Indicators of the health of the North Sea fish community: identifying reference levels for an ecosystem approach to management

Abstract

The shift in emphasis away from the single-species focus of traditional fisheries management towards an ecosystem approach to management requires application of indicators of ecosystem state. Further, an ecosystem approach to management requires the identification of ecological reference points against which management objectives might be set. In applying indicators, identifying reference points, and setting objectives, an obvious requirement is that the indicators respond primarily to the anthropogenic activity being managed and are sufficiently sensitive that impacts of the activity and the responses to management action are clearly demonstrable. Here we apply a suite of 12 indicators to Scottish August groundfish survey data collected in the northern North Sea over the period 1925–1997. These include indicators of size structure, life-history character composition, species diversity, and trophic structure within the community. Our choice of analytical design has two purposes; first to show that fishing has unequivocally affected these various aspects of the structure of the groundfish community, and second to illustrate an approach by which long time-series data sets might be used to identify possible management reference points. The results are discussed in the context of selecting ecological indicators in support of an ecosystem approach to management and determining appropriate reference points for objective-setting.

Ecosystem-based fisheries management requires a change to the selective fishing philosophy

“…Biodiversity has three broad measurable aspects: richness, evenness, and phenotypic variation (8), each of which embraces various biodiversity properties that can be quantified using ecological indicators (9)(10)(11). For example, richness may include taxonomic and genetic diversity.…”

Compensation and recovery of feeding guilds in a northwest Atlantic shelf fish community

“…From a practical perspective, changes in guild and community structure can be difficult to reverse and can alter the ecological benefits that human societies want to achieve through active management (Jackson et al 2001, Pandolfi et al 2003, Jackson 2008. Therefore, defining the relationships between species and their functional roles within communities is critical for understanding the dynamics of community structure as well as developing management approaches for the conservation and sustainable use of biological diversity (Micheli & Halpern 2005, Greenstreet & Rogers 2006. Functional diversity, or the diversity and relative abundance of feeding guilds within a community, is a useful measure of community state and dynamics when considering management of ecosystem properties.…”

Trawl catch composition during different fishing intensity periods in two Mediterranean demersal fishing grounds

“…By applying an analytical design Greenstreet and Rogers (2006) found that variation in fishing effort is the main cause of differences in the size structure of the groundfish assemblage.…”