Size-selective fishing drives species composition in the Celtic Sea

Shephard, Samuel; Fung, Tak; Houle, Jennifer E.; Farnsworth, Keith D.; Reid, David G.; Rossberg, Axel G.

doi:10.1093/icesjms/fsr200

Cited by 50 publications

(52 citation statements)

References 44 publications

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“… The large fish indicator (LFI) reflects the size structure of the fish assemblage, which is assumed to be primarily affected by size‐selective exploitation but is mediated by species composition (Shephard et al . ) as well as the fishing‐induced reduction of life expectancy of each exploited species. This indicator was calculated as: LFI = W >40 cm /W total , where W >40 cm is the weight of fish >40 cm in length and W total is the total weight of all fish in the survey (Greenstreet et al .…”

Section: Methodsmentioning

confidence: 99%

Fishing impact and environmental status in European seas: a diagnosis from stock assessments and ecosystem indicators

et al. 2014

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Stock‐based and ecosystem‐based indicators are used to provide a new diagnosis of the fishing impact and environmental status of European seas. In the seven European marine ecosystems covering the Baltic and the North‐east Atlantic, (i) trends in landings since 1950 were examined; (ii) syntheses of the status and trends in fish stocks were consolidated at the ecosystem level; and (iii) trends in ecosystem indicators based on landings and surveys were analysed. We show that yields began to decrease everywhere (except in the Baltic) from the mid‐1970s, as a result of the over‐exploitation of some major stocks. Fishermen adapted by increasing fishing effort and exploiting a wider part of the ecosystems. This was insufficient to compensate for the decrease in abundance of many stocks, and total landings have halved over the last 30 years. The highest fishing impact took place in the late 1990s, with a clear decrease in stock‐based and ecosystem indicators. In particular, trophic‐based indicators exhibited a continuous decreasing trend in almost all ecosystems. Over the past decade, a decrease in fishing pressure has been observed, the mean fishing mortality rate of assessed stocks being almost halved in all the considered ecosystems, but no clear recovery in the biomass and ecosystem indicators is yet apparent. In addition, the mean recruitment index was shown to decrease by around 50% in all ecosystems (except the Baltic). We conclude that building this kind of diagnosis is a key step on the path to implementing an ecosystem approach to fisheries management.

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Section: Methodsmentioning

confidence: 99%

Fishing impact and environmental status in European seas: a diagnosis from stock assessments and ecosystem indicators

et al. 2014

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“…individuals' role on community dynamic (Zhou, 2006) environmental variability and community dynamic (Maury et al, 2007b;Maury and Poggiale, 2013) Understanding community functioning (CR): spectrum models as test-bed for significant process testing (Andersen et al, 2008;Hartvig and Andersen, 2013) community structure explains individual's properties (Andersen et al, 2009a,b) community level characterizations of diversity (Maury and Poggiale, 2013;Reuman et al, 2014) Managing ecosystems (SM): community spectrum as indicator (Jennings and Blanchard, 2004;Houle et al, 2012) spectrum models as test-bed for fishing strategy testing (Andersen and Pedersen, 2009;Shephard et al, 2012) Modelling full ecosystems (SM):…”

Section: Historymentioning

confidence: 99%

“…For instance, Shephard et al (2012) use a diversified spectrum model to show that fishing larger individuals shifts the specific structure toward the dominance of smaller species. When the specific structure is not affected, the removal of larger individuals can be balanced by the growth of smaller individuals which replace their larger conspecifics, but with a combined extinction of larger species the expected recovery time of communities may extend.…”

Section: Managing Ecosystemsmentioning

confidence: 99%

Modelling the community size-spectrum: recent developments and new directions

Guiet

Poggiale

Maury

2016

Ecological Modelling

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“…Most of the species for which we find a positive fishing effect have L max < 46 cm. It is possible that the observed positive correlation reflects indirect trophic (predation/competition release) responses to the selective removal of larger species; the effect of size-selective fishing on demersal communities is mediated by inter-specific rather than intra-specific size selection (Shephard et al 2012a). …”

Section: Discussionmentioning

confidence: 99%

Footprints in the sand: a persistent spatial impression of fishing in a mobile groundfish assemblage

et al. 2015

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are rarely considered to be localized for management purposes, and associated spatial management is far less developed than for terrestrial habitats (Foley et al. 2010) where most widely distributed species are abundant in only a few 'hotspots ' (Brown et al. 1995). In the NE Atlantic, demersal fisheries are typically managed under the implicit assumption that the target population (stock) can be treated as spatially homogeneous within its range. The justification of this assumption depends on movement rates of fish and the degree of spatial heterogeneity in relevant fishing activity. Many pelagic fishes may indeed experience fishing mortality at the regional scale of management, because these species can move freely across large areas and are targeted by highly mobile fishing fleets. In contrast, the vulnerability of sessile (especially hard bodied and shelled) organisms can vary strongly at the scale of a few metres (depending on the footprint of trawl ground gear, e.g. Kaiser et al. 2006) or even less (for hand-gathered stocks such as scallops, e.g. Morsan 2007). It seems likely that fishing impacts on bottom-dwelling species ('groundfish') operate at an intermediate spatial scale: groundfish communities show strong patchiness, in association with benthic habitat and community composition (Reiss et al. 2010). The spatial distribution of demersal fishing (predominately bottom trawling) is also typically heterogeneous, showing strong patterns of local intensity that can remain stable over the years (Hinz et al. 2003;Shephard et al. 2011Shephard et al. , 2012b.In a marine landscape of patchy fishing activity, the impact of fishing on a given stock may depend strongly on distribution and movement of individuals across activity gradients. Movement patterns and rates of mobile organisms reflect many factors including niche space, habitat selection, optimal foraging and inter-specific interactions. Habitat seems to be a strong driver of groundfish distribution; many species form sub-populations in space (Metcalfe Abstract Fishing is well known to curtail the size distribution of fish populations. This paper reports the discovery of small-scale spatial patterns in length appearing in several exploited species of Celtic Sea demersal 'groundfish'. These patterns match well with spatial distributions of fishing activity, estimated from vessel monitoring records taken over a period of 6 years, suggesting that this 'mobile' fish community retains a persistent impression of local-scale fishing pressure. An individual random-walk model of fish movement best matched these exploitation 'footprints' with individual movement rates set to <35 km per year. We propose that Celtic Sea groundfish may have surprisingly low movement rates for much of the year, such that fishing impact is spatially heterogeneous and related to local fishing intensity.

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Size-selective fishing drives species composition in the Celtic Sea

Cited by 50 publications

References 44 publications

Fishing impact and environmental status in European seas: a diagnosis from stock assessments and ecosystem indicators

Fishing impact and environmental status in European seas: a diagnosis from stock assessments and ecosystem indicators

Modelling the community size-spectrum: recent developments and new directions

Footprints in the sand: a persistent spatial impression of fishing in a mobile groundfish assemblage

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