Monitoring small pelagic fish in the Bay of Biscay ecosystem, using indicators from an integrated survey
|Author(s)||Doray Mathieu1, Petitgas Pierre1, Huret Martin2, Duhamel Erwan3, Romagnan Jean-Baptiste1, Authier Matthieu4, Dupuy Christine5, Spitz Jerome4|
|Affiliation(s)||1 : Ifremer Nantes, Unite Ecol & Modeles Halieut, Rue Ile Yeu,BP 21105, F-44300 Nantes 3, France.
2 : Ctr Ifremer Bretagne, Lab Biol Halieut, ZI Pointe Diable CS 10070, F-29280 Plouzane, France.
3 : Stn Ifremer Lorient, Lab Technol & Biol Halieut, 8 Rue Francois Toullec, F-56100 Lorient, France.
4 : Univ La Rochelle, CNRS, Observ PELAGIS, UMS 3462, La Rochelle, France.
5 : Univ la Rochelle, CNRS, Littoral Environm & Soc LIENSs, UMR 7266, 2 Rue Olympe Gouges, F-17000 La Rochelle, France.
|Source||Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2018-09 , Vol. 166 , P. 168-188|
|WOS© Times Cited||20|
|Keyword(s)||Min/max autocorrelation factors, Time correlation, Survey-based indicators, Marine Strategy Framework Directive, Ecosystem variability, Bay of Biscay, Pelagic ecosystem|
This paper is a practical contribution to two important debates raised by the implementation of marine ecosystem based management: (i) which ecosystem data can be provided by a fisheries survey optimised for ecosystem monitoring; and (ii) how to combine/select potential indicators to derive useful information on marine ecosystem status and dynamics? A suite of 143 potential indicators, including spatial indices, representing small pelagic fish and their biotic and abiotic environments are presented. Indicators were routinely derived from the PELGAS integrated ecosystem survey conducted in spring in the Bay of Biscay (BoB). The general patterns over time in this suite of 5–16 years, non-stationary time series are characterised using a methodology based on min–max autocorrelation factors (MAF), to select the most continuous indicators within, and across, several ecosystem components: hydrology, phytoplankton, mesozooplankton, small pelagic fish and megafauna. Potential interactions between selected indicators and external forcing variables, including climate and fishing, were assessed. The results confirm the importance of river discharges, bottom temperature, chlorophyll-a and mesozooplankton biomass in the dynamics of the BoB pelagic ecosystem. Small pelagic fish species appear to have followed distinct trajectories during the last 15 years. A marked decrease in anchovy and sardine mean weights at ages 1 and 2 over the last 15 years was highlighted; potentially caused by density-dependent competition. The quasi-absence of significant correlation between selected survey indicators and climate and fishing pressure proxies suggests a moderate exploitation rate of small pelagic fish resources, and confirms the so far limited effects of large-scale climate forcing on the BoB pelagic ecosystem. Perspectives for the assessment of marine ecosystem status on the basis of suites of indicators derived from integrated ecosystem surveys are discussed.