The Greenland halibut fishable stock has been declining substantially since late-1980s, according to both surveys and commercial fishery indices, particularly among the ages 10+, which corresponds to the females age at 50% maturity. In this paper the effect of this apparent reduction in the stock abundance on growth and reproductive parameters is examined.Among growth parameters, the analysis of the first year growth is undertaken both by cohort and by geographic areas, assuming that density dependence might be the most severe at younger age classes. This is made using records of the respective first annual ring otolith diameters. Other growth related index such as the condition factor is also analysed. Neither significant differences in the first year growth have been observed between areas analysed, nor between cohorts, during the period 1988 to 1996. Mean condition factor-at-age for ages 1 to 13 were stable during this same period. About the reproductive parameters, two aspects are considered: the interannual variations in length-at-maturity and in the potential fecundity. Female length at maturity varied between 64.5 and 69.5 cm. Female potential annual fecundity ranged between 15 000 and 158 000. It increases with female age, but the mean fecundity-at-age variations were not significant either between years of sampling or between cohorts.A common feature observed is the relative stability of those characteristic through the period analysed, which could support a certain resiliency of the life history traits in this species.

The aim of this study is to test the variability of the assemblages defined in the Flemish Cap area. Data from 951 bottom hauls were analysed, covering depths between 126 and 740 m in the years 1995-2002. The fish fauna in Flemish Cap appears distributed in a persistent structural zonation defined in three assemblages. The first three factors of a Principal Component Analysis explained the 78.4% of the variance in distribution species, and they are consistent with the results of a cluster analysis. The three characteristic assemblages show a temporal persistence, but some changes appear in this period, for instance: displacements of the assemblages limits towards shallower waters, and some changes in relative position of the dominant species in each assemblage. These changes can be related with the constant decrease of the biomass of the main demersal fish species like Atlantic cod and American plaice. The species of Genus Sebastes appear as dominant fish species in the area.

The Relative Condition Factor of Greenland halibut (Reinhardtius hippoglossoides) was analysed for seasonal, annual and geographical variability. Sampling covered commercial fishing and scientific surveys in three areas of the North Atlantic (NAFO Divisions 3M and 3LNO, and ICES Division IIb), comprising a total of 64 984 individuals from 1992 to 2003. Several data sets were established in order to carry out the comparisons: individuals as a whole; by sex -females and males separately; and by areas -each area independently. Condition showed significant differences with regard to the area, season, size range and sex, but it was not always significant among interactions of these factors. Individuals from the Northeast Atlantic had better condition, while those in the Northwest Atlantic suffered a notable fall in condition throughout the studied period, mainly in Flemish Cap. Condition was lightly superior in females, regarding size. A clear increment in the feeding intensity appeared when the condition diminished. When the total weight is used to calculate the condition, more remarkable differences could be expected because this index is sensitive to the gonad weight; in this respect, adult females showed more marked differences. Moreover, the complex maturity schedule and variable maturity at size would contribute to find misleading differences. Feeding habits of Greenland halibut were studied in the same areas based on a sample of 19 001 fish. Feeding intensity was the higher on the Flemish Cap, where the main preys were Pandalus borealis, Sebastes spp. and Serrivomer beani. P. borealis predation increased in the late 1990s. Diet was piscivorous in Div. 3LNO and Div. IIb as well, mainly based on Mallotus villosus and Micromesistius poutassou, respectively. Cannibalism and offal consumption was remarkable in Svalbard (ICES Div. IIb). Fish predation increased when predator size increased. Molluscs took an important place in the diet of intermediate sizes in Div. 3LNO and IIb. Similar diet pattern for both sexes was observed.

The seasonal, annual and geographical changes in the Relative Condition Factor (K r) of a total of 24 410 individual American plaice (Hippoglossoides platessoides Fabricius) were analysed. These samples were collected in three areas of the North Atlantic (NAFO Division 3M and Div. 3LNO, and ICES Div. IIb) in commercial fishing and scientific surveys from 1992 to 2003. Condition presented significant variation in both sexes as far as area, season and year effects were concerned. Condition decreased greatly in Div. 3M, slightly increased in Div. IIb and it was quite constant in Div. 3LNO in the considered period for each area. Relative Condition Factor value showed a remarkable relation with the estimated biomass in Div. 3M. Females showed a better condition than males, and condition in the periods of spring and summer was lower than in the periods of autumn and winter for both sexes. Interannual variation in condition was more evident in small sized (immature) individuals. The spawning period corresponded with the peak of condition in females and with a decrease in males. Feeding intensity and condition were inversely related across season, however when the same period was studied across years they showed a similar pattern. Food and feeding of 8 543 individual American plaice from these three areas were examined. Feeding intensity was higher on the Flemish Cap (78%). The main prey in the composition of stomach contents for this area, were Ophiuroidea (56%), Hyperiidea (13%) and Pandalus borealis (8%). Changes in the main components of the diet were found in the last years. Feeding habits by size range and comparison with the other areas were also analysed.

The Newfoundland Shelf supported one of the world’s greatest fisheries until the main commercial species collapsed more than two decades ago. We calculated three ecological indices for individual populations and five for community from the data obtained in the research surveys conducted by Spain in NAFO Regulatory Area Divisions 3NO between 2002 and 2013. We use data for 24 species to study the dynamics of major demersal fish assemblages (38–300, 301–600, and 601–1460 m depth) and evaluated how they have responded to different levels of exploitation. Trends and changes for individual populations (abundance and biomass, intrinsic population rate of growth, and mean length) and for all the community (ABC curves, indices of faunal diversity, proportion of non-commercial species, mean length in community and size spectra) were used to test ecological trends. Indices showed no homogeneous status and responded to different exploitation patterns, management, and environmental regimes in each assemblage. Our results show an improvement in the shallower and deeper assemblages and that fishing effort does not explain differences among each assemblage.