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This thesis focuses on the implications of exploitation pattern (population selectivity) and population resilience for fisheries sustainability in the NE Atlantic. Novel metrics of exploitation pattern and resilience are introduced and the effects of juvenile protection and resilience erosion on stock size, structure and yields are investigated. Analysis of both empirical and simulated data suggested that high selection of juveniles negatively affects both stock size and yield. A meta-analysis of empirical data for 38 fish stocks showed that fishing mortality of juveniles exceeding half that of mature fish leads to overfishing. Simulation-based analysis illustrated that a mean age-at-capture more than two years higher than mean age-at-maturity secures high yields at low levels of stock depletion. The effects of exploitation pattern on stock status are weaker than those of exploitation rate when empirical data are considered, both at an individual-stock and a cross-stock scale. However, simulation-based analysis revealed that for higher levels of juvenile protection than the ones observed in most empirical stocks, exploitation pattern would be more influential than exploitation rate. These findings suggest that there is a high unfulfilled potential to promote sustainability by protecting juveniles. Besides exploitation pattern, population resilience is another factor whose role in fish population dynamics was examined here. A resilience assessment of Barents Sea cod was carried out using a novel integrated approach combining multivariate analysis and bifurcation theory. This way, the occurrence of a population state shift in 1981, associated with climatic and exploitation effects, was identified. The approach implemented in this resilience assessment is reproducible to any other data-rich population and can be also used at the community- and ecosystem-levels to explain and predict state shifts. As Europe is currently moving towards a more holistic approach in fisheries management through the reform of the Common Fisheries Policy, such quantification and investigation of stock/exploitation attributes beyond stock size and exploitation rate is of great importance.

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During 1980 and 1981 respectively, 2425 and 4028 yellow perch 150-359 mm were Floy-tagged from June through August at four sites in Indiana waters of Lake Michigan. Most of the 6453 perch were tagged from mid-June to early August and almost 90% were less than 210 mm.An overall recapture rate of 3.2% (204 fish) was obtained by April 1, 1982. Site recapture rates were positively related to the numbers of fish tagged. Slightly over 92% of all fish were tagged at sites M and K and 94.5% of all recaptures originated from these two sites. Second season recaptures accounted for 25.5% of all recaptures. Peak recapture rates occurred in July. Sources of recaptures were 67.6% from sport fishermen, 25.5% from commercial fishermen, and 6.9% from Indiana Department of Natural Resources, Ball State University trawl catches and other sources.Most recaptured perch were in the 150-229 mm length interval, but an apparent size selection by both commercial and sport gear existed towards 180-229 mm perch. The recapture of large numbers of 150-159 mm fish indicated survival of small perch was not an important factor influencing size selection. Information on sizes of fish recaptured by sex and age was insufficient for evaluation.Although straight line movements of up to 166 km occurred, most fish remained near the original tagging sites. Distances traveled were similar for fish from all tagging sites in 1980, 1981 and for second season recaptures. Over 76% of all fish were recaptured in Indiana waters and about 86% traveled less than 32.0 km from the original tagging sites. The majority (64%) of fish leaving Indiana waters were captured nearby at New Buffalo and Union Pier, Michigan. About 68% of all recaptures were received within 60 days of release. Even though considerable variability was evident in the distances traveled with time, no seasonal trends were observed for perch of various sizes.Simple regression analysis of data for combined years revealed only 27% of all variation in distance traveled by perch was accounted for by the time at large (days) prior to recapture. Multiple regression analysis revealed the time at large was more important than fish length in relation to distance traveled, accounting for 27.3% and 0.2% of the explained variability, respectively. Data including second season recaptures more accurately represented these relationships and indicated these variables were poorly related to distance traveled. Examination of residuals showed a dramatic and statistically undesirable increase in unexplained variability was associated with far ranging fish. Other factors should be considered in future multiple regression analyses.Indiana yellow perch stocks appear to be fairly discrete entities. The majority of fish tended to remain periods of at least one year.

