When Local Extinction and Colonization of River Fishes Can Be Predicted by Regional Occupancy: the Role of Spatial Scales

BACKGROUND: Predicting which species are likely to go extinct is perhaps one of the most fundamental yet challenging tasks for conservation biologists. This is particularly relevant for freshwater ecosystems which tend to have the highest proportion of species threatened with extinction. According to metapopulation theories, local extinction and colonization rates of freshwater subpopulations can depend on the degree of regional occupancy, notably due to rescue effects. However, relationships between extinction, colonization, regional occupancy and the spatial scales at which they operate are currently poorly known. METHODS: And Findings: We used a large dataset of freshwater fish annual censuses in 325 stream reaches to analyse how annual extinction/colonization rates of subpopulations depend on the regional occupancy of species. For this purpose, we modelled the regional occupancy of 34 fish species over the whole French river network and we tested how extinction/colonization rates could be predicted by regional occupancy described at five nested spatial scales. Results show that extinction and colonization rates depend on regional occupancy, revealing existence a rescue effect. We also find that these effects are scale dependent and their absolute contribution to colonization and extinction tends to decrease from river section to larger basin scales. CONCLUSIONS: In terms of management, we show that regional occupancy quantification allows the evaluation of local species extinction/colonization dynamics and reduction of local extinction risks for freshwater fish species implies the preservation of suitable habitats at both local and drainage basin scales

Knowledge for Fisheries Governance:Participation, Integration and Institutional Reform

As outlined in Chapter 1, the GAP project is situated within a transition zone from a traditional fisheries management approach that relies upon a clear separation of knowledge towards a new ‘bridging perspective’, which aims to establish a common knowledge base for fisheries governance. The transition builds on collaborative practices of participatory research and joint knowledge production, as will be described in the GAP case studies in subsequent chapters. Before these detailed empirical explorations, this chapter will first take a brief look at the knowledge gaps that are created by the dominant perspective of fisheries management and the resulting implications on sustainability of fisheries including the legitimacy deficits created by the traditional approach to fisheries. Second, three key domains of social science research that the GAP project connects with will be presented (participation, knowledge integration and institutional reform). Finally, some central aspects of the overall GAP approach are highlighted, and a brief overview of the GAP case studies is presented