Linking basin‐scale connectivity, oceanography and population dynamics for the conservation and management of marine ecosystems

Abstract

Aim Assessing the spatial structure and dynamics of marine populations is still a major challenge in ecology. The need to manage marine resources from ecosystem and large‐scale perspectives is recognized, but our partial understanding of oceanic connectivity limits the implementation of globally pertinent conservation planning. Based on a biophysical model for the entire Mediterranean Sea, this study takes an ecosystem approach to connectivity and provides a systematic characterization of broad‐scale larval dispersal patterns. It builds on our knowledge of population dynamics and discusses the ecological and management implications. Location The semi‐enclosed Mediterranean Sea and its marine ecosystems are used as a case study to investigate broad‐scale connectivity patterns and to relate them to oceanography and population dynamics. Methods A flow network is constructed by evenly subdividing the basin into sub‐regions which are interconnected through the transport of larvae by ocean currents. It allows for the computation of various connectivity metrics required to evaluate larval retention and exchange. Results Our basin‐scale model predicts that retention processes are weak in the open ocean while they are significant in the coastal ocean and are favoured along certain coastlines due to specific oceanographic features. Moreover, we show that wind‐driven divergent (convergent, respectively) oceanic regions are systematically characterized by larval sources (sinks, respectively). Finally, although these connectivity metrics have often been studied separately in the literature, we demonstrate they are interrelated under particular conditions. Their integrated analysis facilitates the appraisal of population dynamics, informing both genetic and demographic connectivities. Main conclusions This modelling framework helps ecologists and geneticists to formulate improved hypotheses of population structures and gene flow patterns and to design their sampling strategy accordingly. It is also useful in the implementation and assessment of future protection strategies, such as coastal and offshore marine reserves, by accounting for large‐scale dispersal patterns, a missing component of current ecosystem management.

Accounting for ocean connectivity and hydroclimate in fish recruitment fluctuations within transboundary metapopulations

“…), and although basin‐scale models are known to poorly simulate complex coastal currents, our statistical analyses derived from such model provide signals consistent with both inter‐annual variability and geographical discrepancies of LR associated with local topography and hydrodynamics (Dubois et al. ). Moreover, we demonstrate that our connectivity metrics integrate both larval retention and exchanges (Watson et al.…”

“…Following Dubois et al. (), who showed that the greater deviation between SR and LR, the more pronounced is the source or sink behavior, it indicates that the 6 subpopulations mostly behave as sources in which larval export dominates import (Fig. b).…”

“…, Dubois et al. ). The oceanic surface is subdivided in thousands of equal‐area rectangular subregions that serve as nodes (small boxes in Fig.…”

“…The sensitivity and robustness of those connectivity metrics to the most relevant parameters of the LFN were extensively assessed (Dubois et al. , Monroy et al. ; Appendix ).…”

“… , b, Dubois et al. , Krueck et al. ) but they remained eminently theoretical and they mainly focused on the implications for spatial management at transnational scale and long dispersal organisms (e.g., Kough et al.…”