Summary 0[ An understanding of the links between life histories and responses to exploitation could provide the basis for predicting shifts in community structure by identifying susceptible species and linking life!history tactics with population dynamics[ 1[ We examined long!term trends in the abundance of species in the North Sea bottom!dwelling "demersal# _sh community[ Between 0814 and 0885 changes in spec! ies composition led to an increase in mean growth rate\ while mean maximum size\ age at maturity and size at maturity decreased[ The demersal _sh community was increasingly heavily _shed during this period[ 2[ Trends in mean life!history characteristics of the community were linked to trends in abundance of component species[ An approach based on phylogenetic comparisons was used to examine the di}erential e}ects of _shing on individual species with contrasting life histories[ 3[ Those species that decreased in abundance relative to their nearest relative\ matured later at a greater size\ grew more slowly towards a greater maximum size and had lower rates of potential population increase[ The phylogenetically based analyses demonstrated that trends in community structure could be predicted from the di}er! ential responses of related species to _shing[ 4[ This is the _rst study to link exploitation responses of an entire community to the life histories of individual species[ The results demonstrate that _shing has greater e}ects on slower growing\ larger species with later maturity and lower rates of potential population increase[ The comparative approach provides a basis for pre! dicting structural change in other exploited communities[ Key!words] community structure\ _sheries exploitation\ life history\ North Sea\ phy! logeny[ Journal of Animal Ecology "0888# 57\ 506Ð516

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Greenstreet, S. P. R., Rogers, S. I., Rice, J. C., Piet, G. J., Guirey, E. J., Fraser, H. M., and Fryer, R. J. 2011. Development of the EcoQO for the North Sea fish community. – ICES Journal of Marine Science, 68: 1–11. Development of the Ecological Quality Objective (EcoQO) for the North Sea demersal fish community is described. Size-based metrics were identified as the most effective indicators of the state of the community, but such metrics are also sensitive to environmental influence. Redefining the large fish indicator (LFI) produced a metric more sensitive to fishing-induced change and therefore more useful to managers. Fish stocks were thought to be exploited at a sustainable rate in the early 1980s, so in a process echoing the precautionary approach to fish stock management, this was considered the reference period for the LFI, suggesting a value of 0.3 as the appropriate EcoQO. The LFI declined from around 0.3 in 1983 to 0.05 in 2001, followed by a recovery to 0.22 in 2008. However, analyses of the longer-term groundfish survey data suggest that, even were fishing pressure to be reduced to early 20th century levels, the LFI would be unlikely to rise much above a value of 0.3. The response of the LFI to variation in fishing pressure suggested a more complex relationship than anticipated, underscoring the need for operational theoretical size-resolved multispecies fish community models to support management towards broader ecosystem objectives.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. This paper examines long-term changes in the structure and composition of the groundfish species assemblage in three regions of the north-western North Sea. Scottish fisheries research vessel data collected during the months July-September over the period 1929-53 are compared with more recent August groundfish survey data covering the period 1980-93. Trends in the whole groundfish assemblage, and in a subset of the assemblage that is not targeted by commercial fisheries, are described. 2. Long-term differences in species assemblage were subtle, and were most apparent in the dominance structure. Species diversity in the whole groundfish assemblage was marginally greater in the period 1929-53, but no difference was apparent within the non-target species assemblage. For the whole groundfish assemblage, diversity was greatest in the inshore region and least in the offshore area, but there was no obvious spatial gradient for the non-target species assemblage. 3. Multivariate analyses indicated long-term changes and between-area differences in the species composition for both the whole groundfish assemblage and the non-target species subset. More detailed examination of the data revealed that the long-term changes resulted from relatively small and subtle differences in the relative abundance of rarer species, such as grey gurnard Eutrigla gurnardus (L.) and spur-dog Squalus acanthius L.. In contrast, changes in the relative abundance of the more common species, such as Norway pout Trisopterus esmarkii (Nilsson) and whiting Merlangius merlangus (L.), explained much of the between-area variation. 4. Examination of species aggregated length-frequency distributions suggested that by the 1980s there had been a shift towards assemblages in which smaller fish were more highly represented. This was only apparent, however, in the whole groundfish species assemblage; the length-frequency distributions of non-targeted species were almost identical in the two time periods. 5. Overall, the results suggest that, although differences in the structure of the whole fish assemblage can be detected, the non-target groundfish assemblage appears to have remained relatively unchanged, despite a century of intensive fishing activity. 578Fishing and the ground-fish assemblage structure 1985; Gabriel 1992; Solow 1994). Thus, we have a relatively poor understanding of how community properties, such as the distribution of individuals among species or among size classes, have changed in the North Sea during a period in which massive species manipulations have been undertaken by ...

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