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Multispecies Virtual Population Analysis (MSVPA) is based on parameterization of the average relative food compositions for all possible prey-age predator-age combinations in the model by year and quarter. This sets high demands on stomach sampling programmes in terms of spatial coverage of the predator population and of sampling intensity for individual cohorts. In practice, there are many sources of error in the input data and large variances, which call for a smoothing procedure to avoid outliers in the MSVPA output. We investigate the potential of geostatistics (specifically kriging) in improving (1) estimates of total and partial stomach content weights from spatially non-uniformly distributed samples and (2) smoothing of the average stomach content weights over the two-dimensional input array of predator age and years. The examples shown indicate that kriging provides an efficient method to deal with geographical variability in food composition and predator abundance as well as to fill gaps and make extrapolations within a two-dimensional array in temporal space characterized by many empty cells or cells not sufficiently well sampled. [ABSTRACT FROM PUBLISHER]

The most obvious effect of fishing on non-target species is direct mortality. To quantify this effect on the vulnerability of species requires measurement of the current fishing mortality rate and of the tolerance of the species to fishing mortality. These are difficult to estimate for the little-studied non-target species. We describe two potential methods for estimating current fishing mortality rate when data are limited. Their application is illustrated for dab (Limanda limanda) and grey gurnard (Eutrigula gurnardus), two common non-target species in the North Sea. We also develop approaches to define tolerance levels for fishing mortality for little-studied and rare species, based on the potential jeopardy level: the fishing mortality that causes a reduction in spawning stock biomass per recruit relative to the unexploited situation. We propose that for non-target species, models founded on basic knowledge of life history parameters, and on generally established relationships between these parameters, may offer the only practical approach. [ABSTRACT FROM PUBLISHER]

Catch data on 10 non-target fish species from the International Bottom Trawl Survey during the years 1970–1993 are analysed for changes in distribution and abundance by size class. Trends in catch rates of spurdog, starry ray, bib, poor cod, four-bearded rockling, grey gurnard, bullrout, long rough dab, dab, and lemon sole have been compared using correlation and cluster analysis with indices describing different aspects of the North Sea ecosystem, including biomass of pelagic, demersal and industrial species, temperature, eutrophication, and beam trawl effort. Most species appear to have increased over the period. However, the statistical analysis does not provide a plausible explanation of the factors responsible for the observed changes. [ABSTRACT FROM PUBLISHER]

Changes in the status of the major roundfish, flatfish, and pelagic stocks in the North Sea over the past 30 years are reviewed. Synopses are presented on trends in catches, fishing mortality, spawning-stock biomass, and recruitment for eight stocks (cod, haddock, whiting, saithe, plaice, sole, herring, and mackerel), together with an evaluation of the current state of these resources and the most recent management advice provided by the ICES Advisory Committee on Fishery Management. [ABSTRACT FROM PUBLISHER]

A comparison of catch rates of demersal fish during beam trawl and otter trawl surveys carried out in the period 1990–1995 and 1906–1909 indicates lower abundance in recent years for the total assemblage as well as for individual groups. There appear to have been shifts in the community associated with reduced diversity and evenness indices. Length-frequency distributions of roundfish and flatfish show a shift towards smaller-sized fish. [ABSTRACT FROM PUBLISHER]

Information about topics presented at two ICES Symposia on "North Sea Fish Stocks -- Recent Changes and Their Causes" in 1975 and 1995 is presented. The 1995 Symposium covered changes in biota and the marine ecosystem, both natural and manmade, which affect North Sea fisheries. Variations in populations of herring, mackerel, and other commercially important fish are discussed. The effects of factors such as eutrophication, contamination, and the oil industry are evaluated.

A foreword to the April 2000 issue of the "ICES Journal of Marine Science" is presented, which focuses on the papers presented at the 1997 International Exploration of the Sea (ICES) symposium held in Baltimore, Maryland in September 1997.

A foreword to the "ICES Journal of Marine Science," 58: 935 issue, is presented.

The article calls for papers expressing viewpoints, opinions or new ideas relevant to current marine science and management to date.