Integrating spatial indicators in the surveillance of exploited marine ecosystems

Abstract

Spatial indicators are used to quantify the state of species and ecosystem status, that is the impacts of climate and anthropogenic changes, as well as to comprehend species ecology. These metrics are thus, determinant to the stakeholder’s decisions on the conservation measures to be implemented. A detailed review of the literature (55 papers) showed that 18 spatial indicators were commonly used in marine ecology. Those indicators were than characterized and studied in detail, based on its application to empirical data (a time series of 35 marine species spatial distributions, sampled either with a random stratified survey or a regular transects surveys). The results suggest that the indicators can be grouped into three classes, that summarize the way the individuals occupy space: occupancy (the area occupied by a species), aggregation (spreading or concentration of species biomass) and quantity dependent (indicators correlated with biomass), whether these are spatially explicit (include the geographic coordinates, e.g. center of gravity) or not. Indicator’s temporal variability was lower than between species variability and no clear effect was observed in relation to sampling design. Species were then classified accordingly to their indicators. One indicator was selected from each of the three categories of indicators, to represent the main axes of species spatial behavior and to interpret them in terms of occupancy-aggregation-quantity relationships. All species considered were then classified according to their relationships among those three axes, into species that under increasing abundancy, primarily increase occupancy or aggregation or both. We suggest to use these relationships along the three-axes as surveillance diagrams to follow the yearly evolution of species distributional patterns in the future.

Copernicus Marine Service Ocean State Report, Issue 5

“…The set of indicators are the Spreading area (SA), i.e. a measure of the area occupied by the population weighted by the biomass; the latitude of the centroid or centre of gravity of data (CGY), which represents the mean geographic location of the population; the longitude of the centroid (CGX); the distance (D) between the centroid estimated on observations and the centroid estimated on predictions (Woillez et al 2009;Rufino et al 2018). Distribution statistics (first and third quartile, median) and performance indicators (mean absolute error MAE and R 2 ) were also estimated.…”

Contrasting patterns in the occurrence and biomass centers of gravity among fish and macroinvertebrates in a continental shelf ecosystem

“…We have already foreshadowed this potential effect in that the distributional response of species to climate change includes a general movement to higher latitudes (Pinsky et al, 2013), but also has been described to include a movement to deeper depths (Perry et al, 2005). Spatial indicators that can be provided with available analytical techniques are not typically utilized in the management even though they can reduce uncertainties and risks in the management process (Rufino et al, 2018).…”

Contrasted spatio-temporal changes in the demersal fish assemblages and the dominance of the environment vs fishing pressure, in the Bay of Biscay and Celtic Sea

“…Mérillet et al, 2020), as have other similar surveys, to derive indicators of diversity (including abundance), and ecological status (e.g. Rufino et al, 2018, Mahé et al, 2018. Despite those different sources of uncertainty and bias, the different conservative solutions applied in this study enabled us to detect spatio-temporal variations of community composition and reassert the crucial role of standardised LTES to understand community dynamics in a fast-evolving environment.…”