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Long-slit spectra for the photometric axes of a sample of 14 elliptical galaxies, predominantly low-luminosity ellipticals, in the Virgo cluster and in nearby groups, are studied to investigate the galaxy kinematical structure and stellar evolutionary history. To determine the galaxy kinematical structure, the shape of the line-of-sight velocity distribution (hereafter LOSVD) is measured using the Fourier Correlation Quotient method of Bender (1990), adopting the parametrisation of the LOSVD due to van der Marel and Franx (1993). This parametrisation enables the asymmetrical and symmetrical deviations of the LOSVD from a Gaussian function to be measured by the amplitudes H(_3) and H(_4) of the Gauss-Hermite series respectively. Rotation, velocity dispersion (σ), H(_3) and H(_4) are determined as a function of radius for both the major and minor axes of our sample. To summarise, LOSVD asymmetries were measured for the major axes of 12 galaxies which in the majority of cases have been interpreted as evidence for central disk-like components; evidence of both radial and tangential anisotropy were found from the measurement of H(_4); central decreases in σ are measured for 3 galaxies, which is interpreted as evidence that they have undergone some form of merger or interaction. On the basis of their measurements, galaxies are classified into 3 classes: types 1, 2 and 3. "Type 1" galaxies show strong evidence for both disk and bulge components and have the greatest measured values of H(_3) for our sample. Galaxies of "type 2" show strong evidence for embedded disk components and most (3 of 4) are measured to have central decreases in a. "Type 3" galaxies have kinematically-decoupled cores. Other galaxies, not classified, are NGC 3379 and NGC 4468.Measurements of the line-strength indices Mg(_b), Mg(_2), Hβ, Fe5270, Fe5335 and <Fe> are determined as a function of radius for all spectra and established to the Lick/IDS scale. The relations Mg’(_b)-Mg(_2), Mg’(_b), - log(σ), Mg(_b)- <Fe> and Hβ-[Mg(_b) <Fe>] are then studied. The Mg’(_b),-Mg(_2) relation of Wegner et al. (1998) and the calibrations of Worthey (1994) are compared with measurements here: this is used as a check of our calibration of Mg’(b), and Mg(_2). Measurements in the Mg’(_b)-log(σ) plane are considered separately for each galaxy and compared with the central relation of Colless et al. (1998). Measurements for most galaxies are found to be in good agreement with this relation. Measurements of Mg(_b) and <Fe> are similarly considered for each galaxy and compared with the predictions of the models of Worthey (1994). For the majority of galaxies, measurements are clearly offset from the Mg(_b)-<Fe> model grid of Worthey (1994), representing an [(^Mg)-(_Fe)] overabundance. This is an important result which shows that the [(^Mg)-(_Fe)] overabundance detected previously for the giant ellipticals similarly exists for ellipticals of the low luminosities studied here. For most galaxies this overabundance is found to be a constant function of radius. For the "type 2" galaxy NGC 3605, and NGC 4468, measurements are consistent with solar abundance ratios. Finally, measurements of Hβ and [Mg(_b) <Fe>] are compared with the models of Worthey (1994) to distinguish gradients in both age and metallicity. For all galaxies, gradients in metallicity are found with metallicity decreasing as a function of radius. For 5 galaxies (NGC 4564, NGC 3377, NGC 4478, NGC 4339 and NGC 3605) age gradients are also detected, with the galaxy centre shown to be younger than the surrounding galaxy. Interpreting these results together, different formation scenarios are proposed for the different galaxy types. For galaxies of "type 1", formation by homogenous, dissipational collapse is proposed. Galaxies of "type 2" show evidence for a less homogenous evolutionary history involving dissipationless collapse. No conclusive scenario is proposed for galaxies of "type 3".

Many species of farmland birds have shown huge declines in numbers and range since the 1970s due to agricultural intensification, and these declines have been worst amongst granivorous species. Recent studies have suggested that low abundance of invertebrate chick food may have been important in driving the declines of a number of granivorous species, however causation has still only been proved for the Grey Partridge, whose decline has been attributed to low chick survival due to the indirect effects of herbicides reducing invertebrate abundance. We investigated invertebrate declines and how they may have affected farmland bird populations in a number of ways. There is little long-term data on abundance of farmland invertebrates. Thus we first looked at how representative data from a long-running suction trap was of invertebrate abundance on local farmland. Suction trap catches reflected abundance of aerial invertebrates on local farmland, and also to abundance of epigeal invertebrates in many cases, particularly abundances in predominant crop types. Secondly, we looked at spatial and temporal distribution of invertebrates on farmland in order to make recommendations about how to increase invertebrate availability to farmland bird populations. Field margins were by far the most invertebrate rich habitats sampled. Most differences in invertebrate abundance between different crop types were found early in the season, at this time spring barley and spring oilseed rape had very low abundances. Winter wheat had relatively high invertebrate abundance compared to spring barley at this time. Winter oilseed rape and set-aside had relatively high abundances of the crop types sampled. We investigated how low invertebrate abundance may have affected populations of granivorous passerines by looking for evidence of reproductive trade-offs in a population of Tree Sparrows, and by supplementary feeding experiments with Tree Sparrow and Yellowhammer chicks. There was no evidence for reproductive trade-offs within years, conversely an effect of individual quality was found. There was some evidence of reproductive trade-offs between years. Supplementary feeding increased the mass of Tree Sparrow first broods early in May but not later in May, and also of chicks with yearling parents, who had a lower provisioning rate. Chicks fledged early in May had a lower survival rate to the following year than chicks fledged later, supplementary feeding and parental age had no effect on chick survival. Supplementary feeding a parent's first brood had no effect on their later reproductive output that season, or on their survival to the next breeding season. Supplementary feeding Yellowhammer chicks early season increased their mass, but had no effect later in the season. This complies with results from a previous study of Yellowhammers in southern England, which showed that a higher proportion of chicks fledge late in the season. Further analysis of this data showed that this was because chicks were more likely to starve early in the season, and also that chick mass was lower early season, even when just looking at chicks which went on to fledge. Thus, it would appear that low invertebrate abundance was affecting the granivorous passerines looked at most in the early season, and through chick mass and survival. Measures to increase invertebrate abundance at this time would be beneficial to populations of granivorous passerines.

Thesis (Ph. D.)--University of Washington, 1988. / Vita. Includes bibliographical references.