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| Trenkel, Verena; Pinnegar, John; Rochet, Marie-joelle; Rackham, Brian. |
| Choice of sampling method and survey period can have an important impact on the perception of the structure and dynamics of an ecological community. For the Celtic Sea fish assemblage we compared data obtained by three different trawl surveys: an autumn groundfish survey with a GOV trawl, and a spring and an autumn groundfish survey, both carried out with a Portuguese high-headline trawl. Time-series of abundance estimates were not consistent among surveys for all species and were generally very noisy. An analysis of variance components showed that the sampling method contributed more to the variance in abundance estimates compared to survey period, interannual variability, or even sampling variance. Overall community assessments based on indicators such... |
| Tipo: Text |
Palavras-chave: Trawl; Survey; Species diversity; Size spectrum; Celtic Sea; Abundance. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/2004/publication-899.pdf |
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| Rochet, Marie-joelle; Benoit, E.. |
| Fishing impacts on marine food webs are predicted by simulations of a size spectrum community model. In this model, predation is determined by predator and prey size and abundance, and drives predator growth and prey mortality. Fishing amplifies temporal oscillations in the biomass flow. Oscillations appear at lower fishing intensity and have wider amplitude when fishing is selective (removes a narrow size range) and/or when large fish are targeted, than when fishing is more balanced (catching a larger size range) or when small fish are targeted. A novel index of size diversity is developed, and is shown to be sensitive to both fishing intensity and selectivity. To avoid unstable food web dynamics with potential harmful consequences for fisheries, limiting... |
| Tipo: Text |
Palavras-chave: Size spectrum; Ecosystem approach to fisheries management; Biodiversity; Fishing selectivity; Community stability. |
| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00053/16462/14025.pdf |
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| Blanchard, Fabian; Le Loc'H, Francois; Hily, Christian; Boucher, Jean. |
| Within the framework of the 'dynamic equilibrium model', we tested the hypothesis that fishing causes major disturbance to benthic communities on deeper bottoms of the continental shelf. Benthic megafauna on the Bay of Biscay coast of France was sampled on fishing grounds subject to various conditions of exploitation. Samples were taken at around 100 m depth to avoid strong natural disturbances. Species diversity and the largest body mass class of invertebrates were smaller in strongly exploited areas than in moderately exploited ones. Biomass size spectra in strongly exploited areas were characterised by a comparatively large biomass of small invertebrates, hence the K-dominance curve of abundance was either above the biomass curve, or the curves... |
| Tipo: Text |
Palavras-chave: Benthic communities; Community dynamics; Disturbance; Diversity; Size spectrum. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/00000/10896/7578.pdf |
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| Blanchard, Julia L.; Jennings, Simon; Law, Richard; Castle, Matthew D.; Mccloghrie, Paul; Rochet, Marie-joelle; Benoit, Eric. |
| Widely observed macro-ecological patterns in log abundance vs. log body mass of organisms can be explained by simple scaling theory based on food (energy) availability across a spectrum of body sizes. The theory predicts that when food availability falls with body size (as in most aquatic food webs where larger predators eat smaller prey), the scaling between log N vs. log m is steeper than when organisms of different sizes compete for a shared unstructured resource (e.g. autotrophs, herbivores and detritivores; hereafter dubbed 'detritivores'). In real communities, the mix of feeding characteristics gives rise to complex food webs. Such complexities make empirical tests of scaling predictions prone to error if: (i) the data are not disaggregated in... |
| Tipo: Text |
Palavras-chave: Size spectrum; North Sea; Macroecology; Ecosystem effects of fishing; Community ecology; Benthic pelagic coupling; Allometric scaling. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/2009/publication-7318.pdf |
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| Shin, Yunne-jai; Rochet, Marie-joelle; Jennings, Simon; Field, John; Gislason, Henrik. |
| The usefulness and relevance of size-based indicators (SBIs) to an ecosystem approach to fisheries (EAF) are assessed through a review of empirical and modelling studies. SBIs are tabulated along with their definitions, data requirements, potential biases, availability of time-series, and expected directions of change in response to fishing pressure. They include mean length in a population, mean length in a community, mean maximum length in a community, and the slope and intercept of size spectra. Most SBIs can be derived from fairly standard survey data on length frequencies, without the need for elaborate models. Possible fishing- and environment-induced effects are analysed to distinguish between the two causes, and hypothetical cases of reference... |
| Tipo: Text |
Palavras-chave: Size spectrum; Size based indicators; Ecosystem approach to fisheries. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-775.pdf |
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