Search

Biogenic habitats on continental shelves are heavily impacted by demersal fishing, among other human activities, so their protection and restoration is a priority according to the habitats directive. In this context, it is imperative to understand the effects of external biophysical and human factors on biogenic habitats and their associated species. The logistics of sampling deep biogenic habitats are complex and costly, and destructive methods have traditionally predominated. To monitor vulnerable ecosystems, we must move beyond traditional benthic samplers, such as grabs and dredges that may damage the habitats, to non-intrusive methods. Additionally, in complex three-dimensional habitats, such as the Mediterranean coralligen or in rhodolith beds, traditional survey methods may be limited in time, produce incomplete biodiversity inventories and provide a limited view of the small-scale habitat heterogeneity. In this study, we tested cost effective monitoring tools using static video, environmental DNA and hydroacoustics in a rhodolith bed in the Menorca Channel (Western Mediterranean) along a conservation gradient including a well-preserved area. We compared the effectiveness of the different techniques to assess their capacity to inform on the ecological status of rhodolith beds. The comparison was extended to older information available for the area, obtained through traditional, intensive sampling using dredges and benthic sledges. We discuss the results in terms of efficiency, cost, replicability and use in regular monitoring of continental shelf biogenic habitats

Tropical reefs provide livelihood and food security to millions of people. However, tropical reefs are entering new configurations requiring management strategies to incorporate process-oriented measures such as biomass production to determine their dynamics and resilience. We proposed a new framework, comprising three management strategies based on fish standing biomass and productivity which were calculated on 2,027 reef sites over 39 countries. We found that 3.5% of the sites have low fish biomass and productivity, where alternative fisheries like seaweed and bivalve aquaculture are recommended. We identified 24% of high productivity sites where we suggest adaptive management: establishment of partially protected areas sustaining local fisheries when needed, or full protection when possible given their capacity for recovery. For the 5% high biomass sites, we urgently need full protection to maintain high reproductive capacity through large individuals. Our framework can thus guide management strategies by incorporating both static and process-oriented measures, tailoring each strategy to local priorities based on biodiversity and socio-economic objectives.