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    "@id": "http://portal.medin.org.uk/portal/json-ld/Marine_Scotland_FishDAC_1507.jsonld",
    "identifier": "Marine_Scotland_FishDAC_1507",
    "url": "http://portal.medin.org.uk/portal/?details&tpc=Marine_Scotland_FishDAC_1507",
    "name": "Aessessment of the \"State\" of the Demersal Fish Communities in OSPAR regions II, III, IV and V",
    "description": "To date, OSPAR has largely been responsible for the development of an ecosystem\r\napproach to the management of marine natural resources. Ten Ecological Quality Issues\r\nhave been identified, with the intention of setting Ecological Quality Objectives (EcoQOs) for\r\neach issue. Since 2000, this scheme has been developed and piloted in the North Sea.\r\nFish Communities is the fifth in the list of Ecological Quality Issues, and is considered to be\r\none of three community-level issues. In addressing concerns regarding anthropogenically\r\ninduced change in fish communities therefore, a community-level approach has been widely\r\nadopted. This has generally involved the application of univariate metrics to groundfish\r\nsurvey data to quantify change in various aspects of the community\u2019s composition, structure\r\nand function. The element of Ecological Quality for the North Sea fish community focuses\r\non \u201cchanges in the proportion of large fish and hence the average weight and average\r\nmaximum length of the fish community\u201d, thus clearly identifying the need for a community\r\nsize composition metric as the \u201cindicator\u201d on which to base an EcoQO for the \u201cfish\r\ncommunity\u201d Ecological Quality Issue. The chosen metric, the Large Fish Indicator (LFI) was\r\neventually defined as \u201cthe proportion by weight of fish greater than 40cm in length\u201d, based\r\non ICES first quarter (Q1) International Bottom Trawl Survey (IBTS) data.\r\nThe LFI was intended to be an indicator of the \u201cgeneral health\u201d of the demersal fish\r\ncommunity. However, other aspects of the composition, structure and functioning of fish\r\ncommunities, such as abundance, biomass, productivity, species richness, species diversity\r\nand mean life-history trait composition, can also be summarised using univariate metrics.\r\nAny one, or all, of these alternative metrics might also be considered to be indicative of the\r\n\u201chealth\u201d of fish communities. The LFI was chosen ahead of these alternative metrics\r\nbecause it was believed to be particularly sensitive to variation in fishing pressure, and\r\ntherefore to indicate directly the effect of fishing on the state of the fish community. But this\r\nraises the question as to whether one indicator is sufficient to inform on the general health of\r\nthe demersal fish community, or is a suite of indicators necessary in order to provide\r\ninformation on various different aspects of a community\u2019s composition, structure and\r\nfunction? In this assessment of the state of the demersal community in four OSPAR\r\nRegions, fifteen univariate metrics are applied to groundfish survey data to quantify changes\r\nin five main aspects of community composition, structure and function:\r\nabundance/biomass/productivity; size composition; species richness; species diversity; and\r\nlife-history trait composition (Table 1).\r\nBottom trawl surveys have been carried out as part of the traditional annual fisheries\r\nmanagement process for several decades. These surveys routinely provide point estimates\r\nof the abundance at length of each species sampled; therefore providing ideal data sets for\r\nthe application of univariate community metrics. Many of these surveys have run for two or\r\nthree decades now, providing appropriate time series with which to evaluate changes in the\r\ncomposition, structure and function of fish communities. Furthermore, most coastal\r\nEuropean nations have been involved in survey activity, providing data from most of the\r\ncontinental shelf waters in the OSPAR area. In this assessment, otter trawl survey data is\r\nanalysed to assess changes in the fish communities present in four OSPAR Regions (Figure\r\n1).\r\nTo assess the state of the demersal fish community in OSPAR Regions, II, III, IV and V, and\r\nmake a judgement on the changes observed, it was necessary to decide what constituted\r\n\u201cbeneficial\u201d and \u201cdetrimental\u201d change. Emphasis is generally placed on conserving and\r\nrestoring biodiversity; implying that declines in species diversity (both richness and\r\nevenness) are detrimental. The converse was therefore also assumed to hold. The lifehistory\r\ntrait composition responses of populations and communities to anthropogenically\r\nraised levels of mortality have recently received considerable attention. Declines in\r\npopulation age and length at maturity, decreased community average ultimate body length,\r\nand an increase in community average growth rate are all considered to be detrimental\r\nAssessment of the \u201cState\u201d of the Demersal Fish Communities in OSPAR Regions\r\n3\r\nconsequences. Improved management would therefore be expected to induce the opposite,\r\nbeneficial trends.\r\nEstablished population dynamics theory predicts that size-related fishing mortality reduces\r\nthe mean size and proportion of large fish in exploited populations (including non-target\r\nspecies taken as by-catch). This concept underpins development of the LFI as the basis for\r\nthe OSPAR North Sea Fish Community EcoQO. Reductions in LFI are therefore considered\r\ndetrimental. Changes in LFI were generally inversely correlated with changes in the\r\nabundance, biomass and (growth) productivity of the fish community implying that declining\r\nabundance, biomass and productivity are indicative of a fish community returning to a more\r\nnatural state. The von Bertalanffy growth equation makes it clear that larger fish, closer to\r\ntheir ultimate body length (L8), have lower daily specific growth rates. Large fish exert a\r\nstrong predation loading on small fish abundance. Since trophic transfer efficiency is around\r\n10%, every kg of production by larger fish requires 10kg of production in their smaller prey\r\nfish populations. Specific growth rates among smaller fish are approximately twice that of\r\nlarger fish, so 5kg of prey fish are required to support every kg of larger fish. Reductions in\r\nthe abundance of larger fish, with the consequent reduction in predation loading on smaller\r\nprey fish, would therefore tend to result in a rapid increase in the abundance and biomass of\r\nsmall fish; a typical trophic cascade effect.",
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        "description": "The MEDIN portal contains information about 19493 marine datasets from over 600 UK organisations. Metadata are an enduring resource and contact details are publicly available for a long time. \r\n\t\tPlease contact us (enquiries@medin.org.uk) if you find your contact details on the MEDIN portal and do not consent to this. \r\n\t\tYou can now use our GitHub repository to report issues or access related documents. Metadata records are updated daily and were last updated 2026-04-19. Record deletion takes place weekly and the latest occurred 2026-04-12."
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