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The estimation of the age composition of the catch is a prerequisite for the analytical assessment of exploited fish resources. However, most deep-water fish stocks are assessed or managed in the lack of age structure, which would often be of little help and subject to debate. In the case of the roundnose grenadier, the larger macrourid species exploited at the upper and mid-slope depth in the North Atlantic, the reading scheme of the otoliths is quite easily agreed upon between different readers, and they are in acceptable agreement with age validation formerly obtained on the juveniles. In the North East Atlantic, the fishery operates over large areas and does not target fish concentration of pure adult fish like for some other deep-water species. Then, the changes of the age compositions of the exploited populations are likely to appear in the catch and changes in the length distribution of the landings appeared since the onset of target fishing, which is hardly the case for aggregating species such as orange roughy or blue ling. However, the uncertainties on the age estimated are probably wide, growth parameters from the Von Bertalanffy growth model were estimated, the effects of the age uncertainties on these parameters were investigated showing that they cannot be disregarded and the usefulness of such parameters for assessment purposes is discussed. The relationships between length, age and otolith weight were analysed and the otolith weight appeared as a possible alternative solution to estimate the age of the roundnose grenadier. Introduction The roundnose grenadier is one of the major deep-water species exploited in the northeast Atlantic. Although the potential interest for fisheries of this species was noticed more than 20 years ago (Bridger, 1978; Ehrich, 1983) the exploitation did not start before the late 1980s when French trawlers began to fish deeper along the slope to the west of the British isles and south of Faeroe islands (Charuau, et al., 1995). The roundnose grenadier is now the first species in the landings of the French deep-water fleet. The French exploitation is mainly developed to the west of Scotland (ICES sub-area VI). In the ICES area, it is also exploited by Denmark and Norway in the Skagerrak (ICES sub-area III) and, to a lesser extent by Iceland and Faeroe Islands mainly in their respective surrounding waters and by Scotland in ICES sub-area VI. Lastly the catch strongly increased over recent year in ICES sub area XII due to a developing exploitation from Spanish trawlers. Before exploitation in the northeast Atlantic, the species was exploited in the northwest Atlantic and on the midAtlantic ridge from the late 1960s (Atkinson, 1995; Troyanovsky and Lisovsky, 1995). The biology of the species is quite well described; its reproduction was the subject of several studies as well as its distribution and some aspect of its ecology (Allain, 1999; Allain, 2001; Atkinson, 1995; Bergstad, 1990; Gordon, 1979; Haedrich and Merrett, 1988; Kelly, et al., 1996, 1997; Mauchline and Gordon, 1984). However, the stocks and populations identity are as yet

Age Estimation of Roundnose Grenadier (Coryphaenoides rupestris), Effects of Uncertainties on Ages