenadier stock in NAFO Subareas 2 and 3. 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 metric tons (mt), the highest in the time series. Fishing mortality has declined since 1999 and showed the lowest value in the time series in 2005. However, the retrospective analysis indicated a clear retrospective pattern in the model estimates, with fishing mortality underestimated and total biomass overestimated. Over the last few years, there have been two very good recruitments at age 3, which may lead to an increase of the exploitable biomass in the future. The assessment results showed that the current status of the roughhead grenadier stock in Subareas 2 and 3 is acceptable. The values calculated for the yield per recruit reference points were Fmax = 0.130 and F0.1= 0.083.